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Discussion Starter #1
OK - so we all know that when you run low pressures without a security bolt you stand a chance of ripping the valve off the tube as the wheel spins within the tyre.

So ............ I have a security bolt in my back wheel - and it's tight and correctly fitted, but after the Wales weekend my valve has ended up like this



Now to me .............. the valve is angled the wrong for this to be wheel spin in the tyre . .. .. or am I wrong?

Can anyone explain which way the valve would be angled with normal wheel slip within the tyre.

Does the tube stay with they tyre? Must do eh? So surely mine is the wrong way innit?

Not that it matters - new tube and tyre going on as we speak ready for the Cambrian in 2 weeks time :D
 

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no its the right way i think - the wheel has moved slightly inside the tyre (the chain has pulled the wheel round whilst the tyre has stayed in place) - bit more pressure should help and or tighter tyre clamp - what pressure were you running
 

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I think it looks right too. The wheel rim has rotated clockwise (as shown in the photo) further than the tube and tyre.
 

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Is the clamp wiiiide enough to reach the tyre in order to clamp it?

If i remember rightly,i ran 30psi last weekend and had a thorn puncture and another front puncture on the way home which i think happened during the faster/hard ride home where the tube looked 'rubbed'. Dunno how much pressure was in the tyre after the first puncture tho,just hard enough i guess.
 

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Discussion Starter #5
I think it looks right too. The wheel rim has rotated clockwise (as shown in the photo) further than the tube and tyre.
it just doesn't look right - I expected it to lean the other way ...........
 

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What rimlock have you got in there? (also, what rim?)

(FWIW, the tyre can slip either way - under braking or acceleration - but that one there looks to have moved under acceleration)
 

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it just doesn't look right - I expected it to lean the other way ...........
Point at the screen and move your finger in the direction the wheel turns(clockwise),now look at which side the valve core hole on the rim pushes on the core itself if the tyre stays put. I'm sure you already know this anyway.

Anyways,fun time with Timpo etc? Was Loz there? what are they riding these days? I really should get myself on rideouts with them again since they're a great group of guys who i went to Portugal with a few years back.
 

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Discussion Starter #8
What rimlock have you got in there? (also, what rim?)

(FWIW, the tyre can slip either way - under braking or acceleration - but that one there looks to have moved under acceleration)
it's an exel rim with their own (supplied by them) rim lock.

I was running 25psi ........... the rim lock is tight - but I suspect when i fitted the tyre i didn't quite have the valve aligned correctly . . . . but it certainly wasn't this far out and has without a doubt moved.
 

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Point ........

Anyways,fun time with Timpo etc? Was Loz there? what are they riding these days? I really should get myself on rideouts with them again since they're a great group of guys who i went to Portugal with a few years back.
check your PM box mate;)
 

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it just doesn't look right - I expected it to lean the other way ...........
Yours has moved under acceleration. If the valve was angled in the opposite direction then it would have been caused by braking. This is a big problem offroad when using the back brake hard on steep descents.
 

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I've just fitted a second rim lock on the rear of my 690 for the same reason, it took 1oz to balance the wheel to the previous 9oz with one rimlock.
 

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Shep,
Yes, it's moved under acceleration. Check the rimlock for correct size.

Blue,
Timpo was out on the 650XChallenge, I was out on the 400exc, Loz and Shep didn't make it. . . . it was another crackin do.
 

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Shep,

That might just be the soft tyre massaging the inner tube round the tyre as it rotates.
Put tippex on the tyre and rim to see if it moves next time.
Ditch the "steel" dust caps and put "plastic" ones on, They rip off if the tube goes inside the tyre. Gets you out of a sticky situation.

D
 

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Blue,
Timpo was out on the 650XChallenge, I was out on the 400exc, Loz and Shep didn't make it. . . . it was another crackin do.
Cheers,400exc is a cracking bike.
 

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Shep,

That might just be the soft tyre massaging the inner tube round the tyre as it rotates.
Put tippex on the tyre and rim to see if it moves next time.
Ditch the "steel" dust caps and put "plastic" ones on, They rip off if the tube goes inside the tyre. Gets you out of a sticky situation.

D
X2 Wot he said.

You will need that metal cap if you have a puncture as it has a valve key on it. Put it on your spare tube for safe keeping or tape it onto the bike somewhere, replace with a plastic one. Also remove the hexagon nut, then if the tube wants to creep it can, ripping off the plastic cap. Valves will pull all the way through the rim hole if necessary without ripping the valve out. With the hex nut on you have far less available creep before it rips out. Next time you have the tyre off, using a round file held at an angle, you could chamfer either side of the valves hole on the tube side to make creeping easier.
 

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Discussion Starter #16
OK - so i took the tube out, refitted it with the valve straight - tightened my rim lock as much as I could and then drew 2 lines using tyre crayon stuff.

The lines went across the rim and the tyre so i could see if the rim moved in relation to the tyre.

After completing the Cambrian Rally the two lines are still perfectly aligned - no movement - but the tube valve is once again at a severe angle to the rim.

I am guessing this means the tube has 'walked' around inside the tyre - I know for sure the tyre and rim have not moved (the 2 lines).

Why's this happening then?

I was running 20psi all weekend - and yes at times I did get a bit throttle happy ..... :D

Although i had a total of 3 punctures throughout the rally - these were all fronts so the angle of the valve never caused me a problem ........ it's just annoying me when i look at it :rolleyes:
 

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Interesting!
I wonder if you put talc or something similar in the tyre?
IMHO, as the wheel rotates, the depression in the tyre caused by the pressure from the ground chases the inner tube anticlockwise (as shown in your photo). And I recon that talc and low pressure increases the amount of this movement of the tube.
I'm speculating here, but maybe if the tube is allowed to stay gripped to the inside of the tyre, it might not creep round.
I'm sure some one else will come along now with thier theory.
Good luck Shep
 
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