Got a 29er Stans Flow rim in the post today and upon inspection it says on the rim that the maximum tyre pressure is 38psi for 2.3″ tyres and 40psi for 2.0″ tyres? I’ll be running 2″-2.55″ offroad tyres.

Is this normal for Stans rims and do people run them any higher than that with no problems?

I’ll be using tubes, not tubeless and those max pressures should be fine for offroad but these wheels will be going on my Salsa Fargo which will often also be run with 700x42c slicks and i’d be using more than 40psi on the road? I assume i could run slightly higher pressure in the narrower tyre but their website only gives details of the 2 tyre sizes stated above?

If this to do with their ‘Bead Socket Technology’?

So, as usual for STW – will i die???

You might have issues tubeless, tubed I suspect will be alright.

Narrower tyres can be run with higher pressures. There was a thread about it a while ago, essentially they exert less force on the rim for a given pressure. For my XM719s Mavic give limits of 113psi for 1″ tyres and 48psi for 2.3″ tyres. You could try contacting Stans, but you might get a jobsworth response.

You can definitely run higher pressures, but I haven’t a clue what the limits might be.

I imagine the max pressures are to do with the shorter shoulders on the rim. They want to be sure that any loose tyres aren’t going to pop off.
The other possibility is that the side walls are weaker – they are very light so the material must come off somewhere, although I would think shorter rim sholders + thinner side walls = just as strong, but don’t quote me on that!
Tubeless vs tubed shouldn’t make any difference though.

On a 42mm tyre you’d probably want to run about 45psi anyway since it’s still v-wide compared to normal road tyres. I have 42mm on my pashley sovereign and anything higher than 45psi rattles you to death on anything other that the newest smoothest Tarmac. And I’m 12.5st The bike weights 50lb (yes realy) and have a big fat saddle bag loaded on the rear rack so can’t see why you’d run them higher.

Tubeless vs tubed shouldn’t make any difference though.

It might. If the pressure restriction is due to a danger of blowing the tyre off the rim rather than damaging the rim. With a tube, the inside of the tyre would be pressed into the bead socket.Tubeless the air will try to get in between the tyre and socket, effectively weakening the joint.

On the stans website, they say that when running tubes, the limiting factor is the pressure stated by the tyre manufacturer.

HTH

I also run some Alex rims converted to tubeless with strips and Specialized Borough tyres (32 mm) at 60 psi. Have done for a while now with no issues.

Cheers folks. Looks like i’ll live then. 🙂

Onzadog – that is reassuring, thank you. Thought it would be the case but always worth checking