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Old 02-22-2017, 12:19 PM
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m_moses m_moses is offline
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Fit recommendation for way shorter cranks

I recently had my first ever bike fit at a LBS that uses the Guru fit system. All in all, the fit was successful in that I feel more comfortable and can stay in the drops longer.

One aspect of the fit still has me scratching my head and that's their recommendation to switch to 165mm length cranks. I'm 5' 11.5" and have always used 175mm cranks.

I presume others have gotten a similar recommendation. If so, did you make the switch and what was your experience as a result?

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Old 02-22-2017, 02:52 PM
nate2351 nate2351 is offline
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Did your fitter give you any explanations as to what would necessitate the change? Going signigicantly shorter is usually for a morphological reason or reduce the flexion of the joints of the leg.

There's nothing inherently wrong going shorter, it may feel weird at first but after a while your body will adapt. I used to ride 175 and a few years ago played around until I settled on 170 as my ideal length. I'm 5'10" for example.

Last edited by nate2351; 02-22-2017 at 04:31 PM.
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Old 02-23-2017, 01:39 PM
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m_moses m_moses is offline
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Originally Posted by nate2351 View Post
Did your fitter give you any explanations as to what would necessitate the change? Going signigicantly shorter is usually for a morphological reason or reduce the flexion of the joints of the leg.
Not other than my height. That is, for my height, he said 165 would be better because it would make me more efficient and I could generate more power.

My impression is that they have just revised downward the older specifications that said someone of my height should use 175. Another guy at the shop who is 6'3'' says he now rides 170mm as a result of the Guru fit.

I was pretty sure the fitter told me that if I went to shorter cranks, I would also need to lower my saddle height. I just called the shop but my fitter was not in. I spoke to another fitter who said that if I went to shorter cranks I would need to raise my saddle. Either I misunderstood the conversation I originally had with the fitter or there is some confusion.
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Old 02-23-2017, 02:23 PM
guido guido is offline
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I'm 6'1" with a 34" inseam. My fitter suggested I go from 175 to 165 when I was having knee discomfort. 6 years later I still use 165s on everything and the knee issues are mostly gone.
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Old 02-23-2017, 02:30 PM
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When you consider the size difference between the "shortest" and "longest" (with uncommon exception) road crank lengths...... 1 piddly cm.... you realize sizing cranks has nothing to do with height or even leg length. My one 6'+ buddy uses 175s, my other 6'+ buddy uses 165s... and my 5'7" self uses 175

and I could tell you the reasoning behind all 3 choices, but they're unique to each rider, so it wouldn't be of much use to anyone else.. but I can tell you it doesn't have much to do with height
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Old 02-24-2017, 09:19 AM
parris parris is offline
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I wonder how much of moving to shorter cranks has to do with some fitters being married to the particular system that they use. I've got a buddy that has had a couple of Retul fits. He's 6-2 and has gone from 175's to 165's. The way he explained the fitting process he went through the fitter was very numbers oriented in looking at power output and such.

The various fitting tools and systems I believe "can" be a good thing but like any tool or system they're only as good as the person behind the wrenches/computers.

How much experience does the fitter have? How much/long has the fitter ridden for? Is the fitter young and flexible or has he/she been around long enough to have dealt with injuries or age related issues?

These things and more all make the fitter's "tool box" bigger. Just an opinion.
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Old 02-24-2017, 11:27 AM
nate2351 nate2351 is offline
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There is very much a trend in the fit community moving towards shorter cranks and further aft cleat mounting. A lot if it has to do with power meters on fit bikes. It's not just a Guru or Retul thing.
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Old 02-26-2017, 01:39 PM
Johnny P Johnny P is offline
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I'm 5' 10" and switched from 170 mm cranks to 172.5 mm quite a few years ago. I got knee pain on longer rides, i.e. over 40 miles long, with the longer cranks. Went back to 170 mm cranks and the problem went away.
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Old 02-26-2017, 08:23 PM
ultraman6970 ultraman6970 is offline
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Well usually knee pain is paired to leg length problems, meaning or cleat too far back, saddle tad too high or cranks too long. You have 3 ways to fix those tiny disconforts in the knees but if the fitters are using power meters and determine that short crankset paired to all the way back cleats for power is the way to go well, I do not know. For example in the case of johnyP I would have moved the bad leg cleat like 3 mm to the front and that could have had the same effect than using shorter cranks.

