Racer Tech Thread
 

Seems like technical/equipment questions get buried in other threads, like the RTT. I have a question to ask and it seemed like this could be a good catch-all for mechanical (or electronic, these days) questions for racers.

I've got a mass start uphill race -- one of few where weight actually matters. I'll show up as lean as I can be and with as much training as I can. This one is "all-in" for me.

I'm planning to run a single chainring setup on my road crankset (SRM spider). I know I'll need some single-ring bolts. I'll run gears in the back, but I plan to ditch the FD.

* Should I go steel or aluminum? For a true single-speed or a track setup, with standing sprints to 1500W, I'd think one should go with steel. Do I need it for a more steady-state effort? Based on last year's data, I'll have a few out of the saddle surges to 550W, but it will be mostly steady. Are aluminum bolts OK? (Yeah, the weight savings is tiny but it all adds up; I don't want to take undue risk.) Thinking guys like @Hida Yanra may have ideas here.

* Can I just run my DA 7900 34T or 39T inner ring or should I get a dedicated single ring? I'll mostly be in the 19-23 sprockets, but for a few dips in terrain instead of shifting to 50x19 I can simply go to 34/39x14. I think chain line with the inner ring would be preferable to outer ring only. I'd prefer not to run a chain guide. Is this risk worth any thought? (Before someone digs up the David Millar prologue thing, that was a sing

* Should I bother to shorten the chain? Not thinking so much in terms of weight savings (few grams), but if it will materially reduce risk of a dropped chain I should probably do it.

All this may be for naught as I'm facing some other setbacks, but a 250g savings (FD + big ring) on this climb = about 5". If all goes well -- including the weather -- I'll be coming really, really close to my (totally arbitrary and only meaningful to me) goal; seconds may count.

Thanks for the thoughts.

As for using your normal chainring, think David Millar.

Regular road chainrings are designed to derail. I'd use a ring intended to be run as a single.

I would think chain drop would be a significant risk. If you go to all this trouble and even shorten the chain, imagine how bummed you'll be if you drop the chain anyway.

Yep. I did the Regional TT champs couple years back, couldn't use my front derailleur ('nother story), so took it off. Chain dropped 3 times in the 1-hr race!

Alloy bolts are fine- they have a shorter service life because of getting rounded out (metal is too soft for consistent install/removal), but for this they'd be fine. They'll take the torque no problem.

I'd probably go with a 39t or 38t myself, and if you can get one there in time, a wide-narrow tooth chainring. They are SO NIFTY, and seem to fix just a whole mess of problems.
What BCD are you using? (I think you probably have options for both 130 and 110, but checking to be safe)

34x14 isn't a bad gear- but big/big gears do have better efficiency (since we are working the tiny %s here), so 38/39 is preferable.

How does the start play out? Is it a CX style thing where making that first group off the line is critical? How often will you need to react to surges during the race? (in reference to the 550w stuff you mentioned)

How likely is a sprint at the end of the climb? What are your gearing plans for that?
What cassette are you going to use? The Recon stuff works quite well in my experience, and they are both light and cheap (compared to DA/Record cassettes)

I wouldn't shorten the chain unless you're running a max length chain (barely clears the pulleys in the small-small) or you go to a smaller small chainring or cog.

If you're really adamant about no front derailleur then I'd just a N-Gear Jumpstop on the inside of the ring. To the outside… don't know, but a big effort in the small-small (like a 34x11 for example) will pull the chain toward the outside of the bike. If you're leaning to the right, if you hit a little bump or something, the chain will come off. I watched it happen in front of me in a Tues Night race a few weeks ago, some jokers insist on doing the race on single speeds (another one showed up on a fixed gear and was told to pull out of the race).

If you can stand the idea of a front derailleur I'd either use something like the downhill racers use or get an older/worn front derailleur and cut the tail off. You want just the U shape thing at the front. While you're at it you can drill holes in it and stuff. Or you can fabricate something with a light band and some piece of welded aluminum (?) to hang a U shape cage over the chain. Remove all the cables and stuff, you just want the U shaped guide so your chain doesn't want to pop off.

