How important is frame size.

[mig]

^^ does an uncut steerer a la the bike upthread give a more solid, long lasting joint twixt stem and fork from an engineering point of view?

[531colin]

^^ does an uncut steerer a la the bike upthread give a more solid, long lasting joint twixt stem and fork from an engineering point of view?

No....it just means you can sell it to a customer who wants the bars a bit higher....

[smuggers]

I'm trying to get my contact points right on my tourer, but it's looking like I'll have to get a quill stem with a longer post, so I can get my bars & saddle at a similar height.. If I had a larger frame I wouldn't have had this issue.. My contact point - Re: perenium, is taking a bit of a hammering lately.

[531colin]

Here you go, Spa 51 and 57 set up for me......





Admittedly, the 51 would look better with a riser stem than all those spacers, but we were working in my mate's kitchen and we didn't have one to hand.
Now, Freddie, why won't you produce that geometry table that shows the same rider can't fit on a 23" and a 21"?

[gerrymcm]

Here's the trek geo Colin531 mentioned earlier.

[531colin]

Cheers, Gerry, thanks for that......at least one person is reading the thread!.....

[531colin]

I'm trying to get my contact points right on my tourer, but it's looking like I'll have to get a quill stem with a longer post, so I can get my bars & saddle at a similar height.. If I had a larger frame I wouldn't have had this issue.. My contact point - Re: perenium, is taking a bit of a hammering lately.

I'm a fan of Ahead stems. OK, they're bloody ugly, but ....they are available in a huge range of lengths and rises (look at St John St. cycles, and Rose Versand and be afraid,,,,,be very afraid!) but much better than that, you can undo 2 or 4 bolts and the bars come out with the tape still on....you can change the stem in 5 minutes.
You can get a quill to Ahead converter to use them with a threaded headset.....and shims to fit old bars into modern oversize stems.
Or there are adjustable stems, bit creaky, but useful to sort your position out.

[MikeF]

Here you go, Spa 51 and 57 set up for me......





Admittedly, the 51 would look better with a riser stem than all those spacers, but we were working in my mate's kitchen and we didn't have one to hand.
Now, Freddie, why won't you produce that geometry table that shows the same rider can't fit on a 23" and a 21"?

I don't think 23" wouldn't fit me. Contact points in the wrong places

[BigFoz]

Isn't that the whole point though? Different size frames can be made the "same" by using longer/shorter seat post / stems, more/less height on steerer - exactly like the example with 2 different sized bikes set up for Colin, with the contact points the same in spite of the difference in frame size?

There's obviously not an infinite amount of variation, but frame size within a 2-3 inches ( ? ) can be accomodated

[Brucey]

1890 Jackson Fleet (with truss-style seat tube)



The Starley 'Psycho' was a very similar layout. There were lots of bikes made in a similar way around this time, with sloping top tubes and a 'compact' geometry...

cheers

[Freddie]

Now, Freddie, why won't you produce that geometry table that shows the same rider can't fit on a 23" and a 21"?

Where did I say the same rider can't fit on a 23" or a 21", I didn't say that. I said too small a frame is often more problematic, even if you can get the contact points the same. Benefits often come from riding a larger frame than most typically consider. I've said it a number of times now and given good reasons (my first post), yet you do not argue against the reasons. I feel like we are going in circles.

A rider that usually rides a 22" frame (horizontal, not sloping), could probably be fitted to a 25" with little seatpost showing and a short stem and a typical 19" frame (with 75 degree seat tube) with a long stem and a extended laidback seatpost, but are either of these optimal? They both present excessive compromises and as we get nearer to the ideal frame size the compromises become less and less, but there are still reasons to pick one frame over another, even if purely aesthetic. You can fit your 52cm and 57cm frames, but you haven't said why you decided on the 54cm, if the same fit is available on all the frames.

Someone with size 11 feet may well be able to "fit" your 52cm frame, but get toe overlap when riding with mudguards and large tyres. If they ride with a larger frame, this won't happen (the front centre is longer), so the two frames aren't equally optimal. The larger frame will have less standover height, which may be a concern, but these are compromises that have to be weighed up. To say that frame size is irrelevant is reductionist and unhelpful.

