Tandem Cycling - Possible Tandem Carbon Cranks in sizes

Lightening Bikes is 'considering' making tandem cranksets, and even tandem cranksets in various crank lengths if there is sufficient demand.

They currently make a silly light crankset:

Cranks of Carbon crankset (http://www.lightningbikes.com/Cranks of Carbon.htm)

They may just end up making Captain's cranks, they may make stoker cranks. They are looking to get into new markets.

Contact 'em at the following email address and let them know you'd buy carbon tandem cranks and in what lengths, if they made 'em:

sales@lightningbikes.com

service@lightningbikes.com

info@lightningbikes.com

They are also receptive to making very short single bike cranks, and very long ones as well.

The captain's crankset wouldn't take much more than just different thread inserts. Very easy for a small run composite company to do.

Currently available in:

160mm, 162.5mm, 165mm, 167.5mm, 170mm, 172.5mm, 175mm, 177.5mm, 180mm, 182.5, 185mm

Calfee told me that they will be available.
They look too flexy too me.
Cost is around $1500 if I remember right.

Have friend who runs custom (non-carbon) 220mm crankset for captain (he's 6'7").
That's is a huge size selection that they offer.

Cost is around $1500 if I remember right.

Wow, you could buy a set of FSA or daVinci cranks + the Gates Carbon Drive system for that kind of coin!

As someone else noted, I'm not sure I'd willing to step up and drop that kind of coin to be a beta tester on that particular design. The company is sound and makes some awesome 'bents, but I think tandem cranks with those kinds of design limits and that kind of price is a non-starter, even though they are made in the USA.

Wow, you could buy a set of FSA or daVinci cranks + the Gates Carbon Drive system for that kind of coin!

As someone else noted, I'm not sure I'd willing to step up and drop that kind of coin to be a beta tester on that particular design. The company is sound and makes some awesome 'bents, but I think tandem cranks with those kinds of design limits and that kind of price is a non-starter, even though they are made in the USA.

Not to mention that "silly light", unless the manufacturer can at the same time achieve "silly strong", is not a particularly sought after tandem sales point.

I've long been a fan of the Lightning crank (http://www.bikeforums.net/showpost.php?p=6207014&postcount=21), as it was the only light crank that will work with the Quarq powermeter.

I've corresponded (http://weightweenies.starbike.com/forum/viewtopic.php?p=378671#378671) at times (http://weightweenies.starbike.com/forum/viewtopic.php?p=381703#381703) with Tim Brummer, the principal with Lightning, and the holder of the crank patent (http://www.google.com/patents?vid=USPAT6443033).

When I started researching tandem cranks (http://www.bikeforums.net/showthread.php?t=530433&highlight=ritterview) a couple of months ago, I came to the awful realization that our choices were crummy. I emailed Tim Brummer informing him of the dearth of tandem cranksets, and pointed out that since the Lightning already has a triple, it isn't such a large step to make a tandem crankset as well. He's expressed growing interest to me, and I am glad to see that this is getting around.

The Lightning crank has been much discussed on the Weight Weenie forum. A lot of information on these multi-page threads:

Lightning Cranks: now April (http://weightweenies.starbike.com/forum/viewtopic.php?t=40043&highlight=lightning+crank)

Lightning Crank photos (http://weightweenies.starbike.com/forum/viewtopic.php?t=52093&highlight=lightning+crank)

Madcow at Fairwheel bicycles is famous for his reviews of weight weenie components. His crankset review (http://fairwheelbikes.com/forum/viewtopic.php?f=77&t=5991)included the Lightning crank, and is generally favorable.

A Lightning crank could offer significant tandem weight savings. The most modern outboard bearing tandem crankset now is the 1820 gram FSA SLK Carbon Mego Exo (http://www.webcyclery.com/product.php?productid=18023&cat=469&page=2). A Lightning tandem crankset with a titanium spindle would weigh 1300 grams, a savings of 520 grams, or 1.15 lbs. For someone who already had a crankset, this upgrade would cost $3/gram.

For a new build considering cranks, the Lightning would be well within reason on a gram per dollar basis:

FSA SLK Carbon Mego Exo...........1820 gm................ $760 (http://www.webcyclery.com/product.php?productid=18023&cat=469&page=2)
Lightning Carbon Tandem..............1300 gm...............$1500
Difference...................................520 gm..............$740

Price per gram......................... ($740/520 gm =)........$1.4 /gm

As to whether the Lightning crank is sufficiently robust to handle tandem loads, the Madcow review had pretty good stiffness, there is already a heavy duty version, and replacing the aluminum spindle with titanium should further upgrade its capacity, and Brummer can make other modifications to the crank if needed (e.g. stronger spyder).

Too bad Shimano or Campy do not make tandem cranksets.
FSA seems the only option and we all have heard or experienced the pitfalls.
Going back to square taper is not something I can accept.

Going back to square taper is not something I can accept.

Why?

Calfee told me that they will be available.
They look too flexy too me.
Cost is around $1500 if I remember right.

Your $1500 number, is that for a Calfee crank? I don't see the lightning crank being that expensive. We're talking about a company that produces 11 different sizes at the same price point. They aren't charging exorbitant amounts for the outlier crank sizes, I don't think they'll do that with tandem either. Look for their cranks to be nominally a bit more than their regular cranks. Certainly not a full third more than two cranksets, though. I'd be surprised at that. I think two years from now Lightning will dominate the high end tandem crank market.

Lightning is a small shop. It will be very easy to make tandem cranksets for them.

The captains crank is very simple. Left side is a normal right side with a different pedal thread insert. Right side is a normal left side with a different pedal thread insert. I'd expect Lightning to come up with a novel way to manufacture their cranks without setting the thread insert in the glue, so to speak. That way they can 'thread' the crankarms as they are ordered, either as normal cranks, or as tandem cranks.

