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  1. #1
    mtbr member
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    Jul 2016

    Who rides 170mm Cranks?

    Who rides 170mm cranks? I am 5'8" and have moved to 170 on my road bikes. My previous MTBs all came stock with 175's and I never changed them. I think 170 may be better for me on the climbs as I like to spin. Not sure if I would miss the leverage going over big stuff when you need 1 more pedal stroke to power over something.

  2. #2
    mtbr member
    Reputation: Junersun's Avatar
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    Jun 2014
    I'm using 170 and I'm 5'11". My bike has a low bb so it helps me clear things. Leverage and power stroke I wouldn't be too worried about on a mountain bike.
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  3. #3
    mtbr member
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    Jul 2016
    I'm 59 with 83cms inseam and use 170mm cranks. They came with my bike, I don't feel uncomfortable but I haven't tried longer cranks.

  4. #4
    West Chester, PA
    Join Date
    Sep 2006
    I just switched to 170s after a lifetime on 175s. I can't tell any difference, but I have a little more pedal clearance.

  5. #5
    mtbr member
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    Jan 2012
    I changed a few seasons ago and noticed things slightly easier. And then I didn't notice any more. Thin flats and the 170s get more clearance.

  6. #6
    Mr. Buck E. Fikes
    Reputation: Oh My Sack!'s Avatar
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    Aug 2006
    Always been on 175's. Have always had a bit of an unexplained knee pain on my left knee. Not disabling but enough to seek an orthopedist and an MRI proving nothing structural. I read about measuring inseam for determining crank lengths and some issues people tend to have regarding crank length since the default on most mtb is 175. I bought a Race Face Turbine Cinch crankset in 170 to try. My regular pedal strikes were virtually all eliminated. My knee pain was least out to about 17 miles a ride where at about 9 it would always kick in. The one thing I gradually noticed was it felt like my fitness was waning. I was having trouble hitting the gnar on my climbs that I had always been able to hammer through. I was getting worried that I was loosing leg fitness gradually from my neck issue that I had previously experienced.

    I went along with it for a few weeks and actually had a sale for my carbon Sram 175 crankset but before I turned it loose, I put it on the bike for one last comparison run. That 5mm of leverage was absolutely key for me. I was back in the game overnight, albeit the knee pain and the pedal strikes were back. I'm quite astonished at the difference in my case. I sold the RF crankset instead. My new RS Monarch Debonair shock helped a bit with pedal strikes and I just deal with the knee.

  7. #7
    I like turtles
    Reputation: TiGeo's Avatar
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    Jul 2008
    It's usually a function of height. At 5'6" my bikes all have 170s. Usually the small frame of a particular model will have 170s and everything else will be 175.

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  8. #8
    mtbr member
    Reputation: rondre3000's Avatar
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    May 2009
    5'10" here and switched to 170's with my Nomad because of the pedal strikes. I wouldn't say it was a huge change, other than the reduction in pedal strikes.

    I moved those same cranks over to my new Yeti and don't have complaints.

  9. #9
    Reputation: evasive's Avatar
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    Feb 2005
    Like others here, I switched from 175 to 170 when I got a bike with a lower BB. That was in 2012. After the 2nd ride I didn't notice anything but fewer pedal strikes. I'm 6'3".

  10. #10
    Reputation: tigris99's Avatar
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    Aug 2012
    I have 175 on my 29er and went 170 on my fat bike cause of pedal strikes. Don't notice a difference between the 2

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  11. #11
    barely a mtbr
    Reputation: jk13's Avatar
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    May 2012
    5'9"/29" inseam. I actually have MORE pedal strikes after switching because in my mind I should have more clearance so I pedal when I shouldn't...

    Seriously though, my knees feel better and I'm more comfortable at higher rpm.
    92.7% of statistics are made up on the spot.

  12. #12
    mtbr member
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    Jun 2009
    I switched to 170s about 10 months ago due to lower back pain. Im 5'8" and have short legs. I also switched to 165mm cranks from 172.5mm cranks on my road bike.

    The geared MTB was easiest switch, I noticed that spinning was a lot easier, but i'd have to change gear more often. Some pinch climbs initially felt harder, but I'm used to this now. I feel like my riding has improved because of it.

    Switching my singlespeed, was a bit tougher, then in another thread, someone sugested to try sheldon browns 'gain ratio' calculator, which i used to recalculate my effective gear ratio (gain ratio) which takes into considertion wheel / tyre size and crank length, as well as sprocket size. I increased my rear sprocket by 1 tooth, and now the bike feels as it did with 175s
    What crank length are you running?

    On the road bike, flats and downhills feel great, but I've struggled on the climbs, even with changing down a gear or 2, but this is up steepish (>10%) climbs that I wouldn't have comfortablly spun on with my longer cranks (my gearing is probably too high). I've been experimenting with my cleat position (moved cleat back) and will see how this goes.

