Cycling UK Forum

I am 6' 3" with an inside leg of 35". I normally ride 25" 531 frames for touring and general rides. I rode time trials for 20 years on 24" 531 frames. With the move to compact geometry frames i wonder what people think about the smaller frame, longer seat pin approach to bikes. I have a vested interest as i have acquired a beautiful Raleigh Royal frame, 23.5" . . . Too small ? ? ?

I would simply compare the head tube length of the Royal with a bike that fits you.

I am also 6'3" and ride a Dawes 1-Down which has a 57cm ( approx 22.5") frame. Is much more rigid than the 25" Dawes Horizon/Galaxy I used to have which flexed a bit. The smaller bike is more agile at slow speeds, but that is partly the 26" wheels. I have had to work a bit hard to get the reach/seat postion relative to pedals & bar height right, but it can be done and now I ride the bike with a smile on my face. It may look a bit ugly but doesnt feel it. The best bike I have ever had

I generally go of the top tube dimension, or the "effective" dimension if it's a sloping top tube.
ie measure the distance from where the tube joins the headset to where it would meet the seat tube if the top tube was horizontal.
The extended seat post will obviously make up the extra saddle height.

Dimension "C" in the following:-
http://www.spacycles.co.uk/smsimg/uploa ... ometry.jpg

Like Cycleruk,I go with effective toptube length on my Vayas.At 6ft a 57cm ETT is long enough so I've no toe overlap(71.5deg head angle,50mm offset)which with 175 cranks,47shoes,35mm tyres and 20mm m/guard clearances just get me clear,I could ride the next size up (58cm ETT) with a shorter stem but the standover would be slightly higher,and very little gain with toe overlap.
Geometry figures :- http://salsacycles.com/bikes/vaya/2015_vaya_2/geometry/

landsurfer wrote: i wonder what people think about the smaller frame, longer seat pin approach to bikes. ?

But it doesn't matter how long the seat tube or how much seat post is showing in the context of sizing. Reach is what matters most in getting a frame that fits.

Valbrona wrote:

landsurfer wrote: i wonder what people think about the smaller frame, longer seat pin approach to bikes. ?

But it doesn't matter how long the seat tube or how much seat post is showing in the context of sizing. Reach is what matters most in getting a frame that fits.

Quite so, fit-wise. But beyond that, you can make a 'compact' frame torsionally and vertically stiffer at the same weight (or a bit lighter) too. Which sounds wonderful.... but is it?

People think of the 'compact' frame as being a fairly new idea. However, this isn't entirely true; from the invention of the safety bicycle there have been occasional dalliances with more compact frame designs. Yet for about a hundred years or so the most commonplace sight was not a huge extension of seat pin on a small frame but was instead a saddle close to the crossbar, mounted on a frame that was as big as possible, more or less, and wheels that were also as large as possible, more or less.

I have often asked myself why this would be. The wheel size issue is relatively easy; large wheels roll easier, especially on any kind of lumpy surface, and despite the extra weight incurred, easier rolling is desirable for most cyclists.

Regarding the frame size issue, my notion for the longest time was that in times past, no-one knew any better. In hindsight this is a daft idea; it might explain why (for racing) the preferred frame size became a little smaller through the 60s and 70s, but it gives no credit to the skills of bike builders and the preferences of prior generations of cyclists; they could of course have built and ridden smaller frames if they had wanted to, but they chose otherwise.

No, I think that they may well have chosen larger frames simply because they are more comfortable. You might not notice this immediately when test-riding two frames, and indeed if they are both rather stiff, in the modern vogue, you mightn't notice at all. But if you ride (say) a 21" frame and a 25" frame (built with horizontal top tubes, in the same standard gauge tubeset) you would have to be dead from the neck down not to notice the difference. It really is like chalk and cheese.

In theory carbon forks, isoflex systems and all kinds of other modern stuff may make this kind of view irrelevant; you might be able to have some kind of comfort, still with a high torsional stiffness. But not all bikes are built thus and note also that there are also informed opinions that consider there to be a 'right amount' of torsional stiffness, even; more is not always better!

So, if you buy a compact frame and find after a few months that you are hankering after a suspension seat post, fatter tyres, and squishy handlebar grips, give a thought to how people got on without these things in times past; I think that in many cases they very carefully chose frames and forks that were nice and springy; they were not daft!