The stoker crank is a done deal once you have the Captain's cranks made. Left side is the same as a Captain's left, but a bit shorter typically, and Lightning is great at producing a huge size range. Unlike other manufacturers, Lightning understands that bikes from 49-63cm, equipped with varying stem lengths, varying handlebar widths, ridden by cyclists with different size shoes, showing variegated amounts of seatpost, all don't require the exact same size crank.

175mm cranks are cheap to manufacture. However, only a narrow range of frame sizes should actually have 175mm cranks on 'em.

Lightning Cranks are strong, even the silly featherweight stuff. The weight limit is 290lbs currently.

Email 'em and tell 'em you want tandem cranks that come in sizes.

We're talking about a company that produces 11 different sizes at the same price point.

No, we're probably talking about a company that produces one or two lengths of crank arms with an aluminum blank for the pedal holes sitting under a top-layer / veneer of carbon who waits until a customer orders the cranks to set the crank arm length, then drills and taps the pedal axle hole: it's a smart and efficient approach that small-volume boutique producers could easily use.



They aren't charging exorbitant amounts for the outlier crank sizes, I don't think they'll do that with tandem either.

Did you happen to look at their price list? Do the math...

Let's start with a double crank & smallish T6 chain rings @ $720
Now add a second set of cranks @ $580
Now add a pair of aluminum spiders @ $60/ea ($120)
Now add another pair of chain rings for use as timing rings @ $80

I'm pretty sure that adds up to about $1,500 for a double with undersized, less expensive chainrings and aluminum spider. I'm also guessing that's not the configuration that yields a 1,300g tandem crossover crankset either, but that's just a guess. Someone would have to advise if they were spec'ing the more expensive chainrings, how many chainrings and which spiders.



However, only a narrow range of frame sizes should actually have 175mm cranks on 'em.

175 / 170 has been the default crank configuration on tandems sold by the likes of Santana and others since the 80's. While it may not be the correct size for all teams, that's what you'll find as the OEM spec on the vast majority of tandems sold.

Why?

I know you use them. There have been so many advances in bicycles over the last decades.
One of them is the external bottom brackets advantages being simplicity, lighter weight, increased stiffness, ease of installing and maintainance. I have no doubt realized these advantages on my single road bike.
The thing is FSA is not known to have the best or even good external bottom bracket, this can be alleviated some by spending extra money on a Chris King or other high quality bottom bracket. I am not going to argue that the square taper is not working well for you or others, I just don't prefer to use it.

I was quoted $1500 from Calfee for the lightning crank.
The chainrings and spider look to me like there so little material they would not be very stiff.
I could be wrong but I would not pay that price.

I know you use them. There have been so many advances in bicycles over the last decades.

Yes, I use them... as I'm still waiting for something better to come along since I'm heavily invested in square taper BBs given our fleet of 3 tandems and 7 single bikes. Wait, check that: My Calfee Tetra Pro has ISIS and a set of "Leopard" carbon compact cranks bought on close-out that I'm using while my ankle heals. Actually, I'm kinda liking the compact drive and may just keep it.

Anyway, while it's true that there have been all kinds of new BB designs over the past decade it's also true that most of them have had issues, there are all kinds of incompatibility and long-term support issues for short-lived proprietary designs, and newer designs continue to evolve: have you checked out the BB30? Actually, I have to chuckle about the BB30 as Burley used pressed-in bearings and snap-rings for years and took flack for using an arcane approach to BBs.

Anyway, preference always rules and I have no problem with that. I was just interested in hearing your rationale.

I've been putting a tandem build together on a spreadsheet, and I want to use the Lightning Cranks. So, I needed to make up a spreadsheet for the cranks, to know the exact weight, what with chainrings, etc. I've posted screen capture below of the crank build on Excel spreadsheet, the file for which should be accessible here (http://www.mydocsonline.com/pub/painfree/Lightning%20crank%20specs%20titanium%20csv.csv).

This uses TA chainrings, which are well regarded. If I find that they don't shift well I can use something heavier. This is a maxi-light build, with Lightning's carbon spyder for the timing (saves 15 grams x 2), and ceramic bearings (10 gm). These are extra cost items above the quoted $1500. The stoker crank is the HD version, the captain's is the standard. Lightning's spindle now is aluminum. For the tandem stoker crank, the spindle will need be upgraded to titanium or steel. The titanium weighs 40 grams more than aluminum, the steel 130 grams. In this example, I've assumed titanium. If Lightning goes with titanium, it might be more expensive.

http://farm4.static.flickr.com/3412/3616920755_134e4c04af_o.jpg



The chainrings and spider look to me like there so little material they would not be very stiff. I could be wrong but I would not pay that price.

$1500 is expensive, and is a reason to look for a more affordable option. Neither the chainrings nor the spyder, however, are reasons to spurn the Lightning tandem crank.

The chainrings depicted on the Lightning web site are Extralites, which are reputed to be too light for most bikes, as they do not shift well. The chainring you can use on your tandem crankset could be whatever you wanted, including the FSA chainrings you would likely otherwise use.

The spyder depicted on the website is for the double crankset, which you'd not be using. The tandem would use the triple BCD 130/74 spyder, which is considerably heavier. If the triple spyder proves insufficient, I do not doubt that Lightning would devise a tandem specific triple spyder.

I think BB30 would be a great option on a tandem if somebody made it.
You would think Cannondale would the logical choice since they invented BB30 and make tandems.
Must not be enough money in it for them.
But they use FSA on their tandems.
Another thought I had (and have read about) is to buy 3 sets of Shimano Ultegra or Dura Ace cranks and helicoil two cranks. But then I think the spindle would be too short for a tandem BB. Maybe a custom machined spindle extender could solve that problem. That's an experiment I don't want to take on.

