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Thread: 165mm vs 170mm

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    Senior Member piratelove's Avatar
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    165mm vs 170mm

    How much of a difference will the 5mm make with Sugino 75's?

    I ordered some 165mm's today, but they're out of stock until the 15th.

    They're going on a 53cm Soma Rush.

  2. #2
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    not a whole heck of a lot, but if you ride a 53 you're probably toward the point where 170's are bigger than ideal for you. I would try another vendor or just wait it out.

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    dc pirate, 4evah. chimblysweep's Avatar
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    i wouldn't run 170's on a 53 on the street. pedalstrike avoidance is goal #1. granted, the size difference is miniscule, but it's just the peace of mind. if you can avoid it just 5mm more, why not?

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    don't pedal backwards... MacG's Avatar
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    I went from 170s to 165s and couldn't be happier. Unless you're pretty tall (around 6 feet and up), 170s are likely too long for your legs anyways. I read about this one time and found some chart where you measure your inseam (crotch to floor) and it said that 165mm cranks were closest to the theoretical best length for my 33" (or so) measurement. Further reinforcement that it might not just all be in my head. I can say that the slightly smaller pedaling circle feels more comfortable to me. When tucked in on 170mm cranks, my knees feel like they come up slightly too far over the top of the crank rotation (and yes; I have my seat at the proper height for me).

    That said, a lot of short people ride 170s (because they seem to come on tons of bikes as the stock length) and have no complaints. They probably have never tried 165s either, and wouldn't know what they might be missing.

    If you're on a 53cm frame (about 21 inches) and I'm on a 23" frame, you probably would be best off waiting for the 165s unless that frame is actually way too small for you or something. I have a little less than an inch of crotch clearance on top tube of my 23" frame when standing flatfooted on the ground with shoes on, for the record.
    from Minneapolis, with bike love

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    blacksheep the blemish
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    If you're running a gear somewhere in the 60" range, you'll probably want the 165's, cause that takes a lot of spinning and shorter the better for that. But otherwise, the rush has a high bb so I would assume you're not gonna get much strike.

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    Alba-Core baldylocks's Avatar
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    Did you order the crank from Ben's? I did and they didn't have the 165's in stock, so I settled for 167.5's, down from 175's(!) on a 54 cm frame and they have worked out really nicely. Might be worth splitting the difference.

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    Cornucopia of Awesomeness baxtefer's Avatar
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    Quote Originally Posted by chimblysweep
    i wouldn't run 170's on a 53 on the street. pedalstrike avoidance is goal #1. granted, the size difference is miniscule, but it's just the peace of mind. if you can avoid it just 5mm more, why not?
    the frame size is irrelevant here if you're concerned about pedal strike. all size Rushes have the same BB height.
    and to me, a 58mm BB drop is plenty high for 170's. Then again, i run 175's on a conversion.
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    happy medium=167.5. . . . .

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    dc pirate, 4evah. chimblysweep's Avatar
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    Quote Originally Posted by baxtefer
    the frame size is irrelevant here if you're concerned about pedal strike. all size Rushes have the same BB height.
    and to me, a 58mm BB drop is plenty high for 170's. Then again, i run 175's on a conversion.
    sorry, i should have finished saying... pedalstrike and toverlap.

    longer cranks = more toverlap.

  10. #10
    blah onetwentyeight's Avatar
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    frame size is relevant in that it gives me an idea how tall the OP is. I'd guess 165 would just feel nicer for someone with shorter legs.

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    Senior Member mattface's Avatar
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    pedalstrike won't be an issue for you on the rush with 170s, but toverlap might. I get some toverlap on my 58cm Rush with 170s and size 12s. It's much worse with toeclips than with spds, so if you use clipless pedals, and have small feet to overlap might not be that bad. Then again I'm sure it would be better with 165s which are probably the correct length for a 53 anyway.

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    Cornucopia of Awesomeness baxtefer's Avatar
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    Quote Originally Posted by chimblysweep
    sorry, i should have finished saying... pedalstrike and toverlap.

    longer cranks = more toverlap.
    that's better
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  13. #13
    Senior Member mattface's Avatar
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    Quote Originally Posted by onetwentyeight
    frame size is relevant in that it gives me an idea how tall the OP is. I'd guess 165 would just feel nicer for someone with shorter legs.
    doesn't a smaller frame also have a shorter distance between the BB and front axle? Maybe I'm not picturing it right, but I thought shorter TT would mean a shorter distance between bb and front axle.

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    dc pirate, 4evah. chimblysweep's Avatar
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    just trying to keep the people happy on this sunshiney 80 degree day. I'm 63 minutes away from getting back on my bike. i'm smiling.

    but thanks for once again making this girl feel like her input is being picked over with a fine tooth comb.
    smartypants.

