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Discussion Starter · #1 ·
My primer came with 175 mm cranks which I will assume probably most trail bikes to come with. I don't get many peddle strikes but I have gotten a few so when I upgraded to this Ram xx1 gold I opted for the 170 millimeter cranks. My last downhill bike had 165 mm crank so I figured these would be a good in between but I'm not sure if it's my mind playing tricks but it feel like I noticed I did lose quite a bit of torque.

Has anyone ever compared 175 or who rides 170? I'm sure it's just my mind playing tricks on me


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You'll get a range of responses and even a lot of actual data on the subject, but my experience mirrors yours. I tried 170's for an entire season, that was enough to know I much prefer 175.
 

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you do lose torque. it's a much-debated topic, but it basically narrows your torque band and makes it harder to get "on-top" of a gear.

think of stroke in a combustion engine. F1 race cars that are light with efficient gearboxes and spend time in a very narrow rpm range can get away with shorter stroke for more max power, at the expense of a broad torque curve.
 

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Discussion Starter · #4 ·
5mm isnt much, in an engine or any rotating equipment you get short travel with a shorter crank and quicker response. On a bike my legs for sure would never notice the extra distance to travel with longer cranks to complete a full circle and I was figuring the torque loss would be very minimal, but I actually think it is noticeable. Maybe the extra 5mm is worth the torque and the pedal clearance is super minimal.

I'll keep them now as I've used the cranks so I cant return for 175s

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I switched to 170s on both of my bikes. Can't say I notice any difference pedaling. Nice to have a little more ground clearance. Entirely a personal preference thing.
 

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I replaced a set of 175mm XT cranks the paint had worn off on with a shiny new looking set I had in the closet, used them for months without realizing the ones I put on were 170's... oddly I did tinker with the saddle for/aft and hight. Did not feel a difference peddling but the saddle felt off. Some people are probably more sensitive to it than others and like you said maybe its your mind playing tricks on you because you know they are shorter.
 

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following...... as I was thinking of doing the same thing and go to 170's as I have gotten a few pedal "scratches" and one strike.

there's another thread on this topic.
https://forums.mtbr.com/xc-racing-training/170-vs-175-a-1093731.html

Some say they can feel a difference some say none. I think post #12 on this thread sums it up nicely:

The difference in pedal strikes is noticeable (if you've had some). The difference in pedaling is noticeable if you're looking for it, otherwise it's not IMO. The difference in power is negligible if any. Changed all my bikes to 170, but I have fairly short legs.
 

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I had run 175mm cranks for many many years on my bikes. My last bike was a T275c with 175mm. Had a fair amount of pedal strikes with that bike. With my Sniper, I went with 170mm cranks. I don't notice any power loss (even on steep grinders) and I have almost nil pedal strikes. I'm a spinner though (+/-100 rpm) too and maybe just like the smoother pedal stroke.
 

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Your only applying torque with one foot at a time. To the leg spread around the saddle you will notice 10mm

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If you're running clipless pedals you're applying torque throughout the entire rotation, or you should be.

When I changed out my drivetrain to XX1 on my Primer Bandit I went with 170 cranks. I didn't get a ton of pedal strikes with the 175 but at 5'8" on a medium I already had the 150mm stem slammed to the seat post. The 170 cranks allowed me to have the seat post 5mm raised from the collar. I did not notice a loss in power delivery. I noticed a good increase in power with the much lighter and stiffer carbon crank arms.
 
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