I don't understand what the real weight is on FSA SLK and Gossamer cranksets. I have seen numbers ranging from 1600 to 2000. Calfee told me the SLK is 200g lighter than the Gossamer. Not sure how accurate that is.

I don't understand what the real weight is on FSA SLK and Gossamer cranksets. I have seen numbers ranging from 1600 to 2000. Calfee told me the SLK is 200g lighter than the Gossamer. Not sure how accurate that is.

For comparison, DaVinci cranks including rings weigh 1282g. The bottom brackets weigh 362g. So, the total weight is 1644g. They're fairly light for aluminum cranks and are not that expensive.



One of them is the external bottom brackets advantages being simplicity, lighter weight, increased stiffness, ease of installing and maintainance.
...
The thing is FSA is not known to have the best or even good external bottom bracket.

I guess they don't require maintenance. You just throw them away after a couple 1000s miles.

Another thought I had (and have read about) is to buy 3 sets of Shimano Ultegra or Dura Ace cranks and helicoil two cranks.

Am I to understand that Shimano no longer makes the Ultegra tandem crankset?

Anyway, while it's true that there have been all kinds of new BB designs over the past decade it's also true that most of them have had issues, there are all kinds of incompatibility and long-term support issues for short-lived proprietary designs, and newer designs continue to evolve: have you checked out the BB30? Actually, I have to chuckle about the BB30 as Burley used pressed-in bearings and snap-rings for years and took flack for using an arcane approach to BBs.

Anyway, preference always rules and I have no problem with that. I was just interested in hearing your rationale.


IIRC Klein did that back in the day - or some form of integrated bearing/bottom bracket as did my old Fat City Monster Fat MTB.

175 / 170 has been the default crank configuration on tandems sold by the likes of Santana and others since the 80's. While it may not be the correct size for all teams, that's what you'll find as the OEM spec on the vast majority of tandems sold.

Santana is responsible for revitalizing the tandem market in the United States, no doubt. However, they're decisions are not based on specing the best components, making the best frames, or even fitting people properly with the right sized cranks.

Santana, and others, including singles bike manufacturers use 175mm cranks because it saves them money. In Santana's case they spec 175/175 or 175/170 most commonly.

Its absurd that bikes are spec'd with different cycling shoe sizes from 36 to 52, different length stems, different width handlebars, that frames on the high and low side of the 49-63cm range have different seat tube angles, but that every cyclist, by and large, is told that they "fit" 175mm cranks. There is a raging debate regarding what forumula to use to determine proportional crank length. However, I don't think anyone disagrees that crank length should be proportional, the narrow debate is regarding whether a linear relationship exists, and what algorithm to use to determine proper length.

Proper fit is more important on a Tandem than on any other bicycle. It is so much harder to coordinate getting out of the saddle, whether to stretch, or hammer, while pedaling. The place is it absolutely critical to have the right size cranks is on a tandem. Compromises in cadence can cause knee injuries for a Captain or Stoker with too short, or too long a crank.

I've always felt you're not a serious cyclist until you've experimented with crank lengths.

It amazing how many people have a stable of $3000 singles, $8000 tandems, vintage Colnago/Campagnolo rides, high end mountain bikes, and everything is hung with either Shimonoculture 175mm cranks, or the narrow range that Shimano and Campy make from 165mm to 180mm. A serious cyclist isn't just interested in accumulating expensive bikes, but in improving their performance and perfecting their fit. Sadly most cyclists interested in fit will quickly realize that even the fit consultant at their local high end shop contributes very little in the way of the discussion. At best having a Serotta set up or merely just a Fit Kit. I wouldn't spend $1000 on a bike in a shop that didn't have a Sizercycle and offer free Ergostems rentals to people who buy bikes.

Considering the FSA garbage that is available for tandems now, and the nightmare of the design in how those cranks are coming loose, I for one am excited about Lightning cranks.

As a weight weenie and someone who seems obsessed with being an early adopter, I would think you would be too.

Looking forward to seeing their stuff. Imagine saving 10 ounces without sacrificing drivetrain efficiency but actually improving it due to a stiffer style of bottom bracket and stiffer crankset!

Calfee told me the SLK is 200g lighter than the Gossamer. Not sure how accurate that is.

You have to make sure who ever is quoting weights is also specifying which Mega Exo BB they are including in the weight and any other configuration specifics, e.g., Mega-Exo vs. ISIS, etc.

When I last reported on weights for these various different cranks where the Gossamer was lighter than the SL-Ks I was merely passing along what Mark Johnson recorded when he actually weighed the two different cranksets on his trusty shop scale: he was as surprised as anyone when the far less costly Gossamers were the most svelte of the two. Well, what the heck... here's the feedback:


Hi Mark, The Gossamer ME is 1818g as you recalled and the SL-K is 1904g, both 175/170 combos, at least on my trusty non certified gram scale... "comparison weight" if you will.

Mark's about as much of a geek as anyone and can sell whatever he wants, so I have no qualms about believing these were the accurate weights when checked last year. Again, as to what FSA may have done with the BB specs and how those weights might skew the total crank weight for marketing purpose (hey, Keystone on a $700 crankset beats keystone on a $400 crankset every day of the week).

Someone mentioned Shimano's Ultegra tandem cranks, Mark still lists those on his Website (http://www.precisiontandems.com/catframepart.htm) and, well, it's another mystery ( or the miracle of bicycle marketing-made obsolescence ) as to why they still aren't an OEM spec: Weight complete with DA bb's = 1851g, with Ultegra bb's = 1910



For comparison, DaVinci cranks including rings weigh 1282g. The bottom brackets weigh 362g. So, the total weight is 1644g. They're fairly light for aluminum cranks and are not that expensive.