Aluminum chainring bolts are just more sensitive to over-tightening. If you hear creaking then it's probably done. If you buy Ti ones you would have more reliability and you could use them on your bike normally. Just use anti-seize and loosen them regularly so they don't freeze.

Is it possible to use downtube shifters? Or are there parts where you need to be able to go while shifting?

I'm with the others. If you drop your chain the race is over so it's worth 50g to prevent it. I'd run the road 39 or like Hida suggests a cross oriented single chainring. I would do whatever you need to do with the chain not for weight but to keep it properly tensioned so it won't try and drop. Good luck and have fun.

Where else can you try to gain weight savings? I agree with the others, and it may not be worth it.

Knowing Eric I'm sure he has already done everything possible and maybe a few things impossible to reduce the weight of this rig. He's scraping for grams.

To clarify the aluminum chainring bolts I've had eventually popped their top off (of the male piece), usually after several install/uninstall cycles. This ended the serviceable life of the bolt. I never had a problem with power transmission, i.e. I never sheared the bolts.

Cutting the last couple inches of the drops off took 30g off my aluminum bars. I didn't do it for weight but I weighed the ends out of curiosity, plus the scale was right there. Even with heat treated light aluminum bars the weight was similar (3ttt Gimondi). Since those bars are pretty light I imagine cutting a bit off carbon bars would save similar weight.

Have you thought of off-the-bike stuff, like cleats (or specifically cleat hardware)?

For a chain guide thing I'd use one of those thing carbon fiber front der clamps with a bent/welded aluminum thing to position the U shaped piece correctly. If you do it right it might even be adjustable (use alum cable tensioner type things as a left-right barrel adjuster?). If it's aluminum it'll be all of 30 grams or something.

This is the kind of stuff I'd love to be able to work on except for me the extra 40 lbs on the body makes gram searching pointless, plus I don't know how to weld and I don't understand the complexities of mechanical design. For example I like reading bits about when journalists see Contador's bike, how freely everything spins. I've seen this a couple times so I think his bikes are unusually finely honed, or else the mechanic is proud of his work and "lets" the journalists see the results. Obviously other teams want to optimize their bikes as well but for journalists to make a point of writing about it means it is unusual for the journalist to see it.

thanks. in my OP i mentioned Millar but it got cut off for some reason. I was immediately thinking of him. Was that particular issue due, in part, to oval rings?

Anyway, the point is a good one. Thank you.

Thanks for confirming. Removing the FD without a considered plan is not a risk worth taking.

I run 1x10 on my cross bike with an unramped chainring (which I got from you!) and inner and outer chainguards, and I still drop the chain sometimes, even on the road (rarely, but it has happened). If you're moving around on the cassette at all, your chainline is varying and just the tiniest bit of chain suck at the wrong time can bounce the chain off.

There are the new fancy SRAM chainrings, and also RDs with clutches, but I haven't tried any of that stuff.

Is single speed at all an option? You could save a whole lot of weight that way, and no risk of chain drop.

Thanks, Hida!
Good to know. I wasn't aware of that as the reason.

So funny you mention this. Before checking back in on this thread I was thinking about the MTB 1x solutions (wide/narrow) and learned that they now have 110 & 130BCD rings. I know they still have some problems, esp with mud, and they work better with an RD with a clutch, but this isn't bumpy or muddy terrain.

You're right, I could run either; 110 would be slightly easier.


Agreed.

It's a mass start race, but it's not super insane at the start. It is important to be at the front but not so difficult to get there. I.e., it's not like there are 1,000 riders on a narrow road. I'll start in the first row and be fine there. Here's an idea of what the surges look like (yellow). I was in the first few wheels for the first mile. At ~1.5 miles, a rider took off, and I decided instead to settle into my rhythm, guessing that he was doing something unsustainable. (He was; I passed him for good at about 2.25 miles in, probably where that little bump is.

