Riding 25mm clincher tires on rims with a 21mm inner-width?

[slowpoke]

Have an older frame that cannot fit 28mm tires, so would need to ride on 25s.

Continental's ETRTO chart says this is okay: https://www.continental-tires.com/pr...rto-standards/

WTB's ETRTO chart says not suggested: https://www.wtb.com/pages/tire-rim-fit-chart#

What does the collective wisdom here think?

[gravelreformist]

I would have no problem with this. In fact I have a bike set up with this combination that works great. The GP5k TL's inflate to 27.1mm.

[Mark McM]

Actually, the WTB chart specifically states that it is not ETRTO, but WTB's own recommendations. The Continental chart is ETRTO. Also note that the current ETRTO chart is for both hooked and hookless rims. Previously, some wheel manufacturers recommended tire widths down to 23mm on (hooked) 21mm rims. As long as the tire and rim are manufactured to ETRTO specs, you should have no trouble with 25mm tires on 21mm rims.

[ridethecliche]

If 25 is going to be tight I'd check the width as measured before installation. They might be wider as the other poster suggested.

On wider rims like yours, you might get to 25 with a 23mm tire so I'd test fit some stuff if you have anything on hand now.

[NHAero]

I have 25mm GP5000 clinchers on 22mm inside dim. BTLOS hooked rims. At 80 psi they are just over 28mm wide. I run them at 70 psi these days (I'm 140 pounds +/-).

[slowpoke]

Originally Posted by Mark McM

Previously, some wheel manufacturers recommended tire widths down to 23mm on (hooked) 21mm rims. As long as the tire and rim are manufactured to ETRTO specs, you should have no trouble with 25mm tires on 21mm rims.

Oh interesting! Mark, how do I check if the rim was manufactured to ETRTO specs? They're made by HED.

Thanks for chiming in everyone.

[November Dave]

Originally Posted by slowpoke

Oh interesting! Mark, how do I check if the rim was manufactured to ETRTO specs? They're made by HED.

Thanks for chiming in everyone.

I've ridden tons and tons of miles on HED Belgium+ with 25mm Conti 4ks and 5ks.

[Mark McM]

Originally Posted by slowpoke

Oh interesting! Mark, how do I check if the rim was manufactured to ETRTO specs? They're made by HED.

If it is a 21mm internal width HED rim, then it must be one of the "Plus" models (such as Belgium Plus or Jet Plus) - you can contact them to confirm, but I'm pretty sure HED rims meet ETRTO When I mentioned that some rim manufacturers recommended tires down to 23mm on 21mm rims, that included HED. ETRTO recently changed their standard to specifiy a minimum tire width of 25mm on 21mm rims, so HED now recommends a minimum tire width of 25mm on "Plus" rims. But as mentioned previously, the reason ETRTO changed their tire/rim width standard was to account for hookless rims (they don't have separately hooked and hookless standards for tire/rim width) and all HED road rims have hooks.

[RoosterCogset]

With tubes or tubeless? Impacts the max recommended pressure you can use.

[Wunder]

I’ve used a labeled 23 (measured 25-26) GP5000 on 21mm internal HOOKED rims for years without issue. It may not be in the chart now but it certainly was five years ago.

[rice rocket]

Every car tire has a listed rim minimum and maximum for every size and every tire it makes and nobody has ever questioned it.

Not sure why everyone feels the manufacturer (often times the same company) doesn't know what it's doing when it comes to bicycles.

[AngryScientist]

Originally Posted by rice rocket

Every car tire has a listed rim minimum and maximum for every size and every tire it makes and nobody has ever questioned it.

.

yea right. Ever been to a car show?

[AngryScientist]

And to add to the pile, Velocity Quill rims are a hair over 21mm internal and there is absolutely no problem running a 25 on those, similar experience with Belgium+ rims from me. Many many miles like this.

Also, WTOs are even wider. Again, no problem with 25's.

[rice rocket]

Originally Posted by AngryScientist

yea right. Ever been to a car show?

Yes, you are free to do stupid things. Just be prepared to win stupid prizes.


Back to the original topic, if the manufacturer approved it, run it. Not all tires have the same construction, don't try to substitute one manufacturer's approval for another.

[RoosterCogset]

Originally Posted by rice rocket

Back to the original topic, if the manufacturer approved it, run it. Not all tires have the same construction, don't try to substitute one manufacturer's approval for another.

How does this work? Most wheel manufacturers aren't also tire manufacturers.