Low tyre pressure warning

[vectorskink]

Hi guys

Filled my tyres with air last Friday (and reset the pressure checker), and this morning I get the low tyre pressure warning. That's about the typical time it takes for it to warn me.

Does anybody know what the pressure difference is before the systems tells you they're low? Does anybody only get a few days before the low tyre pressure warning comes on?

What I have been doing is resetting it again when it comes on and waiting for the second warning before I fill up. The tyres don't look low at all.

cheers!

[BeigeJet]

Hi Vector,

I understand that it registers when there is a difference of about 3 psi between wheels.

At least it did on my Jetta once. When I checked one tyre was down about 4 psi compared to the other three (valve not completely screwed in therefore slow leak).

You would be surprised how deceptive it is when a tyre has lost 10psi on these low profile tyres. They look OK but in reality they're too low.

Sounds like you might have a slow leak in a tyre (or valve).

I'm running 38 psi all round and not having any issues!

Happy motoring! in the the diesel. Isn't fuel consumption great!

Cheers,

Neil.

[vectorskink]

Thank you Neil!

That's the answer I was after!

Looks like I might have a slow leak then. Right hand rear tyre requires more air than the others.... will look into it.

Fuel economy is GREAT! As you can see by my nerdy sig, my last tank avg was 6.1l/100km around town. I like that a lot.

cheers!

[BarneyBoy]

You would be surprised how deceptive it is when a tyre has lost 10psi on these low profile tyres. They look OK but in reality they're too low.

Too true. Those 45 profile tyres have sidewalls made with stuff like kevlar &c and just don't flex much at all. Try letting a tyre down to 10 psi or so and have a look at it - still looks pretty good

[gregozedobe]

What I have been doing is resetting it again when it comes on and waiting for the second warning before I fill up. The tyres don't look low at all.

Your car is trying to tell you that you have a tyre that has lost pressure and you need to check WHY, and also that you need to get that tyre fixed.

I have trouble believing that you didn't realize that's what you need to do, especially if you have read the appropriate part of your owners manual.

As others have said, looking at a tyre is nowhere near good enough - invest in a tyre guage so you can check your tyre pressures properly (don't trust gauges at what used to be "service" stations).

[vectorskink]

Your car is trying to tell you that you have a tyre that has lost pressure and you need to check WHY, and also that you need to get that tyre fixed.

I have trouble believing that you didn't realize that's what you need to do, especially if you have read the appropriate part of your owners manual.

Yes, I do realise that's what I have to do! Obviously it's not going to tell me a tyre is low for nothing!
I certainly was confused about the tyre not looking stereotypically low on pressure, but now I know that the sidewalls are strengthened so it won't look like it's low like it would a normal tyre.

I have ZERO experience with low profile tyres, but after some help from here, I am wiser in the way of TPMS and low profiles.

What I wanted to find out was the sensitivity of the TPMS so I could get an idea of roughly HOW MUCH the tyre had gone down as it wasn't very obvious visually.

everyone get it????????

[gregozedobe]

I don't mean to be a smart-@rse, and at the risk of labouring the point, rather than ask for possibly unreliable/speculative and/or misleading opinions on here (as on many internet sites), why don't you put your gauge on your tyre when the low pressure warning comes on, and then you will KNOW how sensitive the TPMS is on your particular car (it will almost certainly vary from individual car to individual car).

Sometimes the direct approach is the best course of action.

Then you can tell us

[vectorskink]

I don't have my own gauge......
(SHAME!)

Any recommendations for a good gauge?

I went back to the servo and filled up the tyres with air. I had them all filled to 36psi initially, then checked and filled them tonight again.

They were all 34psi, except for the rear drivers side tyre which was 29psi!
I bought one of those metal valve cap with the valve tightener on top and tightened the valve - I got a good quarter turn on the valve!
Tightened the rest of the valves as well.

Hopefully that will stop the slow leak. I'll see how it lasts before the TPMS dings me again!

[gregozedobe]

Any recommendations for a good gauge?

I went back to the servo and filled up the tyres with air. I had them all filled to 36psi initially, then checked and filled them tonight again.

