How important is frame size.

[landsurfer]

Read a lot about frame fitting services for modern frames but how relevant is frame size ?
I have 3 bikes a Carlton Criterium, Carlton Pro Am and a Raleigh framed 531 framed modern / old school type bike also made in Carlton -in-Lindrick.
Their all different sizes, 23.5, 24 and 25 inch. But they are all comfortable day rides.
I time trialed for 20 years on a 24" Holdsworth but trained on a 25" Dawes framed bike. So different stem lengths, amount of seat post on view etc all seem to have arrived at the same riding position.
Am I just a weird shape or have others found frame size not to be as critical as the retailers would have us believe ???

[tatanab]

Over the years I've ridden everything from a 24" frame with the saddle as low as possible to a 21" frame with the handlebar stem on the minimum insertion mark. Mostly this was due to lack of cash and/or what was available at the time. Stems are available in different lengths and saddle pillars go up and down, so I was happy and comfortable enough. I've not had an off the peg bike since I was 11, always assembling my own so I was never hidebound by what any bike manufacturer thought to supply as parts. These days all my machines are 22" seat tube with top tubes in the range 22" to 23" and stems of a length to suit, 10 cm to 8 cm.

Fashions of course change. 60 years ago small frames were in vogue. Later it was large ones. Seat tube length was important because stems come in different lengths, now top tube length is seemingly more important because longer saddle pillars are available. Just fashion. The important thing is of course getting the riding position right to suit yourself.

[landsurfer]

I know by use of a measuring stick that all 3 bikes have the same bar/stem to center of seat distance and the seat top to bb axle distance is the same. Frame size almost becomes an after thought it seems. It's the bar/stem/seat/bb axle distances that actually count.
We sell a lot of frames and when people call and say they must have a 24.5" frame i wonder if they actually understand their actual needs.

[mercalia]

I think the size of the wheels also determines how a bike feels?

[gregoryoftours]

Sometimes if a frame is quite small for you a bit of a problem can be raising the handlebar high enough - you tend to have a lot of seatpost showing and the head tube is short so you might have to resort to an ugly riser stem or bigger rise on your bar.
I used to ride a Dawes Galaxy that was way too big for me at 22 1/2". When I eventually got the same year model from ebay that was 20" it gave a noticeably harsher ride, I guess because the longer tubes of the larger frame had a bit more give in them.

[531colin]

Came across this old photo the other day......as long as you can get the contact points in the right places, frame "size" is a bit of an irrelevance......but one of those bikes put me at risk of an unwanted "contact point"!

[landsurfer]

All my bikes have 700c wheels

[Freddie]

I think there are benefits to riding the largest frame that leaves you enough standover (dependant upon personal preference), as follows:

Larger frames usually have better head and seat tube angles
Larger frames avoid/minimise toe (clip) overlap
For the tourist/non-racing cyclist, larger frames allows you to get your handlebars higher without resorting to extreme measures (mitigated somewhat by newer sloping tube designs)
Longer headtube puts less stress on headset bearings, allowing them to last longer
About a fistful of seatpost & stem/steerer looks most attractive. I'm sure Thorn's bikes work OK, but they're are exceptionally ugly with their acres of steerer and seatpost showing. Aesthetics do count for something, especially when spending that kind of money
Lastly, no one really wants to look like an adult riding a child's bike (unless you are a wannabe racer!)

To make myself clear, I think frame size and, even more so, whole bike geometry matters, more than anything else, with respect to comfort and handling on the bike. Just because you can achieve the same contact points on a number of different sized frames, does not mean that a 21" frame is just as good for you as a 23" would be, for instance. There are diminishing returns between frames with 0.5" tube length differences, though one size will likely be better than another in some department.

[kylecycler]

...but one of those bikes put me at risk of an unwanted "contact point"!

Well, they say that even 'standover height' is an irrelevance (as long as, in your case, you remembered what frame you were riding when you stopped!) - the theory being, you only really need to put one foot down when you stop, and not two - the other foot can be kept on the pedal, waiting to push off again.

You might find it interesting to check out Competitive Cyclist's 'Three Styles of Fit' - it has fallen into legend in recent years, especially across the pond, and kind of confirms the OP's experiences. Click on the link then scroll down and under 'MORE INFORMATION' click on 'The Traditions of Road Riding and Our Three Styles of Road Fit' - The Competitive Fit, The Eddy Fit and The French Fit.

http://www.competitivecyclist.com/Store ... orBike.jsp

For the same rider, the Competitive Fit might be a 54 cm frame, the Eddy Fit a 56 cm, and the French Fit a 58 cm. Curiously, Lance Armstrong is 5' 10" and always rode a 58 cm frame (top tube length), while most other pro riders of similar stature nowadays would be riding a 54 cm. He had back problems, apparently, but it just tends to confirm the above.