What ive noticed in the last two years in this area is a tendency to disappearance of brute force smashers and that could be the result of this new tendency to use shorter cranks, pretty much you spin more... you load less gear, the knees will be less impacted.

It is interesting what is going on tho...

OP, do you feel differences with the 165 crankset? Do you have the pedal cleats all the way back?

Last edited by ultraman6970; 02-26-2017 at 08:26 PM.
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Old 02-27-2017, 12:05 AM
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m_moses m_moses is offline
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Quote:
Originally Posted by ultraman6970 View Post
OP, do you feel differences with the 165 crankset? Do you have the pedal cleats all the way back?

Haven't switched from the 175s yet. Wanted to hear from others who have made the change before I buy new cranks.

I have been riding with my cleats all the way back for several years.



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  #11  
Old 02-28-2017, 09:59 PM
easysmile easysmile is offline
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Hurting in 175's; 6'2"

I have 175's on a fixie.

This winter I started to practice certain skills that really stress the knee.

Within a couple of weeks, I got my first serious case of tendinitis in my knees. It frightened me, frankly, as it got me thinking that I wouldn't be able to practice/improve at skills that were important to me.

For the first time in *many* years, I have been off my bike for days.

I will buy some 165's and put my seat farther back. The problem with fixies (for me) is the load to the knee when the ball of my foot is behind my knee. These stresses are terrible when you wheelie, as you are constantly correcting/braking with your legs, regardless of crank position, and much of that happens when the ball of your foot is behind your knee, etc. I'm hoping to reduce knee flexion under load with shorter cranks, a common expectation, I guess. I should also learn to pedal with more ankle flexion than I presently use, to share the flexion burden, if you will, with my knee.

E
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Old 03-19-2017, 07:53 AM
Ali1989 Ali1989 is offline
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Maybe they're looking at the hip angle. Shorter cranks would lead to a more open hip angle which reduces the dead spot at the top of the pedal stroke.

I thought that shorter cranks would require you raising the saddle as the bottom is now 1cm closer.

There is a trend to switch the shorter cranks: a lot of the GB track team switched to shorter cranks in the lead up to Rio including Wiggins going from 177s (or thereabouts) down to 170s.
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Old 03-22-2017, 04:06 PM
benb benb is offline
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Quote:
Originally Posted by Ali1989 View Post
Maybe they're looking at the hip angle. Shorter cranks would lead to a more open hip angle which reduces the dead spot at the top of the pedal stroke.

I thought that shorter cranks would require you raising the saddle as the bottom is now 1cm closer.

There is a trend to switch the shorter cranks: a lot of the GB track team switched to shorter cranks in the lead up to Rio including Wiggins going from 177s (or thereabouts) down to 170s.
They are also doing it to allow riding a lower position.

Hip angle is one of the things that determines how low you can go with the bars with the same/appropriate arm bend, etc..

If you shorten the cranks you open the hip at the top of the pedal stroke, raise the saddle to get the extension at the bottom back to where it was, you open up the hip even more. Then you could go lower the bars without the hip being closed down too much.

If the hip angle is too closed your back will do bad things at the top of the pedal stroke when you get low and you'll probably get some pain.

I'm 6'1" and have always pretty much rode 175. I've been for some of these newfangled power analysis fits but no one has ever tried to get me to go to shorter cranks. I did try 172.5 on my own one year and had 165 or 170 on a fixie way back when but 175 has always seemed right. Knee pain for me is about something else, more likely saddle fore/aft + cleat position.
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Old 04-07-2017, 02:38 PM
tv_vt tv_vt is offline
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Switching to shorter cranks usually means raising your saddle, not lowering it.

FWIW, I've been on 175's more or less for decades and over the last year have switched to 172.5. For me, I notice less of a dead spot on the upstroke and find I can spin a little faster when standing up, too.

Can't imagine going all the way down to a 165mm crank, though. (I'm 6'2".)
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  #15  
Old 04-20-2017, 09:08 AM
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m_moses m_moses is offline
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Thanks to everyone for the information. I replaced the 175s with a 165 set last week and raised my saddle 5mm. I've done about 100 miles on the trainer but the biggest test was a 105 mile group ride last weekend. The difference while riding is subtle but the slight soreness I had been feeling in my hip joint after riding is gone. I'm glad I made the change.


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