They were all 34psi, except for the rear drivers side tyre which was 29psi!
I bought one of those metal valve cap with the valve tightener on top and tightened the valve - I got a good quarter turn on the valve!
Tightened the rest of the valves as well.

Hopefully that will stop the slow leak. I'll see how it lasts before the TPMS dings me again!

Sorry, I haven't bought a tyre pressure gauge for 15 years or so. My preference would go to somewhere that sells reasonable quality car tools, then look at medium priced gauges (not the bargain basement stuff, but not the super expensive ones either), and tell them you want to try it out on your car (give them the purchase price to hold why you try it out if they seem reluctant). I would try it out on your car looking for:

How easy is it to use and read the pressure ?
Does it hold the reading after you take it off the valve stem ?
Is it easy to zero after you have read the reading ?
How much air does it let out when you take it off the valve stem (some are prone to releasing too much air, which means the tyre loses pressure after you have taken the reading)
If you measure the same tyre 4 or 5 times, do you get the same reading every time ? Preferably within 1-2 psi. Some gauges have a lot of variability, these should be avoided.
Does it feel robust or a bit fragile ?
Does it fit where you intend to store it in your car ?

You can also check whether a valve is leaking by putting a bit of saliva on the end of the valve stem (with the cover removed). If there is a leak a bubble will form. I always use metal valve caps with an internal rubber seal, so that even if a valve leaks, the cover stops it.

Unless your low pressure is beacause of a leaky valve, you should really get your tyre checked by a proper tyre repairer ASAP. Sorry for shouting at you, but if there is a problem with your tyre it could suddenly go flat at anytime. If it goes flat when you are cornering briskly to the left you will probably lose control and crash (ESP won't be able to save you if your tyre is completely flat). I have had two "sudden deflations", and in both cases it was very scary.

So please, get it checked as soon as you can. Relying on your TPMS to keep you out of trouble is just too dangerous. I am giving you very good (possibly life-saving) advice here, please don't ignore it.

[bazzle]

Go to an ARB 4x4 shop, Repco etc and get a simple dial guage. VDO etc
Doesnt matter how accurate it is (most +/- a lb or so) as long as all tyres read the same.
ex: http://www.arb.com.au/products/gener...e-accessories/
Air pressure gauge

Bazzle

[vectorskink]

Unless your low pressure is beacause of a leaky valve, you should really get your tyre checked by a proper tyre repairer ASAP

Will do! will keep an eye on that back tyre and if it goes down fast again after the valve's been tightened, off to the repairer I go.

cheers!

[Transporter]

I don't have my own gauge......
(SHAME!)

Any recommendations for a good gauge?

You can get Holden HSV 1/4" dr socket set with very accurate digital tyre gauge from SuperCheap Auto for around $40. I bought 3 of them (for all our 3 cars) just for these tyre gauges, included are chrom/moly combination pliers. I bought it when they had 20% off over the weekend.
http://picasaweb.google.com.au/lh/ph...eat=directlink
Good quality non-digital gauge will cost from $20 up.

[Treza360]

The tyre gauges is that you use the same one consistently. If you're using multiple gauges or worse the ones on the pump at the servo you're going to introduce a lot of error in your pressures as the calibration and therefore error of all the meters is going to be different.

By using the same gauge every time this means you will always have the same reading based on that gauge and therefore your tyre pressures can be maintained to the same level.

This will then allow you to start playing with/measuring other variables with your car such as fuel economy, tyre life, handling etc.

Cheers,
Trent

[vectorskink]

UPDATE!

A small nail in the tyre was the culprit!
All fixed and no more leaks, and no more resetting the TPMS every week!

[mrcurlywhirly]

Good news you tracked your problem down. You can keep your shiny new guage in the car at all times now, i keep a decent one in each car - its invaluable.

I had ours chiming for a couple of days, had checked all the pressures, which seemed OK at 34 to 36 psi, then i got off my backside and RTFM - and looked at the pressure recommendations inside the petrol flap! ... should be running 40psi in the R32 tyres so they must have been borderline.

I guess these idiot proof alarms are yet another great primary safety feature that VW loads into their vehicles.