135mm? That's awesome. How tall are you and what size is that bike?

I would raise those pads about 4 inches and probably go about that far out as well, i.e. more reach. Which makes me think that bike is a bit small for you.

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WTF is this sh*t?? (Hope that isn’t too harsh).

Joking aside it’s very similar to riding a child’s tricycle. Your ability to climb hills (or even rollers) will go down.

BTW is this for real or a joke?

You can go too short with cranks, and you might be close. Too little knee flexion at the top of the stroke can inhibit power. You need to drop your saddle a bit which will improve the acute knee flexion situation. 150-155 would be my eyeball estimate of a proper crank length for you.

It’s a 54. I’m 5’9”. About 155...

I appreciate your insight. If I recall correctly, you’ve got a pretty great position so I’ll play around with the reach as you’ve suggested. I’d be surprised if the frame were too small...but maybe a combination of going out and up plus dropping the seat and moving it back will accomplish a little more in being aero.

Haha. That would be a good joke. There is a lot of short crank nonsense. But this is for real. I’ve been on 135s for about a year. For z1-z4 power I don’t think it makes as much difference as you might think. I can climb just fine...but I do suspect maybe sprinting is a little worse. I keep getting beat in Zwift at any rate.

Thanks for the suggestion. Will do some work on dropping the seat and see how it feels.

My aim here is not so much a quest for more power...but to get my back flatter and be more aero.

This is all I'm seeing:



Sorry I can't be more helpful.

Yeah, I guess not. Agree with moving the saddle back and down. That may be all you need to do. Those cranks are really short, probably about 2cm shorter than I would go with if I were to stay that low. You may need to switch to longer cranks just due to not being able to get the saddle far enough back.

Moving that saddle back should give you the reach you look to need if you were to raise the pads. The suggestion for raising the pads comes from your exposed back. Dropping your pads is only going to get your back so flat and then you will start compensating for that pad drop with the flexibility in your shoulders, which exposes your back. Now, that could be a faster position, hard to tell without testing. But if you're searching for a flat back I'd start there....oh, and some 155s.

FWIW, I found that as I raised my front end I no longer felt like "short" cranks were right for me.

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With regards to shimmy...

SWAG

May be a partial byproduct of your rpm with those shorter cranks, seems close to 100. More subtle would be power aspect of pedal stroke is relatively short so I would also suspect you are engaging a bit more for upstroke with other relative force production changes due to shorter moment arm making it bit choppy.

I am a tad under 6’ and I trialled as low as 150 in a 70.3 race and what a disaster. I trialed 155 for an IM and the same result. I thought 160 seemed fine and the tipping point was shorter but my bike has been a bit hit or miss for some time. It’s on the back end of longer races I think you lose power the most.

I wanted to buy into the whole shorter crank thing but I fitted 165 to my bike again yesterday, it felt good and I’m going the other way.

Looking at your pedalling like other posters I at first thought it was a joke and I’m not sure how you could think that was you’re most efficient pedal stroke and what the advantage might be but hey it’s fun to play and you need to work out what works for you. I figure even the shortest pro women are not even close to riding that short and there’s a lot of smarter people working out what is best for them.

Mind you I may be wrong there seemed a really knowledgeable fella that found about that length good testing on a velotron.

Ouch on the velotron comment. Hahaha. Yeah I get it.

I’ve done several races on these small cranks. For IM I’m pretty sure the power loss is not so big. Z1-3/4 it doesn’t matter as much as some might think. Even climbing is not that tough.

I just did IM Wisc on this setup. I went 5:10 on the bike. That’s ok. Was 1x with a 53 tooth front. I lost 17 minutes to mechanicals though. My ELEMNT has me at 4:53. But no excuses. The mechanicals were my fault. (Loose bolts on stem and chain drops on the wrong 1x set up). Point of that is to say that the 135s are manageable on a hilly course over a long time. But perhaps not as fast as I might have been. Who can say...

I’ve been riding 135s because I’ve been playing with the idea of building a bike with a lowered bottom bracket. The shorter cranks allow the bb to be dropped 3cm or a little more without clearance problems. And that would drop my entire profile down...almost fairing me behind the front wheel. My thought is that the power penalty is minimal...and the aero gain could be significant. Maybe?? As low as I can ride comfortably, I’d have my chin on the front wheel.

But...when I race on zwift o get my ass handed to me when I have to sprint. I can hit 800 watts but it’s weird on such short cranks. And I suspect that effort would get me a little more on longer cranks. And on zwift actually being aero is totally unnecessary. So I am handicapping myself there.

I have an ftp of somewhere around 360. Zwift put me at 388, but that’s high. And I’ve never trained to sprint...so every race I get a little better at the top end. But the 135s are definitely a liability for sprinting.

So all of that is to ask...is the idea that dropping the bb to being the whole bike lower a bad theory? Would it fail to get significant aero gains?

If so...then yes...riding 135s is stupid and I’m giving up power on the top end...and therefore probably giving it up a little in the z3 Ironman effort too.

You’re already pedaling ‘heels down’. Dropping your seat will likely make that worse. My first thought as I watched would be to raise the seat a few mm to see how it feels

I’m with Finding Freestyle on the cranks and LAI on the positioning....

My thoughts are 155mm cranks, 56cm P4 frame (ie. more reach and come up some), and lower your saddle 2cm when you go to the longer cranks.

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I’ve followed your advice to others and always think you’re spot on. I’ve got some 150 and 165 cranks coming Tuesday. I can’t really just get a 56 p4 quote as easily...but I’ll see what I can do on reach once I’m on longer cranks.

Thanks all...will report back after making changes. And I hope you are all correct that I’ll get a little more power.

I like that thinking, but where can you get a good TT bike built with a 4cm lower BB? I also think you might have gone too far to be optimal. When I experimented with short cranks I tried ~150mm, and I definitely didn't want to go shorter. Tried it for two years. Ended up with 165 for the short leg and 172.5 for the long leg. I *do* have issues with an acute hip-thigh angle at the top of the stroke, but I still prefer moving my legs through a bigger range.

Riding with so much drop isn't necessarily more aero either. Could be, but need to test.

regardless of crank length, I would say that amount of drop is slower than optimal. looks like a great deal of back exposed to the wind. maybe it tested out fast, but I would not bet money on it

Do you have a leg length discrepancy? One heel is up and the other down.

On a side note I once rode a P5 with 190 cranks for a few months. The bb is lower than your P4 by 1.5 cm.

So basically you could build this bike that you want with a 40mm lower bb and still ride 150s without issue...generally.... a couple pedal scrapes going through corners when I got forgetful, just don’t race it in a crit!

Interesting idea btw.

Maurice

"I’ve been riding 135s because I’ve been playing with the idea of building a bike with a lowered bottom bracket. The shorter cranks allow the bb to be dropped 3cm or a little more without clearance problems. And that would drop my entire profile down...almost fairing me behind the front wheel. My thought is that the power penalty is minimal...and the aero gain could be significant."

I've had a similar idea. I'd love to know if it works as I don't have the means to have a frame built up