Tyre pressure thingies warning.

Don't know why the original posting was lost but here we go again.

Purchased a pair of air pressure indicators for the Sprint when
I was having a new 020 rear fitted last week.
You know the type I mean, they change colour if the pressure drops.
After 150 miles, gave the bike a blast and the front tyre deflated
very quickly at very high speed.
Very hairy moments as I had to use *their* side of the road on a left
hander to stop.
No damage on the tyre but the tubeless front valve was torn almost
of the rim.
The indicator was fitted correctly and not cross threaded.
I can only think that the additional weight on the valve was to much
for it. Strange as I would have thought that the force would be
towards the rim.
I don't know how old the valve is/was but I have been at higher speed
before with no probs.

Anybody else had any problem with them ?

 

I've heard the "extra weight" argument a few times
along with similar stories from an American friend.
He reckons they're fine for car use, which is what
they're designed for, and not for motorcycle use
due to the extra demands put on it.

Mind you, they are a bit gay.

 

Had them on my last bike, a beemer r80rt, and had no problems, mind
you top speed was no more than 105 mph.

 

I've heard of similar problems with 'tyre flies'.

 

<slap> did he fucking ask about them?

 

Using the patented Mavis Bacon "Hunt&Peck" Technique, petrolcan

Grumpy fucker...

 

<sigh>

Guilty as charged, M'lud. I must be getting old...

 

Er, if you depress a tyre valve you *are* pressing towards the rim.

My guess is that at high speed instead of the valve pressing on the
doohickey, centrifugal force is having the opposite effect.

I'd find out how much pressure it takes to operate a tyre valve. Weigh
the assembly that's sitting on top of the valve (because this is what
regulates the pressure monitoring), work out how fast the wheel is
rotating at x mph, work out what this assembly would weigh due to
centrigual force (ok, inertia) at that speed, and see if it's the same
or more.

No, I don't know the maths necessary for this but I bet someone here
does

 

This is all you need to know as a reason not to have them.

Forget the arguments that actually testing the pressures with an
/accurate/ pressure gauge is as important as checking its got engine oil.
While you're checking the pressure you can quickly examine each tyre for
carcass damage.

 

Do you really believe this?

I'm a lazy bastard when it comes to tyres and rarely (if ever) check the
pressure myself relying on the fitter to do it when he fits the tyre.

I do kick them occasionally to make sure they're hard though.

Here's my tip, if it feels a bit wobbly and saggy the rear tyre's
(probably) flat and needs air. If it is hard to push the front tyre's
(probably) flat and needs air.

 

Yes.

Although I probably check the oil more.

 

I'd have thought that your initial suggestion would be right. The thing
telling you the pressure must be allowing a bit of air out through the
mechanism anyway, right?

 

Didn't JP tell us that the force have been using these with great
success?

 

Well yeah, probably about as important, i.e. something you should
prolly do once every couple of months...

 

Just ordered for the entire fleet. Used on the T5s as well as the
"sneaky" blackbirds/12R`s/ Hayabusas with no probs.

 

Could have been a defective one then, I guess.

 

The Older Gentleman wibbled incoherently

IMO it's the sprung goodies inside these contraptions that are causing
the valve to be opened and deflate the tyre.

When you think about it, all the innards are forced to the rim-side of
the wheel, in the same direction you push a tyre valve to release
pressure. If they are sitting against the valve it's bound to open and
deflate. I should imagine there's sufficient inertia created to do this
on a modern motorcycle.

--
Lozzo
ZZR1100D, GPZ500S, CBCBCB750RSRSRS
BOTAFOT#57/70a, BOTAFOF#57, two#49, MIB#22, TCP#7, BONY#9,
ANORAK#9, DIAABTCOD#14, UKRMT5BB, IBW#013, MIRTTH#15a/16,
BotToS#8, GP#2, SBS#10, SH#3, DFV#14, KoBV#3.
Url for ukrm newbies : http://www.ukrm.net/faq/ukrmscbt.html
www.mjkleathers.com

 

When you two have finished !

WTF are tyre flies ?

 

Nope, not a slow leak, a sudden deflation.

Got the tyre of today and have found that the rubber of the valve
was perished and crumbly.

Not been changed with new tyres from the look of it.

Anyhow, spoke to my local tyre man today and he has come across this
B4, he recon's that there is aprox 5 grams flopping about on the end
of the valve which at high speed would put stress on the valve.

 

Them neon light valve cap thingys