Tyre pressure by wear

[phipck]

Hey guys, having changed cars and fitted new winter tyres I have been left looking for the ideal tyre pressure for the new car.

 

With my old Xsara having changed from summer tyres to winter tyres I found that the recommended pressures were resulting in underinflated wear on the winter tyres. So I experimented with pressures and found that with the Xsara 2 or 3 psi more than the book brought the wear into line and improved the drive noticeably.

 

What I also noticed was that although the front and rear pressures were different the area of tyre that you can see making contact with the ground was the same front and rear. You could see this as the sipes of the winter tyre stopped just where the contact stopped.

 

Is this just a coincidence? Is it possible to visually check the contact patch to refine tyre pressure appropriate for the tyre? If so what part of the tyre should be in constant contact with the road and is there a marker on the tyre?

 

As I now have a Grand Scenic I have put winters on and again they appear and feel underinflated. I have over inflated the tyre by approximately 3 psi front and rear over the Renault recommended pressure.

 

Heres a pic of what I mean by visual contact mark and this is the front tyre on my scenic  .

 

[Tony]

The front/ rear contact patch will differ due the difference in camber and the roll effect on the front camber during a turn. The "under-inflated" feel on winter tyres is not uncommon because the lateral flex on them is so much more than normal tyres so the transition comes as a  bit of a shock.

 

You can visually check for the contact patch but it wouldn't be very accurate because the variation between correct and dire in the real world is very small

 

 

You are correct to adjust them to your liking since the OEM pressure is a "suggestion" ( within reason ) to much or to little could place you in one of the images above. Your goal is this

 

Not this

 

 

So although more pressure might feel more stable it doesn't mean there's more available grip.

[phipck]

This is as I though, thank you. Having experimented with my last car I am very aware that the feel of winter tyres is different to summer tyres. Having run winters all year for 3 years on the xsara the wear is perfectly even across the tyre so I believe I found the sweet spot like your image above shows.

 

With the new car I have been trying to find that sweet spot again but wondered if there were a marker on the tyre itself to help show that perfect point.

[Tony]

No there's not, a temperature gun is about as close as you can get to locate the true contact patch other than that it's trial and error.

[chrisgixer]

Would it be fair to say, for the consumer, once wear is evident, that wear is irreversible and could well affect the handling for the rest of the tyres life? Perhaps not so much in a narrower tyre, but on wider performance tyres it's too late if bad wear is evident.

 

Therfor important to get it right from the outset...?

[Tony]

Since there's no real right or wrong way the wear is the only guideline. Your correct in saying the wear is matter of fact but manipulation can work toward damage limitation.