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bicster

Joined:

Dec 04

Posts: 116

bicster says:

Rapid tyre deflation

Bit of a strange problem, was riding on the M54 tonight and the front tyre on my 2008 ZX-10R went flat really quickly, struggled over to the hard shoulder and got recovered back home.  I expected to find something hanging out of the tyre but nothing, got the foot pump out and re-inflated the tyre and it has no leaks at all, bearing in mind it went down on the motorway very rapidly.  Ive pumped it up to 50 psi and still no leaks from the tyre or valve, I havent got a clue whats caused this very worrying problem and any advice would be greatly appreciated

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  • Posted 5 years ago (04 September 2010 23:55)

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jaffa90

Joined:

Mar 09

Posts: 8936

jaffa90 says:

puncture

Have you used soap bubbles over the tyre surface?The safest way is to remove the tyre to find out where it`s punctured by compressing it to open up the hole/slit.

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bicster

Joined:

Dec 04

Posts: 116

bicster says:

Cheers

Cheers guys, its just bugging the hell out of me cos it went flat so quickly (more like a blow out) but ive pumped it back up, wiggled the valve and the sodding thing isnt leaking anywhere, cant see any damage to the rim, tyre or the sidewall of the tyre, it really is a bloody mystery.  At the rate that it went flat I wouldnt be able to pump it back up as it lost pressure so damn fast, I cant work out for the life of me why the thing is holding its pressure now

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bicster

Joined:

Dec 04

Posts: 116

bicster says:

Possible cause?

I think after much head scratching that the problem is the valve, it went down during a high speed run on the motorway and I had new valve caps fitted, the old caps had rubber seals that would stop air escaping in the event of a valve core problem.  When ive had my tyres replaced they have never fitted new valves which is a bit naughty so maybe they are worn.  Im thinking that the centrifugal forces on the valve during a high speed blip could be causing the valve to dump the air out and then when the bike is stopped the forces arent there and there is no leak.  Think ill invest in some metal bolt in right angle valves so the forces cant push the valve open, got to be better than the rubber things on there at the moment.  Would be great to hear of any more suggestions as id like to get to the bottom of this cos its done nothing for my confidence in my bike, if id have had to negotiate a corner id have been buggered so thank god it happened in a straight line on a quiet motorway

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SlowLearner

Joined:

Feb 10

Posts: 1953

SlowLearner says:

bicester:

I'm afraid Mike and Jaffa might have missed the point - it's not going back down again despite being re-inflated.  He's not trying to find the leak - there's no leak to look for now, the cause of the deflation has gone away.


Sounds to me more like an intermittent valve problem than anything else, particularly if they didn't get replaced with the last change.  I'd suggest changing the whole tyre, bite the bullet - then complain and maybe you'll get your money back, maybe not.  But at least you're not worrying about a front tyre going flat while doing the necessary worrying about everything else during transit.

And stop penny-pinching on the tyre/valve thing (and all other vital points) on the bike, eh?  :wink:

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bicster

Joined:

Dec 04

Posts: 116

bicster says:

Thank you

Cheers SlowLearner, im going to remove both wheels today and get a new front tyre plus new valves on both wheels.  Ill get the front wheel checked too for any faults.  I really should have said something when the tyres have been changed and new valves havent been fitted.  Im one very lucky chap to still be in one piece.  Thank you for your advice mate

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SlowLearner

Joined:

Feb 10

Posts: 1953

SlowLearner says:

bicester:

Good move, mate.  So the back one was the same deal, and you're not taking any chances - very wise.  I'm very glad to have been of any help, and if nothing happens, you'll never know how much trouble you saved yourself by taking this precaution!

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Dabbsy

Joined:

Aug 02

Posts: 498

Dabbsy says:

Valve cap

Dunlop always recommends changing the valve whenever new tyres are fitted. Valve springs can weaken with age. Old valve rubber can perish and, like tyres can also be affected by solvents/polishes.
Valves are almost universally replaced when you have new car tyres fitted but it still doesn't appear to be the case with motorcycle tyre replacement.
Dunlop recommend that steel valve caps with rubber o-rings are used. At a push you can use plastic caps with o-rings. But under no circumstances should valve caps without o-rings be fitted, they're your last line of defence against leaking air. They also advise that aluminium caps aren't fitted - they can corrode to the
steel valve stem and are then a real pain to get off.
I hope this helps,


Chris

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bbstrikesagain

Joined:

Nov 08

Posts: 879

Yes...

Dunlop always recommends changing the valve whenever new tyres are fitted.

...so why don't fitters and dealers suggest it?  Surely it'd be more profit they could tap in to.

If you're changing tyres once or twice a year then changing the valves every time does seem like overkill.  Discrete (light and less likely to be nicked) stainless steel caps with O rings are a must though.

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Dabbsy

Joined:

Aug 02

Posts: 498

Dabbsy says:

..so why don't fitters and dealers suggest it?

Probably because they are lazy or don't think they can charge.....

I still stand by regular valve changes, Bicster was lucky, and I'd rather not have to deal with the aftermath of an expensive crash for the sake of a 50p (or less) valve. Or am I being a nanny-state apologist:winkie:

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robsot

Joined:

Feb 10

Posts: 871

robsot says:

tyre deflation

my bandit was doing this wen i took it over 120mph, tyre just went flat instantly..i was as confused as you.. i ogt some sealing gel put in my tyre.. its been fine ever since, these people saying that it is ulikely to leak from the bead could be worng mate, dont rule it out

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