Does size matter?

by TheHatter   October 26, 2010  

I've always thought that size matters - I've even had Mrs Hatter kneeling in front of me with a tape measure before now.
This was of course to determine my vital measurements that I then keyed into a specialist website

However despite the fact that this fitting site and other research suggests I need a 57cm/58cm frame I've recently been wondering how much this matters. A few things have changed my view - one was a comment in the last Rouleur where frame builder Ron Cooper seems to suggest that since we now have new style (ie non quill) stems and greater options on seatposts there is less importance on frames size. Also looking at Webline the very experienced Alf Webb offers only one size in his winter bikes (which I was very tempted by).

However the question has come to the fore for me due to the opportunity to purchase a rather lovely Condor tourer/cyclocross machine which has a compact seat tube of a mere 50cm (c-t). The effective top tube is 55cm.

So what are the thoughts of the esteemed forum - should I buy a smaller frame and make it work or will it always be a poor compromise?

6 user comments

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Mike Burrows takes the same line as Ron Cooper on this - he always intended the compact bikes he designed for Giant to be only offered in S, M, or L for exactly that reason. He maintains that the vast amount of the population can get a bike to fit by swapping things like stems, and bars, using seatposts with different amounts of layback etc.

i've got to say that over the years i've ridden bikes that are the 'wrong' size with a bit of tweaking more often than I've ridden one that's the right size - with no ill effect. Although I'm pretty sure that riding with handlebars that are slightly too wide for the last few months is reponsible for the pain I get between my shoulder blades when I've been out on the bike for a while.

Tony Farrelly's picture

posted by Tony Farrelly [4144 posts]
26th October 2010 - 23:12

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Cheers Tony that's all really interesting. There seems to be so much contradiction out there as I've also read that offering bikes in on SML was due to the production costs of having many different sizes when it came to carbone frames

tony_farrelly wrote:
I'm pretty sure that riding with handlebars that are slightly too wide for the last few months is reponsible for the pain I get between my shoulder blades when I've been out on the bike for a while.

The only pain I get after a long ride is also between my shouler blades/lower neck. I've put it down to either a badly set up bike or weak muscles. It never occurred to me that it could be the bars.

I've now got a new Condor cross bike that I'll be taking for its first ride on the weekend and it has 40cm bars compared to the 44cm on my Colnago. Hopefully I'll notice the difference.

TheHatter's picture

posted by TheHatter [810 posts]
27th October 2010 - 19:53

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I love compact frames 55cm seat tube and a 57 top tube for me keeps me in aero but my winter bike is traditional tour geometry and a 57cm top tube but long seat tube - makes my nads sore and making some adjustments.

Best thing is to get a bike fit - and go from there.
I'm getting myself fit then another bike fit before buying a frame.

I like my bike but it needs a hidden 25cc motor Smile

Fish_n_Chips's picture

posted by Fish_n_Chips [325 posts]
29th October 2010 - 14:09

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This is how I see bike fit...

You determine how high your saddle should be and how much setback you need.

You determine how much reach you need to the bars and how much drop.

Saddle and bar position can be measured in relation to the same fixed point. The bottom bracket.

Correct saddle height and setback can be obtained on a large vairety of frame sizes through height adjustment, saddle rails and various setback seatposts. Watch for the seat post angle to determine wether the desired setback can be achieved with any given seat post. For example personally I cannot achieve correct setback on a 72 dgree angle even with a zero setback seatpost.

Correct bar height postion however can not be so easily compensated for. A frame too small will result in a bar too low, a frame to big will result in a bar too high. Spacers and flipping the stem can only compensate to a point.

Therefore it is my opinion that the most important measurements on a compact frame is the head tube length and seat tube angle.

Determine the saddle and bar position in relation to the bottom bracket on an x and y axis. Then determine whether a given frame size can allow you to achieve this postition.

Napalmhaze's picture

posted by Napalmhaze [80 posts]
29th October 2010 - 14:41

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some good advice there napalm. bar height is certainly hard to fix if it's wrong, especially on a threadless headset. The reach of a bike is important too, you can compensate using a longer/shorter stem but you can quite seriously affect the handling if you go to extremes.

Dave Atkinson's picture

posted by Dave Atkinson [7401 posts]
29th October 2010 - 21:11

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Yeah the reach is pretty important but this is measured as bottom bracket to handlebar on x and y axis.

Many say to size a compact frame based on the virtual top tube length. This is wrong as unless you know the seat tube angle and how it affects top tube length the measurement is meaningless.

Napalmhaze's picture

posted by Napalmhaze [80 posts]
30th October 2010 - 19:01

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