Short Crank Help

Discuss light weight issues concerning road bikes & parts.
Finx
Posts: 67
Joined: Wed Jun 15, 2016 1:14 am

by Finx

I put a Praxis 160mm crank on my g/f gravel bike.

I can't find it now, but a few years so we sourced a 155mm crankset (cut down from a 175mm SRAM Apex if I remember correctly).

I believe the guy was based on Minnesota.

by Weenie


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Lelandjt
Posts: 525
Joined: Tue Jan 19, 2016 7:10 am

by Lelandjt

TobinHatesYou wrote:
Wed Mar 20, 2019 9:19 pm
Glad I could help. In a way I wish manufacturers would stop offering half sizes like 167.5mm and 172.5mm in favor of a broader range...
Much agreed. Having owned one I don't think 172.5 is neccessary but 165 should be much more commonplace and 160 should go from nearly non-existant to available.

Finx
Posts: 67
Joined: Wed Jun 15, 2016 1:14 am

by Finx

Finx wrote:
Wed Mar 20, 2019 9:36 pm
I put a Praxis 160mm crank on my g/f gravel bike.

I can't find it now, but a few years so we sourced a 155mm crankset (cut down from a 175mm SRAM Apex if I remember correctly).

I believe the guy was based on Minnesota.
I found the place.
http://bikesmithdesign.com/Short_Cranks/index.html

TheKaiser
Posts: 643
Joined: Thu Sep 05, 2013 3:29 pm

by TheKaiser

Finx wrote:
Wed Mar 20, 2019 10:49 pm
Finx wrote:
Wed Mar 20, 2019 9:36 pm
I put a Praxis 160mm crank on my g/f gravel bike.

I can't find it now, but a few years so we sourced a 155mm crankset (cut down from a 175mm SRAM Apex if I remember correctly).

I believe the guy was based on Minnesota.
I found the place.
http://bikesmithdesign.com/Short_Cranks/index.html
While you're in such a helpful mood, can you provide any info on the Praxis that you bought? :) I may be in the market for just such a thing. I was thinking of going for the 160mm 105 but, as it is going on a gravel bike, would be interested in other options that don't lock me into the Shimano bolt pattern for rings.

TheKaiser
Posts: 643
Joined: Thu Sep 05, 2013 3:29 pm

by TheKaiser

TobinHatesYou wrote:
Wed Mar 20, 2019 9:19 pm
Glad I could help. In a way I wish manufacturers would stop offering half sizes like 167.5mm and 172.5mm in favor of a broader range...
Agreed. The research on crank length indicates that most of us have a 40mm+ range that can work in terms of power output, but for fitting purposes we may want to focus in on a much smaller portion of that spectrum, however there are very few options outside of the standard 165-180mm range. Imagine if everyone had to use a stem from 115mm to 130mm and they offered stems in 2.5mm increments. We would find that ridiculous. Instead, we are happy to have stems from 30mm - 150mm in 5mm increments, and for the occasional super sensitive case, they measure different examples of the same stated "length" and pick the one they want.

I suppose for cranks there is an argument to be made that they can use the same forging and just drill it slightly differently for the 2.5mm increments, rather than needing to do a new forging for a 20mm different length, but still, it would be the same number of SKUs to enlarge the increments and broaden the range.

Finx
Posts: 67
Joined: Wed Jun 15, 2016 1:14 am

by Finx

TheKaiser wrote:
Thu Mar 21, 2019 1:54 am
Finx wrote:
Wed Mar 20, 2019 10:49 pm
Finx wrote:
Wed Mar 20, 2019 9:36 pm
I put a Praxis 160mm crank on my g/f gravel bike.

I can't find it now, but a few years so we sourced a 155mm crankset (cut down from a 175mm SRAM Apex if I remember correctly).

I believe the guy was based on Minnesota.
I found the place.
http://bikesmithdesign.com/Short_Cranks/index.html
While you're in such a helpful mood, can you provide any info on the Praxis that you bought? :) I may be in the market for just such a thing. I was thinking of going for the 160mm 105 but, as it is going on a gravel bike, would be interested in other options that don't lock me into the Shimano bolt pattern for rings.
Praxis Alba M-30.
https://praxiscycles.com/product/alba-m30/

Call them. They are really helpful....

