To prevent article pages from being miles long, but preserve all the useful questions and answers provided over time, I've decided to copy/paste the website comments to the forum - and "move" further discussions here.
These are the comments from the article:
Bicycle tyre sizing and dimension standards
This topic is closed for further replies.
If you can't find the answer to your question in this thread, please open a separate thread with your question/problem, in an appropriate forum section (this is the Wheels, hubs, rims and tyres section).
Relja
These are the comments from the article:
Bicycle tyre sizing and dimension standards
This topic is closed for further replies.
If you can't find the answer to your question in this thread, please open a separate thread with your question/problem, in an appropriate forum section (this is the Wheels, hubs, rims and tyres section).
Relja
- Gergely Toth
06/04/2016 at 18:43
Thank you, really!
BW from Hungary! -
gr8bkset
26/01/2018 at 19:14
I have a road bike and hybrid bike with front tire sizes 700×23 and 700×40. I want to get one wheel that can fit on both bikes (the wheel has an electric motor). I believe the road bike rim inner width is 15mm. Is it possible to fit a wheel with 17mm inner width on the road bike? Can the road brakes be adjusted to fit wider rim? Can i get brakes that will fit wider rim?
Relja
26/01/2018 at 22:55
Short answer: yes, no problems.
Brakes on a rim with a 2 mm more outer width need to go out by just 1 mm at each side.
There is a tendency for road bike rims (and tyres) to go wider. For both comfort and aerodynamics (wider tyres being more aero on wider rims, than narrower tyres).
Timmi
23/03/2020 at 19:25
Your image showing the cross-section of 2 tires mounted on 3 different rims at different pressures looks like it may contain many errors.
The same tire is shown as being wider and taller on a wider rim, than it is on a narrower one. Assuming all have 622 bead seat, how is this possible? What’s more, it appears taller and wider at 75psi than it does at 100psi on the same rim.
Relja
23/03/2020 at 20:38
It is counter intuitive, but yes, a tyre can get both wider and taller on a wider rim. Depending on rim’s inner width (bead seat width) and tyre’s width.
As for the rest – which cases in particular you think are problematic?
Timmi
20/04/2020 at 20:49
Most of them are problematic actually.
A 25mm GP4000@75psi is same height but wider than the same tire @100psi on the same Ardennes rim.
A 23mm GP4000@75psi is same height but wider than the same tire @100psi on the same Ardennes rim.
(the only 2 I’m not questioning is on the narrowest rim).
—————————————————————————–
PS: can you follow the link to my website that I entered ( Velo76.com ) – it will redirect you to my FB group, you can see me there as admin (Timm S…) and add me. I’d like to bring something else up with you – it might be more productive to do it in messenger than a reply every few months on here.
Relja
20/04/2020 at 21:12
Will do – though I reply almost daily on most comments here. Definitely not “every few months”.
As for the graph – GP4000@75 is mounted on a 20.7 mm inner rim width, while the 100 PSI graphs are made for 17.8 and 13.6 mm rim widths.
Wider rim makes tyre’s circumference effectively larger. That is the point. So it can be wider, while not being of lower height, even under a bit lower pressure.
Timmi
20/04/2020 at 21:18
I’d also like to raise the question of the TIRE VERSUS RIM WIDTHS in the table.
These types of tables can be very helpful, but I would like to give a word of caution about it. I’d like to illustrate my point with a personal experience, if you’ll just bear with me:
I went to slightly wider tires, up from my usual 23c-25c, to 28c, but didn’t change my wheels.
700x28C tires, mounted on 15mm inner width rims, at 80psi (this is the max for many affordable 28c tires, although a Continental can go much higher. The ones I had on that day were the Michelin Dynamic).
Cornering on asphalt, I could feel the back wobble as the tire tried was folding under the rim and redressing itself, ove and over, as it went over a very slightly uneven paved surface (just your usual city road). It would bend, then redress itself with rotation when the road dipped down slightly, then folded again. This felt very dangerous. Luckily it didn’t fold under completely, but had I gone a little bit faster, it surely could have.
So in this example, for a 15mm rim, 32c should be stricken off that line, and perhaps the 28C as well (80psi is the max on many 28c tires from Kenda to Michelin, so you can’t just say to up the pressure).
True, tire width and pressure depends on riding style and type of riding. A mountainbike, on dirt trails, can take much wider tires per rim width, than a road bike can. The MtB will slide on dirt surface, the road bike’s tires will grip and not slide, when cornering hard (unless you have very hard budget tires on the road bike).
I think you need to err on the side of safety here. And take off a at least 1 checkmark from the right on some of those “acceptable” tire sizes per rim widths. It won’t help a young enthusiast who likes to ride fast, and has an accident, slipping under a truck in a turn, because the tire flopped over, sending him into a high-speed slide (or off a cliff). It won’t help the more tame cyclist who is in an emergency situation and makes a sharp turn.
A 32c on a 15mm rim is definitely a no-no. 28C on the 15mm rim is debatable (sometimes safe, sometimes not as in my anecdote). In fact, the entire table could be shifted to the left, in order to be more accurate. I realize that some manufacturers will publish overly optimistic numbers, but that’s just because they want to sell more tires – and if they tell people to buy new wheels to get wider tires, they won’t be selling wider tires to folks who already have tires.
Relja
20/04/2020 at 21:33
I ran 28 mm Continental Grand Prix 4 seasons on 13.5 mm wide rims with no problems. At 5 to 6 bar pressure.
For all I know, the table is more on the conservative/safer side – at least in my experience.
It is also my experience that manufacturers are more often “too conservative”, than “too optimistic” – probably in order to avoid any law problems.
Your feedback is valuable to me – it certainly requires more looking into. However, it does not align with my own previous experience, nor with the experience of other riders I know. For the given table, I took info from Mavic (as a rim manufacturer) and Schwalbe (as a renowned tyre manufacturer) – using the more conservative option in cases of any mismatch – and making sure it does align with my own experience.
Paul
16/07/2020 at 16:58
I actually run Bontrager 28mm AW1 Front and 32mm H1 Rear on my 23mm rims very successfully for over 18 months now mostly road but some gravel paths too.
These are both off your chart on the left hand end of the scales.
These tyres were both ‘last in stock’ at my LBS at the time (hence different sizes) and sales assistant assured me it was ok and a good move from my 36mm Clement X’plore MSO chunkies provided with my gravel bike which made so much noise on the roads.
bertie
19/03/2021 at 16:20
What you describe is tyre squirm, and it’s common with wider tyres at low pressure on narrower rims. I use 28mm tyres (various types over the years – IME those Michelins cut very easily on gravel) on 13.5mm internal width MA40 rims at about 80 PSI and have never felt that a tyre was going to roll off the rim or dump me on the ground – maybe I just don’t corner fast enough. I also use oversized tyres on skinny MTB rims and at low off-road pressure they will squirm on tarmac, so I just take it easy or add some air. There is another form of squirm, that’s caused by the tread moving relative to the tyre carcass, but that’s usually only noticeable with soft sticky knobbly tyres.
Stu
22/04/2020 at 16:29
Hi, What size wheel do i need for a (58 – 559) 26 x 2.35 tyre and 7 speed.
Relja
22/04/2020 at 18:18
Rim diameter should be 559 mm ISO (26″), while the rim’s wall inner width should be at least 21 mm.
As for the 7 speed cassette – see this article:
https://bike.bikegremlin.com/1259/bicycle-rear-hub-compatibility/
Last edited: