new tyres front or rear?

[stefan einz]

That would be a challenge for me, given that the tyres on my GT3 come with around 4.5mm when new!

That's different. Unlike perfomance tyres, road tyres come with 8 to 8.5 millimeters of tread depth. So we see eye to eye. Four years are a good maximum age limit (including storage time), but some tyres age within three and a-half, three or even two and a-half years. They will probably last a bit longer in the UK than under the mediterranean, where most tyres dry out after three years.

I also agree that awareness to the state of the tyres is important, so I have the habit of checking the tyres visually (by a brief walk around the car) each time I enter the car. The alignment is something I check each year, or after 6,000 miles, when I get the tyres removed, inspected all around and rotated.

Just to be clear, the GT3 tyres are road tyres, just performance oriented (in this case Michelin Pilot Sport Cup). They are actually quite capable in the wet, provided one keeps the speed down. They even coped with this downpour at the Nurburgring!





Very few tyres in the UK come with more than 8mm of tread - most are actually between 7 and 8mm when new.

[TVP-Mike]

Hi. As a police collision investigator for many years I can confirm that it is best practice to put the tyres with the greater tread depth on the rear irrespective of whether it is front/rear or four wheel drive. There are a number of reasons but I will illustrate potentially the most serious. Some real world serious crashes prove the point. Take the scenario of a large amount of surface water on a fast road or motorway. It is bad enough to aquaplane with the front tyres as you will lose steering but the driver will at least feel the lack of traction and hopefully have the time and opportunity to reduce speed to regain grip. However, if the rear tyres aquaplane when the fronts grip then effectively the rear of the car steers and the result can be a violent irrecoverable loss of control with the driver having no time to correct it. Someone might argue that as the rears follow in the tracks of the front tyres then it is very unlikely that the rears, (with less water to contend with) will ever lose traction before the front. The simplified response is that this is true when the car is travelling straight and level. However if the car is steered to follow a corner or to perform a lane change on a motorway then as the rears then follow a track inside that and separate to the rears then suddenly the rears may have to do as much work dissipating water as the fronts. The most undesirable of surface water cases is when the front tyres with greater tread depth have grip and the rears with less tread depth lose grip and aquaplane. Add to this the angular (steering) force of a lane change then the car will violently rotate as the rear of the car overtakes the front. Hope the explanation helps.

[Renny]

I think you may have a point regarding tyre type/manufacturer, Gareth. In the Formula Ford racing championship regulations the competitors were only allowed to use a particular Dunlop tyre. It was claimed, by Dunlop, that a tread depth of 1mm was still good and was thus written into the regulation as the minimum tread depth. This is in opposition for most other racing championships regs. which allow minimum tread depth down to 1.6mm.

However, in the wet, most competitors would fit tyres with a much greater depth than 1mm. In the dry, one of the issues was tread movement, so it wasn't unknown for competitors to buff the read to about 2-3mm depth.

[jcochrane]

I think you may have a point regarding tyre type/manufacturer, Gareth. In the Formula Ford racing championship regulations the competitors were only allowed to use a particular Dunlop tyre. It was claimed, by Dunlop, that a tread depth of 1mm was still good and was thus written into the regulation as the minimum tread depth. This is in opposition for most other racing championships regs. which allow minimum tread depth down to 1.6mm.

However, in the wet, most competitors would fit tyres with a much greater depth than 1mm. In the dry, one of the issues was tread movement, so it wasn't unknown for competitors to buff the read to about 2-3mm depth.

Very true. Don't remind me about buffing of tyres. Had a nightmare in one championship where buffing was not allowed. "No you've got it wrong. Put the tyres on my road car and did a lot of wheel spinning." was a common reply.

[f3racer]

Defnitely put the best tyres on the rear. If the front loses grip on a wet road, you'll apply more lock, scrubs a bit of speed off then regain grip, hopefully before you've understeered into oncoming cars! If the back goes first, you'll probably crash.