**Important safety issue** serious thread

[1200Pete]

TYRE PRESSURE WARNING VALVE CAPS

I know quite a few people who have started using these things but I have some disturbing news.

I picked up an old wheel in my workshop a couple of days ago and noticed that the valve was bent over at an angle, I thought this looked odd and wondered what had caused it, the valve rubber was also very weak and almost floppy (queue Bert)

I pushed the valve easily over on to the wheel rim (something that is normally quite hard to do) and just touched it with a blunt knife blade and it tore right round the base of the valve.

This wheel used to belong to Frenchuk until he had his off and it was replaced with a new one. When frenchy paid me a visit on Wednesday I noticed two things. His vales where laying at a slight angle and he was using pressure sensors on the valves.

The front valve was again very weak and the new rear valve was starting to lay over and loose it's strength. We compared these valves to several wheels I had in the workshop and all the wheels I had where fine.

These things do not weigh a lot but they extend the length of the valve, the Bird uses a 10mm short stubby valve so that it stays upright at high speed. The wind and centrifugal forces at even 70 - 80 mph are huge

When the valve is repeatedly flattened against the rim, it is put under a lot of strain and there is a very real possibility of a big failure.

If you run these things check your valves now! if they are weak or laying over slightly, bin these things and buy yourself a pressure gauge.

YOU HAVE BEEN WARNED

 

[reefer]

pete..can you post up a pic of the stubby valve stems:dunno:
just incase some peeps have had the wrong size stems fitted when the tyres have been changed:blush:

%$fan

 

[Supabird1100]

Clive Is Quite Right !!!!

Tracey was running her bike with those 'light-up' valve caps and they almost caused a real nasty 'off' on the M25 as we approached Dartford Tunnel.

The weight of the valve cap had caused the valve stem to rip just above the wheel rim. A front wheel puncture is not pleasant at the best of times.....but the sudden pressure loss these things cause by taking out the valve stem is bloody frightening.

Good advice there Pete.....bin the fookin' things !!!!!!

 

[1200Pete]

Originally posted by reefer
pete..can you post up a pic of the stubby valve stems:dunno:
just incase some peeps have had the wrong size stems fitted when the tyres have been changed:blush:

%$fan

Dont worry Reefer, the wrong ones can't be fitted, they only make one length in the 10mm size.

If you need to run things on your valves, then wait and get steel valves fitted at your next tyre change.
They are about ?2.50 - ?3.00 each

 

[birdinflight]

Good Post Pete............

I did have those tyreflies on my bike, but after reading reports I decided to remove them.

Thanks again Jaws for a freeby pair after mine were nicked at Brands.

I wonder if the person who nicked them has had any tyre problems..............................hope so..................but hopefully not hurt.

Still haven't found anywhere else to stick them though!!!!!!

 

[dpbxx]

Valves

Thats the sort of post that makes this site so brilliant. Cheers Pete. Like a few others I removed the metal caps when this problem first appeared, now plastic rules.

Maybe spread the word across other forums?

:beer:

 

[Space Invader]

I noticed the other day, that one of the big bike magazines, (can't remember which one) is giving away a pair of the "Tyreflies" light up valve caps on it's fromt cover this month.

c7u8

 

[Pugwash]

I think the red caps on mine are aluminium. I used to have tyreflies until a local yoof stole them one night.

 

[1200Pete]

Metal caps are generally OK, just make sure, and the same goes for plastic ones, that they have a sealing O ring in them.
At high speed the valve can be depressed by centrifugal force and if your dust cap is leaking or missing the tyre can deflate.

I think in the case of the pressure sensors it is more there length than weight. The wheel is rotating forwards and both Pierre's valves where bent backwards at 100mph the valve is rotating forwards at 100 mph and if I have got my head round this the valve is sitting in 200 mph of wind, once it starts to bend then g force will take over.

 

[fat bert]

Pete - serious question~~~

are we talking here about the lite-up Tyre Flies ONLY

or are you saying that those green/yellow pressure indicators are potentially unsafe as well?

 

[1200Pete]

Re: Pete - serious question~~~

Originally posted by fat bert
are we talking here about the lite-up Tyre Flies ONLY

or are you saying that those green/yellow pressure indicators are potentially unsafe as well?

It was the green/yellow pressure indicators that was fitted to Frenchys bike and yes in my opinion from the actual evidence I have seen they are definitely UN SAFE

And stop posting serious posts Bert, it's worrying

 

[reefer]

intresting point about the valves being depressed at speed..never even thought of that:beer:

 

[Grampi]

Limpy,

Good to know that you're not the only thing depressed round here.............:neenaw::neenaw: :f

 

[Grampi]

Seriously folks.....

A long time back has a GPZ400 [jap import in Hong Kong] that had 16 in rims and I fitted those rt angle extender valve thingies.

Within 2 months both valves had failed[both overnight or low speed]............. hadn't thought of it til now........... nothing new there.

V. valid point and one all should be aware of. Thanks for the info; it makes a nice change from Limpy's [un]wisecracks! :f

 

[R2B2]

Couldn't agree with more with what Pete says.

It's no coincedence that Honda fit short valves. There will be plenty of R & D behind that decision.

To extend the length and mass is just asking for trouble at higher speeds.

It would be interesting to know what velocity (feet per second) the valves are subject to at, say, 100 mph - and then convert that into g-force. Anybody know how to work it out??

 

[Grampi]

Anybody know how to work it out??

With a pencil said the constipated mathematician!!:} :}

I got this far:-

100mph = 1.667 miles/min = 2933 ft/min = 48.88 ft/sec. then it's pi x radius squared..........:dunno:

Cue genius Lumpy - he's got an answer for everything else!! :f

 

[ianrobbo1]

WELL ??

Were all waiting Lumpy,:dunno:

 

[DB on CBR1100XX]

As a rough guesstimate...............

..............have a look at this link and fill out the blanks

http://hyperphysics.phy-astr.gsu.edu/hbase/cf.html#cfc

I got 6.78 lbs of force on a 5g valve travelling at 80 on a 17" rim

but I guessed the weight and the radius.............don't think it's far out nearly 7 lbs......and that's at a constant speed.....acceleration will affect dramtically too cos there's centripedal as well as centrifugal forces.......apparently !!

Formula is M*(V)2/R

ie. mass times acceleration squared divided by radius

This is all for a horizontal circle, mind, have a look at the link for vertical circles.....though I don't think it'll affect the outcome greatly..............

Fekking ell eh ? the things we discuss !!

 

[1200Pete]

And at 180 ?? :dunno:

 

[1200Pete]

What about the extra length and weight? Going on that even a 1gram dust cap would weigh 1lb at a ton