28mm tyres on a 13mm rim??

[bgnukem]

Well the tyre widths looks fairly conservative for the two narrowest rim widths (13, 15mm) but what happens with the 17C rim?? Suddenly the tyre width increases by 20mm. It's the sort of mis-match I've only seen on early mountain bikes.

Makes for a highly stressed rim (angle between tyre sidewall and rim sidewall) and more likelihood of worn rims blowing apart.

[tim-b]

Hi
The newer standards seem to look more at narrower tyres on wider rims, the wider tyres sizes haven't changed too much. The big change has been tyre pressures that are now specced where X marks the spot on the charts reproduced above. It's also about tubeless rims now
Regards
tim-b

[The utility cyclist]

Well the tyre widths looks fairly conservative for the two narrowest rim widths (13, 15mm) but what happens with the 17C rim?? Suddenly the tyre width increases by 20mm. It's the sort of mis-match I've only seen on early mountain bikes.

Makes for a highly stressed rim (angle between tyre sidewall and rim sidewall) and more likelihood of worn rims blowing apart.

Specialized fitted as standard a 42mm folding tyre on their top spec Globe Pro ladies, I think there were other models with this width, some were 37mm, the 'Globe' rim is only 16mm, the misses has been riding with that set up since 2008.
Surely with the wider tyres the pressures are lower so the stresses on a rim are less in any case aren't they?

[Brucey]

IIRC spesh supplied their own tyres with most of their bikes, so were free to

a) engineer the rim/tyre combination so that the tyre wasn't going to blow off the rim
b) limit the load/pressure pressure rating written on the tyre accordingly

To take that example and infer that all such ostensibly 'similar' combinations are therefore 'safe' is somewhat flawed logic. There are a few bike and/or wheel manufacturers that also 'tyre manufacturers' and they are free to develop their own recommended fitments. For everyone (and everything) else a different set of rules apply.

Best to stick to ETRTO recommendations and in addition to that obey the tyre or rim's maximum pressure ratings, whichever is the lower. Very many rims have different maximum tyre pressure recommendations depending on the tyre width; depending on the combination, either the rim or the tyre can limit the pressure that can be safely used.

cheers

[bgnukem]

Surely with the wider tyres the pressures are lower so the stresses on a rim are less in any case aren't they?

Swings and roundabouts..... Lower pressure but worse angle of loading, plus sometimes it's necessary to increase the pressure above what might be optimal for the wider tyre to stop it flopping sideways when cornering, when using a narrow rim.

E.g. I use 32mm tyres on 13mm (internal) rims and need 80-85psi to stop the tyre laterally flexing too much in corners, I'm 80kg so not that heavy.

I have some 17mm (internal) rims for the rebuild when the time comes....

[The utility cyclist]

Surely with the wider tyres the pressures are lower so the stresses on a rim are less in any case aren't they?

Swings and roundabouts..... Lower pressure but worse angle of loading, plus sometimes it's necessary to increase the pressure above what might be optimal for the wider tyre to stop it flopping sideways when cornering, when using a narrow rim.

E.g. I use 32mm tyres on 13mm (internal) rims and need 80-85psi to stop the tyre laterally flexing too much in corners, I'm 80kg so not that heavy.

I have some 17mm (internal) rims for the rebuild when the time comes....

I'm 95-97kg and even with 15-20kg load I'd never have more than 80psi in a 32mm on my narrow rims. I can't fathom why you'd need such a high pressure for your overall weight I've often cycled to work + loaded bag and found after being a bit lazy that I only had 60psi in the back and not had the issues you mention, I'm not exactly a slow rider around rbts/corners either.
Sounds to me like you're putting undue pressure on your narrow rims and a rock hard ride not that putting 80psi seems to be an issue on what is a near 30 year old rim with most the ceramic coating missing.

[Brucey]

I'm 95-97kg and even with 15-20kg load I'd never have more than 80psi in a 32mm on my narrow rims. I can't fathom why you'd need such a high pressure for your overall weight …

The sensation of the tyre flopping around on the rim is both revolting and (for several reasons) unsafe too, on the road. That this doesn't seem to worry you is irrelevant; some people like different colours to others too.... Not a good way of addressing a safety issue....?