You gotta spend some pretty serious coin on better quality square taper BBs to get the daVinci's in the 1650 gram range, but that's the wild card on cost and weight. At $599 for whatever length, triple spider BCD of your choice (road, compact or MTB) and a set of FSA chain wheels with daVinci's 34t spiderless timing rings, you can't go wrong. Oh yeah, and with square tapers you can still pick your spindle widths: ours are 108mm front & 111mm rear. Of course, because daVinci cranks are polished aluminum (unless you pay a few bucks extra for anodized crank arms /spiders) you do need to decide if you will keep them looking shiny a new or if you'll just let them become stained and etched by your sweat and sugary drink drips. I tend to wipe ours down after each ride and hit them with some Mother's rim polish about once a month.

Now, to be fair, the FSA Gossamers are much less expensive but your options are limited when it comes to BCD, rings, crank length, color, spindle length and they aren't made here in the good old USA.

Someone mentioned Shimano's Ultegra tandem cranks, Mark still lists those on his Website (http://www.precisiontandems.com/catframepart.htm) and, well, it's another mystery ( or the miracle of bicycle marketing-made obsolescence ) as to why they still aren't an OEM spec: Weight complete with DA bb's = 1851g, with Ultegra bb's = 1910

hehe! Thank you, TG. That just made my day ..... that the plain old Ultegra Octalink crankset that came stock on our Trek T2000 is just as light as FSA's hi-zoot carbon cranks! Think I'll go shine `em up with some Mother's myself! :thumb:

As a weight weenie and someone who seems obsessed with being an early adopter, I would think you would be too.

WheresWaldo is probably gonna bust a rib from laughing so hard when he reads that one....

I'm neither a weight weenie nor an early adopter, that is unless someone gives me something to play with for gratis AND I'm confident it's suitable for use on a tandem.

I happen to have a lightweight carbon tandem because (1) I've known the builder for 10 years, (2) the decision to do so was nearly 7 years in the making, (3) the more affordable open frame design had been in production for over a year without any reported problems before I pulled the trigger and (4) the most compelling reason I found for selling a perfectly good, $7,500 custom steel travel tandem built by Glenn Erickson came after doing some long-term saddle testing on a Calfee single bike which allowed me to conclude that an unpainted carbon tandem would afford my wife unparalleled comfort while also being durable and repairable enough to last as long as we did. Oh yeah, and our combined weight is under 280lbs with me @ 5'8" and Debbie @ 5'2", which just happens to make for smaller frames that aren't as heavy as larger frames or frames built for larger and heavier teams.

While there are some light components on our tandem, most were selected for other reasons such as durability and strength (Thomson & Chris King components), personal preference and over a decade of use (Campy & daVinci... all three of our tandems have daVinci's cranks), or because I was able to get a great price on some cool parts (E3 bars & Zona stem).

The Rolf and Topolino wheels were actually acquired as a learning exercise and based on what I've learned I'm an even bigger advocate of well-built conventional wheels that typically cost less and weigh more than the uber light or race stuff.

In looking at the Lightning Cranks what I see are some chi-chi cranks originally designed for recumbent enthusiasts that may or may not be robust enough for long-term & trouble-free use on a upright tandem ridden by large or strong teams and, from a value standpoint, are simply off the charts the wrong way. You want lightweight for lowest cost possible, FSA Gossamer and/or Gossamer & Gates Carbon drive if you have a 28.5" stoker compartment. If you want lightweight in an heirloom quality crankset, daVinci cranks will last as long as you do if you pick your bottom brackets wisely and give them just a little Periodic Maintenance: we have one set with nearly 30k miles that have gone through 3 sets of bottom brackets. The first set shouldn't count because they were stupid light titanium jobs. The next set were replaced because they were prone to surface rust, even though the guts were just fine. The last set has been in there for 15k miles and look to be good for at least another 10k. I'm guessing our Phil Wood Mag/Ti BBs in the Calfee will still be in there when the frame's warranty expires in 25 years. Like I said, I like to go with the proven path.

Hey, if in a couple years Lightning cranks are holding up well on tandems and the cost comes down I may even recommend them to folks who are in the market. However, I can't imagine them finding a way onto our tandem... that is, unless the daVinci's spontaneously combust from heat build-up generated by all of the purported energy lost due to bottom bracket spindle and crank arm deflection.

However, they're decisions are not based on specing the best components, making the best frames, or even fitting people properly with the right sized cranks.

Santana is a manufacturer who sells to dealers: if you buy a tandem with the wrong size cranks don't blame the manufacturer... blame the dealer or yourself.

However, despite this conspiracy about 90% of the folks who buy tandems easily adapt to whatever size cranks are on the darn things. They also adapt to the various tread widths (Q-factor for devotees of Grant Peterson) and to absolutely awful riding positions on frames that are either too big, too small or simply not fitted quite right.

How about recreational cyclists who aren't exactly in the under 10% body fat club who feel they must have the lightest weight racing bike with racing wheels an skinny tires and the evil shops that don't do the right thing by refusing to sell the wrong bike to their clients?

Bottom Line: Much ado about nothing, once again.

Consumer beware and do your homework, or not... Some of the happiest tandem teams I know don't know squat about their tandems and some of the strongest teams we know can ride anything in any condition and with a screwed up riding position faster than a weekend warrior on a $10k uber tandem (ask me how I know).