Cadence is in green. That dotted line is at 81rpm (my average for the climb). Speed is in blue. It ranged from 8mph to 19.3 (blue dotted lines @ 8 & 18).

I put in a little dig at the end. The 32:00 marker was approaching, but I finished at 32:08. In theory, I should not have been able to surge that hard.

Last year I ran 50/34 + 11-25. I'm not sure I used the 25 at all. The way I'd typically ride is to start in the big ring for the first 60", then shift down. After 2' in there's a flat/fast spot. I'd normally shift to the big ring for a minute. I then settle into something like 34/21-25. At ~5 miles in there's a short dip. I'll usually shift to the big ring here, but I also usually need the little break. Every second may count, so I'll need to push here, but I get less bang for the buck in this section. There are a couple steep bits at the end.

I used a gear calculator; 39x13 = 19.25mph @ 82rpms. @90rpms, 39x14=19.7. On the lower end, though, 39x25=9.7mph @ 82 (what I averaged on the steeper, consistent middle section).... I'd have to drop cadence a bit more vs what I prefer. Actually, a 39T wide narrow isn't possible, I think, so it would be 38 or 40.

36Tx12 would be 19.25 @ 82rpm and 36x25 @ 80=9mph.

34x11 = 19.8 @ 82 and 34x25=8.5 @ 80.

I didn't want to go 11-28 (bigger sprad in the back = longer chain = slightly higher chance of a drop.


I have 1190 11-25 and 11-28 available. An aluminum cassette scares me a bit, esp as this could involve shifting under heavy load. 124g claimed (recon 11-28) vs 154 (for 11-25; few grams more for the 11-28). Hm.

Wide/narrow rings are a 30g penalty vs a DA inner ring, but the alternative is a chain watcher + outer guide. Weight savings for no FD & no big ring = 1/2 a pound for me -- more when I factor in no front shifter.

Thanks for the thoughts. Obv geeking out on the gearing

Thanks, CDR.
Shortening it is mainly to reduce the chance of derailment. That is the idea, at l


we're looking at 30g or so for the n-gear or similar device. I generally don't drop the chain to the inside--and that would most often happen on a front shift. The chain line for the inner ring only would be untouched. I'd be using the inner ring + a few smaller cogs than I'd normally use, so I think the bigger risk is throwing the chain to the outside....esp as you and a few others say with the inner ring ramped to shift to the outside. A chain guard adds ~60g...so then we're not far off from just keeping the FD on there.

Yes. Good point. I remember those on DHer bikes.

Thanks! I need the shorter bolts for this application, but then I'd switch back to my normal DA 7900 rings, with the Shimano bolts.

I'm going to run one di2 shifter on the bars.

You need something to keep the chain on the chainring regardless of whether you use just your inner ring or a specific single chaingring.

I have my CX bike set up as a 1x10. I previously just had a FD on there, but now have a K-Edge single chain catcher the inside and an FSA carbon bash guard where the big ring would be.

Body (working on that...I'm weighing in at 5-7# lighter than last year and I was already pretty lean for that. I may be able to drop 3-4# in the next 4 weeks).
Kit (I'll pick the lightest stuff I have; will also ditch little things like sunglasses and gloves. Minor, but 30g here, 30g there....)
Bike (I've pretty much thought of every place I can trim weight. I could do something like ditch the SRM. It adds ~80g or so. I don't really need it for pacing. I know my body well enough at this point, but I'd like to have the data. That said, I'll probably use my Garmin 500 instead of the PC7/speed sensor. :))

You are right, though: I don't want to save a second and lose a minute due to a part malfunction.

:)

My rig was fairly light for last year. Over the winter I bult a super light set of wheels and more recently have been figuring everything else out. Quick calculation shows more than 1.5 kilos of weight savings for bike+kit. Totally ridiculous in any other context (hell, maybe even this context), that that could be 30".