FWIW when I've used a 32mm (actual width) tyre on a 13mm internal width rim, at lower load, on the road, I need at least 70psi in the tyre else it flops around too much. Over 80psi I think the stress on the rim is too much, but this is not explicitly forbidden by either the tyre or the rim. What is likely to protect other people trying to use this combination is that it is forbidden by ETRTO.

... not that putting 80psi seems to be an issue on what is a near 30 year old rim with most the ceramic coating missing.

the coating does not contribute noticeably to the strength of the rim; it is pretty much irrelevant unless it is all gone and so is the metal beneath.

There is a big difference between what folk appear to have get away with somehow, so far, and what is demonstrably safe and can be recommended to others.

cheers

[tim-b]

Hi
ETRTO recommendations were sensibly conservative rather than forbidden. Manufacturers have tested 15mm rims with tyre widths ranging from 20 to 35mm while the ETRTO recommend 22mm to 32mm
The newer ETRTO standards are likely to be wider ranging than the current standard, BUT, 15mm is the lowest rim width that the manufacturers have published that I've seen, generally they're tubeless rims and they now include a max pressure for the tyre/rim combination (assuming that the tyre/rim will take that pressure)
Regards
tim-b

[gxaustin]

10 years of running a 32mm n the rear of my commuter says absolutely no problem whatsoever, the rim is an Open 4 ceramic, also run a 32mm on an Open Pro. Zero squirm even at speed/heavy loads around corners. That's me at 95-97kg + loads up to 25kg.
28mm is equally as fine as this is the front set up on both the commuter and the audax/tourer/winter racer.

That's interesting - maybe I should have persevered?

I tried 28mm tyres on my Open Pros and didn't like the feel when cornering at speed. Pumping them up harder seems to defeat some of the benefits of a wider tyre doesn't it?

I went back to 25mm at 85psi.

[The utility cyclist]

I'm 95-97kg and even with 15-20kg load I'd never have more than 80psi in a 32mm on my narrow rims. I can't fathom why you'd need such a high pressure for your overall weight …

The sensation of the tyre flopping around on the rim is both revolting and (for several reasons) unsafe too, on the road. That this doesn't seem to worry you is irrelevant; some people like different colours to others too.... Not a good way of addressing a safety issue....?

FWIW when I've used a 32mm (actual width) tyre on a 13mm internal width rim, at lower load, on the road, I need at least 70psi in the tyre else it flops around too much. Over 80psi I think the stress on the rim is too much, but this is not explicitly forbidden by either the tyre or the rim. What is likely to protect other people trying to use this combination is that it is forbidden by ETRTO.

... not that putting 80psi seems to be an issue on what is a near 30 year old rim with most the ceramic coating missing.

the coating does not contribute noticeably to the strength of the rim; it is pretty much irrelevant unless it is all gone and so is the metal beneath.

There is a big difference between what folk appear to have get away with somehow, so far, and what is demonstrably safe and can be recommended to others.

cheers

It doesn't flop at that pressure at all and certainly isn't dangerous, your anecdote doesn't counteract my real world experience over a long period of time, But tell us when was the last time you rode a 13mm internal with a 32mm tyre at that pressure and was able to take turns/corner at 20mph, I'm guessing never?

Over 10 years with a 32mm rear tyre on the commuter, I've even had another person on board and pumped up even higher for short periods. And I never said the coating had anything to do with the strength, merely that the coating was long gone thus the surface underneath was exposed to continual braking, and that's on a rim circa 30 years old, has had a lot of heavy use and still no sign of the supposed dangers of stress from the 80psi I put in the tyre.

People like yourself seem to find danger/worry in everything, remember when you started making out having a single pannier on one side was a danger because that one time someone had a failure that you didn't actually have evidence that's what it was, your continual bashing of carbon fibre with no numbers for failure rates and so on.

[The utility cyclist]

10 years of running a 32mm n the rear of my commuter says absolutely no problem whatsoever, the rim is an Open 4 ceramic, also run a 32mm on an Open Pro. Zero squirm even at speed/heavy loads around corners. That's me at 95-97kg + loads up to 25kg.
28mm is equally as fine as this is the front set up on both the commuter and the audax/tourer/winter racer.

