smaller frames and larger riders

henderson_mk
henderson_mk Posts: 637
edited December 2008 in Workshop
hi folks,
just wondering about making a smaller frame fit a larger rider.
the frame is a bh connect 54cm..... and looking at the geometry it looks to be a bit too small for me. ( i ride a large planet-x with 90mm stem and large tcr 2 composite, both of which I find very comfortable)

Going by the geometry, it should be possible to make it fit ok, taking the seatpost up a touch, a longer stem to stretch the front out and maybe some shallow drop bars to compensate a bit for the shorter headtube?

What disadvantages to doing this sort of thing are there? Any? Or is it no big deal?

Marty
========================================
http://itgoesfasterwhenitmatches.blogspot.com/

Comments

  • hi folks,
    just wondering about making a smaller frame fit a larger rider.
    the frame is a bh connect 54cm..... and looking at the geometry it looks to be a bit too small for me. ( i ride a large planet-x with 90mm stem and large tcr 2 composite, both of which I find very comfortable)

    Going by the geometry, it should be possible to make it fit ok, taking the seatpost up a touch, a longer stem to stretch the front out and maybe some shallow drop bars to compensate a bit for the shorter headtube?

    What disadvantages to doing this sort of thing are there? Any? Or is it no big deal?

    Marty

    Two minor things I'd watch out for - taller riders tend to use (a) longer cranks and (b) have larger feet, so keep an eye on the 'toeclip overlap' (it's still called that even though not many pedals use 'em any more!); you don't want your feet in the way of the front wheel when steering sharply.

    David
    "It is not enough merely to win; others must lose." - Gore Vidal
  • Monty Dog
    Monty Dog Posts: 20,614
    A 90mm stem's pretty short for a frame of that size - really need to know the comparison in reach ie top tube length between the frames to make a comparison
    Make mine an Italian, with Campagnolo on the side..
  • Ty length on tcr is 58 with 80mm stem, planetx is 57 tt with 90mm stem
    The by connect I'm looking at is a 49 centre to top seat tube and 54 tt according to site.
    I'm about 6 feet tall with longish legs about 86 cm inseam....

    Hopefully that helps! Advice all welcome.
    ========================================
    http://itgoesfasterwhenitmatches.blogspot.com/
  • Infamous
    Infamous Posts: 1,130
    A smaller frame should be faster in theory. It'll be lighter, stiffer and lower at the front end.

    I'm 6'3" with 89 cm inseam and long arms and I ride a 56 compact frame. Rides great and I can get the front end pretty low (5.5 inch saddle to hbar drop, could be lower tbh).

    disadvantages are, it looks a bit too small.
  • If you buy shallow bars, chances are the reach will also be compact.
    Better to flip the stem over if possible...

    You can also get a seatpost with more setback. Look at FSA and Easton.

    These days there's a proliferation of parts to make incorrectly sized frames 'fit' the rider better. Don't ask me how I know. :wink: :oops:
  • k-dog
    k-dog Posts: 1,652
    You don't want to play around with seatpost layback to make the bike "fit" though - the seat position should only be determined from the BB - for efficient pedalling.

    Changing the stem is the only way to do anything - but you'd need a pretty long stem to make that bike "fit" and that does funny things to the handling as well as causes the toe overlap mentioned above - which is a pain if you intend riding in traffic - doesn't really matter for faster riding on open roads as you don't turn the bars.

    You might get away with it though - it sounds like you have a relatively short upper body so a stem of 120mm or so might be enough - and that's not especially long.
    I'm left handed, if that matters.
  • bill57
    bill57 Posts: 454
    Infamous wrote:
    A smaller frame should be faster in theory. It'll be lighter, stiffer and lower at the front end.
    The Tooth Fairy, Easter Bunny and Santa Claus are real as well!
  • wilwil
    wilwil Posts: 374
    Infamous wrote:
    A smaller frame should be faster in theory. It'll be lighter, stiffer and lower at the front end.

    I'm 6'3" with 89 cm inseam and long arms and I ride a 56 compact frame. Rides great and I can get the front end pretty low (5.5 inch saddle to hbar drop, could be lower tbh).

    disadvantages are, it looks a bit too small.