    With shorter cranks, you put your saddle up by the difference in crank length, so 5mm if going from 175 to 170, but your knee comes up 10mm less whilst pedalling. This is why you may reduce some knee of back pain, if you have flexibility issues or have short legs.
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  13. #13
    Life Is Short
    Reputation: fatcat's Avatar
    Join Date
    Mar 2006
    me too
    Attached Thumbnails Attached Thumbnails Who rides 170mm Cranks?-dsc07511.jpg  

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  14. #14
    MTB Addict
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    Jun 2007
    As someone with short legs (for my height) and a massive preference for spinning over standing and mashing, I love my 170mm cranks.

  15. #15
    mtbr member
    Reputation: Davide's Avatar
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    Jan 2004
    Quote Originally Posted by Geocyclist View Post
    Who rides 170mm cranks? I am 5'8" and have moved to 170 on my road bikes. My previous MTBs all came stock with 175's and I never changed them. I think 170 may be better for me on the climbs as I like to spin. Not sure if I would miss the leverage going over big stuff when you need 1 more pedal stroke to power over something.
    I do. I am the same height and I have been using 170 cranks for twenty years plus. Fit my legs better and gain 5mm ground clearance ...

  16. #16
    Trail Ninja
    Reputation: Varaxis's Avatar
    Join Date
    Mar 2010
    5' 7" (170.5cm) height
    30.5" (80cm) inseam

    First experimented with 165 last year, due to severe knee pain when pedaling an Evil Following. Tried all sorts of things along with it, like shoe wedges and pedal extenders (clear pronator). Only change noticed was that my gearing became instantly taller, which made me more conscious of my gearing choice and pedaling efficiency, opting to accelerate hard then spin a high cadence. Wasn't going any slower overall, in terms of average speed, actually faster when I didn't give up and walk, since I was forced to ride a higher gear on a climb. Was a very modest change, like going up 2-4t in chainring size. Was able to raise my saddle height a little higher, so it was above my grips (problem for 29ers, especially since I prefer to upsize, 17-19/M/L), and gained more pedal clearance. In some cases, the cranks themselves seemed to be just as long, just had its pedal mounting hole drilled further from the tip.

    Can't find any lighter weight 165mm cranks besides in alloy form (XTR is the best I've found), but that's okay since I use pedal extenders, which are likely to kill carbon cranks. Besides this, I find no reason to stick to 175, other than because it came with the bike and it would cost extra to replace it. I only have 1 set of 165s, and use 170s on my other bikes. Waiting for XTR 165s to be blown out. I love it when I see stock bikes spec'd with anything shorter than 175.
    We're all on the same ship, and it's sinking.

  17. #17
    Fat-tired Roadie
    Reputation: AndrwSwitch's Avatar
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    Nov 2007
    I always had 170s on my bikes in the '90s and 2000s. I didn't think about it at all until I bought one from a friend several years ago that had 175s. It felt like I could never quite nail my saddle height. I actually haven't changed the crank on that bike - I try not to spend too much money on it - but did switch another bike from 175s to 170s.

    I do have somewhat flaky knees.

    I also have a bike with 165s. I feel pretty neutral about them.

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  18. #18
    Formerly of Kent
    Reputation: Le Duke's Avatar
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    Mar 2009
    5'5.5", 31" cycling inseam. 170s all my life, currently trying 175s.

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  19. #19
    mtbr member
    Reputation: OwenM's Avatar
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    Oct 2012
    5'7", 30" inseam. 170mm on the mountain bike. 175 on the hybrid, and thinking of changing them, since I'm having some knee pain in the highest gear. I switched to an oval chainring the same time as the 170s on the mtb, so am hesitant to credit either/or(though it was a nice combo, apparently!). Interested to see if I can tell much difference from just dropping 5mm on the cranks...

  20. #20
    mtbr member
    Reputation: LadyDi's Avatar
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    Apr 2005
    170s on Trance X 29er and Salsa cyclocross bike since shortly after a big knee surgery two years ago. During recovery knee wouldn't bend enough to pedal 175s and I really wanted to ride so I made the change. Both knees are now repaired and fully recovered but I am keeping the 170s. I find it easier to spin up steep stuff, for one thing. I am 5' 7".

    After I went from 175s to 170s I had to raise my saddle a corresponding amount (5mm) for comfortable climbing. Long legged and nearly maxxed out to start, I ended up having to find an extra-long seatpost for the Trance. My 3rd mtb, a 26er, still has 175mm cranks. I haven't been on that bike since the surgeries but I intend to ride it this weekend and compare.
    Last edited by LadyDi; 08-18-2016 at 12:07 PM. Reason: Clarity
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