JoeOxfordCT

Hi All,

Up until now I have been riding a Gary Fisher mtb w/100psi slicks on the roads. Have done some centuries this summer and have an itch to go faster and maybe join a club to do some group ride. My mtb has 175cm cranks. I've ordered a 56cm Motobecane (https://www.bikesdirect.com/products/...an_rec_ltd.htm) road bike from BD (Please let's not turn this into a referendum on BD). The bike will come with 172.5 cranks. How much of a difference will I notice, if any with going to slightly shorter crank arms ? I am 5'10" with normal proportions. I must also note that I with my mtb I had suffered from some illiotibial band syndrome (ITBS) which I've hopefully addressed by switching to Eggbeater SLs with canting wedges which will go on the new bike. I'm hoping the shorter crank will be easier on my knees ? I ride alot of hills and the new bike will be running a 50-39-30 and I've ordered an 11-32 10spd from IRD (https://www.interlocracing.com/cassettes_steel.html). Will I lose alot of leverage on the hills ?

Thanks !!

Joe
Oxford, CT.

botto 

big difference? nope.

in april i went from 170 cranks, which i'd been using for years, to 172.5. in july i borrowed a set of shimano compact cranks, that were 175s, for a few weeks. never noticed the difference.

btw IMO you can't really compare the 175 mtb cranks with Road bike crank lengths.

JoeOxfordCT

Why is that ??

botto 

when's the last time you spun out on a mtn bike, and actually had speed?

JoeOxfordCT

Well my biggest gear is a 46-11 (104gearinches) and with 1.5 100psi slicks I'm probably faster than you might think. I had no problem keeping up with the majority of roadies at the couple of centuries I rode this summer including one 100 miler. Granted these aren't races and you can't gauge how hard people were riding at any given time but for the CT Summer Breeze Century I clocked a time of 6:43 for just over 100 miles. I had many people tell me how much faster I'd be on 700c wheels on a bike that would likely be 5 or 6 pounds lighter. I really liked riding with other riders since I normally ride solo. Had a road bike(s) in my 20's and belonged to Sound Cyclists. Would like to be able to do group rides again....don't think folks would look kindly as I unloaded my mtb for an A-B ride...

FormerBMX'er

Reminds of this past weekend when some guy in our group showed up with a full-on fixed gear track bike...no brakes . Caught me out once or twice as he faught the rear wheel to slow. That's what I get for not going out with the faster group .

waterrockets 

All the time on my single speed

recursive

I ride with 175. A test ride with 172.5s proved that the difference was immediately obvious to me. The shop owner was surprised by this and gave me another bike to test, which quickly and correctly identified as 175.

It probably depends on the person, because 2cm of handlebar width change is not noticeable to me.

DrPete 

(scratching head, pondering... processing....)

Nope, I still don't get it.

John Wilke

I think you'll feel the difference immediately, but it should be a rather easy adjustment.

jw

mollusk

Metric vs. Imperial?

mollusk

Everyone is different.

I had ridden 170mm cranks since dirt was new (well over 100K miles ago) and then I bought a used bike with 175mm cranks. I felt a a difference right away and it took me about 500 miles to get my stroke smoothed out. Now that I'm used to the 175mm cranks when I take my old bike out for a ride the stroke just isn't quite right. For some folks it won't make a difference, but for me it was a big change.

DrPete 

I hope so.

Proximo

2.5mm is a bit more than the thickness of a US penny. I'm sure some folks could tell the difference between a 172.5mm and 175mm crank but I'd bet the great majority couldn't.

JoeOxfordCT

Yes, by that I meant one metric & one imperial.....

My followup question would be: are shorter cranks, smaller circles, easier on the knees in general ?

ticka

Does it make a hugh difference...

YES IT DOES......

not 2.5mm it is really this times two...

from a physilogical reason you should match the crank length to match your body..

if you have long term knee problems like I did moving down from 175 to 172.5 changed my whole world....No more pain....

you wouldnt think it would have made much of a difference .....but it did ....

5 years of knee pain for nothing......now I have my life back

bitingduck

It's a pretty minor difference. I have 165s on my track bikes, 172.5 on the road, and 175 on the mtb. I ride the road and track bikes pretty regularly, often on the same day (even using the road bike to warm up for track events). There have even been times when I've been on all three in one day. You might notice a small difference, but it's pretty minor. And on your mtb you're not likely to notice much at all. And don't worry about bringing an mtb on an A/B ride-- way back before I had a lot of bikes I used to ride A/B rides on an mtb, since it was my only bike. And I generally rode it to and from the rides, too...

M_FactorX19

i was curious about this as well but i am use to a 170 and found some 172.5s cranks that i wanted for a killer deal but wasnt sure if they would work for me or not. now i might give them a try if they are still for sale.

3373jones

wow. you get the 'bringing a thread back from the dead' award of the week. this ones 5 years old!

UCIMBZ

Way to go dude. Your first post is a reply to a 5 year old thread. On the other hand nice to see botto was as graceful as he is today.
!

mutantdunk

Depends. I rode for over 20 yrs on 170's. EBAY'd a bike that had 175's and liked it immensely. My new Scott has 172.5's. I like it alot.

Now I can't stand the 170's. It feels like I'm spinning tiny circles on a kid's bike. But it really is all up to you. I've read power, etc are almost the same for any rider on all these crank lengths. You may notice a difference but whatever it is you may become accustomed to it.

Sassonian

I went from 175's to 210's on my custom Zinn.. Now that is a difference that will blow your mind...



Best decision I ever made..