smashndash

Wait does OP not have clipless pedals? Trying to sprint over 100rpm without proper foot retention is quite dangerous IMO. I can see why you'd think 35mph is scary (which, btw, is really fast for a flat sprint).

cubewheels

The wheel could lose traction in that case but hasn't happened so far so maybe it's lateral flex?

I drop heel during pedaling to a large degree. Sitted or OOS. Considerably less perceived effort for me.

cubewheels

Would have been a very good solution except I only got very few friends and none of them have high end bike. My fault. I should probably keep to slow sprinting speeds like steep uphill sprints for the meantime just to be safe and also to test how strong my $250 bike is without putting myself in grave danger.

cubewheels

It doesn't feel that dangerous once you get used to it (just need to be in perfect sync with the bike movement) although I will not advice trying it. I never had a foot even move a mm. It's only dangerous over "wavy" or bumpy roads where the feet can be jolted off the pedals.

I don't know why 55 kph on a bike looks like 550 kph. I do often feel like the bike might disintegrate under me. I'm definitely worried about the bike breaking apart than loose footing for me.

Dean V

Ever watched a BMX race.
They spin way over 100 rpm, in fact closer to 200 with no foot retention and definitely out of the saddle.
They do have a trend nowadays to clip in pedals but traditionally it was always just flats.

waters60

Watching countless road race sprint finishes I can’t recall ever seeing someone standing and spinning maniacally at 120 rpm. BMX riders don’t have the option of changing gears!

eduskator

Sprinting at 110-120rpm? I don't even get past 100 when climbing a hill at full pace with my arse down on the saddle.

WhyFi

I'm surprised that so many are expressing dismay at 110-120 out of the saddle. I'm also surprised that people are suggesting to "sprint" in the saddle.

topflightpro

110-120 rpms really isn't that much if you train for it. BMX was already mentioned, but track cyclists also routinely hit huge cadences. Many can turn 200 rpms on the rollers or 170 out of the saddle.

63rickert

For decades the standard gear on track bikes was 46x14. Big riders might use slightly bigger chainrings, except that there were hardly any, or no, riders weighing 200# so this was immaterial. Figure that in old days where everyone was on 36 spokes and flat rims, no aero nothing, doing 200 meters in 12 seconds meant you were competing, 200 meters in 11 seconds meant you were good. Get on the calculator and solve for rpm. Using 675mm for rolling diameter I get 143rpm for 12 seconds. And remember that is an average for 200 meters, not peak pedal speed.

Small guys on track often did ride 45 teeth in front, even 44. They went same speed as anyone else.

Somewhere in past twenty years everything changed and sprinters are now weightlifters on wheels. Gears used now are simply enormous. The riders are simply enormous. Spinning has gone out of fashion. And most don’t even know that pedaling at 120 rpm is real normal for a rider weighing 124.

Tires could have something to do with it. Pressure gauges are unreliable. Most will give the same reading today as yesterday, but being 5 or 10 psi off is ordinary. So experiment with both higher and lower pressure. Recommended pressures are just a guess at a starting point. Speed and sprinting load the tires differently than ordinary riding. If the whole bike is $250 the tires are probably basic. Basic tires won’t sprint that well.

Doing the speeds you are reporting with no pedal retention and a basic bike sounds difficult. Also sounds like really good training.

gregf83 

Here you go. Sprinters don't very often share their power data but this is Andre Greipel from 10 yrs ago. Might be a little hard to read but the blue line is cadence and you can see he starts his sprint at a cadence of 100.8 and shifts at 120RPM

cubewheels

Yeah, it maybe the tires. I have since upgraded the stock tires to Panaracer Ribmos which costed me less than $60 including new butyl tubes.

The tires I bought are "tall profile tires" 35mm wide which I think is meant to better absorb road bumps. It's a long-wearing, low 27 TPI, urban / tour tires with anti-puncture protection. It actually is "springy" by itself at the recommended pressures for my weight + bike with significant lateral flexing if I try to push the bike sideways.

Unfortunately perhaps, I'm probably restricted to these tires as these tires proved to be quite durable and long lasting in our poor quality roads. Quite affordable for me too.

njkayaker

???

The tire is much more flexible than the frame is.

You aren't flexing the tire enough to lose traction. So it has to be the much less flexible frame?

This doesn't make sense.

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Moisture

He weighs 120lb, and rides a MOUNTAIN BIKE which is an XXS (he needs a Large size frame , as he is 5ft8) has a 100 something mm stem facing downwards, with drop bars, and rides with the seat lower than baseline. Nothing is flexing here. Doesn't matter

Moving along, folks

njkayaker

There's some chance that, even with his feeling of "springiness", there is no springing (other that tires) going on.

It takes time for things to rebound (for "springing" to occur).

It would be somewhat odd that the springiness increased with a cadence of 120 (from 110).

There is probably less force per rotation (meaning less energy going into the compression reflected by something springing back).

The shorter time of the period also means there's less time for the compression/release cycle to occur in.

Both those things suggest he should be feeling less springiness. And even 110 might be too fast to feel much springiness.

smashndash

OK I promised to make a video so here it is:

I'm fully prepared to be mercilessly roasted over this. But the point is that 150ish RPM out of the saddle (for a VERY short burst) is possible. I never sustain anything close to this, obviously.

Moisture

I think that is pretty impressive.

But if you have trouble outputting a solid amount of watts in the saddle (albeit at a lower cadence) it could mean that you need slightly different geometry to get the best performance.

See if you can take another video, maybe in a slightly higher gear, slowing things down a little to try and avoid that side to side wobble and get as much power down, as efficiently as possible.

WhyFi

Oh, stop.

The point was that 120 out of the saddle, in a sprint, isn't absurd. And it's really not.

cubewheels

Yes, the tire is much more flexible and even worse since I have a tall profile 35mm wide tires installed (it's taller than wider).

I've been testing how flexible the entire bike setup by holding the bike upright with my hands and pushing the BB away from me with my feet. It didn't took much effort to visibly flex the frame and the tires flexed laterally even more. I can definitely feel it even when simply attacking out of the saddle. It's disconcerting to say the least.

I suppose it's simply the fact, a Walmart quality cheap bike isn't going to cut it. Or I'm just too sensitive to these things.

njkayaker

Most of it is the tires (guessing about 95%).

Things aren't going to change much with a different (more expensive) frame.

cubewheels

Oh darn... Looks like that's the solution but it won't be cheap.

That requires replacing my whole wheelset. I currently have 18mm internal rim width which is good for our bumpy roads but maybe not for performance.

cubewheels

There was one sprint finish I saw the top sprinters in TdF sprinting at the same cadence!

It's fairly achievable to anyone training for it unless you have physical issues preventing you from doing so. It's very rare that any cyclist would just train for it and because it's actually difficult to be even decent at it!

cubewheels

My seat is actually too high in that older picture. I'm a "heel dropper" which requires a lower seat to have correct knee angle at max leg extension.

Below is my present setup with the corrected seat height. I also needed a large seat setback to further unload my arms to help improve comfort in our poorly maintained, very bumpy roads.

cubewheels

Not sure if you're giving advice to sprint out of the saddle without swaying the bike or just sprint in the saddle. And those few who can actually do a good sprint in the saddle does it at even much higher cadences (~200 rpm!!), not less than 120 rpm!!

Very strange, all advice I read in the internet from the pros, scientific studies is telling the opposite of what you're saying here.

colnago62

most track sprinters are shooting for about 140rpm. What has been found is that higher cadence, which usually requires a smaller gear, doesn’t actually produce more watts. 140 rpm is kind of the sweet spot.