Tyre valve replacement

**Gixxer 4 ever** · 27th June 2004, 21:27

Quick question. How often do those of you that change your own tyres replace the valves in the rims? "tubeless tyres" And those that have it done at the shop?

**Holy Roller** · 27th June 2004, 21:31

The shop puts new ones in when changing the tyre.

Question?
Does anyone know if there are 45 or 90 degree valve stems or attachments? I find it differcult to inflate the tyre with most air lines at the service stations, usually have to bend the filler pipe stem just to get it onto the valve.

**pete376403** · 27th June 2004, 23:50

There are 90 degree stems (guy at work has them in his Speed Triple) and I wanted TTS to put one in my wheel when they put on the new tyre. They said the old GS wheels are not suitable so sold me a 90 degree adapter that screws onto the standard stem. Handy and only $5

**Motu** · 28th June 2004, 07:48

It's a pain trying to get air into tyres with what is supplied at the service station - a 90deg valve is a good idea....but at speed it will bend and weaken the stem where it goes into the rim,of more concern to criminals who speed,but over time the stress will still weaken it.

**scumdog** · 28th June 2004, 08:29

Originally Posted by Motu

It's a pain trying to get air into tyres with what is supplied at the service station - a 90deg valve is a good idea....but at speed it will bend and weaken the stem where it goes into the rim,of more concern to criminals who speed,but over time the stress will still weaken it.

Yep there are enormous centirfugal (sp?) forces at work when a wheel is spinning at speed, avoid the 90deg fittings if you can, use a longer valve stem and you might get more flex out of it to get the service station fitting on to it a bit easier.

Years ago a drag racing team couldn't figure out how it was that after a fast run the front tyre went flat, they discovered that the wheel was spinning so fast that the centrifugal force was causing the centre of the valve to get flung outwards enough to let the air out (just like when you push it in with a nail)but when they stopped it was back in position - valve caps was the cheap fix

**curious george** · 28th June 2004, 15:46

Jeez scumdog, I thought that old hooey about centrifugal force and flat tyres died out years ago!!! To get anything like that effect, you need to spin the wheel at about 20,000rpm or something! It just aint gonna happen. Ever.

What about those little valves which can spin on its insertion point? Anybody used them before? They look neet, and a lot easier to inflate at the garage

**scumdog** · 28th June 2004, 16:05

Only quoting what I read in the write-up on the dragtster, funnily enough the problem went away when they started using valve caps though.

Maybe some physics geek could weigh the centre out of a tyre valve and then calculate how fast a rim would have to spin for the spring to be overcome?

**vifferman** · 28th June 2004, 16:32

Originally Posted by scumdog

Maybe some physics geek could weigh the centre out of a tyre valve and then calculate how fast a rim would have to spin for the spring to be overcome?

It's not just the spring - doesn't the air pressure also work to push the valve shut? Or not?

**Big Dog** · 28th June 2004, 18:59

Originally Posted by firestormer

It's not just the spring - doesn't the air pressure also work to push the valve shut? Or not?

That and the valve opens the other way. the centre needs to go in.

**Milky** · 28th June 2004, 20:55

On a slightly related note, I know you can put tubes into tubeless tyres on the BM - 4.00/18 style tyre, I guess that means 100 profile... is it possible to do the same to lower profile tyres?

**Motu** · 28th June 2004, 21:16

No problem with that,but I've found sometimes they won't seat with a tube in them - just yesterday I saw a guy beating a 4.00x18 on his TLR200 to death with 60psi in it,but no way would the bead seat...that's a trials tyre though....

**Milky** · 28th June 2004, 21:25

where there's a will there's a way my friend.....

**Gixxer 4 ever** · 29th June 2004, 06:51

Originally Posted by Motu

,but no way would the bead seat...that's a trials tyre though....

A good wetting with a soapy dish water or if that will not work I use CRC over the water. Now do not shout at me as the CRC will not affect the rubber. (plastic or what ever they are made of) Read the label. I have used it from time to time for years and had no tyre rubber problems. Also use this to fit tyres to alloy rims on the wife's car. Hate them alloys.