Why have wheels remained the same?

[tatanab]

I remember circa 1980 being able to switch from 27 x 1.25" to 700c on both my then solo and a tandem without needing co change anything else, not even the brakes - since the Mafac cantilevers on both bikes had enough adjustment to work perfectly well on both.

We used to do that regularly, take out general purpose 27x1 1/4 and put in racing wheels with tubular tyres (700C). It was also possible to fit a larger wheel! My first time trial bike was a roadster frame with the 26x1 3/8 three speed hub wheels replaced with 27x1 1/4.

[MikeF]

Ha... if only. There are plenty of metric sized wheel rims out there too; so there are in fact exactly the things you say there are not, which are lots of rims that are between integer inch sizes. If you look at all the diameters and rim widths alone you have many dozens of wheel sizes, and once you allow for offsets and stud patterns, hundreds. And to mount on those rims there are (literally) thousands of different tyres, with different widths, profiles, speed and load ratings. And I'm not even getting into different rim profiles with the same nominal diameter, or different tread compounds, temperature ratings etc.

The popular car tyre sizes are subject to the whims of fashion as much as anything else (remind you of anything?), thus the net result is that for cars that are only 25 years old you can get to the point that you cannot easily buy new tyres in many cases, either easily or at all, even. Which is daft, because functionally, many of these car tyres, wheels etc could be made to be the same as one another for little if any loss in performance... does this sound a familiar story?

cheers

Plenty of metric rims? Any examples? As far as I'm aware 99% of car rims are still sized in integer inches. See http://www.national.co.uk/tyres/ as an example typical of many. The integer number (in green on this web site) is the rim diameter in inches. A metric rim diameter isn't even listed. Even Citroen and Peugeot have non metric rims and I think only BMW were ones that did at one time.

Yes there are different tyres which will fit a given rim and will give a different diameter "wheel" but that isn't any different from a 622x18 bicycle tyre having a smaller overall diameter than on of say 622x42.

The stud patterns etc aren't really relevant to rim diameter.

There are "thousands" of different car tyres and in theory there is a choice of tyres that will fit on a given rim, just as there is a wide choice of tyres that will fit say a 622 cycle rim. The point I was trying to make. However if I were to choose a 571 rim I could buy a skinny tyre or er another skinny tyre, ie no choice at all. If I wanted a larger tyre I would need a new rim as well.

There is a difference between car and cycle tyres in that the tyres of cycles are a much smaller proportion of the wheel size which in my view is a good reason for having standardised rim diameters.

[Brucey]

Plenty of metric rims? Any examples? ...

Well I'm not sure what your point is exactly but in the interests of factual accuracy; metric tyres and rims were fitted as standard equipment on models from Alfa Romeo, Audi, BMW, Citroen, Ford, Ferrari, Mercedes-Benz, Peugeot, Renault, SAAB, and Austin-Rover. Possibly others too. There are at least five different rim diameters, several rim widths, and numerous tyre fitments. There were millions of cars fitted with these blessed things originally and there are still many thousands of these vehicles trundling around. Most of them will have been fitted with different wheels by now. The reason you didn't find any metric sizes listed is because you didn't look hard enough. You can still buy about 14 metric tyre sizes new but they are manufactured by one maker only in limited quantities; just like obscure bike tyre sizes.

The stud pattern and offset is of course relevant when the time comes to fit new/replacement wheels and tyres, just as the hub size etc would be if you needed to replace a set of obsolete 597 wheels on a bicycle. Car tyre sizes are more numerous because they have both width and height; both need to be correct, as well as speed rating, load rating and a few other things too. You certainly can't swap different fitments around willy-nilly and there are plenty of 'mixtures of tyres' which you could fit which would be 'legal but not recommended' and actually flipping dangerous. Specific tyre models in the same sizes and nominal ratings often behave quite differently; they will have originally been designed for a specific chassis and may have different slip angles and all kinds of other things.

Yes there are different tyres which will fit a given rim and will give a different diameter "wheel" but that isn't any different from a 622x18 bicycle tyre having a smaller overall diameter than on of say 622x42...

Not so; you can usually fit tyres that vary in width by 40% or more on a given bike tyre rim (presuming they will run through the frame OK) but you can't do that on a car tyre rim.

There are "thousands" of different car tyres and in theory there is a choice of tyres that will fit on a given rim, just as there is a wide choice of tyres that will fit say a 622 cycle rim. The point I was trying to make.

Actually when you dig into it, you often have nothing like as much choice as you seem to think. There are lots of 'ordinary' tyre fitments for quite commonplace cars that are no longer popular for some reason and you may have a choice of two or three tyres (in one or two approved sizes) to fit those vehicles now. You can't just change to a different size; it won't work in the same way and may well invalidate your insurance too, so please don't try that!

However if I were to choose a 571 rim I could buy a skinny tyre or er another skinny tyre, ie no choice at all. If I wanted a larger tyre I would need a new rim as well.

And a new bike too, probably.

Most that have been supplied with (say) 23-571 tyres in recent years won't take anything much bigger because the frame won't allow it. They will take 20, 23, 25mm tyres and these are available (as are 19mm and 28mm ones if you really look hard). You can still buy 'proper' 650C tyres eg

http://www.sjscycles.co.uk/delivery-bike-rigid-tyre-26-x-2-x-1-3-4-inch-(54-571)-prod10161/

(although you might have to wait a few days) but these are 54 mm wide and they won't fit into any modern road bike fitted with '650C' (571) rims. This should have been obvious when you bought the bike; no room under the brakes.

All of which brings us back to the original point; that (as well as different wheel sizes for different bikes to fit different folk) if you want to fit different width tyres into a single frameset, at some point you will need a different rim size to do it. So you can't 'standardise'.

cheers

[TimP]

Wheels have stayed the same because round still makes more sense than square.

Seriously though, mountain bikes have a number of purposes and in general are not used as road bikes are used. For events that are not very local people load them up and drive to the event, ride and then load up to go home again, meaning they are never far from either a means to get home or a cache of spares. With road bikes commonality of size means a bit more. It really doesn't matter where you go you will be able to get a tyre for a 700C rim - most of the world in fact.

I was cycling during the change over from 27" and have one bike designed for 27s that really doesn't work with 700C but where I live now there are no 27" road wheels or tyres. During the change over period it was hard to decide which to go for.

On a road bike bigger wheels would mean longer chain stays to fit the rear and a longer frame to avoid to much foot-on-pedal overlap with the front wheel. That would change the seating position that we have all become happy with.

[[XAP]Bob]

Road bikes generally ape the UCI pro peleton, so they have wheels determined by what's carried on the neutral service vehicles...