Tyres - reading the wear pattern

[Richard]

As we seem to have a bit of a wheel and tyre theme today here goes a bit of understanding the wear on tyres, feel free to correct / augment.

One thing in my research for Kit car builds is that the ability to adjust suspension settings / camber etc. is superb, it does bring with it a few things to consider, anyway here is my awareness of tyre wear.

Tyres worn on outer edges and central tread less worn  -  typically under inflation of the tyre   

Tyres worn more quickly than expected and heavy wear on the "shoulders" of the tyre  - typically over inflation of the tyre   

Tyres wear happens across the surface from one side quite quickly - typically poor mis-alignment (toe in or out)   

Tyres bulging on side wall or other visible damage - typically caused by impact of some kind, drive more carefully    

Tyres wear on outer shoulder, a difficult one this one this one if you have 2 sets of wheels with different sized tyres to get the "balance" (pun intended) - geometry set up needs reviewing   

[Retired Ronnie]

  Found this post interesting and informative especially as I have just taken a look at my back tyres on my Robin Hood. I was quite taken aback to see how much wear has taken place from new to now (about 1.5 to 1.8k). Bearing in mind what I have just read about pressures, can any one suggest a suitable tyre pressure for road use. The guy who fitted them said 28psi, but I seem to remember RH saying about 17psi !!  HELP!!

[Richard]

As a general rule from reading all over the place the place to start on tyre pressures is the max as indicated on the tyre wall -10%, then adjust up / down from there in 1psi changes over a week to find what you feel is right for you and your car.

If you are using one of the old pen style tyre pressure gauges, keep it on one side for nostalgia and buy a new one, they are quite inaccurate.

Edit: It did occur to me that both of your advisors could be right and be talking about different tyres.

[Mark G]

I'm affraid I have to disagree with Richard with where to start with tyre pressures.

Tyres are designed for all sorts of cars ranging from 400kg up to 2000kg+.  The max pressure would only really be used with a heavy car,  Our cars are all very light.  I run the tyres on my Indy at between 18 - 22psi depending on the weather and temperature,  The hotter it is the lower pressures you can run.  Remember that tyre pressures will increase by 2-4psi when warm so always check your tyres either hot or always check them cold or you will end up with inacuracy's.

This is of course just my opinion but when it comes to tyre pressures it really is a matter of personal prefference as to what feels best for your particular vehicle.

[Richard]

Fine to disagree.

My thinking and the various reading I've done over the odd year or two off and on has led me to believe what I have written is the only really basic rule that can be applied across tyres.

Most tyres are designed by the manufacturers to work within a certain range of tyre pressure. The main contributor to that is the construction of the side wall. It is in my opinion wrong to assume the vehicle weight between a kit car and a typical road car would on the same tyre mean it is massively inflated to a different value, the adjustments for weight are relatively small because of the construction of the tyre in questions side wall dictates the working pressure range and not the actual weight of the vehicle.

Most kit cars have fully adjustable suspension and it is this that should be altered not the tyre pressure massively, it is fine within a couple of psi but not something like 10psi.

You should use a pressure suitable for your tyre and the temp when inflated to account for the impact of hot / cold. If you are running soft yoko's the tyre wall is very very different to a harder tyre typically found on a mid-size saloon.

If you are having handling or other problems that a little adjustment of tyre pressure is not curing the issue will not be the tyre pressure but more likely the suspension set up.

As said all opinions are fine BUT there is not really one pressure for any car without knowing the tyre in use. The only approximation I have found is that -10% rule and then it is not exact but a pretty good starting point.

['The Gaffer']

I run mine very low, if I pumped them up they would be rock solid and not offer any contour or grip.

My car is very light also.

[Bulldog Bri]

I've always run mine at about 18 - 20 psi, as recomended by the pilgrim club from the 80's

[PhilW]

Another thing to bear in mind, tyres tend to go off after 2-3 years.

[fcmmotorsport]

tyres always cause a discusion in our place we cant belive the amount of people who dont see how important important a tyre is and also having the geometry corect. as a general ruel of thumb we say exes wear on inner part but not outer is over inflation exes wear on outer edges but not center is under inflation scuffing on inner or outer eges is toe related or camber related. all depending on tyre quality also depends on how they wear and also life span. a lot of people also dont no their is a date code on the side wall of the tyre when it was made and when it should be fitted bye (shelf life). also tyres like toyo 888 (road legal cut slicks) shouldent be left inflated on a car if it is being left stood over the winter or used or stored in close to or below freezing conditions or driven in these conditions as they can crack and or perish. i could go on and on but prob boared you enough now 

[David H]

My car is approx 600kg. I run AO48s with 17-18psi front, 15-16psi rear. This is so the pressures increase slightly when warm/hot. If i inflate the tyres much more my teeth shatter and i loose grip. Westfield recommend 21 all round on their kits, but i run mine slightly lower. I tried 21psi yesterday when warm at Combe and was having fun trying to keep it on track. There is a matter of preference but weight seems to have a lot to do with it. When I was sent my wheels back from Image, they had inflated them to 28psi, no way would i use that. They had forgotten i wasn't driving something a lot heavier.

[Hairy Santa]

Tyre Pressures are extemly important, and to hard can cause you to bounce down the road, also shatter your suspension components as well as your teeth

Sold a landrover many years ago which I had fitted huge commercial tyre's on to increase the ground clearance
When I saw the chap a few months later he told me he had had to replace 3 of the leaf road springs ( Strange as they were all new for the new set up from me) eventually found the problem when he said he sets the tyre pressures to what is written on the side of the tyre's
90 PSI MAXIMUM --- well I ask you     

Pete

[David H]

yeah! my van is max 55psi and i will only use this level of pressure on the rears when i have a FULL load or the tyres become squashed and the van rolls a tad. stands to reason.