...why wheels are the exact size they are?

cycle tramp · Post by **cycle tramp** » 13 May 2024, 8:13am

..and from the perspective of a bicycle built to carry loads.. smaller wheels can be made stronger with less materials and the loads can be carried more easily, over the wheels with a lower centre of gravity, making the loaded bike (either touring or shopping( easier to handle..
Indeed, I don't know why there are more 20 inch wheeled touring bikes - you could even carry a complete spare wheel

rareposter · Post by **rareposter** » 13 May 2024, 8:40am

cycle tramp wrote: ↑13 May 2024, 7:47am It's more than possible that 26 inch wheels might come back on the provision that some develops a light enough tyre with a deep enough tyre wall to give the wheel the same diameter as a 700 wheel...

Fat bikes (usually) have 26" wheels but with tyres around 4" wide (and I've seen up to 5").

But they're far from ubiquitous because (unless you're riding sand or snow) you simply don't need tyres that big.

cycle tramp wrote: ↑13 May 2024, 8:13am ..and from the perspective of a bicycle built to carry loads.. smaller wheels can be made stronger with less materials

This is just not true any more. Sure, in the days when a bike wheel was basically a standard 14mm wide rim, drilled either for light weight (32h) or touring (36h), it was the only way to achieve "strength". Modern wheels, especially when combined with disc brakes which frees up the rim profile completely, are way stronger than all but the most overbuilt things from "back in the day". Even many DH bikes now use 29" wheels.

Tern's new monster truck SUV style cargo bike (the wonderfully bonkers Orox, see : https://www.bikeradar.com/reviews/bikes ... r14-review ) uses 27.5" wheels and that's got an all up weight capacity of 210kg, easily 5x more than any normal bike (and slightly more even than their regular cargo bikes on 20" wheels) would ever be expected to carry.

As others have mentioned, I think wheel size has been arrived at through a combination of human height, handling, bike geometry, practicality and a degree of standardisation.

LittleGreyCat · Post by **LittleGreyCat** » 13 May 2024, 9:05am

cycle tramp wrote: ↑13 May 2024, 7:21am Small wheels explained... (a bit)
https://hadland.wordpress.com/2012/06/2 ... -bicycles/

Led me to look up the current price of Moulton bicycles and then step slowly and quietly away from the computer.

rareposter · Post by **rareposter** » 13 May 2024, 9:29am

LittleGreyCat wrote: ↑13 May 2024, 9:05am
cycle tramp wrote: ↑13 May 2024, 7:21am Small wheels explained... (a bit)
https://hadland.wordpress.com/2012/06/2 ... -bicycles/
Led me to look up the current price of Moulton bicycles and then step slowly and quietly away from the computer.

To be fair, it's the same buying into any completely proprietary system. Brompton is similar and (as with Moulton) you're buying into a bit of a "high end community" type thing as well. Even a fairly entry level Brompton now is £1500, the highest price ones are over £4000

531colin · Post by **531colin** » 13 May 2024, 9:44am

Penny farthings had a big wheel so that they went a reasonable distance for one turn of the pedals.
By the time chain drive and pneumatic tyres came along the bicycle was practical transport, but in towns and cities roads were cobbled, in the countryside we had dirt roads. To cope with poor surfaces, you need big diameter and width; early rod braked roadsters had 28 x 1 1/2 inch tyres ; my Schwalbe 700 x 40 tyres still have 28 x 1.5 on the sidewall. By the 20th century** 26" had taken over, being more suitable for average height people, and roads were improving; 26 x 1 1/4" for lightweight club bikes (at least, between the wars), 26 x 1 3/8" for roadsters. (with a different rim size, the diameter is supposed to represent the outside diameter of the tyre) I think 27 x 1 1/4" was a bit later, but certainly commonplace in the secondhand market in the early sixties, which I remember.
The 28" size was converted in Europe to 700mm. Again, 700mm was supposed to represent the outside diameter; 700C was for a fat tyre to be 700mm outside, 700B for a middling tyre, and 700A for a skinny tyre. Of the three sizes, 700C was the one size which persisted (maybe because with skinny tyres it suited the average height?), but of course when you fit skinny tyres the overall diameter is less than 700mm. 650A, B and C also used to exist. (hasn't one of them been resurrected as 27 1/2 or something equally daft?)
When the Americans started to invent downhill mountain biking they simply used the fattest tyres which were available to them, these being 26" wheels and tyres used on American "beach cruisers".
In short, the whole sorry mess is a series of accidents of history, there is very little logical design involved.

** on reflection, I'm prepared to be wrong!

Jdsk · Post by **Jdsk** » 13 May 2024, 10:07am

Nearholmer wrote: ↑13 May 2024, 6:41am Once things progressed from the ordinary bicycle to the diamond-framed safety bicycle*, there was a bit of experiment or vacillation about exact wheel sizes (plural, because they weren’t always the same front and rear), but things fairly quickly settled into the area of roughly 600 to 700mm overall diameter including tyres.

The “why” must have to do with:

- feasible gearing ratios to give a single-speed or two speed (that’s all there was initially) machine that could be ridden by most people over most roads while achieving a decent rate of progress;

- the size-range of adult humans and how that interacts with bike frame dimensions;

- the dynamics of cornering at a wide variety of speeds work out OK;

- how various wheel diameters cope with different degrees of bumpiness in the road surface, remembering that very few roads outside towns were hard-paved, and that the larger the wheel the better the “angle of attack” when it comes to going over small lumps and bumps;

You can sort of see all this by going to extremes: a huge wheel as in an ordinary simply can’t be used in a practical safety bicycle, and a tiny little wheel like a roller-skate gets stuck on anything but the smoothest surface (early roller skates had quite big wheels, as it happens).

Once into this “Goldilocks zone” of wheel sizes, naturally a zillion micro-variations arose due to proprietary manufacture, national standardisation etc.

The idea that much smaller wheels are “ideal” seems very curious to me, and I’d like to see it explained. So far as I can see, small wheels are really only desirable for special purposes like folding bikes, and are a literal PITA on rough ground.

*In fact, if you go back to wooden hobby-horses and boneshakers, the wheel sizes were in the same range as most modern bikes.

I strongly support the approach of listing the many different requirements and constraints that led to any design decisions. There's a tendency in historical writing, technological or otherwise, to pick one or a few causes as explanation. This is convenient but it's often misleading.

Specifically on technological history there are often designs that built on the state of the art although that has been lost while its offspring flourish. Are there any of these factors for HPV wheels... what would the innovators have been familiar with in other domains?

And then there's the attraction of round (!) numbers.

Jonathan

PS: Wheels using metal spikes in tension seem to have first been used... in a glider:
https://en.wikipedia.org/wiki/Wire_wheel
https://en.wikipedia.org/wiki/Bicycle_wheel

simonineaston · Post by **simonineaston** » 13 May 2024, 10:08am

Hopping around looking at pages with something to say about bicycle wheels, I came across this site. There's some nice bikes on here!

IMG_0311.jpeg

https://restoringvintagebicycles.com/

tatanab · Post by **tatanab** » 13 May 2024, 10:53am

531colin wrote: ↑13 May 2024, 9:44am 650A, B and C also used to exist. (hasn't one of them been resurrected as 27 1/2 or something equally daft?)

650A still exists and is known to us as 26x1 3/8, 650B is now called 27 1/2.

Nearholmer · Post by **Nearholmer** » 13 May 2024, 10:58am

what would the innovators have been familiar with in other domains?

If you think about other light, wheeled vehicles that were around, and coping with the road conditions, there were huge numbers of hand-carts and light pony/horsedrawn things, which must have yielded clues about the range of wheel sizes that worked. There was a bit of scepticism at the time about whether moving down from the very large wheels on ordinaries’ to the sizes used on ‘safeties’ was really going to work.

Bmblbzzz · Post by **Bmblbzzz** » 13 May 2024, 11:03am

I think manufacturers like having a standard size wheel for all frame sizes.

I think consumers and retailers like it too! Imagine how difficult it would be if one bike had rim diameter 622, another 624, a third 625.5, and so on. Rim and tyre standardization is simply practical, and used in motor vehicles of all sorts too.

531colin · Post by **531colin** » 13 May 2024, 11:13am

tatanab wrote: ↑13 May 2024, 10:53am
531colin wrote: ↑13 May 2024, 9:44am 650A, B and C also used to exist. (hasn't one of them been resurrected as 27 1/2 or something equally daft?)
650A still exists and is known to us as 26x1 3/8, 650B is now called 27 1/2.

Thank you! I'd forgotten that 650A was the same as 26 x 1 3/8 (although that in itself doesn't match up...."A" should be the narrowest tyre, but 1 3/8 " is the larger)

531colin · Post by **531colin** » 13 May 2024, 11:20am

Bmblbzzz wrote: ↑13 May 2024, 11:03am
I think manufacturers like having a standard size wheel for all frame sizes.
I think consumers and retailers like it too! Imagine how difficult it would be if one bike had rim diameter 622, another 624, a third 625.5, and so on. Rim and tyre standardization is simply practical, and used in motor vehicles of all sorts too.