This whole plan could easily go up in flames -- unfavorable wind conditions on race day, not being able to squeeze out 102% power from my body that morning for any reason (esp considering I am trying to come back from injuries). Last year I did not really get any major draft advantage. I was disappointed and thought the pace might be higher there, for free. I don't think that could go worse this time; maybe it will be better. I would never ask someone to work for me in that first mile, though.

thanks for clarifying. power transmission is what i'm most interested in here. sounds like there is no issue.

I could have gone with a light road bar but instead chose a bullhorn bar. I did shorten the ends (saved 5 or 10g, can't recall without checking), but the main reason was for reach. Bullhorn bar is slightly heavier but it allows me to use a light di2 brake/shift lever which is 1/2 the weight of an STI shifter. in fact, the shifter portion of it essentially adds no weight over a TT brake lever.

lighter helmet vs more aero one.
lightest jersey/bibs.
no base layer.
light socks. (sock less = not worth it, i don't think. maybe i could wear something more like a sanitary sock (super thin)? don't really want to get blisters.)
no gloves/glasses
shoes -- have 2 pair but they're the same weight.
cleats -- i use looks. i think my cleats are already as light as they can be. the look bolts are aluminum, i think--it's pretty easy to round the head of them.

i've often heard people say "lose weight off your gut" when discussion of a light part comes up -- or my favorite: "train more." they're not mutually exclusive.

also, who is to say (for you) whether subtracting weight off your bike is not worth it even if you are 40# heavier than you want to be? i mean, i'm sure you can lose the weight with time and discipline, but there's no reason you couldn't do the bike stuff if it was your desire.

every single item i'm looking at is ridiculous when taken individually--but i've been amazed by how much the 10g here, 30g there has added up to. it would still be fair for someone to say 1.5kg savings is ridiculous--who cares about 30"?

gottta control the food i put in my mouth. toughest part of that for me will be that i'm traveling to race/vacation with family up to 4 days prior to the event, and i'll likely want to celebrate after racing, so i could undo a lot of hard work there. i've been very slowly/steadily cutting weight. it's come out to 1/2-1# per month.

also, i've got a 40' TT the day before this hill climb.

i'll be as trained as i can be for it, so the bike/kit weight savings is a bonus (but probably crucial if i am to have any chance.)

Di2 with SRAM? It's gonna essplode.

i've got a k-edge catcher and bash guard on my CX rig (1x10), too. i just run it with a 7900 42T ring.

the thing is (correct me if i'm wrong) a CX bike is being lifted, slammed down, jumped on, run through dirt/mud....more chances for drops without those protections.

a hill climb bike? some power surges but smooth terrain and more steady-state.

some folks are running wide/narrow rings on MTBs without any guards. some of them have clutch RDs.

i dunno--i'm thinking it could work but maybe i am wrong.

if i have to add back 90-95g i might as well keep my FD (105g) on.

PS i think i'd need to use a braze-on compatible inner chain watcher. most are for round tubes.

:)

unfortunately, with the 9000 series i cannot trust DA cassettes. i think that in the past (7800 & 7900), DA cassettes that were kept clean ran for a long, long time.

1190 is lighter weight. definitely prefer shimano drivetrains, but i made a call here to go lighter.

open to the recon cassette that hida mentioned....but i'd need a STRONG recommendation to get over the alu cog risk.

After I lost all that weight in 2009-2010 I was on the Tsunami for the first time. It was at least a pound heavier than the Cannondale, bare frame was 1600g (Cannondale, in a larger size, was 1150g). I also used a 450g fork vs the 300-something gram Cannondale top of the line Slice fork. Yet I was using 200-300w less power to get up the hill at Bethel, I was dragging the brakes on the easy laps, and I felt like I could do anything on the bike. I realized then that a pound on the bike was nothing compared to 30 or 40 pounds off the rider.

Now I focus first on fit/ergonomics. If I have some deluxe stuff then I'll do weight. Except wheels. Wheels I look at rotating weight.