"Some of the happiest tandem teams I know don't know squat about their tandems"

Hey! You're talking about us!:lol: That's ok, we don't mind. What do we know, we're riding a Santana.:love:

I suppose it's just about to fall apart, and every component is the wrong size...but we're smiling.:thumb:

What do we know, we're riding a Santana.:love::

... and there's a lot to be said for going with a proven brand and company. :thumb:

We made the right call for our first tandem because we didn't know squat either: 175/170 on a small size frame and with a 30" inseam. Seemed just fine to me and never bothered to change to 170 until 8 years later. Debbie's only 5'2" and she's been as happy as can be with 170mm, despite my attempts to put her on the 'right' size cranks, which she didn't like at all. Go figure. Could be Santana has always gotten it right for us first timers.

You gotta spend some pretty serious coin on better quality square taper BBs to get the daVinci's in the 1650 gram range, but that's the wild card on cost and weight. At $599 for whatever length, triple spider BCD of your choice (road, compact or MTB) and a set of FSA chain wheels with daVinci's 34t spiderless timing rings, you can't go wrong. Oh yeah, and with square tapers you can still pick your spindle widths: ours are 108mm front & 111mm rear. Of course, because daVinci cranks are polished aluminum (unless you pay a few bucks extra for anodized crank arms /spiders) you do need to decide if you will keep them looking shiny a new or if you'll just let them become stained and etched by your sweat and sugary drink drips. I tend to wipe ours down after each ride and hit them with some Mother's rim polish about once a month.


You have daVinci cranks? No wonder you didn't notice the inefficiency of the Gates belt drive. You've got the most spindly cranks I've ever seen since the old TA cottered cranks. I took one look at the daVinci cranks and considered 'em flex-o-matics...

Cheap to machine, but not a sophisticated design.

About on par with:

http://www.hscycle.com/Pages/customcrankset.html

or

Zinn non-integrated cranks

I always wondered why more people didn't get their tandem cranks from these guys:

http://www.customcranks.de/en/

Is there a reason. I can't believe for a second that they would hesitate to make tandem cranks.

I can't wait for the Lightning cranks, however I've got to skinny up to ride 'em (weight limit of 290).

You have daVinci cranks? No wonder you didn't notice the inefficiency of the Gates belt drive.

As usual, you're in error once again. I've never posted any information regarding first hand (i.e., my) riding impressions of the Gates belt drive system or anything that could even be miscontrued as such.


You've got the most spindly cranks I've ever seen since the old TA cottered cranks. I took one look at the daVinci cranks and considered 'em flex-o-matics...

You'll have to help me out here because I'm at a loss to understand your analysis process. You have previously admitted (and provided more than enough evidence to verify) you are not a mechanical engineer and it doesn't appear you have ever actually ridden a bicycle fitted with the daVinci cranks; yet, by merely 'looking' at the cranks you have come to the conclusion they will exhibit excessive deflection.

When you took your 'look' at the daVinci cranks was it via photos on the internet or have you actually seen a set in person and examined how the two-piece CNC'd drive cranks or spiderless timing cranks are shaped and mated to each other? Did you evaluate the different alloys used for the crank arms and spiders, how they are made and machined? Or is it just the mere fact that they still use a JIS square taper interface that causes you to dismiss them as having excessive deflection when compared to other lightweight crank offerings?

Please elaborate.

Please elaborate.

This is gonna be fun........

grabs popcorn :)

this is gonna be fun........

Grabs popcorn :)

+1

This is gonna be fun........

grabs popcorn :)

You betcha! I got some sodas if you'll share that popcorn!

I'm ordering pizza to have with my beer on this one.;)

As regards the stiffness of the Lightning Crank, this was tested by Madcow at Fairwheel Bicycles, along with many other high end and WW cranks, in his crankset review (http://www.fairwheelbikes.com/forum/viewtopic.php?f=77&t=5991).

The Lightning came out middling in the stiffness rankings.

http://fairwheelbikes.com/jw/cranks/avgdefl.jpg

I asked Lightning engineeer Tim Brummel about whether the stiffness would be increased by replacing the aluminum spindle for one of steel or titanium (as will be done for a tandem specific crank). He replied that the spindle would make little difference for 'stiffness', as most of the deflection occurs in the crank arms.

While we want a tandem crankset to have stiff crank arms, that is not our specific tandem concern. The special consideration in tandem cranksets is the increased power arriving at the stoker crank via the timing chain, and transmitted in turn through the stoker timing chainring, L spyder, spindle, R spyder and chainrings to the derailleur chain. The stoker crank arms are outside this route of power transmission, contributing only the power of the stoker.

So, we want a 'stiff' crank with less deflection, but as this measures mainly the stiffness of the crank arms, it is not how we would specifically evaluate a crank's suitability for tandems. We are interested especially in robust stoker chainrings, spyders and spindles.

For the Lightning tandem version, we should be encouraged that the stoker's relatively thick (http://www.fairwheelbikes.com/forum/viewtopic.php?f=77&t=5991) 30.1 mm diameter aluminum spindle will be replaced with titanium or steel, which should sufficiently address spindle strength. I do not know if Lightning plans a tandem specific spyder. Spyders do not appear that difficult to design and fabricate, so I believe spyder strength will be addressed if needed. The chainrings are chosen by the user, as Lightning uses conventional Shimano spyder BCD's, so here too there is no limitation. Even though prominent experts have described the Lightning design as 'chi chi' (;)), I think that the tandem version should be particularly well designed for our use, as it will be fortified specifically where a tandem needs it, and light everywhere else.

I don't know about the DaVinci crank, except that much would depend on the bottom bracket spindle. Any discussion of the DaVinci would need to start with the relative strength of a steel square taper spindle.

Needed some more
:popcorn

We all know that it is a combination of factors that will influence crankset stiffness. To me, this is another "gates belt drive" issue - in that it may or may not be worth the money you spend on it and it may or may not provide tangible benefits over what you may have now ie. lighter/stiffer etc.

