jma1st3r

Hello

those that went to a shorter crank, due to less leverage did you scale down your chainring as well?

**oh crap, i cant delete post here. my bad

I need to monitor this longer. Seems like I was over pedaling since change. butter smooth strokes tho.

Iride01 

Shorter crank was only 5 or 7 mm for me. So it wasn't much of an issue with gearing. Even if it was, I'd ride like that for 500 maybe a 1000 miles and see if I got used to it.

I suppose if you are already at your physical limits climbing or such with the previous setup, you might have to do something. But again, if you aren't changing drastically the length, then probably not an issue. Might make you stronger.

Moisture

How much shorter are talking about and why? What percentage of your inseam is your current crank arm and what percentage do you wish to switch to?

generally yes, crank arm lengths change your gearing and you'll want different rings and cassette to compensate but it's not necessary if you are simply switching to the correct crank arm length or the difference is not major.

jma1st3r

I went 160...think i lost some ground speed in that(just a feeling, not scientific) , and the effort for the same gear increased(a feeling too, but more definite). But overall is good, and i dont have the top dead spot anymore.

​​I swap back in the 170 crank... And it feels significant bigger. Guess i am a 160 guy now.

*requires a little more effort on the same rear cog...

Trakhak

With almost no exceptions, track sprinters (and track pursuiters, keirin riders, etc.) of all sizes use 165-mm cranks. That length was chosen for the practical reason that the use of longer cranks can result in a pedal hitting the track surface at its steepest, causing at least that rider to crash, but success on the track clearly doesn't depend on whether a rider's height or leg measurement happens to correlate to 165 mm as the theoretical ideal length.

jma1st3r

Oh i believe that. I also think shorter or longer than optimal crank gives the same result, it takes longer(t) to max power.

For regular day to day riding it wouldnt matter since its more about the fit.

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Helderberg

I just changed from a 175 to a 165 crank length. My reason was knee pain and it has helped as the angle of my knee at the top of the stroke is less. It has given me the impression that I have lost speed but my Wahoo does not substantiate that. For me, at 72, speed is not as much of a concern as comfort. I also was able to remove the peddle spacers, known as knee savers in some ads, as my legs now stay over my foot on the downstroke. Again, just my situation and what works for me but it has given me the desired result and that is what I was hoping for. As for the rear cogs, I had changed them from the 11-34 to 11-36 before the crank swap. A lot of hills here and needed help on the low end.
Good luck, Frank.

Carbonfiberboy 

160/170 = .94 You lost 6% of your crank torque at the same pedal pressure. To keep pedal pressure the same as it was with the 170 cranks, you'd reduce your gearing by 6% and pedal a 6% higher cadence to maintain the same speed. 6% isn't a whole lot - it's the exact difference between a 16 cog with your 170 cranks and a 17 cog with your 160 cranks. Either cog/crank choice will result in the same pedal pressure at the same speed, but cadence will be different. Say with the 170 cranks you were pedaling 85 cadence at some speed, with the 160 cranks and the lower gear, you'd pedal 90 cadence for the same speed. TANSTAFL

However by the sound of it you don't have a bike computer which shows speed and don't care about that anyway, so none of this may matter to you.

jma1st3r

The reason i even asked was it felt harder. 6% harder? It feels like more.

I dont know if zwifting and kickr snap count as "computorhs" but the numbers match what you said. My cadence is up, but power is slightly less. Therefore, i wonder if gearing down to a 48-32 will give similar experience.(therefore i asked about the chain ring at another post).


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Iride01 

I don't quite follow the concern here. Does your trainer not let you vary the resistance? If it doesn't then I guess that's why you are asking about a 48F / 32R. Although I don't have an issue with cross chaining, that still isn't something you need to be doing for hours on end on a trainer.

I'm assuming your bike is at least a 2x. So likely your small ring is either a 36 or a 30 tooth ring. The 36 front paired with a 24 rear will give you the same ratio as the 48F / 32R. Or the 20 tooth cog on the back if your small front is a 30T ring.

Or is this only a 1x bike?

jma1st3r

Yes sir two by, 50/34.

Just wonder if this has been done? If not. I will ride more and get stronger.

Iride01 

Well it's sort of sounding like you are wanting to have the power output you are imagining others have. Don't do that. Your power output is what you can do. It will get better the more you train or just simply ride your bike.

There probably aren't any of us here that can ride at the same continuous power that another does. And if we are close to another in our average power, then we may use different cadences and gearing than the other person.

Some cyclists climb hills at high cadence. Some climb hills at low cadence. Both can reach the top at the same time.... or not.