As far as discipline I am pretty low on that, so losing the weight is tough for me. I can get to about 167-168 but 160 is tough and 150 was virtually out of reach. I ought to be in the 150s, even 145. To be really cut I think I'd be close to 140.

ctrl-f colonic

not mentioned yet. If you care about 250g you should get a colonic a day or two before. Like 5lbs!

of course!

i'm definitely considering a very special case here -- but my earlier point is that if you just want to buy/make/use something light on the bike, it is still a benefit to you, whether you are 5% BF or 25%.

i'm of the opinion that rotating weight, on a bike, makes no difference vs non-rotating weight. there eIS a difference, but it is so incredibly minor as to be inconsequential--for me. not all feel the same.

i've been shocked. when i got my first DEXA scan a few years back, what i thought was 10% BF was definitely not. really opening my eyes to where fat was hiding and what i could actually trim. at that point i thought there was nothing i could lose.

anyway, the whole discipline thing is a can of worms. there's a huge industry around selling people tricks to lose weight, but it comes down to resisting temptation. it is amazing how quickly one can undo so much hard work. for me, with slow and steady losses (e.g., an extra 30' of tempo a day + trying to resist that dessert at night)...that daily redux is something i could erase in a few minutes post-ride.

wow....recon 11-25 saves more like 50g than 30g. ridiculously light.

just correcting my earlier guess as i thought it was about 125 (recon 11-28) vs 154 (1190 11-25) -- realized that there is a recon 11-25 @ ~110. also, 1190 11-28 is more like 169g.

I hear ya regarding the DA9000 cassettes. Shimano could be handling it better. I didn't know Recon made 11 speed Shimano cassettes. I have a K-Edge braze-on if you need it.

This seems to be the best advice so far!

For me there's a substantial difference in rotating weight, although I can't prove it using numbers. Basically if I have heavier wheels I don't have the same jump and I burn a lot of matches doing my whole tail gunning thing. In 2010, at my peak fitness, I didn't finish any races with my heavier but pretty aero Jet 6/9 set up, and in fact I did better in the same Tues races with the non-aero Bastognes/Ardennes (same tires, same hubs, same spokes). With lighter wheels I can accelerate more quickly. The faster my start speed, the less important rotating weight is, so starting a sprint at 35 mph means I'd want an aero wheel set, starting at 25 mph means a light one. From 25 mph my whole jump is used to get me up to speed. I haven't started a sprint at 35 mph in forever but if I started at that, then applied the jump and stuff, I think I'd be going a bit faster and therefore aero becomes significant. Nowadays it seems that my start speeds are lower therefore rotating weight is more important.

At some point I want to do some experiments regarding rotating weight or have someone who knows math/physics + cycling do some number crunching. Theoretical only gets so far, like the physicist that did some calculations regarding a particular NASCAR race. He figured that based on the curve etc of a particular track the max speed of the cars would be 165 mph. The actual speeds were 163-167 mph so he was pretty close. He also points out that the quickest 0-60 times for cars should be in the high 2 second mark, based on the assumption that it would be hard to get more than 1:1 coefficient of friction between tires and pavement. His assumptions fall short here and there and there's a lot of hoopla on how dumb he is but those making the calls aren't taking his assumptions into consideration (1:1 coefficient of friction, no aero factors involved; once you negate those assumptions then obviously his calculations go out the window, or you have to recalculate to get new values). Anyway theoretical is good but I want to see how weight affects acceleration at high wattages, where 50 or even 100w is not that significant in the scheme of things, meaning it'd be 5-10% of total, not 30% or something. At 1000-1200w 50w is close to the margin of error, i.e. statistically not significant. That's what I want to test.

Aluminum cogs? The big ones especially.

Have you optimized your pedals? Ti axle, esp for the short event. I think the Look hardware is steel, just soft. There are ti bolts out there for Looks. Alum spacers if they're not already, I don't know what they are. If it were me I'd make my Aerolites work. About 70g per pair with cleats and hardware (they say 38g per side, that's about right), but it's the devil to set up, you have to drill into your shoes. In fact I still want to make my Aerolites work but it's such a pain.