We all know that it is a combination of factors that will influence crankset stiffness. To me, this is another "gates belt drive" issue - in that it may or may not be worth the money you spend on it and it may or may not provide tangible benefits over what you may have now ie. lighter/stiffer etc.

I don't think the Lightning crank is another Gates. The carbon drive kerfuffle (Gatesgate), has to do with the drivetrain efficiency, which is unknown vs. the modest known (120-250 gram) weight advantage. The Lightning crank has no question of drivetrain efficiency, a modest question of robustness/stiffness, and a known and tangible >one pound weight advantage.

This is how things compare with the Gates vs. a lightweight chain/chainring, and a Lightning vs. an FSA.

.............................................................Gates........................Lightning
Weight advantage....................................130 gm.......................500 gm
Drive efficiency......................................Unknown......................No difference
Stiffness................................................Improved......................Unknown
Cost difference..........................................$300............................$740
$/gram difference.....................................$2.30..........................$2.03

By stiffness with the Gates I refer to the oft-remarked reduced slack in the system in comparison to a chain. These two scenarios are quite similar, save for the Gates drivetrain efficiency question. If the Gates drive incurs any watts lost in efficiency, then any weight gain advantage is Pyrrhic.

I don't think the Lightning crank is another Gates. The carbon drive kerfuffle (Gatesgate), has to do with the drivetrain efficiency, which is unknown vs. the modest known (120-250 gram) weight advantage. The Lightning crank has no question of drivetrain efficiency, a modest question of robustness/stiffness, and a known and tangible >one pound weight advantage.

This is how things compare with the Gates vs. a lightweight chain/chainring, and a Lightning vs. an FSA.

.............................................................Gates........................Lightning
Weight advantage....................................130 gm.......................500 gm
Drive efficiency......................................Unknown......................No difference
Stiffness................................................Improved......................Unknown
Cost difference..........................................$300............................$740
$/gram difference.....................................$2.30..........................$2.03

By stiffness with the Gates I refer to the oft-remarked reduced slack in the system in comparison to a chain. These two scenarios are quite similar, save for the Gates drivetrain efficiency question. If the Gates drive incurs any watts lost in efficiency, then any weight gain advantage is Pyrrhic.

I wasn't making a direct comparison - but more so in terms of $$$$ spent vs the advantages of the equipment and as you've illustrated - the unknowns. Is it really worth the "upgrade" whether it is in terms of weight savings, efficiency, stiffness etc.

Seems I could save $1500 (2 lbs) by cutting back on a few donuts?

I wasn't making a direct comparison - but more so in terms of $$$$ spent vs the advantages of the equipment and as you've illustrated - the unknowns. Is it really worth the "upgrade" whether it is in terms of weight savings, efficiency, stiffness etc.

This is pretty straightforward. The primary Lightning advantage is is in weight savings (another being the flexibility in sizes, as per the OP), and $2/gram is fairly reasonable as far as WW tradeoffs go. For someone looking to build a tandem, and willing to spend some more to make it lighter, this would be low hanging fruit.


Seems I could save $1500 (2 lbs) by cutting back on a few donuts?

Yes, however weight lost on a tandem build doesn't come back a year later.


http://www.39kf.com//uploadfiles/image/15897/TXT-20081228161944627.gif

FIGURE 1.. Weight by randomized group. •, Standard behavior treatment group (n = 66); , high physical activity group (n = 75).

...and $2/gram is fairly reasonable as far as WW tradeoffs go.

What's your cost basis on the Lightning tandem crankset that you spec'd?

The reason I ask is, the $1,500 mentioned earlier was based on using the Lightning cranks with aluminum spiders, standard bearings, standard axle and less expensive, heavier chainrings. What you spec'd earlier in the thread to achieve the 1,295 grams seemed to use some of the more expensive, optional upgrades, e.g., carbon spider, ceramic bearings, Titanium spindles, etc... but I don't recall seeing an updated total cost basis number for that uber-light configuration.

Notes:

As joe@vwvortex already noted, this is purely an academic / vanity exercise, as are most gram-counting, bicycle part / frame stiffness dialogs. The only critical parts of the tandem's drive train to be attentive to relative to added robust / higher loads is the stoker's crank axle, spider and chain rings + the rear cassette and hub.

The captain's cranks only have to deal with the captain's power inputs and has already been discussed in various tandem frame deflection discussions, the front bottom bracket even on the stiffest tandem frames ain't all that stiff to begin with. Since deflection migrates to weakest link, all of the chit-chat about crank arm and bottom bracket deflection for a tandem captain's cranks is interesting, but of little consequence.

The sync chain and timing rings also only serve one purpose and that is to carry the captain's power from the front cranks to the rear bottom bracket axle. The only thing the stoker can do to increase the load on the sync drive system is to not pedal efficienty, i.e., increasing the resistance the captain must deal with (unless it's a daVinci with ICS).

The stoker's crank arms must only deal with the stoker's power inputs, whereas the stoker's bottom bracket bearings and axle have to handle the combined power of the stoker and captain that come in rotational as well as lateral forces associated with the cross-over crankset design. In turn, the combined power needs to be transmitted through the drive side chainring spider and chain rings to the cassette and rear hub.

Just something to consider when evaluating the individual components. Again, IMHO and at the end of the day discussions regarding crank arm deflection are interesting but really not all that critical and it's fun to see how many grams you can get out of bicycle hardware before it reaches YOUR point of dimished returns.

As usual a very detailed analysis of the stoker crank function from TG. Personally I think a standard Lightning crank design will do just fine for the stoker. I was a little puzzled about the whys and wherefores of Ti or steel spindle - this seems unnecessary to me. I have read the Madcow reviews of crank stiffness and reviews on weightweenies and am satisfied that the crank is good quality as those guys are an exacting bunch.

