Tyre: Continetal GP 4 season 25mm
Tube: Continental Race 28 – 18-25mm
Rim: Stans Grail
95 PSI.

Bit of an odd one, this: the tyres were fitted last Thursday, and I did about 100km on Saturday without incident. This morning, I found that the rear tyre had blown off the rim, but the front was ok. My first thought was incorrect fitting (e.g. a pinched tube) but it’s curious that the tyre went a few days and a longish ride before letting go. My second thought was that if my track pump gauge under reads, that coupled with the recent warm weather (it gets hot in my garage) could’ve increased pressure enough to exceed the limit. The front tyre was inflated 10 PSI less and is unaffected.

Any thoughts?

Tyre bead is a little loose and when you inflate it the tyre doesn’t sit tight under the bead all the way around the rim on both sides. Deflate, reseat the tyre and inflate again. I’ve seen it a few times, including Saturday on a brand new Aksium tyre/wheel.

Once you notice it, all you can think is BANG!!!

Can Stans Grail’s take those kind of pressures? Stans Iron Cross specifically state no more than 60psi as I recall.

And wasn’t there a thing about their 340 rim being a bit liable for shedding tyres at high pressure as well?

Can Stans Grail’s take those kind of pressures? Stans Iron Cross specifically state no more than 60psi as I recall.

100psi limit for a 28mm tyre, so mine should’ve been fine.

Tyre bead is a little loose and when you inflate it the tyre doesn’t sit tight under the bead all the way around the rim on both sides. Deflate, reseat the tyre and inflate again. I’ve seen it a few times, including Saturday on a brand new Aksium tyre/wheel.

What do you mean by “under the bead”? Deflating has already taken place courtesy of the tube going bang!

100psi limit

how accurate is your pressure gauge? I would expect a bit if margin but they can’t rate for every rim combo.

Can Stans Grail’s take those kind of pressures? Stans Iron Cross specifically state no more than 60psi as I recall.

Max pressures with tubes: 116psi (23mm tire with tube), 100psi (28mm tire with tube)

From stans website

how accurate is your pressure gauge? I would expect a bit if margin but they can’t rate for every rim combo.

I wondered about that but the previous tyres (Michelin pro 4) were inflated to the same pressure without problems – probably did about 500 miles on them on these rims, only changing because they were worn out.

Deflating has already taken place courtesy of the tube going bang!

I didn’t read that it had gone bang, only that the bead had lifted. I’ve dislodged some beads from rims during inflation (at up to 100 psi), them let the air out, reseated the tyre and reinflated with no problem. Some tyre rim combinations can be loose. I could imagine riding might also have the same effect for a barely seated rim. I was surprised at the (brand new) Mavic combo doing that on Saturday (was helping a new rider in a pub car park after my lunch).