wildbill6949

Hello, Tandem riders,


I'm not a frequent user of this forum, so the answer may be easier than it seems to me. My wife and I have a 2001 Cannondale RT1000 tandem we bought about 8 months ago. It was hardly used, and sat in a garage for years without use. All cleaned up now, and in frequent use, we love it! It's our third tandem, and we plan to keep this one because it's in fantastic condition, and fits us well. While I do have a few other questions, the main one is that's got me preoccupied now is my quest for a captain's crank that's shorter than the 175mm that it has. The bike is all Shimano 105, with FC-1057 captain's crank (square drive BB). I'm only 5'9", and that's a big crank for me. My single bikes are all 170mm crank arm length, and the larger circles I'm pedaling aren't very comfortable, particularly when standing!


I've looked around a few times on the web, and I find it very challenging to locate any Shimano left-side drive cranks, let alone one with 170mm lengths, but I likely don't know where to look. We're happy with the rest of the drivetrain, and frankly, I don't want to change out both cranks to have a matching crankset. Anyone know if there are Shimano captain's cranks in 170mm length? Can anyone help direct me to a place that could help?

CliffordK

I've seen cranks that were helicoiled. That is an option. But, I'd try E-Bay and many of the tandem builders and suppliers.

One thing to keep in mind....

What is the difference between your preferred cadence, and your stoker's preferred cadence? Rider heights?

If your cadence is faster than your stoker's cadence, then a longer Captain's crank will actually compensate for the difference somewhat.

bwebel

You are looking for something pretty rare indeed. My knees get unhappy if I go longer than 170mm so I've got a search set up on ebay for 170 tandem cranks and they don't come across very often at all. If you tried the various tandem retailers (Precision Tandems, Tandems East would be where I would look first), your best shot for a truly matching crank is probably to find a single crank and heliocoil it, or just install it backwards and us loctite on the pedal threads. You can get the Davinci or the Sugino XD new in 170, but they aren't a great match for the grey color of those shimano cranks.

CliffordK

I think there are several US Tandem builders. For example, I believe Co-Motion is local to Eugene, Oregon. But, there are probably quite a few small tandem companies across the USA.

Bike Friday also produces locally made tandems here in Eugene.

They may either have the cranks in stock, or have experience with helicoiling them.

Cannondale, Trek, and the big builders are now mostly imported, but there are still quite a few small builders.

Carbonfiberboy 

I'm 5'6" and captain just fine with 175 cranks. 5mm is less than 1/4". It's tiny, really, less than 3%. I don't notice the difference going back and forth with the 170 cranks on my singles. Of course we've had the tandem 11 years now so we're used to it. Stoker has 170 cranks, though she has 165 cranks on her single. She doesn't notice that either.

wildbill6949

CliffordK, Thanks for mentioning helicoiling a RS crank. Honestly, I'd considered whether it's possible to use a RS crank, and simply tighten it up a bit, or even use blue Loctite. I've never seen helicoils for LH threads for pedals, but, I trust they exist. Seems like a good strategy. My wife's cadence is similar to mine, and that hasn't been an issue. Stoker crank is a 170mm, which is what's on her single bikes, too.


bwebel, You've confirmed my suspicion that what I want is rare. It almost seems that 175mm cranks are standard on all non-custom tandems. Loctite is a brilliant suggestion, at least it's an inexpensive way to try it! Thanks for your reply.


Carbonfiberboy, While I thank you for reading and replying, the message feels like what I'm trying to resolve isn't legitimate. I've ridden numerous bikes, and have over 80K miles of riding bikes in last 7 years. While I'm not much of a bike mechanic, I'm a fair rider. I'm happy you don't notice the difference of 5mm with your cranks, but I do. Why else would I trouble you all to post about this? It really bothers my hips when I stand to pedal, and my knees know the difference, too. I have the captain's cockpit set to same dimensions as my road bikes, as well. I'm going to pursue the 170mm cranks, and if it doesn't resolve my issues, I'll be writing to you to let you know....

bwebel

Just don't forget the loctite. The one time that I did, one of the pedals came off within 5 miles. I've never had a problem with loctite'd pedals, but I do think it's worth checking and retightening every so often. I was lucky that the pedal came off when I was sitting down. If it happened out of the saddle and really pushing hard, it could have been ugly.

CliffordK

Bicycle pedal threads are pretty unique. 9/16 x 20 tpi, I think.

It is not a standard bolt thread size and pitch.

However, as you might expect, more than a few people have destroyed crank arm threads, and there are helicoil thread repair kits available which can be used to reverse the right/left sides of the pedals.

Since they are very much bicycle specific, they aren't cheap, but they are available.

bwebel

One other thing to note about reversing the cranks and using loctite...it will depend on some flexibility with the pedals us are using. Either something like speedplays, which are symmetrical, or pedals on which you can swap the left/right axles. Otherwise you end up with the pedal pointed the wrong way when you install them.


If you get them heli-coiled, the inserts themselves are not all that expensive, but the install costs from a bike shop may be. A full install kit with a taps and a half dozen inserts by Unior is about $150 on amazon, inserts themselves are about $10. I'm not sure if the Unior design is better or worse than the Heli-Coil. Looking at the install video from the Unior website and the Park tool page on pedal bushing repair, doing the repair doesn't look all that difficult. I'd maybe worry a little about having the new threads perfectly square with the crankarm face, I don't know how well the tool lets you ensure that this is the case.

Dean V

I would be reluctant to get helicoils put in by a bike shop.
As you have to remove the good thread and replace it with the opposite thread you really need to have some equipment (ie machine shop) to get it done nice and square.
I have also done quite a few miles with pedals on the wrong way around. Never had them come undone and didn't use loctite. Just did them up good and tight.

OneIsAllYouNeed

There are a handful of legitimate options for you. I would not recommend using left pedal threads on the right side, and vice versa.

The most straightforward would be installing a brand new set of Sugino XD tandem crankarms. They're available in 170mm and 175mm for both captains and stokers, and sold as individual crankarms. Retail price is around $120.

For lighter stock tandem cranks, you could check out Davinci ($240 retail for captain cranks), Middleburn RS8 ($480 for complete tandem), Rene Herse ($800 for complete tandem worth), and Lightning ($1680 for complete tandem, requires installing new BBs).

Threaded inserts for converting standard single bike cranks are a good option too. Helicoil brand doesn't make the 9/16-20 inserts, but Unior and Eldi make specific taps and inserts for bicycle crankarms. Drilling and tapping a good crank does require a proper setup to get the hole square. I've made more than my fair share of tandem cranks this way. Contact your LBS for pricing if you have some donor cranks lying around.

You can hunt for a used or NOS tandem crankset.

You can find some used/NOS Stronglight or new Aerozine cranks that use their ALS insert. You can install these cranks backward, but put the pedal inserts on the correct side of the bike.

CliffordK

I wonder if small semi-custom shops would take on the task.

For example, IRD makes and sells a number of cranks.

Their cranks are apparently forged and CNC machined.

It woudn't take much for them to make reverse sets for the Captain, and dual spider cranksets for the stoker.

Anyway, it wouldn't hurt to send them a note.

Velo Orange? Origin8?

Philly Tandem

Depending on your pedals, sometimes you can also just switch the pedal axles left to right to use with "regular" cranks on a tandem.

PDub62

Chris_W

My wife and I both prefer to use 165 mm cranks. The best solution that I found on the tandem is to use regular triple road cranks front and rear. We use the outer ring position for the timing chain and the middle and inner rings for the drive train. We're currently using 28-42 chainrings with an 11-40 cassette. The 42-11 top gear yields around 50 kph / 30 mph at 100 rpm, then we're happy to coast, so we don't miss not having a big chainring. Another advantage is having the left side of the bike entirely clean and chain free. We haven't found a disadvantage in the 5+ years that we've used this setup.