wens

Last year I started working back into the gym with super light weights for the first couple weeks, which was awesome in that I didn't feel like I was completely decrepit getting out of bed every morning. The down side is squatting 65 lbs the first day just doesn't make you feel like a badass, pretty much the opposite actually.

MarkWW

It looks like the price is now either for one or 2+. I have a couple sonderklasses that came with a wavy base tape job from the factory, so I thought about sending them down for new base tapes and latex tubes. I guess first I should pull the base tape off and see if the tire will sit cleanly on a rim like that, or if it's a problem with the casing as well.

gycho77

Another question about my bike fit
https://youtu.be/069ZwV386Jk
Do I have to change anything?

taras0000

Looks good to me. Could be a bit smoother and relaxed, but that will come with time.

gycho77

Thank you for your advice.

carleton

+1

queerpunk

oh dang. their prices went up quite a bit since the last time i looked at their stuff. :/

wheelsucker8263

How do I choose crank arm length for training and racing on the track?

I am a master's roadie, but I built a 58cm Cervelo T1 a year ago (I rode a less aero road fixie on the track before that), and have ridden or raced Trexlertown a few times over the past few years, Forest City once (track 1) and now Mattamy/Milton once (Track Certification B). I have three crank arm length choices, as I have three Shimano 7710 cranksets 172.5mm, 170mm, and 167.5mm. The bottom bracket is high enough that I did not have any problems with clearance with the 172.5mm crankset riding at Forest City (I passed their clear the 2x4 test easily). I don't think clearance is going to be an issue at the other tracks, if I am good at Forest City. I am 6 foot tall with slightly long legs for my height (about a 33" jeans inseam), and ride 172.5mm on the road and TT bikes. I used to have 175mm on the TT bike, but I can get my torso very slightly lower/more aero with the 172.5mm, so switched a few years ago.

In case it matters, I am not a sprinter, but can hold my own with other newbie's in a pursuit, and I once chased and caught good track riders when they eased up after a sprint in a points race. I think the only way I could "be there" in a points race, scratch race or miss and out would be to somehow get away and perhaps gain a lap, or chase down a breakaway and hang on.

The "conventional" wisdom appears to be shorter cranks on the track than on the road for faster spinning. Does anyone have any evidence that this is true? Do riders use different crank arm lengths for pursuit versus mass start events?

I would prefer to pick one crankarm length, stick with it, perhaps put a crankarm-based power meter on, and sell the other two cranksets.

So which crankarm length should I go with? 172.5mm? 170mm? 167.5mm?

Thanks,

carleton

Hi welcome to the forum and the sport!

To be honest...

Some folks will say, "Between 165 and 172.5...it doesn't matter. Your times will be the same."

Some folks will say, "Ride the longest cranks you can spin comfortably." (I had a UCI elite international coach tell me this.)

Some folks will say, "Spin to win, baby! 165 all the way!"

Some folks will say, "I ride the shortest cranks I can get away with." (I had a UCI elite international sprinter tell me this.)

There is no formula or rule of thumb. It will probably come down to whatever you coach suggests (if you have one) or simply trial and error based on your riding style and gearing choices. There are definite and measurable pros and cons to each. They come in 2.5mm increments for a reason

On tip from a guy that raced a full season each on 165mm, 167.5mm, 170mm, and 172.5mm (me): Don't put the cranks on and declare that they feel weird after one or two workouts and ditch them. As with any equipment change, they will all feel better after a few workouts. Give them a chance before evaluating.

I know this didn't answer your question and probably made more questions. Maybe start with 172.5 and work your way down?

carleton

I even recall a story about a US domestic pro who raced elite track nationals and used shorter cranks on his bike for mass start races then swapped them out for longer cranks for his pursuits.

There are lots of ways to answer this question

taras0000

Ooh! carleton +1'd me! Now I know how Beliebers feel like when Justin responds to their fan mail!

gtrob

So in summary, it probably doesn't matter.

Total agreement, Ive been on 165-175 and currently ride 170s (mostly to conform to a very steep track). I hopped on a friends bike and thought they were 165s and turned out to be 175s, so clearly I have no idea whats going on lol

All the studies Ive read show basically no difference from even extremes (150-190). Easiest answer is ride whatever you ride on the road.

carleton

Your my #1 fan, [fan_first_name]. I think about you all the time. I can't wait to get back to [fan_home_city].