That's interesting - maybe I should have persevered?

I tried 28mm tyres on my Open Pros and didn't like the feel when cornering at speed. Pumping them up harder seems to defeat some of the benefits of a wider tyre doesn't it?

I went back to 25mm at 85psi.

I don't particularly ride for comfort but for my load 80psi isn't very high for the size of the tyre, that's what a decent saddle is for, for my weight/load, 80psi is about where it's at for the rear without too much deflection of the tyre, currently it's a Vittoria Voyager Hyper (I only run the 32 on the back), previously it was 32mm 120tpi Specialized Borough Pro folders. When I got the bike some 11.5 years ago I put on 25mm Gatorskin, they were a bit rubbish for no benefit in puncture protection and worse than the 23mm Rubino pros I used to commute/tour on in the early 00s onward.

I put a lot of miles in on that bike when I first got it so persevered with the gators but they were bang average and not an improvement on the 23mm Vittoria Rubin Pros I used to commute/tour/audax on.
Instead of buying more narrow tyres and because I'd got another race bike with skinny tubs I put the Borough's back on and so impressed with them that I bought another 4 NOS that I found on ebay, now down to my last one, currently a 32mm Vitt Voyager Hyper will have to do for the time being on the back (saving the Borough for my other bike) but it's the same assured feel going round corners at speed.

Maybe others report differently, possibly wheels, bike, rider confidence/ability/type of riding differentials, but I can honestly say having the 32 on the back and absolutely ragging the bike, in excess of 40mph at times and daily I hit 30mph on the way to work plus mid 30s n the back road a couple of times a week.

[djnotts]

Pretty sure that when mtb tyres first started getting popular in c. 2" and above the rim manfrs, especially Mavic, suddenly dropped stating max tyre sizes until they started making wider rims! I've never even thought about rim width relative to tyres, mtb or road, and surprise surprise never (ok, yet) had any problems. And thats at least 100 bikes of many ages/types with lots of swopping and altering over last 20 years or so.
If they'll fit and inflate without blowing off the rim, that's all I require.

[bgnukem]

I'm 95-97kg and even with 15-20kg load I'd never have more than 80psi in a 32mm on my narrow rims. I can't fathom why you'd need such a high pressure for your overall weight I've often cycled to work + loaded bag and found after being a bit lazy that I only had 60psi in the back and not had the issues you mention, I'm not exactly a slow rider around rbts/corners either.
Sounds to me like you're putting undue pressure on your narrow rims and a rock hard ride not that putting 80psi seems to be an issue on what is a near 30 year old rim with most the ceramic coating missing.

Just based on experience, ride feels sluggish at lower pressures. I've gradually reduced to 76psi front / 82 rear but that's as far as I'm going. The Paselas are thin-walled tyres and there's a lot of curvature in the sidewalls with the narrow rims so I reckon excessive sidewall deformation at lower pressures makes for a slow ride.

I fitted some 32mm Panaracers to my new build bike last night, with Kinlin rims around 20-21mm internal width and they felt a lot stiffer at just 70psi so I expect to be able to use lower pressures on my winter bike with the new 17mm width rims when the wheels get rebuilt. Also will be less stressful worrying about premature rim sidewall blowouts as I've had a couple of those in the last few years....

[Brucey]

It doesn't flop at that pressure at all and certainly isn't dangerous, your anecdote doesn't counteract my real world experience over a long period of time, But tell us when was the last time you rode a 13mm internal with a 32mm tyre at that pressure and was able to take turns/corner at 20mph, I'm guessing never?.....

try every day for the last fifteen years. Duh.

[SimonCelsa]

After suffering a snakebite puncture this Sunday on the continental 25's I thought I'd change to bigger rubber earlier. Fitted some 32mm Schwalbe Marathon 'original greenguards' (the 32mm version were £8 each cheaper than the 28mm variety for some obscure reason).

Pumped them up good and hard and they haven't popped off the rims yet, will slowly reduce the pressures over the next few weeks and see when they start to feel a bit dodgy! They have the dyno track so will be good for when the days start getting shorter. Cheers.