    Are you made out of rubber?
  • Ah ! an excuse to trot out another pic of my 'pride and joy' .

    I had the same dilemma in so far as I got the frame before thinking too much about anything else - the 'right price', y'see . I knew it was a lot smaller than my usual - 53 as opposed to 56 - but thought I could make it fit . The stem is a 140 and the cranks are 175 and that's about all really . It works fine . The 'toe-overlap' is there too , but in this case would be there anyway as it's a fag-paper clearance between tyre and steep'ish seat tube .

    Resized800x600_4.jpg[/img]
    "Lick My Decals Off, Baby"
  • Brassknocker
    Brassknocker Posts: 209
    edited December 2008
    I'm 6'1" with long legs and short body + have gone from a 58cm straight-tubed road bike to a compact 54, (both bikes have same effective toptube lengths) I usually find that the bikes that 'fit' my height in size-tables to be too long for me.

    I have a 54cm 'compact' Kinesis kr810 with 90cm stem and have the post out far... think it fits me perfectly!

    Go by top tube length rather than seat tube.
    I have 175cm cranks and don't have a problem with toeclip overlap.
  • bill57
    bill57 Posts: 454
    I find getting the bars high enough the biggest problem.
  • Infamous
    Infamous Posts: 1,130
    bill57 wrote:
    The Tooth Fairy, Easter Bunny and Santa Claus are real as well!
    I did say "in theory".
    wilwil wrote:
    Are you made out of rubber?
    Just ordered the frame for my next bike, it will have far more saddle-bar drop. Although it will be a TT bike.
  • bill57
    bill57 Posts: 454
    Infamous wrote:
    I did say "in theory".
    I know you did........... :wink:. It's the same theory that keeps us spending our hard earned on shiny new bits, in the usually mistaken belief that it'll make us faster.
    Apart from TT situations, do you think that any theoretical speed advantages might be cancelled out by the likelihood of poor positioning or discomfort from the smaller frame?
  • Infamous
    Infamous Posts: 1,130
    Oh no, clearly position is very very important, but here we are assuming that you can get the same position on a smaller frame (which, considering seatpost and stem are changeable, is quite possible if the frame is not wildly smaller), in which case it should indeed be ever-so-slightly faster.

    Isn't this why compact frames are used so much? because they are lighter/stiffer than the same size horizontal tt frame?
  • bill57
    bill57 Posts: 454
    Compact frames are/were just a fashion foisted on the cycling public by the manufacturers.
  • Infamous
    Infamous Posts: 1,130
    Isn't everything?

    I thought compacts are used more because they fit a larger range of people.
  • redddraggon
    redddraggon Posts: 10,862
    Infamous wrote:
    I thought compacts are used more because they fit a larger range of people.

    Not really, the important dimensions are still the same - reach, Seat tube angle, headtube angle, hedtube length and virtual top tube - these are same no matter whether the frame is a compact or traditional horizontal.
    I like bikes...

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  • Monty Dog
    Monty Dog Posts: 20,614
    I disagree regarding compact frames - it means that shorter riders get some decent standover clearance and also a longer headtube if needed, which means that your headset bearings last longer. Small 'traditional' frames aren't that great aesthetically, so compacts are an improvements.
    Make mine an Italian, with Campagnolo on the side..
  • nickwill
    nickwill Posts: 2,735
    I can't see how you can get the same position.
    Yes you can get the relationship between saddle and bars to be similar. But a long stem will totally alter the fore aft weight balance of the bike, and you are likely to be in the wrong position in relationship to the bottom bracket. You are also likely to have far too great a drop to the bars.
    Bike fit is without doubt the most important factor in whether a bike is right for you.
  • Infamous
    Infamous Posts: 1,130
    Infamous wrote:
    I thought compacts are used more because they fit a larger range of people.

    Not really, the important dimensions are still the same - reach, Seat tube angle, headtube angle, hedtube length and virtual top tube - these are same no matter whether the frame is a compact or traditional horizontal.

    I mean that shorter people can ride a larger compact frame than normal frame, which means more people can buy the same frame.