Tyre valve

[Colin]

I came across a problem I have not met before. Trying to check the pressure in Wendy's scooter tyre, the separate tyre gauge would not register at all and the pump gauge registered max (ie 100ppsi) on the first stroke of the foot, but clearly would not put air into the tyre..
Investigation showed that something was lodged around the pin of the valve. I finally extracted the blockage with a piece of fine wire bent in a hook.
It turned out to be a small rubber seal from the top of the cheap plastic valve cap. It was obviously intended to be a second seal against air escape, but became detached as the cap was screwed down hard, and jammed around the pin of the valve. Difficult enough to see and extract in the workshop, but I suspect it could be a bl---y nuisance if you were trying to top up your tyres at a garage.
Perhaps it would not happen with a quality metal cap (I have at least one on any bike with a valve extractor top) but examination of some cheap plastic caps showed all had loose or detached rubber seals.

 

[davidd]

Colin,

Never had the problem (you are a trailblazer!) Because we are not allowed to use plastic caps by the racing organization, I don't have any around to tempt me. I guess the racing organization was onto something.

David

 

[Mike 40M]

Local tyre shop routinely change valves when changing tyres. Throwing discarded caps in a box. I sometimes find good metal caps in that box. Free, period and race approved.

 

[Nulli Secundus]

Colin,

Never had the problem (you are a trailblazer!) Because we are not allowed to use plastic caps by the racing organization, I don't have any around to tempt me. I guess the racing organization was onto something.

David

That is interesting David because I use plastic caps on my race bike and didn't think metal ones were allowed here, at least those that double as a valve insert removal tool. I assume it is because if one fell off on track it might just cause a puncture.

Regards

David

 

[davidd]

David,

That is interesting. AHRMA never mentioned the core remover valve cap. However, I checked the rules today and they have eliminated all rules about tire safety.

The rule used to require metal valve stem caps (I used the flat tops) and I remember one race meeting where the referee mentioned that a rider had a valve cap failure and it caused a crash. The rider was at the meeting and spoke up about it.

The rule also required "a rim strap." In fact, the rule suggested the rim strap be made of duct tape, which I did not like at all, but complied with. It has all been removed.

I do think a flat metal cap is the best. I had some plastic caps on the car that a tire place put on. They had a metal threaded insert. The insert welded itself to the stem and the plastic cap turned in place. I did not realize this until I was on the road and needed to top up a tire. Since then I buy metal caps from Pegasus Racing. They do what I want. 4 caps for $3, which is not free, but they are good quality.

Racing organizations often change rules based upon the latest accident. ECTA used to be quite strict about chain guards being sturdy and covering the entire length of the chain, including CS sprocket. Then someone had a chain break and jam in the guard at a high rate of speed. The rule changed to make chain guard use optional.

Something similar happened at Bonneville years ago. A bad accident was traced to the front tire tube overheating. After that, cast wheels with tubeless tires became mandatory in most classes. I certainly went to cast wheels.

I do like metal valve stem caps as they have never been a problem. I run a core remover on the rear wheel on the street, but I often slip a rubber tube over it. It is not much use if it is not there when you go to use it.

David

 

[vibrac]

The only UK racing rule relating to valve caps is a desultory one I have seen enforced occasionally of not using the metal caps that include an extractor tapered nose evidently sombody had a blowout on track and the cause was a cap falling off and being picked up by a following bike and piercing piercing their tyre.

 

[Nulli Secundus]

Thanks for that, that ties in with my recollection. As David says though rules change after incidents, so if there is one concerning flat metal caps, or plastic caps, all bets will be off.

 

[Canadiancomet]

Well Colin..your bigger problem is you spelled TIRE wrong.....LOL Cheers

 

[Colin]

Sorry about that Canada! I will try harder next time

 

[Canadiancomet]

You're a good sport....