I can't find the post in Dave Moulton's blog where he surmised that modern Tdf riders seem to crash more often (at least that was the impression he got), especially in the wet, because he felt they were riding frames at least two sizes too small (for stiffness and aero benefits). It's an established principle that any vehicle handles best when its weight is kept as far as possible within the wheelbase, and with too small a frame, the rider's weight is hanging off the ends...

[Freddie]

I know by use of a measuring stick that all 3 bikes have the same bar/stem to center of seat distance and the seat top to bb axle distance is the same. Frame size almost becomes an after thought it seems. It's the bar/stem/seat/bb axle distances that actually count.
We sell a lot of frames and when people call and say they must have a 24.5" frame i wonder if they actually understand their actual needs.

That is a little condescending. Maybe they are just perfectionists and know precisely what they want with regards to performance and aesthetics. A 23" top tube with a 12cm stem, all else being equal, will handle differently to a 24" top tube with a 9.5cm stem. Whether the difference is significant, is a matter of judgement, I suppose.

[mercalia]

what is rather funny is when u see big beefy guys on small bikes?

[pga]

In the good old days, when I was a cycling coach and frames were often built to order, I advised riders to ensure that the bicycle was a good fit by aiming to make sure that 4 inches of seat tube projected, enough to be gripped by a hand. The formula I used to get to this was to take two thirds of the inside leg length to give the frame size, ie seat tube measured from centre of bottom bracket to top of top tube. This produced the optimum look for those of us who cared about how a bicycle should look. Nowadays with sloping top tubes it is not so easy and best tried out in person. Better a smaller frame than a bigger one - you don't see the top racers riding around on oversized frames as many tourers do. If it is good enough for the Tour de France it is good enough for my tour of France.

I don't follow the logic behind larger is best. Weight is important as is centre of gravity.

[Tonyf33]

I'm 5ft 11, 32.5" IL, extra long arms for my height..two bikes in my pack at either end of the range, one is a traditional diamond racing bike, 62cm (c-t) & 110mm stem, my every day bike (flat bar/sloping top tube) is 51cm c-t with 130mm stem (though a 140 would probably be better). I have +2- 2.5cm saddle height and a -3cm top of bar height differential from the racer to the flat bar. The different cleats/shoes for the former are most of the reason the saddle is a little higher, body position the latter..both are comfortable but they are different bikes.

As colin says so long as you can get the contact points to match with what you need then the frame size isn't that important, but there are reasons why getting the right size frame can be important, if you're a weight weenie, smaller frames with about 12 inches of seatpost stuck out is the way to go
Mark Cavendish's bike is a 49cm he's 5ft 8, looking at it and the measurements given
Saddle height from BB, c-t: 680mm
• Seat tube length (c-t): 467mm
• Seat tube length (c-c): 400mm
• Tip of saddle to center of bar: 526mm
• Head tube length: 100mm
• Top tube length: 518mm (effective) and he uses a 120mm stem apparently but did have a 140mm on his 2014 TdF bike?
it would seem he has a long trunk, approx 30" inside leg and shortish length arms, he downsized from a 52cm previously but the contact points are virtually identical from 2011 to 2014 through different bikes.

[531colin]

...................... A 23" top tube with a 12cm stem, all else being equal, will handle differently to a 24" top tube with a 9.5cm stem. Whether the difference is significant, is a matter of judgement, I suppose.

By that logic, my bike will handle differently depending whether I'm on the tops, the hoods, or the drops. I'm not sure it does.

[reohn2]

I'm with Colin,the contact points are the main thing,though not the whole story for different reasons.
I like a low stand over to protect the crown jewels when off road should I need to put my foot down on the low side.
I also much prefer compact frames aesthetically,YVMV.
My two Vaya's are 57cm ETT size(110mm stem),I could ride either a 58cm or even at the extreme a 60cm frame with correspondingly shorter stems,but the 57's front centres give toe clearance with 40mm tyres and generous mudguard clearances.
The seatube angle on the 57 is slack enough at 72.5 deg for me to get my saddle back far enough with 25mm layback post and is only slacker on the 60(72deg).
So I'm happy ,but I'd be equally happy on a 58,though not a 56 due to the front centres and a 73 deg s/tube,a 60 would be a bit spacious.

There's always some overlap with OTP compact frames that's the purpose of their design,less sizes to fit more people IMO that works for 90+% of folks.

In answer to the OP's question,framesize isn't as critical as it used to be,and IMO relates mainly to SO and ETT sizes,and also perhaps for a significant minority of people seat angle matters a lot especially if they ride a Brooks saddle or have long thighs.