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Mark.S · Post by **Mark.S** » 17 Jun 2012, 19:59

I was out green laning today and got, what i thought was a puncture, but when i got the tyre off the whole valve had been ripped out of the tube. When i got the bike a few months back it had a flat tyre which again turned out to be the valve ripped out.

I know this isn't a CRM thing, just wandered if i'm doing something wrong?

Some one suggested to leave the valve nut off/loose, does anyone do that?

Any hel would be much appreciated.

Cheers
Mark

Post by **knackeredMk1** » 17 Jun 2012, 20:01

You need to have a rim lock and run at 13-15psi rear and ~15psi front.

Mark.S · Post by **Mark.S** » 17 Jun 2012, 20:10

Sorry, should have said , it has got a rim lock and the pressure in the rear was 15psi

Post by **Eddie Evans** » 17 Jun 2012, 20:33

2 things that might have happened.
You had a puncture the tyre went flat. The tyre then span on the rim ripping the valve stem free from the tube.
The rim lock will not stop a completely flat tyre spinning.

The other reason is that rim lock was not holding the tyre. This might be because it is damaged/broken. It should be tightened at the pressure you run your tyre at. If you run it at 13psi then tighten the rim lock after you have set the pressure.
I always screw the valve stem nut up against the valve cap and not against the wheel rim. This allows it some movement and notice the valve starting to go at an angle then you know the tyre is starting to creep.

I think that new Honda off road bikes come with rubber collars for the valve. They hold the valve in position but if the tube moves the collar will allow the valve to be pulled into the rim and not ripped off.

Mark.S · Post by **Mark.S** » 17 Jun 2012, 20:47

Thanks Eddie, some good advice there, I didn't know about tightening the rim lock after setting the pressure, i must admit i tightened it when i put the new tube in about 4 months ago and have never thought about checking it!

And thanks for confirming the bit about the valve stem nut, that makes a lot of sense, sort of an early warning.
I think i will also buy a good quality tube (known brand) instead of something from china!

Cheers mate

Mark

Post by **fallenmikethebike** » 17 Jun 2012, 22:23

Also, I have found some heavy duty tubes creep within the tyre, I think it because they have a smaller Diameter, but other than that it's a +1 to Eddies advice.
Mike

njhardy · Post by **njhardy** » 18 Jun 2012, 07:15

I take my valve nuts off, for that reason when trailing- it doesn't prevent ripping the valve off (as it can get sliced on the rim edge if the inner tube slips) but it does reduce the chance of it- you can see that the valve isn't straight, then re-seat the tube and tighten the rim locks when the tyre is up to pressure. If you reduce your tyre pressure (for boggy or sandy ground) it makes tube slipping much more likely.

Mark.S · Post by **Mark.S** » 18 Jun 2012, 12:31

I know it would make changing the tyre a bit of a pain, but would it be worth drilling another hole and fitting a second rim lock......just a thought?

M

Post by **Eddie Evans** » 18 Jun 2012, 18:03

I've run my rear tyre down to 7PSI when running trusty C02's on wet Devon rock. That was on a 450berg trying to rip it off.
Think your issue is likely to be that you have had a puncture then the tyre has spun causing the valve to rip out or a faulty rim lock.
I have drilled my valve holes out to 11mm, mainly to make them easier to fit.
I'd try that leaving the nut off, fitting a rubber collar first before fitting a second rim lock.

Post by **fallenmikethebike** » 18 Jun 2012, 18:48

Add a dot of paint as well to the rim and tyre, this may also show what's moving.
Wire brush the rims own outside gripper serrations, to make sure their doing their job.
Mike

Post by **Mudfacetony** » 18 Jun 2012, 19:17

Mark.S wrote:I know it would make changing the tyre a bit of a pain, but would it be worth drilling another hole and fitting a second rim lock......just a thought?

M

One is fine as long as it is in good condition. Talon do cracking rim locks or the KTM/Gas Gas one's are good as well. The cheap one's bend over time

Mark.S · Post by **Mark.S** » 18 Jun 2012, 20:56

Eddie, I put a patch over the valve hole tonight and pumped it up to see if there was a puncture (in case there was something in the tyre somewhere) but couldn't find one so i think, as you have all suggested, the rim lock is at fault, or i didn't tighten it properly last time i fitted it.

Lots of good advice from all of you, i will tighten the bugger properly this time, and make a bigger hole and mark the tyre and leave the nut off and fit a rubber bush and wire brush the rims!

Many thanks
Mark

Post by **Eddie Evans** » 18 Jun 2012, 22:13

It is important not to overtighten the rim lock, using 2 fingers on the spanner was the recommendation that sticks in my mind.
Too much and it starts to pull the bolt off the clamp.
Good luck as punctures are a pain in the arse and happen like buses. 2 come along together and thankfully in this case you won't see another for months.

Mark.S · Post by **Mark.S** » 19 Jun 2012, 19:52

Sorry don't mean to drag this topic on but looking at the rim lock with the tyre off, it doesn't look very wide compared to the tyre width, its 51mm wide at it's widest point.

Are the front and rear rim locks the same width, just wandered if it was a front one on the back?

Cheers
Mark

Post by **Eddie Evans** » 19 Jun 2012, 20:46

Rim locks are matched to the width of the wheel rim.
The front is 1.6
The Rear 2.15
Not that expensive if in doubt buy a new one.
http://www.ebay.co.uk/sch/i.html?_nkw=t ... &_from=R40

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