Firstly, sorry about the stupid title. Is that classed at clickbait

Right, stupid question of the day!! I have a Halo carbon rear rim/wheel. Was used in its previous life as my 650b wheel on the (sub standard, in my case, yours may be positive exp) Sonder. Now, money is rather tight and the sheds are a, mind my language, a sh*t-show.

So, the outer rim width is 35mm (will get the tyre off shortly and measure) and it was saved for little ones bike when I eventually built his big-boy bike. I am already living on the limits of compatibility as I mounted a 2.4 tyre to it. It being a 35mm outer width carbon rim.

now, in plain english if the above is a bit muddled.

Q. Is adding a 2.1 tyre to a 28mm inyernal rim width, rather very very stupid. Especially as I'm gonna be using it tubeless!?

For reference, it's a rear tyre and the 2.4 (to be fair it was a DH type tyre so super strong/stiff) was already a bit tight getting on.

It's fine

Shaf, look up ETRTO for min and max tyre widths for any rim size. Here's WTB's take on it https://www.wtb.com/pages/tyre-rim-fit-chart

whitestone wrote: ↑Tue Jun 03, 2025 1:02 pm Shaf, look up ETRTO for min and max tyre widths for any rim size. Here's WTB's take on it https://www.wtb.com/pages/tyre-rim-fit-chart

That's the thing Bob. Technically it's not advised on most of the tyre/rim charts I've seen. But I reckon I'll be able to mount it, just that the profile will be more square than rounded!

Obviously it's gonna be a tight fit and I did look at transferring the spokes/hub over to another rim. But that's equally as wide and I'm trying to get him riding ASAP

I'm hovering somewhere here. Obviously I could go for a 2.2 but then it will most definitely not be too safe due to very tight clearance and the chainstay/seatstay inners. I remember James explaining once that it's not advised running as tight tolerances as some people do as it can sometimes be detrimental if the wrong stones catches in the right place.

Dot = compatible on that chart and you're closer to the "optimal" than "incompatible". It'll be fine.

atk wrote: ↑Tue Jun 03, 2025 2:22 pm Dot = compatible on that chart and you're closer to the "optimal" than "incompatible". It'll be fine.

Aha, and yes. Why didn't I notice that that means I might even be able to look for 2.0 x 27.5. Thanks very much.

A couple of decades ago that would be seen as a wide rim, we didn't die

V true. They were obviously classed as fat bike rims back then right? I had em as 650b.