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  1. #1
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    170mm to 175mm.....worth it??

    just actually looked and noticed i have a 170mm crank set on the bike.will it help to go to a 175mm arm?

    also i am 5'8" if this makes a diffrence.

  2. #2
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    Quote Originally Posted by ROG30Y
    just actually looked and noticed i have a 170mm crank set on the bike.will it help to go to a 175mm arm?

    also i am 5'8" if this makes a diffrence.
    Depends on how you ride. Do you do a lot of fast trails or grinding up long hills? A longer crank is a longer lever and allows slightly more power. A shorter crank will allow you to spin a little faster and smoother. Noticeably so? Eh, maybe, maybe not. Are you having trouble getting enough power on climbs?


    Most importantly, what is motivating you to look at the 175's? Are you having any problem with the 170's? If not, stay with them until a reason can be made to change (which might merely be "I feel like it").

    I used to ride both 170 & 175mm (and I used know a guy who rode the longest bullseye cranks which I think were 220mm, but I could be wrong on the mm). For the next cranks, I couldn't decide which way to go and when I found out that the manufacturer had a 172.5, it was a natural to go with them.

    I just bought a Syncros Revolution 175's on ebay and I know that I will have no issues going between the different lengths.

    Penguin

  3. #3
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    I just did this

    Quote Originally Posted by ROG30Y
    just actually looked and noticed i have a 170mm crank set on the bike.will it help to go to a 175mm arm?

    also i am 5'8" if this makes a diffrence.
    I just replaced my 170mm cranks with 175s. I rode the 170s for years, and honestly, I can't tell any difference with the 175s.

    For your height, most will say use cranks longer than 170, but my opinion is to use what you have until you need to replace them and then get something longer.

    op
    www.msmtb.org - Mississippi Mountain Biking

  4. #4
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    I do a lot of DJ and raced BMX. I used to alway spin fast so I had to use 170mm cranks for smooth spin.

    165mm gave me a smoother spin while I had a slightly better snap at 175mm cranks but I felt too choppy.

    I would prefer 160mm or 165mm cranks on my MTB to be honest.

  5. #5
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    thanks for the replies.the only reason i was asking was becouse everybody i know runs 175 arms and i didnt even realise i had shorter arms.i seem to climb well so i guess its not hurting me.

  6. #6
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    I have tried both 170 and 175 crank arms, I currently have a 170 one bike and 175's on two others. I have really strong legs but tend to spin way too fast (100-120 rpm) to begin with so I like the longer cranks to slow my legs down a bit. I do notice the difference in the size of circle I spin and the effect it has on torque output.
    There is no added value to my participation - in fact, just more confusion.

  7. #7
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    I Wouldn't Really Call That Too Fast

    Quote Originally Posted by GearHead
    I have really strong legs but tend to spin way too fast (100-120 rpm) to begin with so I like the longer cranks to slow my legs down a bit.
    But like most things it's personal preference right?
    I try to keep my cadence around 115...if it drops below about 95 it feels like my legs aren't even moving.
    But to address the original post I'd say stick with the 170's until you have a need to switch them out. I have a 33" pants inseam and prefer 172.5 crank arms but they can be hard to find so I usually end up with 175. The 2.5mm diference is noticible to me but I also dont think it really makes much difference. My legs adjust quickly enough.
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  8. #8
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    Quote Originally Posted by standard235
    I do a lot of DJ and raced BMX. I used to alway spin fast so I had to use 170mm cranks for smooth spin.

    165mm gave me a smoother spin while I had a slightly better snap at 175mm cranks but I felt too choppy.

    I would prefer 160mm or 165mm cranks on my MTB to be honest.
    I remember some so called scientific study at some big time sports science place that said the ultimate length for most mtb riders is somewhere between 160 and 165mm. Who knows if it's correct.

    I was about to post a thread asking if my 172.5mm cranks were hurting my performance in climbing after years of 175mm use, but after reading some of the good replies here I think I'll just keep riding what I have. Truth be known I think it is a case of upgrade-itis which leads me and most others to buy new products without needing them. "Need" is a tough definition.

  9. #9
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    Quote Originally Posted by westin
    ultimate length for most mtb riders is somewhere between 160 and 165mm.

    Truth be known I think it is a case of upgrade-itis which leads me and most others to buy new products without needing them. "Need" is a tough definition.
    Very good thought on 'need'.

    I dont' know where the standard 170-175 came from. Not saying it isn't the best one rather that most of us have only used cranks in this range and haven't tried a shorter crank like a 160 mm. crank or a really long one.

    I looked up Bullseye cranks and it was 222 mm. that my friend had. They have cranks from 152-222mm. My friend was strong as an ox with legs the size of my middle section. He often DNF'd in races because he broke parts but he could really grind up a hill. Of course, with a 222 mm. crank, I don't know how he managed more than 50 rpm but he was pretty fast. Look here for more on bullseye and the lengths:

    http://www.bikepro.com/products/cranks/bullseye.html

    Just as a side note I remember that my friend was fast out of the start, but I would usually pass him about 2/3rds of the way through the race. One race I passed him in the first few miles and I said, "Hey Jason, how's it going?" His reply, word-for-word was, "Not good. I just yakked my powerbar." I can't forget that direct and accurate response.

    As to your case of 'upgrade-itis', thats why I said one's reason to change might be only that you want to. So, I too will be sticking with my 172.5 & 175 mm's.

    'Guin

  10. #10
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    Quote Originally Posted by ROG30Y
    just actually looked and noticed i have a 170mm crank set on the bike.will it help to go to a 175mm arm?

    also i am 5'8" if this makes a diffrence.
    It's a pretty small difference, and you may want to also get a good inseam measurement.

    Found this link in the Clyde forum for some interesting info on crank sizing.

    http://www.nettally.com/palmk/crankset.html

    I think the guy who wrote that is onto something - now, if only I can find a 185 mm crank at a low price. (I'm 6'2" - 185 mm is probably not the right size for a rider who's 6" shorter than me!)

  11. #11
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    Standard -

    Just curious what your inseam is (crotch crushing w/book type)? Mine is 30" and both Zinn's web calculation and John Castellano (ibis silk ti designer) indicate that I need 165's and I'm used to pumping with 175 most of mt life - sometimes w/too much torque on uphills giving me wheelies.

    Just hoping to compare w/ your experience and body geometry (30" inseam and 5'6" 3/4 height) to before buying expesive 165 XT cranks, as that's all that's around in that size.

    ben

  12. #12
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    170 mm to 175 mm is only 3/16", but I've read that it could make your knees hurt because of the sharper angle @TDC

  13. #13
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    Yeah - I was thinking about that . You may have to move your seat a tiny bot back as the forces become non-linear, prehaps exponential, when your knee is out of line - at least to my v. limited knowledge.

    nevertheless, the 175 is even worse if off due to higher torque. someone mentioned knee tendonitis - which is hard to recover from (and I've had plenty of war wounds, not that one though, b/w biking and climbing) - something I prefer to avoid.

    Another source someone posted indicated 165mm - I'm just looking for someone who uses them and prefers them, vs. 170mm.

    Proper ergonimics does not seem to be a frequent concern to many if not most companies, except the few blessed (which unfortunately means shimano in this case).

    I'd most like to buy FSA xc cranks but noone but the big S has 165mm if that truly optimal for performance.

    Anybody gone a diff. direction w/a true 30" inseam (not pant leg)?

    thanks,
    ben

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