[edit; FWIW I think the OP has bought a frame that (for a frame with a horizontal top tube) is probably a bit too small. Most people that height on that frame will struggle to get the handlebars in the right place (heightwise, if not lengthwise) without some adaptation. If in doubt you could always build it up and see how you get on with it....]

cheers

its only an issue for tall people? I suspect the frame size thing has a simpler explanation. big feet big shoes etc the taller you are the the bigger the frame. it takes a lot to buck ideas like that & tall people on small conventional shaped frames look a bit ugly unless sloped, they dont look right, look as if you made a mistake and bought a frame to small?

Hi,

Lets remember the UCI effectively didn't allow compact frames for a long time.

rgds, sreten.

I always struggle to understand Brucey's analogy of bigger frame/horizontal TT being more comfortable.
It seems to me the safety bicycle frame is built in triangles for stiffness,in planar movement.
Sticking with steel frames,torsionally,longer smaller diameter tubes of the same wall thickness or even thicker walls,will bend easier,so bigger frames in standard tubes will flex more when subjected to sideways stress such as cornering and when power is applied.
I understand flexing of the frame when cornering which isn't desirable and can lead to serious bad handling problems IMHO.
I also understand the BB flex when power is applied.
There's a theory that if the rider is in 'tune' with this BB flex the frame gives something back in the returning springiness.
If this rider to frame tuning,is harmonious and the frame gives back on the return spring,then the frame will be more suited to the rider and as a result the rider will be more comfortable due to not expending as much power or the power expended is somehow evened out or multiplied(?).
However the return spring needs proving to be beneficial in the first place.
To my mind given power is watts and a random figure of 200watts is put into each pedal stroke that is total expended power.If the frame 'stores' 50 watts(random) of the total and gives it back somewhere else on the pedal stroke(in a harmonious relationship situation),the rider gets the 50watts back.
The same rider on a frame with non or not much BB spring/movement still puts in the 200watts of power but non is stored/returned will put the full 200watts through the cranks to the chain and rear wheel.
Theoretically the power to the rear wheel is the same but the 'spring back' frame could if we are to believe the theory,even out the power feed.
Whereas a non springy frame the power output is still the same but not as even for the same watts expended due to no frame 'spring back'.
That is unless the rider works with the lack of 'spring back' and evens out his/her power delivery,this requires technique or an adjustment of technique for optimum efficiency.
Another source of comfort could be that longer tubes could absorb more road buzz especially if riding narrow high pressure tyres on less than perfect roads.

FWIW,IMHO I need convincing of the springback theory,I'm prepared to believe there could be something in road buzz theory.I'm not for noodliness when cornering.

IME the front fork is the only item to provide 'suspension' in a DF bicycle and can be improved greatly by tube choice and type of bend,if it has flex in the plane thereby evening out small bumps especially at speed and resists flex in torsion giving accurate steering it's going to be more comfortable.
Straight tubes in a frame don't provide suspension AFAIK.


All that said,IME most comfort comes from tyres especially on less than perfect road surfaces and on those roads bigger supple tyres run at the correct TP's for load make the biggest difference in comfort.

IMO,comfort is subjective,I'm not the same person I was even ten years ago,but twenty years ago my body could stand far more discomfort without even noticing it than it does now,back then I rode mainly 23 and 25mm and 32mm touring, tyres on 531 traditional steel frames with a more aggressive riding position.
Today I ride oversized steel tubed compact frames,with straight bladed forks,supple 35mm tyres,a far less aggressive riding position and compact drop bars.
I also use lower gearing mainly because I need lower gears for climbing as I don't have the aerobic capacity I had then to climb out of the saddle,also at the high end I've no use for 50x13 preferring a top gear of 46x14 which I can spin up to 30mph on a good day with a serious tailwind .
My ride times aren't a lot slower,but my comfort levels are much higher even though my pain acceptance levels being a lot lower.

On frame that stands out as being as dead as a Dodo and seemed to drain energy out of me was a 231/2 inch,traditional horizontal TT 531ST throughout,touring frame,loaded it 'worked with me' unloaded awful!

I'm always willing to be educated if I've misunderstood anything.

mercalia wrote:its only an issue for tall people?

