Ash T and Dom_'s Potentially Fatal Experience.....Dustcaps

[ash t]

yes, it could have been fatal i suppose..



If you have Dustcaps that are not standard, get rid of them.

Me and Dom_ went to see some friends in derby tonight, and because of an Anodised dustcap (we think) the front tyre COMPLETELY DEFLATED. To think we were doing the speed we were on a flat tyre. I didnt notice until the steering felt really heavy and unstable on a roundabout.

GET RID OF THOSE ORRIBLE THINGS!
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[Jrod]

How can that cause it? They get stuck to the valve so you can't get them off but that's all I had.

[Dom_]

[ash t]

Centrifugal Forces on the valve, fair bit of force when you think about it. Heavy Dustcap.....

I threw away the dustcaps and pumped it up...it was Ok on the way back

Going to get it checked out anyway!
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When You're Starting To Choke, Take Some Pills With Your Coke, Its Hyserical

[Jrod]

They can't weigh much more than the plastic ones.

[Gazdaman]

Centripetal force.

And I suspect if you'd pumped it back up and put the dust cap back on you would have had the same thing.

Maybe a dodgy valve? keep an extra close eye on your tyre pressures for the next few weeks!

Gaz

[Dom_]

We threw the valve cap away...

Ash said "Dom the front end feels funny on roundabouts" i replied, "yes Ash, this is because you have a flat tyre " lol.

[ash t]

LOL i was commenting on the temperature of the front tyre...and as usual, you had to play with it and noticed it was flat Good thing really!
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When You're Starting To Choke, Take Some Pills With Your Coke, Its Hyserical

[Gazdaman]

All I'm saying is how do you know the dust cap was at fault? It would have to be pushing in on the centre bit of the valve to deflate it.

I'd suspect a dodgy valve or even a puncture is more likely.

Gaz

[ash t]

We pumped the tyre back up and its fine now after a 40 odd mile trip back, 2 up doing natonal speed limit
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When You're Starting To Choke, Take Some Pills With Your Coke, Its Hyserical

[cagiva gezzer]

I fail to see your logic. I can see how tyre flys can cause issues, but not alu versions of normal caps.
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"because one stroke isnt enough and four strokes waste two"

[divuk83]

I don't see how there is any difference in weight between ALU dustcaps and plastic ones. Stupid ones with LED's and other novelty things on them would be heavier. Only thing with alu ones is they need cooper greasing or they will never want to come off.

Dave

[ash t]

They are heavier.

Just had afriend tell me his mates tyre did the same and it turned out that it was the valve core which needed replacing.
I will have to take it to the local tyre place in the morning.

cant be having a dodgy tyre!
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When You're Starting To Choke, Take Some Pills With Your Coke, Its Hyserical

[Mr C]

we have had problems with the plastic dustcaps causing rapid deflations at VERY high speeds

at over 180mph the centripetal force on the inside of the valve is enough to open it wide - just liek sticking an object in

the pressure in the tyre is then enough to either pop the cap off or split it in two


now when top speed racing most of us will only use the little steel ones with the rubber o ring inside as they stay on, don't split and don't let the air out


fucking about with "novelty" dustcaps is inexcusable
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187.3bhp = 201mph

[ash t]

What else could it be?
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When You're Starting To Choke, Take Some Pills With Your Coke, Its Hyserical

[Jrod]

Riding too slowly?

[ash t]

Definately not
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When You're Starting To Choke, Take Some Pills With Your Coke, Its Hyserical

[TOM M]

its a good thing that you didnt bin it............thats one very sexy cbr to bin
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Now owner of a 1200 Bandit

[loply]

My tire had an anodised cap on it (previous owner) and I had to have the valve ripped out and revalved at a tire shop, because it completely seized itself to the valve.

All the BAD stories Ive heard about anodised caps- And you still get idiots buying them!
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Yamaha SZR660 Caution to the wind, the throttle pinned!

[ash t]

Checked they tyre pressures thismorning and they are all hunky dory.

Im rather confused!

I would go and get it checked but i dont have money to pay anyone to fix it

My dad just says keep and eye on it over the next few days
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When You're Starting To Choke, Take Some Pills With Your Coke, Its Hyserical

[Major_Grooves]

[mchaggis]

On a slight tangent I nearly got clobbered by a flying plastic wheel trim from some orange Fiat thing the other day. I noticed the car had lost two on one side, you'd have thought they might have checked to see if they were secure?

Anodised dust caps will sieze onto the threads of a valve, requiring the whole valve to be removed in order to get them out.

I would like to clarify that the dustcap cannot be pulled off by the mythical centrifugal force. It is pushed into the valve by the reaction to the centripetal force. All dust caps will suffer from it to some degree, plastic or metal, just metal ones, being heavier, will exert a greater force on the valve for the same wheel speed. Hence why you can get special ones for high speeds as Mr C described.

One of the main benefits to plastic ones in my eyes anyway, is that plastic ones can be pulled off without damaging the thread on the valve itself. They're also cheap as chips.
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I must not be a troll...
Mmmm, Guinness
Discovering the delights of Hammerite and a 3/4" brush.

[Mr C]

you miss the point mate

at high speed, the valve opens due to centripetal force acting on the little pushy down bit in the middle being greater that the spring and tyre pressure keeping it closed

plastic caps don't contain the pressure once this has happened

steel ones do
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187.3bhp = 201mph

[mchaggis]

Ah, of course! I can't believe I didn't think of that.

That makes better sense.

What do they make the cores from? Ordinary steel? There'd be some mileage in composite valve cores I reckon, though the pressure proof caps would still be cheaper and easier.
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I must not be a troll...
Mmmm, Guinness
Discovering the delights of Hammerite and a 3/4" brush.

[stinkwheel]

If you try to enter the Manx Grand Prix with plastic dust caps on, your bike will fail scruitineering. They claim this is because under the sustained high speed round the circuit, the centre of a plastic cap can deform and press down on the valve.

I would suggest the problem is either a slow puncture, dodgy valve core or the tyre isn't quite seated propely on the bead and is leaking a little (which in my experience reaches a certain point then goes completely flat all of a sudden).

Throw away the anodised alloy valve caps anyway or I will send the fashion police round. They are like, soooo late 80's man.

Get some of those nice metal ones with the built-in valve core extractor on top. Functionality of design
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.