See you soon!!!!

dunderhi

I'll give the old-school answer - short cranks for spinning and long cranks for pushing. Simple enough. So, if you want only one crank, then think about what type of rider you are of want to be. For me, I know what type of rider I am (pusher) and I know what type of rider I want to be (spinner), so I came up with a slightly expensive solution: A training bike with 165's and small training gears, a pursuit bike with 172.5's and a big gears, and a weekend racing bike with 170's and just any gear that I can make work in my favor that day.

brawlo

From everything I've read, it doesn't really matter what crank length you use. You will adapt the gearing to compensate. A common thread in the scientificcy stuff I've read is that your limiting factor is the speed at which your foot can move through the air or the tangential speed of your foot. A number of smart people think that everyone has a limit on their foot's tangential speed. So for the same tangential foot speed, a shorter crank arm will yield more rpm than a longer crank arm. If you have a shorter crank arm you will typically use a smaller gear to give you more RPM and vice versa.

Then there's the more nitty gritty stuff where I overheard that a change of a couple of mm in crank length for a certain national sprinter of ours fixed a 'hole' in her power profile. Very few people have the resources available to them to suss that stuff out though.

carleton

EXACTLY.

I came to the same conclusion on my own. But, I didn't call it tangential speed. I called it "circumferential speed" (the speed at which your foot is moving in the circle) or simply "foot speed".

Cadence, foot speed, & torque are all related when it comes to making power on the bike. The often forgotten variable are the "micro-rests" our muscles get (or don't get) between contractions. These micro-rests can benefit a fast-twitch athlete.

So, for a given foot speed, if you give the athlete longer micro-rests between when you call on a muscle to activate, you'll get more power and/or less fatigue. The only way to increase the micro-rest is to lower foot speed, cadence, or...increase crank length.

Baby Puke

Yeah, it really doesn't matter. EXCEPT: You can get a lower faster position with a shorter crank, so short is the answer. Actually this is starting to be a trend on the road too, not just track. There's a techie article out there that hit recently, but I'm too lazy to look for it. So: 165.

carleton

To calculate foot speed:

Cadence = Revs/min
Distance = Pi * r^2 = pi * (cranklength)^2 = divide by 1000 to get meters
Speed = Distance / Time
Footspeed (m/s) = (pi * cranklength^2)/1000 * 60s

So, if you are going 120rpm using 165mm cranks, that's

Pi * .165 * .165 = 0.0855m

Your foot is traveling 0.0855m 120 times every 60s. So it went 0.0855m * 120 / 60 = 0.1711m/s

Take that number and reverse the math and you'd see that if you used 172mm cranks, the same footspeed (0.1711m/s) would equate to 109.8RPM.

So, your RPMs are 10rpm slower. But, now you get more torque (meaning you can ride bigger gears) and longer micro-rests.

There are downsides, too. But, that explains the upside.

carleton

On a related note...there is a magic cadence number that should be used with all of the above. This number shows up in all sprint events (F200, TS, Match Sprints, Keirin).

Conventional wisdom (actually the wisdom of a few high-level athletes and coaches) used to be that 150rpm was the magic number. Maybe it used to be. But, now it's not. It's much lower....but footspeed is about the same as humans can only move their limbs so fast. So why are speeds going up?

queerpunk

fwiw, high-science pro teams are moving toward shorter cranks on the road.

worth noting, too, that with wheelsucker riding a 58cm frame, 170mm cranks count as short.

gtrob

Ive heard sky is starting to use shorter cranks claiming some efficiency gain but Im not sure if was related to being on the bike for 3 weeks at a time.

BP makes a good point though, a shorter crank does let you have more open hip at the top of the stroke. A picture would help, but if you shorten the crank 5mm you actually gain 10mm at the top as you are opening your hips more, can go lower, etc. Power difference or not, could help get a more aggressive fit out of a bike.

gtrob

Lets ask Russia

carleton

I know, right?

I'm reminded of Bauge being pissed at the fact that he'd always owned Kenny up until the Olympic final where Kenny beat him in 2.


https://www.telegraph.co.uk/sport/oly...012-Games.html

taras0000

I seem to recall that Kenny beat him because he had rounder wheels.

carleton

Hahahaha

Bauge was totally hinting that there may have been some "Performance Enhancing" going on. But, really, he's just an athlete that was really confident and very surprised to be beat by a guy that he'd beaten nearly (if not actually) every time they'd met in the past 4 years.

Imagine his confidence going into the gold medal final as the World Champ of the past few years and facing someone that you've beaten several times before. He literally couldn't believe it. These guys race each other over and over for years. They may as well be teammates.