Regarding whether it's worth the money or not, it's not that much in the big scheme of things. There are a lot of people over at weightweenies.com who spend $$$ on Clavicula cranks for their five bikes and many more who spend more money on much more marginal upgrades for their car, house, RV, boat etc...so no problem on either front IMHO.

Overall I am really looking forward to seeing the pictures when the bike is finished.

Not sure which FSA you are comparing it to. But for the Gossamer it's more like $1100 price difference.

I wasn't making a direct comparison - but more so in terms of $$$$ spent vs the advantages of the equipment and as you've illustrated - the unknowns. Is it really worth the "upgrade" whether it is in terms of weight savings, efficiency, stiffness etc.

You forgot to mention the other advantages of the Gates which is less noise, less lag, less mess, no lubing, 2-3X life of belt vs chain.

You forgot to mention the other advantages of the Gates which is less noise, less lag, less mess, no lubing, 2-3X life of belt vs chain.

Or the disadvantages that it is only designed to fit one manufacturers cranks, one specific length wheelbase and gets noisy when drying after being wet.

Regardless - I wasn't talking about the advantages or disadvantages - but more so the bang for the buck relative to it's benefits.

What's your cost basis on the Lightning tandem crankset that you spec'd?

The reason I ask is, the $1,500 mentioned earlier was based on using the Lightning cranks with aluminum spiders, standard bearings, standard axle and less expensive, heavier chainrings. What you spec'd earlier in the thread to achieve the 1,295 grams seemed to use some of the more expensive, optional upgrades, e.g., carbon spider, ceramic bearings, Titanium spindles, etc... but I don't recall seeing an updated total cost basis number for that uber-light configuration.

Geez, TG, you don't miss a trick. I'd spec'd the Lightning out for my purposes, which is maxi-light, and didn't delve back into the spreadsheet to spec out the standard tandem configuration of more general interest here. But you catch this, so I've got to rummage around in the spreadsheet again.

I had assumed the titanium spindle for the stoker before, so that is unchanged. Tim Brummel was equivocating between titanium and steel. I've optimistically assumed that he could produce a titanium spindled crankset for the same $1500 price. I've substituted the aluminum for the carbon spyders (15 g x 2) and the steel for the ceramic bearings (10 gm x 2). So, this works out to a 475 gm difference between the FSA (I'd estimated 500 gm). I had put the price per gram difference at $2, but I'd miscalculated. The $/gram is actually $1.55 if choosing between a FSA and a Lightning, and $3.16 if you already have an FSA and want to substitute a Lightning. I do hope I've avoided any further miscalculations here on this screenshot of the spreadsheet:

http://i41.tinypic.com/2u9ib0y.jpg

$1.55/gram is pretty cheap as far a WW'ism goes, especially since as far as I can tell, Lightning cranksters will not be giving anything else up in terms of performance or robustness.



Personally I think a standard Lightning crank design will do just fine for the stoker. I was a little puzzled about the whys and wherefores of Ti or steel spindle - this seems unnecessary to me. I have read the Madcow reviews of crank stiffness and reviews on weightweenies and am satisfied that the crank is good quality as those guys are an exacting bunch.

The Ti or steel spindle idea is Tim Brummel's. He doesn't think the aluminum will be sufficiently strong, so much so that if he did make a prototype aluminum spindled tandem crank, he'd want the captain and stoker's cranks offset.

How much of what's on paper REALLY affects how the bike rides? My Santana is miraculously holding up well. I'll keep my fingers crossed...

Yes, however weight lost on a tandem build doesn't come back a year later.


If you are going to spend this sort of money to save two pounds, you would be better off putting the money to the largest component of the bike which is the frame and likely you will save more than 2 lbs.

Likewise, the crank and arms need to be bullet proof. Failure of a crank arm is an extremely dangerous failure. Worst case is a crank arm in your leg and bleeding out. This is not where I would "save a few pounds" of weight.

If you are going to spend this sort of money to save two pounds, you would be better off putting the money to the largest component of the bike which is the frame and likely you will save more than 2 lbs.

I don't think there is that much play in choosing frames. For weight savings and comfort I am going to get a carbon frame, and there my choices are essentially a Calfee Tetra or Dragonfly, of which I will get the lighter latter. The Ruegamer frames have been lighter still, but that source has been sketchy. I figure in L/M the frame will weigh 2900 grams, or 6.4 lbs. That is lighter than a Co-Motion aluminum frame, but I don't know by how much.


Likewise, the crank and arms need to be bullet proof. Failure of a crank arm is an extremely dangerous failure. Worst case is a crank arm in your leg and bleeding out. This is not where I would "save a few pounds" of weight.

It isn't like the maker of the default tandem crank choice, FSA, has the greatest reputation for crank reliability. Bike boards are rife with examples of FSA failures, something I've personally experienced on my half-bike with the FSA, and which partly explains my FSA aversion. As I've discussed above, the Lightning crank has a thick spindle, and this in titanium should be quite sufficient for tandem demands. Just as the FSA's heaviness is insufficient to render it reliable, neither does the Lightning's lightness make it perilous.

Hey, if in a couple years Lightning cranks are holding up well on tandems and the cost comes down I may even recommend them to folks who are in the market. However, I can't imagine them finding a way onto our tandem... that is, unless the daVinci's spontaneously combust from heat build-up generated by all of the purported energy lost due to bottom bracket spindle and crank arm deflection.

Anybody who follows the tandem forum that didn't find this funny just doesn't have a sense of humor...

Santana is a manufacturer who sells to dealers: if you buy a tandem with the wrong size cranks don't blame the manufacturer... blame the dealer or yourself.