QFT- this was a big one when I was a multi-sport kid, thought I was pretty darn lean... numbers don't lie, and the majority of the weight-centric industry has grasped that it is easier to help people feel better about themselves than it is to help them fix the real problems.


I've heard of Recon cassettes shearing- but those were older ones, and used in an MTB context (yeah, don't do that)

I'd certainly use them myself without worry, but I think that my level of caring about this stuff is lower than yours.
Yes, the weight differences are NUTS- the first time I picked up a Recon cassette was a similar "WTH" sensation like the first time I picked up an 808 rim... doesn't seem like it should be possible.

Risk thresholds vary- I use Ultegra or Chorus everywhere, recently sold off my last carbon wheels, and alloy tubulars + Ultegra makes this stuff superfluous on my bikes. Mine won't break, but race bikes also weigh 16-17 lbs.

I'd say get on the narrow/wide bandwagon and do some testing. See if you can drop a chain, I didn't believe in Di2 when it first came out until a bike company that sponsors my team and is our main brand at the shop handed me a long-term loaner bike and said, "go ahead, try to make it mess up." I couldn't make it drop a chain, even when I legit tried- testing makes a believer out of me, and the narrow-wide stuff is similar for me.
Not having access to a clutch-style RD on the Di2 setup makes it a bit trickier- but I think it'd work for you pretty darn well. YMMV.
I'm just back from Bend, spent some time with a friend/ex-coworker who moved there a month or two ago. He's gone narrow-wide, scraped together all the parts, nothing fancy pretty well only the chainring and not a clutch style RD or anything else, using a XT double crankset (so not perfect chainline).... he hasn't dropped a chain yet, and he's a fast "DH-get-rowdy" kid.

Aerolites- worth looking into. Mercury/TriRig has gotten rights to use the patent (or something of the sort, it's legal at least), and they are claiming 35g per side, and they work with standard cleat mounting standards. Read the reviews, its frankly right up your alley on a project like this.

How about cables- are you using standard cables and housing? There are lighter weight options, some work better than others, but it'll free up a few grams.

Tyres- I assume you are running those fancy-euro-pro contis?

Bar tape- given you are going with a bullhorn setup (nice thinking, I was going to suggest this after thinking about the theme- it's pretty standard for British hill-climb bikes), what tape are you using, and what weight are you at?
For a bullhorn setup, you shouldn't need to wrap the center section of the bars- and since it is a short event, have you considered skateboard deck tape or similar? Weighs just about nothing.

To save the grams from the mounting hardware, just put the head unit in your jersey pocket/leg band?

how esoteric do you want to get?

you could

-remove bar tape and just go with a few pieces of electrical tape to hold any wiring in place
-lighter cages (i'm sure you though of that)
-consider taking the cover off your saddle (or an old one). I know some guys that took the cover off their old SLRs and then drilled the body for more weight savings. the cover doesnt really effect comfort and wont be a factor over a shorter race. i have this chinese carbon thing on my bike and its fine. Hylix Road Bike Carbon Saddle Seat Fit MTB Riding Ergonomics 91g Touple SL | eBay
-are you running clinchers? veloplugs are reported to be lighter than rim tape. I have them on one of oldest clincher sets....works fine
-i think some water bottles are lighter than others...you should look in to that
-finally my oakley half jackets are boat anchors compared to my smith pivlocks or no sunglasses at all

i'd read about the recon cassettes in the past but always dismissed them. didn't know about the 11s until this morning when i searched. yeah, the da9000 cassette thing is a shame. i like the 6800 cassette, but for this (silly) case it is extra weight.

i have k-edge catchers on my road bike, but they work in concert with the FD (the front of the FD is curved to mate with the braze-on clamp). i'm not aware of k-edge making one of their single chain watchers (CX style) with a braze-on clamp--i think they all require a round tube. maybe i'm wrong. i could maybe rig up a curved washer. i'm less worried about tossing the chain to the inside, though. maybe that is a bad assumption.