Tyre Pressure Monitoring Systems

[Roger Mills]

Have any of you bought the system currently on offer from Maplin?

so, what are your experiences of it?

It is quite a lot cheaper - and seemingly easier to install - than systems using sensors *inside* the tyre. But it seems to me that it may have several downsides, so I'm wondering whether these are real or not:

1. It presumably has to keep the valve pin depressed in order to 'feel' the pressure and thus relies on sealing on the thread. Does this result in loss of pressure?

1. Because the sensors are external, they could potentially be nicked. There is apparently some security device to prevent the sensors from being unscrewed. How does it work, and how secure is it?

2. Each sensor weighs 15 grams and could potentially unbalance the wheel. As far as I can make out, wheel balancing seems to be carried out to a tolerance of about 5 grams - so 15 grams may be significant. Is it necessary to have the wheels re-balanced after fitting the sensors?

Any general comments on accuracy, reliability, ease of use, etc.?

TIA.

[The Natural Philosopher]

I know if tyre pressures are 'not right' by the way the car handles..

[Nkosi (ama-ecosse)]

de quoted text -

Likewise, followed by a visual inspection which generally brings out the little compressore that plugs into the car's power socket

[Andy Dingley]

With fuel at the price it is, I want to be a _lot_ more precise about keeping pressures correct than just to the point where I can feel the difference, especially for a car I'm only driving everyday down an everyday commuter road.

[dennis]

I would imagine the balance would change with speed as the weight on the end of the rubber valve moved about. I have no idea how much you would notice it. You could fit a 15g lump of blutak on and try it.

Its not exactly cheap.. the one on my car was a factory fit option and cost £125 and it does more (like comparing the pressures to the load to see if they are suitable). It also got several free upgrades like a better driver display in the instrument panel so it could display the car outline, etc.

Its a bit of a luxury really, but it does mean you can walk around the car for a visual inspection and let the computer check all the pressures, oils, washer fluid, lights, etc.

I have only ever had two flats, both on the M6 and they were easy to tell that they had happened. I wonder why they only happen in the dark?

[Andy Burns]

There are also some factory fit ones that don't actually measure the pressure, instead the ABS unit measures the long term difference in wheel speeds ... they charge £75 for enabling a feature that exists in the ABS controller anyway ...

[ARWadsworth]

Punctures are not only supposed to happen in the dark but also when it is raining. Also, the better your clothes and the urgency of the journey are directly proportional to the chance of a getting a puncture.

[Dave Liquorice]

Will, not potentially, and I wonder how the valve stem will like having the force that 15g whanging round at 200 rpm will exert. 250g (1/2lb) or there abouts.

I know if tyre pressures are 'not right' by the way the car handles.. Yep, the handling starts to alter before a tyre starts to look "soft".

[dennis]

Mine has the sensors inside the wheel. You can see where they bolt trough the rim and you only replace the core when changing tyres. I must see if I can find out how long the batteries last, if they are lithium cells they probably last the life of the car.

[dennis]

Hmm, I was never in a hurry to get to work, it would wait till I got there, nobody else knew how to do it so I wasn't worried. I was going to say they only happen in road works, but one of them as after I had passed the lane closures. I just drove on the flat at 50 mph for a couple of miles for the other one. Centrifugal force (yes I know its a myth) keeps the tyre "inflated" at that sort of speed.

[The Natural Philosopher]

So? use a tyre pressure gauge and pump them up regularly.

IF you are losing pressure, you still need the time to pump them.

And IF you are losing pressure, you shouldn't be running a tyre fior any length of time. Tyres do not magically lose pressure.

There is always a reason - leaking valve or puncture.

And either of those will rapidly lead to a situation where you KNOW there is something wrong.

[Jules Richardson]

Our van's three years old and three of the four sensors are dead (it does have over 160,000 on the clock) - it seems they're quite prone to distance-related failure.

The service warning* it flashes up on the dashboard LCD is annoying; I'm not sure how much the sensors cost, but with a three year life I'm rather reluctant to find out, and would rather it just didn't have a monitor system in the first place.

• although some black electrical tape takes care of the accompanying light :-)

cheers

Jules

[Dave Liquorice]

Define "rapidly". One of my rears would loose about 2psi a month, enough to become noticeable. I just kept pumping it up, don't know if it was a leaky valve or a poor seal onto the rim. Not worth bothering about. Stopped when the tyre and valve was changed.

These days I get more variation in tyre pressure due to the ambient temperature. Several psi between freezing and 15C.

[The Natural Philosopher]

Lose, dear, not loose.

I bet you didnt need a radio gauge to notice..

I just kept pumping it up, don't know if

a valve change is peanuts and a bit of spiitle over the valve is easy.

Exactly.

Tyre pressures are, anyway, a compromise between handling, wear rate, fuel economy and comfort.

There is no magic 'correct' pressure.

[Harry Bloomfield]

Roger Mills used his keyboard to write :

As a quick / cheap method of reguarly checking my pressures, I fitted some of those mechanical pressure indicators to my car. If you imagine a clear plastic top to a tyre valve cap, with a fixed green bit inside and a red bit down the middle to indicate pressure. They unseat the valve to let the air into the sensor and auto calibrate themselves assuming you start with the correct pressure when screwing on the cap. They just indicate the pressure has changed since they were last fitted, by the red section protruding out of the green in the lens.

I've not noticed any change in the balance, nor has any air been lost as a result of fitting them - though I was initially concerned about the loss of one of the seals.

[Harry Bloomfield]

Jules Richardson wrote on 06/07/2011 :

Perhaps the batteries in the sensors have a limited life and are not replaceable?

[Dave Liquorice]

That's one of my worms that I trouble with. I do try and get it right, honest.

Correct.

What gets me is why they change the whole valve stem everytime you get a new tyre fitted. The old one is almost certainly working perfectly well and with a good non-leaky typre has propbably only been disturbed by and airline or guage a few dozen times if that.

Aye, and the makers book pressures are known to be "incorrect". They recommend 28psi on the front of my car, if you use that the handling is a bit soggy and you get the classic under inflation wear pattern (both edges faster than the middle). Use 30psi and you get dead level wear and better handling.

[Bob Eager]

I remember selling those (or something very like them) back in 1969, when I had a garage job!

[fred]

In article , Dave Liquorice writes

Customer gullibility :-? They buy them for 10p and charge £1.50 for them.

[BartC]

I believe I had a flat rear tyre in Belgium once, and wasn't aware of it until I'd driven back to the UK!

(The next day a driver next to me pointed it out. And I vaguely recalled a thud while approaching Lille.)