Asked for 175mm cranks,got 172.5mm...does it matter much?

simonn
simonn Posts: 88
edited November 2009 in Road buying advice
Hello,

Just took delivery of my new bike,and it has been supplied with 172.5mm cranks instead of 175mm which I specified.

I'm just wondering if there is any real or noticeable difference:I asked for the longer length cranks because I am 6' 1" with relatively long legs.

Any advice is welcome.

All the best,

Simon.

Comments

  • akkers
    akkers Posts: 140
    shouldnt make much difference at all - you can simply adjust the seat height if it feels awkward
  • maddog 2
    maddog 2 Posts: 8,114
    no big deal but 175s sound better for you
    Facts are meaningless, you can use facts to prove anything that's remotely true! - Homer
  • ride_whenever
    ride_whenever Posts: 13,279
    I doubt you'll notice!

    You might want to stretch a bit more as you'll be using less range of movement so the msucles might shorten up more.
    Neeermad
    Carbon 456
    456 lefty
    Pompino
    White Inbred
  • Harry182
    Harry182 Posts: 1,170
    Don't compromise. Get the ones you want.
  • Percy Vera
    Percy Vera Posts: 1,103
    Harry182 wrote:
    Don't compromise. Get the ones you want.

    Agree
  • rake
    rake Posts: 3,204
    edited March 2010
    .
  • Barteos
    Barteos Posts: 657
    175 or 180 depending on type of riding
  • eh
    eh Posts: 4,854
    Interesting this as I have road bikes with 170 and 172.5mm respectively and both my mtbs are 175mm and I don't notice the difference at all. At the end of the day 5mm is sod all really. Now if you'd wanted 165 and they'd put 180 on, then I would be demanding a change.
  • andyp
    andyp Posts: 10,580
    I regularly ride bikes with 165, 172.5 and 175 mm cranks and, like eh, don't notice the difference.
  • Lunar Tick
    Lunar Tick Posts: 62
    The notion that longer cranks will automatically gain you an advantage is not necessarily born out by the evidence. Here's a summary of a recent study just published on this topic and which appeared in Peak Performance (www.pponline.co.uk) - I'm the editor by the way :)

    Crank length and cycling performance
    Cyclists among you will be aware of the choice of different crank lengths when purchasing a bike or new chainset. In days gone by, almost all crank lengths were a standard 170mm in length, but these days, most manufacturers offer three lengths – 170, 172.5 and 175mm. The theory is that shorter crank lengths are biomechanically more efficient for shorter riders and longer crank lengths better for taller riders. However, a new study by New Zealand scientists on elite female mountain bike riders seems to cast doubt on this assumption.

    In the study, the seven cyclists performed a maximal peak power/cadence (supra-maximal) test, a power test at a constant 50rpm and a maximal test of aerobic capacity, all conducted under controlled conditions in the laboratory. The test was repeated for each crank length with 5-7 days between tests to allow full recovery. The saddle height and fore/aft position (to pedal axle distance at a crank angle of 90 degrees) were kept the same controlled across all trials and the cyclists were blinded to the condition (ie they didn’t know which length cranks they rode).

    The results showed that there were no significant differences in the 50rpm power test or maximal aerobic capacity. However, when using the 170mm cranks, the time to reach supra-maximal peak power was significantly shorter (regardless of leg length) compared to using 175mm cranks (2.57 vs. 3.29 seconds) - a mean performance advantage of 27.8% for the shorter cranks.

    The researchers concluded that the decreased time to peak power and greater rate of power development with the 170mm cranks could offer a significant advantage in race conditions where the advantage of being able to respond quickly to a change in terrain could be of strategic importance to elite mountain bikers.
    Eur J Appl Physiol. 2009 Sep 22 [Epub ahead of print]
  • ride_whenever
    ride_whenever Posts: 13,279
    Cadence for that study is a little low...
    Neeermad
    Carbon 456
    456 lefty
    Pompino
    White Inbred
  • rake
    rake Posts: 3,204
    edited March 2010
  • Lunar Tick
    Lunar Tick Posts: 62
    Naturally, you can't read too much into one study - indeed, it raises more questions than it answers. However, the interesting point here is that the women (who were all elite riders) couldn't tell which length cranks they were riding, which supports many of the observations made above.
  • tenor
    tenor Posts: 278
    Lunar Tick; very interesting conclusion. Generally in discussions on crank length, most views are anecdotal with very little informed research available.
    Are there also studies for the Q factor (width between outer crank faces) as this dimension is never mentioned in terms of different rider physique although one might expect it to have an even greater effect?
    C+ often refer to this value in their crank tests, but never with any objective data.
  • Lunar Tick
    Lunar Tick Posts: 62
    Hi Tenor - no studies I'm aware of but then I'm by no means an expert on cycling research! You would certainly expect Q factor to affect pedalling biomechanics though.
  • cougie
    cougie Posts: 22,512
    You wont notice any difference. I noticed a crack in a crank just before a challenge ride so had to put on the only crank I had spare - I was riding with one 172.5 and one 167.5.

    Put it on and forgot about it til the end of the year.

    I've ridden with many different crank lengths and never noticed any difference. 5mm as a percent of your total inside leg is very small.
  • andy_wrx
    andy_wrx Posts: 3,396
    cougie wrote:
    You wont notice any difference. I noticed a crack in a crank just before a challenge ride so had to put on the only crank I had spare - I was riding with one 172.5 and one 167.5.

    Put it on and forgot about it til the end of the year.

    I've ridden with many different crank lengths and never noticed any difference. 5mm as a percent of your total inside leg is very small.

    In a similar vein, the cleat on my left shoe is usually more worn than the cleat on my right shoe, as that's the foot I put down if I'm stopping at junctions, etc.
    I say usually, because sometimes I've just replaced that one and left the part-worn one on the right, so it's been the other way round too.
    I notice that I have a bit more float, but that's all !

    And I have 175 & 172.5 on my roadbikes, 172.5 on my TT bike and 175 on my MTB
    - can't say I can really tell any difference in 2.5mm.

    However Mrs wrx has 175's on her Sirrus and as she's 5'6" that seems a bit much.
    I think her women's-spec Scott has 170's.
  • simonn
    simonn Posts: 88
    Hello,

    Thank-you to everyone for taking the time to reply...I'm going to stick with what I've got.

    Another funny thing,I asked for a 105 triple gears and the bike has an Ultegra front derailleur-is the bike shop using up it's odds-and-sods I wonder?
    I suppose as long as it all works,does it matter?

    Cheers,

    Simon.

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