GothicCastle
Posts: 234
Joined: Mon Jul 04, 2016 1:52 am

by GothicCastle

Mr.Gib wrote:
Wed Mar 20, 2019 8:20 pm
.Not to turn this into a crank length phylosophy discussion, but I just finished watching a super high-end fit on my wife involving pressure mapping, power output throughout the pedal stroke, the whole deal. Watching the power curve smooth out and increase in her bad leg as the crank was dialed shorter was eye openning. Change was from 170 to 160mm.
Just out of curiosity, is she thinking about changing gearing as a result of the crank length change?

moyboy
Posts: 447
Joined: Thu Aug 18, 2016 12:19 am

by moyboy

Its superhard getting a 155 crankset. I bought a rotor 3d24 one for my wife but havent seen anymore. Bought from velo tech services in uk.

Mr.Gib
Posts: 3601
Joined: Fri Mar 18, 2005 4:12 pm
Location: eh?

by Mr.Gib

GothicCastle wrote:
Thu Mar 21, 2019 8:07 am
Mr.Gib wrote:
Wed Mar 20, 2019 8:20 pm
.Not to turn this into a crank length phylosophy discussion, but I just finished watching a super high-end fit on my wife involving pressure mapping, power output throughout the pedal stroke, the whole deal. Watching the power curve smooth out and increase in her bad leg as the crank was dialed shorter was eye openning. Change was from 170 to 160mm.
Just out of curiosity, is she thinking about changing gearing as a result of the crank length change?
That's a really tough question. I haven't done the math but a short crank will theoretically mean a higher cadence which in turn would call for some easier gears. This whole evaluation process started as a response to an nagging injury and preparation for an epic climbing trip - 2000 km and 50,000 meters in 10 days, so of course she already has a 32 tooth cog (anyone would be nuts to try with less). Where do you go from there? Fitting a 34 on the back would mean switch the big chainring down to a 48 to manage accidental cross chaining. My inclination is to leave things as they are, although I do wonder if she will run into a leverage deficiency when we get into 15 - 20% gradients.
wheelsONfire wrote: When we ride disc brakes the whole deal of braking is just like a leaving a fart. It happens and then it's over. Nothing planned and nothing to get nervous for.

GothicCastle
Posts: 234
Joined: Mon Jul 04, 2016 1:52 am

by GothicCastle

Mr.Gib wrote:
Thu Mar 21, 2019 4:59 pm
My inclination is to leave things as they are, although I do wonder if she will run into a leverage deficiency when we get into 15 - 20% gradients.
On one bike, I went from a 172.5/mid-compact to a 170/standard and I definitely feel it on the hills. Somewhat of a different change, but you made me think about that bike.

Finx
Posts: 67
Joined: Wed Jun 15, 2016 1:14 am

by Finx

Speaking from experience, I would suggest leaving the gear ratios the same.

Let her get used to the new crank length for a bit, see how she does on the climbs, etc.

In my case, her initial response was a much higher cadence. However after a few rides it settled down a bit. We ended up leaving the 11-32 on there and she couldn't be happier. It was like a night and day difference in how she felt both during and after the rides.

She rides further and more often now and doesn't experience the dreaded knee and hip soreness she had using the old cranks.

Last edited by Finx on Thu Mar 21, 2019 5:22 pm, edited 2 times in total.

Krackor
Posts: 262
Joined: Tue May 31, 2011 9:48 pm

by Krackor

Good compilation of short cranksets here:

https://web.archive.org/web/20120826155 ... _2862.html

Image

dereksmalls
Posts: 2224
Joined: Tue Aug 02, 2011 9:20 pm
Location: New Zealand

by dereksmalls

What about Lightning cranks?

This is their specs

Arm lengths 160, 162.5, 165, 167.5, 170, 172.5, 175, 177.5, 180, 182.5, 185, 190mm
Bottom Bracket BSA (English), 68mm (Road) or 73mm (MTB), Italian threads, BB30, BB86/BB91, BB90/BB95, Press Fit 30, OSBB, BB Right, EVO386.
Available spyders 110, 130, and 94 double, 130×74 road triple, 64×104 reversible double or triple, SRAM XX1 single

Finx
Posts: 67
Joined: Wed Jun 15, 2016 1:14 am

by Finx

Krackor wrote:Good compilation of short cranksets here:

https://web.archive.org/web/20120826155 ... _2862.html

Image
The Praxis Alba I linked above are not listed there.

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