Tyre pressure indicators
Discussion
Chilli said:
Very true. Anyway, did mine last week, after thinking there was sopmething wrong as spotted the rear overtaking me on a roundabout...they were down to 30....should be 42....which was nice.
No wonder you and the hedge are best of mates! When was the last time you checked them?Write out 100 times -
I will check my tyres weekly from this day forth.
JackHolroyde said:
Chilli said:
Very true. Anyway, did mine last week, after thinking there was sopmething wrong as spotted the rear overtaking me on a roundabout...they were down to 30....should be 42....which was nice.
No wonder you and the hedge are best of mates! When was the last time you checked them?Write out 100 times -
I will check my tyres weekly from this day forth.
note: Newbies, this isn't clever or funny. I'm just an idiot.
Having witnessed one 150MPH+ rapid tyre defation I dont recommend plastic valve caps on sportsbikes..they just don’t seal as well as a metal one.
As for those flashing valve cap things, I cant believe shops are still selling them.
I told my mate about his flashy ones being a potentially lethal, being the owner of a tarts hand bag of an R1, he just laughed at the time...a month later he came up to me at our local meet and told me the front went down at speed , valve ripped out from the rim, flashy cap being the cause. He was lucky to stay on..Leave them to the scooter boys.
I dont know what additional weight these indicator caps carry over a "normal" one but combined with the amount of centrifugal force at high speed its unwelcome.
Tin caps with a rubber seal are the only way to go, light weight and seal properly at any speed.
As for those flashing valve cap things, I cant believe shops are still selling them.
I told my mate about his flashy ones being a potentially lethal, being the owner of a tarts hand bag of an R1, he just laughed at the time...a month later he came up to me at our local meet and told me the front went down at speed , valve ripped out from the rim, flashy cap being the cause. He was lucky to stay on..Leave them to the scooter boys.
I dont know what additional weight these indicator caps carry over a "normal" one but combined with the amount of centrifugal force at high speed its unwelcome.
Tin caps with a rubber seal are the only way to go, light weight and seal properly at any speed.
Valve caps don't have to seal at all, the valve does that. Metal caps esp the ally ones) can stick to the valve putting strain on the valve when you take them off. This happened with my westfield and resulted in a complete loss off pressure although fortunately at a standstill. The only thing a plastic one has to do is keep the dirt off and are the best option. The indicator ones work y holding the valve open so you are relying on the indicator to keep the pressure in and not the valve which is a bad idea.
dern said:
Valve caps don't have to seal at all, the valve does that. Metal caps esp the ally ones) can stick to the valve putting strain on the valve when you take them off. This happened with my westfield and resulted in a complete loss off pressure although fortunately at a standstill. The only thing a plastic one has to do is keep the dirt off and are the best option. The indicator ones work y holding the valve open so you are relying on the indicator to keep the pressure in and not the valve which is a bad idea.
Sorry Dern, your wrong, the secondary seal is provided by cap..Should have expanded on that,as i said in my first post use tin only not alloy ,its lighter and wont corrode and most alloy ones dont have the vital secondary rubber seal.
A car valve isnt exposed to the centrigfugal forces that a bike valve has to cope with (think about where they are both situated , one (car)is "outside the rim, one (bike)is "inside" the rim...), on a bike at speed the inner core of the valve is sometimes pushed in, releasing air pressure, with a plastic valve or a valve without this secondary seal, it can cause total deflation.
TBH I wasnt aware of this until 2 years ago when I went and had my Hayabusa timed at a StraighLiners event but i can promise you after seeing the riders faces first hand a cap with a secondary seal is essential if you want to ride near top speed..
If you pop over to ukbusas.org and do a search you can read for yourself what was said about these caps after the event.
Edited by podman on Friday 18th January 14:11
The pressure indicator valve caps are notoriously inaccurate.
I had a friend who had them on and they both indicated the tyres were fine, however the bike handled like custard.
We checked them with two different pressure gauges (and again at a local garage airline) and they were both well under.
Also, I once got a set of four free with something (can't remember what) and put them on correctly inflated car tyres and two were showing the tyres were under inflated (and yes, I did have the correct ones).
Regarding tyre valves themselves, the valve internals can fail (not as often these days as it used to be) so you should always use a correctly fitted valve cap; one with a sealing washer inside.
Metal ones should only ever be brass as the difference in metal with the valve stem thread can cause a reaction effectively bonding the two together making it a nightmare to get off again or causing you to damage the valve.
Big chunky steel ones can exert a lot of force on the valve when the wheel is revolving quickly (centrifuges again...!) causing quite dramatic failure.
I had a friend who had them on and they both indicated the tyres were fine, however the bike handled like custard.
We checked them with two different pressure gauges (and again at a local garage airline) and they were both well under.
Also, I once got a set of four free with something (can't remember what) and put them on correctly inflated car tyres and two were showing the tyres were under inflated (and yes, I did have the correct ones).
Regarding tyre valves themselves, the valve internals can fail (not as often these days as it used to be) so you should always use a correctly fitted valve cap; one with a sealing washer inside.
Metal ones should only ever be brass as the difference in metal with the valve stem thread can cause a reaction effectively bonding the two together making it a nightmare to get off again or causing you to damage the valve.
Big chunky steel ones can exert a lot of force on the valve when the wheel is revolving quickly (centrifuges again...!) causing quite dramatic failure.
podman said:
dern said:
Valve caps don't have to seal at all, the valve does that. Metal caps esp the ally ones) can stick to the valve putting strain on the valve when you take them off. This happened with my westfield and resulted in a complete loss off pressure although fortunately at a standstill. The only thing a plastic one has to do is keep the dirt off and are the best option. The indicator ones work y holding the valve open so you are relying on the indicator to keep the pressure in and not the valve which is a bad idea.
Sorry Dern, your wrong, the secondary seal is provided by cap..Should have expanded on that,as i said in my first post use tin only not alloy ,its lighter and wont corrode and most alloy ones dont have the vital secondary rubber seal.
A car valve isnt exposed to the centrigfugal forces that a bike valve has to cope with (think about where they are both situated , one (car)is "outside the rim, one (bike)is "inside" the rim...), on a bike at speed the inner core of the valve is sometimes pushed in, releasing air pressure, with a plastic valve or a valve without this secondary seal, it can cause total deflation.
TBH I wasnt aware of this until 2 years ago when I went and had my Hayabusa timed at a StraighLiners event but i can promise you after seeing the riders faces first hand a cap with a secondary seal is essential if you want to ride near top speed..
If you pop over to ukbusas.org and do a search you can read for yourself what was said about these caps after the event.
Chilli said:
I just got a ramdom email from M&P offering tyre pressure "warners"!!
it's basically a valve cap that has i little green indicato on it, which turns red should there be a deflation. Not sure of the sensitivity of it, but anyone think its a good idea....or one huge pile of sh!t?
As everyone has said they are cr@p, just check the pressure with a £10 gauge from Halfords before you ride out.it's basically a valve cap that has i little green indicato on it, which turns red should there be a deflation. Not sure of the sensitivity of it, but anyone think its a good idea....or one huge pile of sh!t?
If you must buy them get the hedge coloured ones
p.s. not convinced about Podmans centrifugal force theory between car and bike wheels.
Edited by slim_boy_fat on Friday 18th January 23:27
slim_boy_fat said:
Chilli said:
I just got a ramdom email from M&P offering tyre pressure "warners"!!
it's basically a valve cap that has i little green indicato on it, which turns red should there be a deflation. Not sure of the sensitivity of it, but anyone think its a good idea....or one huge pile of sh!t?
As everyone has said they are cr@p, just check the pressure with a £10 gauge from Halfords before you ride out.it's basically a valve cap that has i little green indicato on it, which turns red should there be a deflation. Not sure of the sensitivity of it, but anyone think its a good idea....or one huge pile of sh!t?
If you must buy them get the hedge coloured ones
p.s. not convinced about Podmans centrifugal force theory between car and bike wheels.
Edited by slim_boy_fat on Friday 18th January 23:27
Kawasicki said:
slim_boy_fat said:
p.s. not convinced about Podmans centrifugal force theory between car and bike wheels.
Podman is spot on. Depends on the angle of the car valve obviously. At high speeds the force pushing the valve open is sufficient to unseat it.Edited by slim_boy_fat on Friday 18th January 23:27
The force is a function of mass, speed and radius from center of rotation.
I may be a newbie and my advice means nuthin to you experienced guys..but sounds like a pile of popp to me... i used a motrax pressure gauge...have an airman thing you stick in fag lighter socket of car..has gauge on it so gave me rough idea - then checked again with motrax checker until I got what manual said...always seemed to work for me.....but now I'm bikeless...and only refer to this forum for my bike fix........
Craphouserat said:
I may be a newbie and my advice means nuthin to you experienced guys..but sounds like a pile of popp to me... i used a motrax pressure gauge...have an airman thing you stick in fag lighter socket of car..has gauge on it so gave me rough idea - then checked again with motrax checker until I got what manual said...always seemed to work for me.....but now I'm bikeless...and only refer to this forum for my bike fix........
Mate, if it helps at all.... I miss ya!How's the back mate?
slim_boy_fat said:
Kawasicki said:
slim_boy_fat said:
p.s. not convinced about Podmans centrifugal force theory between car and bike wheels.
Podman is spot on. Depends on the angle of the car valve obviously. At high speeds the force pushing the valve open is sufficient to unseat it.Edited by slim_boy_fat on Friday 18th January 23:27
The force is a function of mass, speed and radius from center of rotation.
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