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    jack of one or two trades Aeroplane's Avatar
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    Quote Originally Posted by chimblysweep
    but thanks for once again making this girl feel like her input is being picked over with a fine tooth comb.
    smartypants.
    +1. Bikeforums has made me a better speller.
    Quote Originally Posted by Dr Irwin Goldstein
    Men should never ride bicycles. Riding should be banned and outlawed. It is
    the most irrational form of exercise I could ever bring to discussion.

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    Cornucopia of Awesomeness baxtefer's Avatar
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    Quote Originally Posted by chimblysweep
    just trying to keep the people happy on this sunshiney 80 degree day. I'm 63 minutes away from getting back on my bike. i'm smiling.

    but thanks for once again making this girl feel like her input is being picked over with a fine tooth comb.
    smartypants.
    nothing personal. i'm an equal-opportunity nitpicker.
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    Senior Member piratelove's Avatar
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    I'm impatient, but I'm going to wait for the 165mm's. Thanks for all your input.... I'd probably be fine with the 170's it seems, but I'd rather stay on the safe side.

  18. #18
    ass hatchet slopvehicle's Avatar
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    I need to wrastle me up a set of 165s...stupid toeverlap! Caught me off guard last night in a very precarious traffic situation (trackstanding in a turn lane among four lanes of 45mph traffic).

  19. #19
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    Piratelove,

    If it helps you to feel better about waiting, think about this: Five millimeters may seem small, but your total height difference that your legs have to travel is a full centimeter. If you had to run up a flight of stairs with 1 cm extra rise per step, you'd find it a lot harder and if one step was 1 cm higher than the rest, you'd certainly trip. On the track, the torque is different but the difference is equally dramatic. The 170 mm cranks might let you pump a slightly larger gear, but at the risk of your knees and ankles and definitely at the cost of your snap and leg speed. People quote BMX riders with their hugely long cranks as an example of how someone can still accelerate or spin fast with long cranks, but it's harder and if you do more distance than BMX riders do (and most fixie riders do) your knees will feel it. Plus 12 year olds seem to be able to do anything.

    Those 165 mm cranks are more salable and get a higher price if you go to sell them. Pedal strike is a bit of an issue with 170 mm cranks but your choice of pedal and riding style have more effect on your propensity for striking concrete. Toe overlap at your front wheel is an overrated issue -- the only place you're actually turning the wheel hard enough to risk a touch is either when you flop the bars around while standing on one foot at a stoplight (where it doesn't matter) or occasionally in a trackstand. Even in the latter, you should be able to trackstand without turning your wheel that far, or you're really slow coming out of the track stand. As for rider size, even with 6'3" 215 lb track sprinters turning 51x14 gears and 10.1 second times at the world-cup level, most are still on 165 mm cranks. For your size, I wouldn't even worry about length -- you're so far down the size range that for track or fixed, almost any track coach would put you on 165's. Check www.fixedgearfever.com for some threads recently on crank length, which capture about as much diversity of opinion as you'd ever find.

    Hope I'm not encroaching on Chimblysweep's replies. She's very sharp and worth listening to.

  20. #20
    Senior Member piratelove's Avatar
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    Wow, thanks for the detailed response/explaination.

  21. #21
    C21 H30 O2 plantdude's Avatar
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    I ride a range of crank lengths on a regular basis: 175's on the road bike and single speed mountain bike, 170's on my everyday track bike, and 165's on my custom track bike. While I do notice a subtle difference from one to the other, they are all just fine and I never have any complaints.

    To answer the original question, if you can bare to wait, I would. You'll decrease the risk of pedal strike, and 165's are better for the track, if you ever plan to ride there. If you can't wait, get the 170's, and you'll be happy too. If you are not running a brake, I would also recommend waiting; going around corners quickly (if you don't have a brake) can be a little sketchy sometimes. Either having a brake to slow you down, or running 165's will make it a little less so. However, if you purely plan to ride on the street, 170's will give you a bit more leverage, whereas 165's slightly less but a bit easier to spin.

  22. #22
    works for truffles pigmode's Avatar
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    Quote Originally Posted by mattface
    doesn't a smaller frame also have a shorter distance between the BB and front axle? Maybe I'm not picturing it right, but I thought shorter TT would mean a shorter distance between bb and front axle.
    Yeah, that measurement is call front-center. Steering geometry can also affect F-C length. A frame with slack frontend geometry will have a longer F-C than one with steeper geometry.

  23. #23
    Banned zelah's Avatar
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    i run 170s after coming from 165s, i'm riding a 50cm frame too (aka i'm short) and i dont have any problems

    slightly more toe overlap, but other than that i'm not complaining

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