What does the "Set" button do?

[funkythumbs42]

As per below



What does it do excatly? 

[Davstylee]

It’s to do with the tyre pressure sensor. Don’t take this as 100% but when you change your tyres, or after one has gone flat and you pump it up, you press it to set it to that tyre pressure. Then if a tyre goes below that pressure it warns you via the instrument dial.

There should be something about it in your owner’s manual.

[ub7rm]

^^ What he said.  Hold it down to calibrate the system to your tyre pressure.

[jaydubveedub]

Yep. Basically hold it down until it beeps everytime you pump your tyres up (or have new tyres).

I have to say that it's near useless, as it seems unable to detect sever drops in tyre pressure until it's too late.

[Steve30]

No its not useless at all , I rate it very much. This last month I have had 2 screws in a tyre, one of which had I not stopped streaght away, would have gone right through. I managed to pull it out  before it went through the tyre!! Saved me buying a tyre becuse it was right on the end. The other tyre at the front had a punture, the set button told me imadietly!! 

[sambo]

How?

You must have been losing pressure for the sensor to activate the system?

I let my 2 front tyres down on wednesday to gain a bit of grip in the snow. I did it when the car was turned off and locked up mind. But the system never reminded me the tyre pressures had been reduced???

Sam

[stealthwolf]

There is no tyre pressure sensor. Just something that measures the rolling radius of each wheel and warms when there's a drop in the rolling radius. Problem is that you need a significant enough drop in pressure before the system detects it. I've lost around 10psi before the warning comes on.   

[sambo]

Yep I know exactly how it works, but still having a screw in the tyre but not enough to reduce the pressure is not going to reduce the rolling radius?

Saying that low profile tyre dont help as the side wall is a lot stiffer

Sam

[Steve30]

Hi Sambo, Last Sunday I had a screw in my tyre and the ping went off on the dash. I stopped right away noticed a screw had gone in the tyre. Got the punture fixed 15 quid. Its as simple as that its never let me down before!! Brilliant little gadget IMO thanks Steve 

[TagnuT]

I managed to just catch a ratchet strap on the motorway. The hook caught the inside of the tyre. I thought that it was ok as the steering felt fine. But as I came off at the next junction the warning light came on. I pulled over, hopped out and watched the tyre go flat.  Shame it doesn't tell you which tyre it is though.