It is daft, though.
See somebody 5 feet nothing cycling next to somebody 6 feet 4, and they are very often using the same size wheels....700C.
Somebody five feet nothing riding 700 c wheels is at risk of toe overlap and too long reach.
But in my experience, small women are very much against buying a bike with (say) 26" wheels.
Spas Tourer, the first bike I designed, had 26" wheels in the smallest size, so did the Audax..
Due to customer resistance to the smaller wheels, I designed later bikes with shallower head angle and more fork offset to get more toe clearance for the same reach.

pjclinch · Post by **pjclinch** » 13 May 2024, 11:47am

LittleGreyCat wrote: ↑13 May 2024, 9:05am
cycle tramp wrote: ↑13 May 2024, 7:21am Small wheels explained... (a bit)
https://hadland.wordpress.com/2012/06/2 ... -bicycles/
Led me to look up the current price of Moulton bicycles and then step slowly and quietly away from the computer.

But you're not paying that because it has small wheels, you're paying that because it's a small UK based builder making a particularly complex space frame (though the space frame isn't integral to being a Moulton, the original Moulton F-Frame that made the brand's name is far more conventional, the space frame came later on when Moulton was deliberately aiming at a higher-end niche so he could do whatever he wanted and never mind the price, as long as there was enough demand to make it sound business, and it turns out there is).

My first Moulton was a second hand TSR 8 I bought on eBay for £700 about 15 years ago, on the back of trying out a second hand AM that I just loved riding. And I'm about to decommission that TSR 8 and get an SST 11 as my new general purpose hack, because as a general purpose do a bit of everything bike I find the Moulton says "Ride me!" better than anything else I've ever tried. It's not as fast as a road bike, but it's fast enough to get places, it's not as comfy as a full-sus recumbent, but it's much comfier than most upwrongs thanks to the suspension, it's not as manoeuvrable as a BMX, but it's not far off, it won't take as much luggage as a tourer or a cargo bike, but it takes enough for typical shopping trips. And as a bonus it has a convenient step-through frame, splits in two for easy transport, fits in to smaller bike spaces on buses etc. better than big-wheelers and is easier to manhandle up stairs etc.

While even the bottom of the range TSRs aren't cheap (starting at about £2K) they're certainly in the ballpark of "decentish road/gravel/mountain bike" that a lot of folk are willing to pay for. Yes, £20K for the Double Pylon is bonkers and I wouldn't pay that even if I had it, but that costs as much as it does because some folk are willing to not only pay that, but wait months in to the bargain! Ben "Kinetics" Cooper told me about someone in the US who had two DPs, one to ride and one to hang on the wall. Some people just have too much money, methinks...

Pete.

axel_knutt · Post by **axel_knutt** » 13 May 2024, 12:03pm

The reason there's always work for engineers is that there's no such thing as an optimum which is universally applicable. All design is a compromise between conflicting requirements, so any 'optimum' depends on which parameter the end user wants maximised for his own application, and to what extent he's willing to sacrifice other performance in the pursuit of it. Chris Hoy doesn't race a cargo bike round the velodrome for the same reason as a mum doesn't take the kids to school on a track bike: they're the wrong tools for the job.

On a few occasions a new development comes along which improves multiple parameters with little or no compromise, but in those cases the new becomes a de-facto standard whilst the old just goes obsolete, and then the variations and compromises continue in the new designs.

cycle tramp · Post by **cycle tramp** » 13 May 2024, 12:46pm

rareposter wrote: ↑13 May 2024, 8:40am
cycle tramp wrote: ↑13 May 2024, 8:13am ..and from the perspective of a bicycle built to carry loads.. smaller wheels can be made stronger with less materials
This is just not true any more. Sure, in the days when a bike wheel was basically a standard 14mm wide rim, drilled either for light weight (32h) or touring (36h), it was the only way to achieve "strength". Modern wheels, especially when combined with disc brakes which frees up the rim profile completely, are way stronger than all but the most overbuilt things from "back in the day". Even many DH bikes now use 29" wheels.

Tern's new monster truck SUV style cargo bike (the wonderfully bonkers Orox, see : https://www.bikeradar.com/reviews/bikes ... r14-review ) uses 27.5" wheels and that's got an all up weight capacity of 210kg, easily 5x more than any normal bike (and slightly more even than their regular cargo bikes on 20" wheels) would ever be expected to carry.

For a moment I got really excited about a bike which can carry both its rider and 210 kg, but then reading the article that turns out to include the riders weight, which means it's not carrying too much more than a tandem used for loaded touring. Certainly from the wheel building point of view that's a rolhoff hub being used in the back wheel - which by virtue of being dishless is already super strong..

..and again from the point of view of this bike being useful - the compromise is already there, say the larger back wheel fills the space, which a smaller 20 inch wheel would have left open - certainly if they had used a 20 inch wheel in the rear, the bike designers could have created an open flat platform allowing you to carry things like fridges, freezers, and small items of furniture...

Whilst I appluade the style of the machine as a way to attract people to cycling, who may not otherwise be that bothered... there have been better designed machines.

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