However, despite this conspiracy about 90% of the folks who buy tandems easily adapt to whatever size cranks are on the darn things. They also adapt to the various tread widths (Q-factor for devotees of Grant Peterson) and to absolutely awful riding positions on frames that are either too big, too small or simply not fitted quite right.

How about recreational cyclists who aren't exactly in the under 10% body fat club who feel they must have the lightest weight racing bike with racing wheels an skinny tires and the evil shops that don't do the right thing by refusing to sell the wrong bike to their clients?

Bottom Line: Much ado about nothing, once again.

Consumer beware and do your homework, or not... Some of the happiest tandem teams I know don't know squat about their tandems and some of the strongest teams we know can ride anything in any condition and with a screwed up riding position faster than a weekend warrior on a $10k uber tandem (ask me how I know).

I think fit on tandems is more critical than any other bikes. I also think that considering how low volume tandems are that it just makes no sense to shoot for the mean in terms of what gets spec'd. Considering that every tandem team is going to make some compromises in terms of cadence I think custom length cranks make more sense on a tandem than on any other bike (talking about normal sized people here, obviously tall and short folks need different cranks on any bike).

I don't think 175/170 cranks should be sold on a $3500-$10000 bike. I think the marginal cost of either perfectly proportional, or cadence adjusted cranks is very small considering how much the change will affect the tandem experience.

In my book fitting any tandem is a 'custom' job, even if its a production frame. I think the average bike shop does a wretched job fitting customers to bikes (other than for something like a Serotta fit), and I think most tandem dealers aren't much better. The sad reality is that tandems are very expensive, and most shops don't have the full size range of every make/model.

Some of the pictures I see make me think people have tandems that fit as poorly as ours do. However, barring a custom, we didn't have a choice. I think some of these people were sold tandems because that is what the tandem dealer had, not what was the best fit.

My perspective here is based on the notion that, largely, the stoker on a tandem doesn't have the same cycling background as the captain. Considering that this will be the one and only bike the stoker rides with regularity, for a great many teams, I think fit, including crank length, is paramount to getting the most out of the tandem experience.

I think fit on tandems is more critical than any other bikes.

Hmmm. Probably not; it's about the same as is the degree to which folks end up with what they feel is comfortable, albeit sometimes without having a clue what comfortable really is.


I also think that considering how low volume tandems are that it just makes no sense to shoot for the mean in terms of what gets spec'd.

The low volume is what drives the small-volume tandem production houses to offerings with the 175/170 standard crank offerings. If you go back in the archives here or at Hobbes you'll find that for the past two seasons there have been several periods where tandem cranks were in very short supply from the major suppliers like FSA and TruVative, noting that they've come to dominate the market that Shimano, RaceFace and others have left to the boutique crank makers like Specialites TA, daVinci and more recently Middleburn and of course we are talking about Lightning's potential entry to this niche market. That's one of the reasons that Santana has been sourcing their own cranks and Calfee recently followed suit. However, when it come to ordering cranks there's only so much capital these very small tandem manufacturers can have tied up in odd sizes that it's better to deal with customer special order on a case-by-case basis when a problem develops, which is true of most single bike manufacturers.


Considering that every tandem team is going to make some compromises in terms of cadence I think custom length cranks make more sense on a tandem than on any other bike

Actually and whether intended or not, the 175/170 already deals with the normal demographic and cadence differences on the average tandem buyer buy putting the captain or a set of cranks that are longer than the stoker's. Bigger pedalling circles will tend to slow down someone's cadence and having a shorter set of cranks on the same bike for the stoker means they're spinning smaller circles which can make keeping up with the captain and his longer cranks a bit easier. Again, if there's a real specific need for different crank lengths by a team they can always pursue a swap out or upgrade with their dealer and the manufacturer, which is very much the same for single bike buyers.


The sad reality is that tandems are very expensive, and most shops don't have the full size range of every make/model.

When looked at as an individual bike (instead of as a replacement for two), tandems are indeed expensive. In this regard and in the big scheme of things the Santana-zine has always done a pretty good job of explaining 'tandem economics' and their cost models have held up over time. A good tandem is about twice the cost of a good single bike and as you get to the more expensive tandem models they actually become a bit less than twice the price of an equivalent grade of single bike.

As for what bike shops have in stock, there aren't many that have any tandems in stock. Those that do will certainly only have one UNLESS they are a tandem specialty dealer. Of course, in those cases it's rare to find a full size range of a given model of tandem at even the higher-volume tandem speciality dealers. It's just not ecomonically feasible to have that much rolling stock sitting around given normal inventory turn times in the tandem biz.


Considering that this will be the one and only bike the stoker rides with regularity, for a great many teams, I think fit, including crank length, is paramount to getting the most out of the tandem experience.

The one point that I always try to make with all new tandem teams is this: your first tandem is just that, your first tandem. If you find you don't like tandeming (and a bad fit is not what dooms most new tandem teams) your first tandem was probably your last unless you find a new mate or draft your kids into tandeming once they're able to ride. If you do like tandeming you'll figure out what you like and don't like about your first tandem as you spend more time riding and -- hopefully -- attend some tandem gatherings or at least hook up with a few other local tandem teams so that you can share lessons learned and refine your 'must have list' for your next tandem. If crank size was an issue on the first tandem, be sure to address it on your next tandem.


Bottom Line: I don't necessarily disagree with your thesis; however, most of the fit issues that plague tandem bike buyers -- entry, mid- and high-end level -- are the same issues that single bike buyers must face. Most buyers simply make due with the basline equipment and do just fine. In those situations where there are fit issues that could be limiting a team's ability to ride as long, strong or comfortably as they like... there are options.