Spa bikes are purposely left long on the steerer, most bikes aren't. Your bikes are atypical in that the smaller sizes have a sensible seat tube angle. This is a design you used so that laidback seatposts weren't necessary, so I imagine you find such things a kludge and sub optimal. If you have to get into the realm of buying non-standard fittings (laidback seatposts) to fit a frame, then the sizing is sub optimal, as far as I am concerned.

Getting the right frame is not solely a question of can I achieve the contacts points I need.

[531colin]

.............. I said too small a frame is often more problematic, even if you can get the contact points the same. Benefits often come from riding a larger frame than most typically consider. .............

If you prefaced that with "For people over 5' 10" tall" it makes a bit more sense, but even then, there are plenty of people who complain of "too long a stretch" to the bars.
How many people 5' 5" and shorter do you regularly ride with? For them, the main issues are too long reach, too steep seat tube angle to kludge the reach, and toe overlap.
Last time I googled it, the average height for women in the UK was given as 5' 2" or 5' 3", which means that most women are riding bikes which are too long already, going a "size up" will be worse.....and its the same for men under about 5' 5".
Of your "reasons" for riding a bigger frame
"steep seat tube angles" and "toe overlap" are features of poor frame design, which occur in small frames. Large frames however often have steep head angles without corresponding reduction in fork offset, giving steering which is too fast for my reflexes, and often blamed for shimmy. But neither small or large frames must have these design faults, its poor design, not the length of the seat tube, that governs it.
As for weight distribution, have a look at this geo. table that Gerry kindly posted for me, and my post of April 13th @ 5.23....chainstay length varies a couple of millimeters across the whole size range, wheelbase all of 3 centimeters. The main difference between "next sizes" is seat tube length, the easiest thing to adjust is saddle height.
Reach and top tube length vary by a lot less than "size" ie height of the frame. Most people will know whether they are "small, medium or large", so can get within a size of "ideal"....and from there on if you can get the contact points in the right place, thats the main thing.

[Brucey]

....How many people 5' 5" and shorter do you regularly ride with? For them, the main issues are too long reach, too steep seat tube angle to kludge the reach, and toe overlap.
Last time I googled it, the average height for women in the UK was given as 5' 2" or 5' 3", which means that most women are riding bikes which are too long already, going a "size up" will be worse.....and its the same for men under about 5' 5".
Of your "reasons" for riding a bigger frame
"steep seat tube angles" and "toe overlap" are features of poor frame design, which occur in small frames.....

FWIW I think that smaller people have a much harder time of it (getting bikes that fit right) than most taller people, for the reasons you describe. The frame design kludges appear to come from trying to use 700C wheels in every (small) frame size and then trying to keep a short wheelbase (for why????) in the larger ones.

But people do vary in their build and this give troubles too.

This is an interesting read

http://davesbikeblog.squarespace.com/blog/2006/2/27/a-different-thought-on-frame-sizing.html

I mean, I don't agree with it, but it is interesting...

cheers

[bgnukem]

My smallest frame is 56cm and the largest, 64cm. Used to think I'd need at least 61-62cm but actualy managed to fit on a Giant 58cm compact. I'm 6'5 with a 37" inside leg.

The limiting factors for me are available seatpost length (I use a 400mm 'post on my Giant, a 450mm 'post on my commuter, which is only 22" / ~56cm) and stem rise (A 130mm x 40° on my commuter & 110mm x 40° stem on the Giant).

An issue I've had which I always thought affected only smaller riders / frames is toe overlap. I tend to use 28-32mm tyres, mudguards and 175mm or longer cranks, and together with size 13 feet, overlap has been an issue even with frame sizes >60cm.

Funnily enough, there is slight overlap on my Dawes tourer, with 64cm frame and laid-back angles, but not on my Giant Rapid, a road-style frame with steeper angles, much shorter wheelbase and which is only the 58cm size.

[Vorpal]

I'm 5'8" and leggy (I wear the same inseam as Mr. V, who is is 6'1" or thereabouts). So, I have a short torso, and my problems with bike fit are legion, though reach is usually the first eliminator.

When I was younger, I sized by height, and fitted shorter stems. That wasn't always an ideal solution, and one 10 speed I had, I could only just reach the brakes on the drops. It was a good position for going fast, but not so much for stopping

When I had my first bike fitting as an adult (1993), I ended up buying one size smaller than I expected to, but I still have that bike, and it is still comfortable to ride.

I've had several bikes with toe overlap, and frankly until I read otherwise on this forum, I had though it was all but inevitable in frame sizes that fit me.