Tyre Pressure Indicator didn't go off and tyre damaged

[macdoc]

I got a nail in a tyre, the pressure drop required to trigger the warning light was approx 4 psi after about 2 days from when I spotted it.

Also I have noticed that the warning light will activate after 10,000Kms exactly to make the operator check the tyres and reset the TPMS irrespective of pressure loss. I found this out in an earlier version of Vagcom. ie. 'time since last reset mileage - TPMS fault code mileage', somewhere in the ABS section I think.

Macdoc.

[gregozedobe]

I check my tyre pressures, oil and coolant levels every time I fill up. It doesn't take long and it gives me peace of mind.

If you don't check your oil level and you happen to have an engine that uses a bit of oil (I don't) you won't know until (unless ?) the warning light comes on. As some people have noticed, the warning lights don't always function as you'd expect.

I think modern cars are generally so reliable people get into the habit of rarely checking anything - this can be expensive sometimes. It is also common these days to "just get in and go", without reading owner's manuals and other boring stuff like that, then look for someone else to blame when things go wrong.

IIRC there was a similar thread to this a while ago from someone who never looked at his engine oil levels and was wanting to blame the dealer for not checking at the PDI - he got similar responses to those in this thread.

To be blunt, " Read the Owners manual and do the checks it tells you".

[PassatB6]

The TPMS should have alerted the driver no matter how fast the leak happened though I can't see how the alert would have made any difference as it sounds like the tyre went flat immediately. Mine worked perfectly alerting me minutes after I hit a pothole that the tyre pressure had dropped. In Sylvester's case checking tyres regularly would have made no difference .

[VW Convert]

The TPMS should have alerted the driver no matter how fast the leak happened though I can't see how the alert would have made any difference as it sounds like the tyre went flat immediately. Mine worked perfectly alerting me minutes after I hit a pothole that the tyre pressure had dropped. In Sylvester's case checking tyres regularly would have made no difference .

Given that TPMS works by monitoring differences in the rotational speed of individual wheels over a period of time, how would TPMS possibly alert the driver if the tyre went flat immediately?

Cheers

George

[gregozedobe]

Given that TPMS works by monitoring differences in the rotational speed of individual wheels over a period of time, how would TPMS possibly alert the driver if the tyre went flat immediately?

Maybe they expect the driver to notice if a tyre suddenly goes completely flat ? The few times its happened to me it has been pretty obvious, especially if you are trying to go around a corner at the time

[PassatB6]

Given that TPMS works by monitoring differences in the rotational speed of individual wheels over a period of time, how would TPMS possibly alert the driver if the tyre went flat immediately?

Cheers

George

As far as I am aware it tells you immediately the tyre pressure has dropped beyond a certain level. It only needs one rotation to work this out, so why would it wait?

[olcoop]

If it's using rotations to determine tyre pressure, how is it monitoring the pressure in the spare wheel?

[gregozedobe]

If it's using rotations to determine tyre pressure, how is it monitoring the pressure in the spare wheel?

It is probably not monitoring the spare. The only way to do that would be to have a transmitter in the spare and a receiver in the car. IIRC that was how the original TPMS on the early GTIs worked, then some bright engineer realized they could use the ABS sensors to measure wheel rotations, thus saving costs.

So it is up to owners to check the tyre pressure of the spare manually (and going by some of the posts on this forum I'll bet an awful lot of people can't be bothered to do so).

[VW Convert]

As far as I am aware it tells you immediately the tyre pressure has dropped beyond a certain level. It only needs one rotation to work this out, so why would it wait?

I'm no expert on TPMS but thinking about this logically, it would be impossible to use a single tyre rotation as the basis for determining rotational speed. Every time you turn a corner (or go around a bend) there is a difference in the rotational speed of the wheels on the inside of the corner Vs the wheels on the outside of the corner (thus the need for a differential on the drive wheels). There are numerous circumstances where rotational speeds would vary momentarily so if TPMS acted instantaneously it would give repeated false alarms. Therefore, I would think it can only operate by monitoring over a period of time.

Cheers

George

[VW Convert]

If it's using rotations to determine tyre pressure, how is it monitoring the pressure in the spare wheel?

Is it monitoring the spare wheel? I doubt it.

Cheers

George

[olcoop]

I was told by the sales person that it monitors the spare wheel as well.
A friend's Dodge Caliber monitors all five wheels so I didn't think it was science fiction!!!!

[VW Convert]

I was told by the sales person that it monitors the spare wheel as well.

Perhaps the salesman was mistaken (or dare I say, lying) that has been known to happen.

A friend's Dodge Caliber monitors all five wheels so I didn't think it was science fiction!!!!

This may be true but in order to do so would require a pressure sensor in each wheel transmitting to a monitoring system or alternatively some sort of voodoo magic system. In my VW there are no sensors in each wheel, are there in yours?

Cheers

George

[tryingavw]

This may be true but in order to do so would require a pressure sensor in each wheel transmitting to a monitoring system or alternatively some sort of voodoo magic system. In my VW there are no sensors in each wheel, are there in yours?
e

its not voodoo - some in fact do have some radio type device.

[VW Convert]

its not voodoo - some in fact do have some radio type device.

In VWs?

Cheers

George

[R36 Dreamer]

In VWs?

Cheers

George

Yup, the Phaeton made a big deal of this.

I am pretty sure they abandoned the idea as it used to trip out all the time.

As the MFD used to be able to say "low pressure - right front" it made a huge mess when tyres were rotated etc. as the system needed to relearn where the tyres were on the car. It also meant if you changed a flat tyre the MFD would continue to show a fault after you repaired it.

I think the R36 System relies on ABS sensors, to monitor wheel rotations. It does this over a long period of time, not just one rotation, as someone said there is flex in a tyre and it would go off every time you went around a corner or hit a bump.

It is not a failsafe system. Nothing replaces the need to regularly check tyre pressures and fluid levels in your car.