Cycling UK Forum

ANTONISH wrote: ↑29 Oct 2024, 4:40pm I find that beginners (apologies if you're not) sometimes tighten the locknut on the valve onto the rim before fitting the tyre - I usually dispose of the locknut.
I usually put a little air into the tube before fitting.
Once you have managed to fit the tube into the tyre and got the tyre into the rim, try pushing the valve into the tyre so that the tyre isn't seated on top of it.
Inflate the tube partially and go round the tyre to ensure that the tube is not trapped anywhere.
At this stage you should be able to inflate the tyre fully.

I once had a faulty Continental tube that had excessive wall thickness in one section which gave the impression that the tube was trapped.

I presume your rims aren't tubeless ready ?

AndyK wrote: ↑29 Oct 2024, 4:37pm At the risk of starting a religious war...

A question:

When you start to put the tyre back onto the rim, do you start near the valve hole, or at the opposite side of the wheel from the valve hole?

And an experiment to try:

While the tube is deflated, try shifting the tyre around the rim a bit. (E.g. if you've started with the word "Pirelli" close to the valve hole and the valve hole is at the 12 o-clock position, slide the tyre round until the word "Pirelli" is at 3 o'clock.) Careful not to ruck up the inner tube while you do it. Then re-inflate.

If the unseated section is still at the valve, it's a problem with the valve or the inner tube or the way you're putting the tyre on. If the unseated section has moved with the tyre, maybe it's a problem with the tyre.

ANTONISH wrote: ↑29 Oct 2024, 4:40pm I find that beginners (apologies if you're not) sometimes tighten the locknut on the valve onto the rim before fitting the tyre - I usually dispose of the locknut.
I usually put a little air into the tube before fitting.
Once you have managed to fit the tube into the tyre and got the tyre into the rim, try pushing the valve into the tyre so that the tyre isn't seated on top of it.
Inflate the tube partially and go round the tyre to ensure that the tube is not trapped anywhere.
At this stage you should be able to inflate the tyre fully.

I once had a faulty Continental tube that had excessive wall thickness in one section which gave the impression that the tube was trapped.

I presume your rims aren't tubeless ready ?

Cycling Oldie wrote: ↑29 Oct 2024, 4:05pm Went out today and got an impact puncture, fine and dandy stopped and put a tube in only to find it felt odd. Got home and discovered the tyre is not seating properly where the valve is. It's a Pirelli PZero 700x28c and the tube I had with me is a 700x20-28. The valve is only 40mm and I should have a 60mm valve but that shouldn't matter with the seating. I've tried deflating and pushing the tube further into the tyre then pulling down but it's still doing it. Driving me nuts. Any ideas?

rjb wrote: ↑29 Oct 2024, 4:51pm I've a tyre that not seating properly. I've tried it on a different rim and it seats fine. Does this mean I need to build the seating area up on the original rim with an extra layer of tape. BTW These are normal rims not tubeless.

531colin wrote: ↑29 Oct 2024, 6:25pm As above....if you have got a hump, the tyre is too big so an extra layer of tape over the bead seat can fix the fit.
If you get a dip, the tyre is too tight.

Cycling Oldie wrote: ↑29 Oct 2024, 5:21pm They are tubeless ready and I'm considering it given this bloody hassle. Shouldn't cost any more than around £70?

rareposter wrote: ↑29 Oct 2024, 6:34pm

531colin wrote: ↑29 Oct 2024, 6:25pm As above....if you have got a hump, the tyre is too big so an extra layer of tape over the bead seat can fix the fit.
If you get a dip, the tyre is too tight.

From the OP's other recent posts, it's a new(ish) Ribble Endurance with Mavic Ksyrium wheels, I believe about 30mm deep so a 40mm valve is probably pushing it for correct placement and inflation, you'd really need a 60mm valve.

But the tyres should be pretty new and good condition I'd have thought, they were obviously fitting fine at the point of purchase!

Cycling Oldie wrote: ↑29 Oct 2024, 5:21pm They are tubeless ready and I'm considering it given this bloody hassle. Shouldn't cost any more than around £70?

If the tyres and rims are tubeless ready, go for it. You'll need tubeless valves (may even have been included with the bike?) and some sealant. It pretty much eliminates pinch flats unless they're so severe that they ding the rim too.