Crank lengths, 170mm or 175mm?

Home Forum Bike Forum Crank lengths, 170mm or 175mm?

Viewing 16 posts - 1 through 16 (of 16 total)
  • Crank lengths, 170mm or 175mm?
  • Zedsdead
    Member

    You need 175mm.

    I’m 6ft tall with 32″ inside leg and always ride 175 on the MTB. 180mm on the BMX, even used 185’s on the BMX.

    I have 170 left and 175 right – can’t tell the diff :o)

    markd
    Member

    you will be fine. you wont die.

    i run 170’s on the zesty, 170 on the anthem and i think 175 on the whyte 19…

    i cant tell any difference. its 5mm…. a pair of insoles is 5mm.

    anyway i still hit stuff all the time so it hasnt helped that.

    just ride em you will be fine.

    wellhung
    Member

    I run 170 172.5 and 175 can’t tell the difference really so as all the other replies don’t worry.

    Premier Icon Vortexracing
    Subscriber

    27.5″ inside leg and always run 170’s

    pimpmyride
    Member

    Ok I know this has probably been answered before but its doing my head in!
    I have a Cove Stiffe (still not built) and i’m still unsure about the cranks.
    I have bought and fitted some 170mm saints reason? because 1 they are black and my frame is black so they look mint, 2 they have steel pedal inserts as the bike is going to be ridden hard at times, and 3 I should get more rock clearance with the shorter crank arm length.
    Thing is not been able to test ride it yet as i’m still waiting for my brakes and pikes to turn up! i’m now unsure due to reading many conflicting reviews/opinions if the 170mm arms will be ok as iv’e always had 175 cranks.
    I am 5ft 11″ and my inside leg measurement is 32″ who else is this height and leg measurement and what bike/cranks do you ride? will I see a huge difference and feel like i’m riding with a flat tyre as some suggest!!!!! (sounds obsurd to me but hey)

    Anyone?

    Samk
    Member

    It’ll feel different not bad different, just different. 170’s will give you less leverage but at the same time will spin slightly faster per given gear (circumference that the end of the crank arms move around is shorter hence each rotation will take less time) The only way that the bike will feel like it has a flat will be if it has a flat.

    matthew_h
    Member

    will spin slightly faster per given gear (circumference that the end of the crank arms move around is shorter hence each rotation will take less time

    What a load of bollocks. One revolution will take exactly the same time for the same speed and gearing. The only difference would be a slight decrease in the actual pedal velocity (with the 170mm cranks) as the actual distance covered per revolution is slightly less. Not that you would notice this.

    Basically, you are fairly unlikely to notice a difference between running 170s or 175s and you’ll be fine. If you really want to have 175s then I’ll swap you for my 175s

    One revolution will take exactly the same time for the same speed and gearing.

    correct, but if the diameter of the pedal path is smaller then you’ll have to push harder to exert the same torque, so it feels the same as a (slight) increase in gear ratio. But probably too small to notice. 5mm in 175 is equivalent to one tooth on a 34 tooth sprocket…

    mtbmatt
    Member

    I’m a fair bit shorter than you, but recently switched to 170’s.
    I can notice the difference, but it is very small. You will be fine.

    Extra pedal clearance is another bonus of short cranks, although its marginal.

    Nicknoxx
    Member

    There are some cranks advertised in thsi month’s mag which are adjustable between 170 and 175. Don’t have the mag in front of me and can’t remember who made them, but someone will be along who can,

    pimpmyride
    Member

    matthew_h what cranks do you have mate?

    Samk
    Member

    oops brain was working backwards at that point.

    matthew_h
    Member

    Pimpmyride, I’ve got a pair of original Saints in 175mm on my jump bike but would prefer 170mm if possible. No great rush or anything and I’d happily cope as things are.

    Premier Icon crazy-legs
    Subscriber

    175’s on all my bikes except the roadie SS which has 170’s.
    Shorter cranks are easier to spin but generally most people only notice this on road/track bikes.

    If you look on Sheldon Brown there’s a gear ratio calculator which takes crank length into account when working out gear ratios, it does make a (slight) difference.

    pimpmyride
    Member

    matthew_h me too not desperate as I havn’t even ridden the bike yet due to being p****d around with some forks and brakes that never turned up!
    As soon as the bike is finished which should be this weekend (brakes and pikes on order from someone else) I will let you know if I want to swap, are yours in good condition?

Viewing 16 posts - 1 through 16 (of 16 total)

The topic ‘Crank lengths, 170mm or 175mm?’ is closed to new replies.