I seems to follow that small people riding small frames would be more uncomfortable due to the harshness of the shorter tubes of a trad frame and even worse with a compact frame.

I suspect the frame size thing has a simpler explanation. big feet big shoes etc the taller you are the the bigger the frame. it takes a lot to buck ideas like that

Taller people will need bigger frames and naturally longer ETT due to the reasons you mention,but with compact frames the seatube needn't be longer,which gives more latitude to frame fit

& tall people on small conventional shaped frames look a bit ugly unless sloped, they dont look right, look as if you made a mistake and bought a frame to small?

Taken to the other extreme,it could be argued that people riding frames with only an inch or two of seatpost showing look far too big for the rider......... It depends on your POV.

sreten wrote:Hi,

Lets remember the UCI effectively didn't allow compact frames for a long time.

rgds, sreten.

And also talks out of it's rear end mostly!

reohn2 wrote: I always struggle to understand Brucey's analogy of bigger frame/horizontal TT being more comfortable.
It seems to me the safety bicycle frame is built in triangles for stiffness,in planar movement...

Except they are not, not really. The 'main triangle' is actually a quadrilateral! There are very high bending stresses in all the main frame tubes and especially the steerer. Quite small changes in tube length have quite (disproportionately) large effects on the tip deflection of tubes etc in bending, so different sized frames ride very differently and so do frames that are designed differently to fit a person of a given size.

Generally most people will notice most differences, but not everyone will. A frame that is too flexy is fairly easy to spot, but one that is too stiff is less easy (and possibly it is less significant, also); the effects can be masked by fat tyres etc.

Something that isn't always easy to spot is the difference between a frame that is flexy and springy, and one that is flexy and not springy. It has been my observation (and I hear the same thing from other folk too) that a badly made lugged frame can often feel a bit 'dead' and flexy at the same time. I think this can happen if (say) the tubes have been overheated and softened excessively, or simply not mitred correctly in the head lugs. With these faults present, the frame can flex more than normal, but in a way that doesn't conserve energy properly (hence the dead feeling) and this can mean that the frame is doomed to break prematurely, e.g. in the lower head lug.

cheers

Brucey wrote:The 'main triangle' is actually a quadrilateral!

Which can't be denied

There are very high bending stresses in all the main frame tubes and especially the steerer. Quite small changes in tube length have quite (disproportionately) large effects on the tip deflection of tubes etc in bending,so different sized frames ride very differently

I'll have to take you word for that as I don't have that breadth of knowledge or experience of different tube lengths/frame sizes.

and so do frames that are designed differently to fit a person of a given size.

Outside of bespoke frames does that really count for most people.

Generally most people will notice most differences, but not everyone will. A frame that is too flexy is fairly easy to spot, but one that is too stiff is less easy (and possibly it is less significant, also); the effects can be masked by fat tyres etc.

One man's mask is another's made good.
A rear HP narrow tyre will still punch me up the backside on rough roads far more than a supple carassed fat one and I'm very comfortable with straight bladed front forks with the same fat tyre on the front.I'm sure I'd be more comfy with the same front tyre in a fork with a nice tight radius bend and made of springy steel

Something that isn't always easy to spot is the difference between a frame that is flexy and springy, and one that is flexy and not springy.

I'll agree with that.

It has been my observation (and I hear the same thing from other folk too) that a badly made lugged frame can often feel a bit 'dead' and flexy at the same time. I think this can happen if (say) the tubes have been overheated and softened excessively, or simply not mitred correctly in the head lugs. With these faults present, the frame can flex more than normal, but in a way that doesn't conserve energy properly (hence the dead feeling) and this can mean that the frame is doomed to break prematurely, e.g. in the lower head lug.

cheers

Again lacking the breadth of such experience I'll have to take your word for it.
Sticking to the three steel ones I own,all I can say is that non are lugged, but Tig welded,so I'm assuming,going off the very small and neat weld beads,they've been mitred very accurately.The two same frames(the Vaya's)have slightly different diameter toptubes, the larger diameter one feels ever so slightly stiffer but it's very slight.

reohn2 wrote:

Brucey wrote:The 'main triangle' is actually a quadrilateral!

Which can't be denied

Or perhaps it can ..... Any idea what this shape could be called - in polite language preferably