The valve keeps pulling out of the tube on my front wheel after about half an hour of riding every time I go out. I've tried various makes of tubes and recently replaced the rim tape after I noticed the original fabric tape had shrunk and was partly obscuring the hole where the valve goes through, which made no difference. There's no damage to the rim

The rim is a Mavic XC717 and has the little plastic insert still in place and the tyre is a Bonty ACX. The back wheel is the same set-up, and is fine.

Help, its driving me crazy and costing a fortune!

How old is the tyre? Sounds very much like the bead has stretched.

By the way, who built your wheels? The two spokes that are visible look like they're running a good few mm difference between them. Not that it's relevant to your original question.

had a similar issue a while back. my tyre was slippin on rim. if it's not an old tyre as ^ then take it off and clean the rim and tyre and it should be sweet

I have to admit I can get the tyre on and off without levers.

The wheels were built by Dave Hinde – I know! I know!

What would the bead stretching do?

I had this on the downhill bike when breaking really hard on tatmac at the end of the run,upped the pressure a bit and no probs since,was suggested using the other type of valves would help also

stretching/worn. Just above the bead there are usually little "bars" that grip the rim when pressurised by the tube. Withiout these, the tyre can spin on the rim. To be honest, I've normally only seen it on the rear wheel.

bead stretches, tyre doesn't grip rim so well & slips round, taking the tube with it if they're sticking together

stuff a load of talc inside the tyre or (better) get a new tyre

I used to get this on the rear wheel with an ancient Panaracer Smoke – it too was a floppy fit and I was running it pretty low pressure. Seemed to stop when I upped the pressure and I've never had the problem on newer tyres.

apply some talc to the tube, stops it rotating with the tyre.

My Jones ACX is really tight to get on and off, its a 2.1. My mate has the 2.3's and they literally fall off his rims so I'm guessing you have the 2.3's?

Cheers guys. I was thinking of replacing the Bonty's so this has made my mind up!

Spooky – they are 2.2's