cubewheels

I have 35mm wide road tires. Wheels are alloy with 36 spokes front and rear. Inflated to little bit higher pressure than is recommended for my weight (124 lbs) 50 psi rear / 45 psi front (Recommended is 45 / 39 psi)

As my sprinting cadence reaches 110 to 120 rpm, pedal strokes start feeling springy. My tires don't bounce, bike is stable but I literally feel like I'm jogging over springy mattress like a 5 year old. I feel it most strongly at the bottom of the stroke.

Tires? Pressure? Frame flex? Crank flex? Crank and frame is alloy. Bike is locked down tight every nut and bolt and smooth, no unsual noise during sprinting, just the soft hum and buzzing of the drivetrain.

I don't experience nor perceive this springy feeling when climbing out of the saddle at lower cadences.

waters60

Out of the saddle at 110-120 rpm? It would seem that negates the reason for being out of the saddle, power generation. While sitting high rpm’s can be isolated. Standing it is much harder to isolate high rpm’s to the legs.

Fox Farm

Also low inflation of tires could add to that bouncy feeling

cubewheels

Note, I have 700 x 35c tires. They are 35mm wide. And I am only 124 lbs. So I'm a lightweight rider on wide road tires and my inflation pressure is expected be lower.

50 / 45 psi is actually slightly overinflated for me. Recommended for my weight and tire size is 45 / 39 psi.

topflightpro

I doubt you're flexing anything on the bike. And at that cadence, I'm curious as to how you can isolate the springiness to be coming at the bottom of the pedal stroke? At 120 rpms, you're bottoming out 4 times per second (2x for each side.)

Wildwood

Sprinting with fatties.
Swimming in Jello.

cxwrench

Sit down. Trying to stand at 120 rpm is crazy.

popeye

+1

woodcraft

Practice at 130 rpm,

then your standing sprint at 120 rpm will feel more smooth.

Moisture

Right

Problem solved.

I cant recall the last time I've had to spend any time whatsoever out of the saddle. Oh wait, I did when I was riding a bike about 4 sizes too small for me.

jadocs

Are you using proper cycling shoes or are you still riding in flip flops? Not trying to be a smart a$$, I'm being serious.

MoAlpha

Muscle thixotropy!

chaadster

Ah, isokinetic closed-cell foam plantar rebound disorder, a.k.a. flip-flop flap!

smashndash

I'm gonna be a contrarian in this thread. This should be fun.

I weigh more than you. 145ish lbs. I run narrower tires than you (25mm). I run similar pressure to you (55ish psi, but I've run 45 sometimes). If you calculate the hoop stress of my tires, they are much less stiff than yours.

I sprint VERY fast out of the saddle. My peak power is generated somewhere around 140rpm. I'm pretty sure I can hit 150rpm or more. My peak 1s power is 1255W (probably was higher back when I used to lift, but I only recently bought a PM). 5s power is around 1150W. 15s power is around 900W.

I think if your technique is off, it's possible for the bike to feel springy due to the compression of the tires. I think I feel it sometimes if I'm in too hard of a gear. If your technique is smooth and your rpms high, not only will you not feel the bouncing, you'll probably also make more power.

Do you have a power meter? Also what kind of bike are we talking here? It's possible that your BB setup has some flex in it, but it's unusual for someone of your weight to be able to detect such things.

Reflector Guy

A picture might help if he has one handy.

Ferrouscious 

First, if you are not attached to the bike at 120+ rpm, you should be. Way too easy to come flying off the pedals. Second, work on your technique. Third, move forward on the saddle. The faster your cranks rotate, the bigger the percent of time your muscles are "reversing". By moving forward, you are effectively delay the timing of your stroke. The likelihood of accidentally putting power down before top dead center is thereby reduced. The law of diminishing returns applies here.

njkayaker

Frames are much, much stiffer than tires. Wheels have more flex than the frame but much less than tires. Tires have no support without pressure.

That leaves your "springy feeling" as most-likely the result of relative lack of pressure.

smashndash

Covid makes this a bit complicated, but I would recommend trying out a close friend's bike if possible. Ideally a high end one that you know is stiff.

My biggest reason for using SPD-SL pedals is that it lets me try out my friends' bikes

tomato coupe

Better than swimming with fatties and sprinting in jello.

Moisture

Im curious to see what 150rpm cadence looks like.

soon, you'll be able to compete with an idling engine.

DrIsotope

Tangentially related at best, my average standing cadence is 57. I've never once desired to manage a cadence of 120 out of the saddle, but should the inclination strike me, I'm 99.9% sure I couldn't do it.

The OP's query implies that he is sustaining this kind of cadence for extended periods, seemingly without any kind of sensors to record it. So get out your art supplies, and color me skeptical.

MAK

A suggestion learned from spinning class. When standing, shift to a lower gear or two. The added resistance makes you more stable and your stroke will smooth out.

cubewheels

I forgot to mention I have internal rim width of 18mm for those 35mm tires. I don't detect any squirm during fast, leaning turns and never really had any issues unless it's related to the springy sprint issue. However, if I'm standing on the ground beside the bike, and I hold the saddle and handlebar while I push down on one pedal with one foot, the tires have visible lateral flexing and it only takes a little effort to induce flexing.

Man, that surely rocks! Didn't think anyone can get above 120 rpm but really good to know it's actually possible! I've been training to increase my sprint cadence rpm. As you can see, I only weigh 125 lbs, I cannot produce much force but I could still crank some power if I could just raise my rpm but I'm starting to get bouncy feeling at the pedals at the bottom of pedal stroke.

I always sprint at a gear where I could sustain 120 rpm without looking like a mad gorilla on the bike. I only feel the springy feeling but remain smooth in my movements, no bobbing, no lateral movement, just the bike rocking left and right beneath. Just concerned it might be a critical bike part flexing and then fail without warning.

No power meter I ran out of budget for those. I only have a simple and cheap speedometer. Bike is a gravel bike with semi-slick 35mm urban/touring tires and road 2x9 drivetrain with compact 50/34 crankset. Highest sprinting speed I hit with that bike on the flat is 55 kph which is absolutely scary, especially on a very cheap $250 bike. Nowadays, I practice sprinting mostly uphills to avoid sprinting past 40 kph.

I ride with 35mm wide tires due to our very poorly maintained and very bumpy roads. We have plenty of large cracks and gaps on the road which are unavoidable and you have to ride through them.

Thanks, appreciate it. The most helpful reply I got. That 140 rpm of yours is invaluable tip. I never thought one would be good at that high cadence. I'm still exploring, experimenting, still working out the highest cadence I can pull on sprints. I really run out of leg force at high sprinting speeds due to wind drag so the higher rpm is my only way past that. Or I can also do weighed squats to strengthen my legs and core muscles at the same time. Gyms are still closed but I something that weighs 60 kilos that I can use for weight training.

Carbonfiberboy 

It's the flats. When one uses foot retention, the force on the downstroke pedal will shift to point aft at the bottom of the stroke and then shift to point up on the upstroke both seated and OOS. You're just like a piston acting on a crankshaft through stiff connecting rod. Yes, it makes power, but with a good bit of shaking if you've ever ridden a single cylinder motorcycles. Your downstroke goes on too long and compresses the tire which then rebounds when the pressure is removed. You're supposed to spin smoothly even OOS, but you can't because that demands foot retention. You'll have some habits to get over when you do get pedals and shoes.

smashndash

I'll see if I can get a recording of myself. It seems like 110-130rpm isn't unusual, especially for smaller guys like me (5' 7"). I only have one source of info (cadence sensor) so it's possible that it's wrong. Video evidence would be cool.