Why no 172.5 MTB cranks?

[bcroslin]

I was recently having some fit issues on my mtb so I went to my fitter and he pointed out that since I'm on 172.5 cranks on my road bike (which I spend 85% of my time on) and on 175's on my mtb I could solve part of my fit dilemma by riding 172.5's on both bikes. So I go looking for 172.5 cranks for the mtb and low and behold no one seems to make them - especially Shimano which is what is on my mtb. Any idea why no one seems to manufacture 172.5's for mtb's?

And as a follow-up question, should I consider going to 170's on the mtb? I don't mind a little more spin versus a little less leverage of the 175. My fit issue has to do mainly with saddle height and hamstring issues. I'm on a 29'er so maybe the "spinner" 170 would allow me a little more acceleration?

[christian]

XTR is available in 172.5.

[bcroslin]

Originally Posted by christian

XTR is available in 172.5.

Yep, my buddy the fitter just texted me the same thing. $400 though. Sigh.

Any more cost effective options?

[DHallerman]

Originally Posted by bcroslin

Yep, my buddy the fitter just texted me the same thing. $400 though. Sigh.

Any more cost effective options?

I have a pair of Suntour XC Pro cranks, no chainrings, excellent condition -- and they are 172.5mm. BCD = 110/74

If you don't mind going old school, with a tapered bottom bracket, these are both attractive and would work well. Cold-forged, Sugino-made.

Let me know if you're interested, and I can send you pix.

Dave, who notes that the cranks themselves say "XC Comp" but they are actually "XC Pro" models which he can show you with photos of those cranks too but they are only 170mm

[John H.]

Is your bike bb30/pf30?
If so, I have a set of 172.5 Rotor 3D plus that I could sell you?

[skouri1]

I have a few gens old XTR triple crankset on my mtb. Used to be on 175, much nicer when it matches your road crankset, in my opinion. worth the investment, and should last for many years. never will sell it. (unless i sell my bike and renounce mtb'ing all together)

[John H.]

If the past is a predictor, 172.5 XTR will be hard to come by.
Historically they have made about 1 batch per year.

[bcroslin]

Originally Posted by DHallerman

I have a pair of Suntour XC Pro cranks, no chainrings, excellent condition -- and they are 172.5mm. BCD = 110/74

If you don't mind going old school, with a tapered bottom bracket, these are both attractive and would work well. Cold-forged, Sugino-made.

Let me know if you're interested, and I can send you pix.

Dave, who notes that the cranks themselves say "XC Comp" but they are actually "XC Pro" models which he can show you with photos of those cranks too but they are only 170mm

Thanks for the offer but I think I'll probably go with the XTR's.

Is your bike bb30/pf30?
If so, I have a set of 172.5 Rotor 3D plus that I could sell you?

It's a standard english.

[vqdriver]

i just bought the xtr in 172.5
available, yes. expensive, yes. common, no.

with as much moving around as people do on mtb, the 2.5mm shouldn't be an issue, especially since your saddle is probably lower on the mountain bike. but if your fitter says it's too long, try going 170 and see if shorter is better.

in reality, trying to accommodate the 172.5 on a mtb is going to be a PITA down the road. trust me on that.

[John H.]

Or even consider 170- I know someone who dropped down to 170 and he like them a lot.
But he likes to spin more than grind.

[Idris Icabod]

If you end up going 170 or 175 XTR, backcountry is selling them for less than 300 bones right now.

[bcroslin]

Originally Posted by Idris Icabod

If you end up going 170 or 175 XTR, backcountry is selling them for less than 300 bones right now.

If I go 170 I'll just go XT for under $200. I'm trying to replace 175's.

[old fat man]

Originally Posted by vqdriver

i just bought the xtr in 172.5
available, yes. expensive, yes. common, no.

with as much moving around as people do on mtb, the 2.5mm shouldn't be an issue, especially since your saddle is probably lower on the mountain bike. but if your fitter says it's too long, try going 170 and see if shorter is better.

in reality, trying to accommodate the 172.5 on a mtb is going to be a PITA down the road. trust me on that.

This. I find it highly unlikely that 2.5mm on an mtb will solve your problems. Unless, you ride the mtb on flat trails with very little out of the saddle or shifting around?

[bcroslin]

Originally Posted by old fat man

This. I find it highly unlikely that 2.5mm on an mtb will solve your problems. Unless, you ride the mtb on flat trails with very little out of the saddle or shifting around?

I'm in FL and it's F L A T. Lots of riding in the saddle.

[John H.]

If you are curious try it out.
I think it will make a difference. Especially if the goal is to free up some pedal stroke room.

Originally Posted by bcroslin

I'm in FL and it's F L A T. Lots of riding in the saddle.