Poll on where to fit new tyres

Hi Guys,

Just a general observation/off RR topic rant!

I was reading an article in this weeks Auto Express on the legality of fitting lower speed rated tyres than the OE equipment. All good (Admiral said that load/speed ratings of tyres was not classed as a notifiable modification) until I got to the last sentance in the article:

"Campaign group TyreSafe recommended fitting a pair of new tyres to the rear axle and replacing worn-out front tyres with the old rear ones"

I find it astounding that this is still being advised.

A search of old threads on the subject will find old fogies talking about rear wheel drive Anglias and Escorts on crossply tyres spinning like 911's with lift off oversteer if you didn't put the new tyres on the back. They may have had a point, I never drove an Anglia on worn cross plys to argue that.
What I have driven is superbikes, RWD rally cars and a plethora of FWD hot hatches plus just about every 4x4 on the market. And I can tell you there is only one place I'd put two new tyres, and that is most definitely on the FRONT!!

The market place at this stage is dominated by front wheel drive, at least 80%, probably closer to 90%. The days of lift off oversteer for the great unwashed general public died with the ford sierra (which wasn't even that prone to oversteer). The predominant danger in motoring (for everyone outside males 18-25) is rear ending the car in front of you. Your front wheels will do at least 75% of the braking (pushes 95% on bikes). Thats where you need the grip, particularily in the wet.

If you've gotten yourself into a situation in a FWD car, where the difference between crashing and not crashing is down to the relative thread depth between the front and rear tyres, you are driving so far beyond your limits, that you're going to get intimate with armco/walls/other cars very soon anyway.

The proof of this is to be seen at every clubman rally where you will often see crews with only enough money for one new set of tyres. Where will the tyres go, on the FRONT every time because thats where you need the grip.

The only thing I can possibly think of is that at some stage someone advised putting new tyres on the rear until they are scrubbed in before switching them to the front, 100 miles or so, and this got morphed into the above piece of advice.

Would any of you mechanically and engineering minded gents/ladies care to put up arguments for either campop2:

Try to replace all 4 tyres at the same time, on a vehicle with permanent 4WD. To help out in this, "rotate" the tyres regularly eg every 6 months or so, to even out wear. For example:

Front left --> Rear left
Rear left --> Front right
Front right --> rear right
Rear right --> Front left.

If you want to incorporate the spare tyre in there too, you can do.

I'd put one on the bonnet and the other on the roof.

paul_c said:

Try to replace all 4 tyres at the same time, on a vehicle with permanent 4WD. To help out in this, "rotate" the tyres regularly eg every 6 months or so, to even out wear. For example:

Front left --> Rear left
Rear left --> Front right
Front right --> rear right
Rear right --> Front left.

If you want to incorporate the spare tyre in there too, you can do.

Click to expand...

If you have directional tyres moving them around in this fashion would probably end up with you in a ditch.

I don't, though.

If I did (which I don't) then its still possible, for example just moving front --> rear regularly.

paul_c said:

Try to replace all 4 tyres at the same time, on a vehicle with permanent 4WD. To help out in this, "rotate" the tyres regularly eg every 6 months or so, to even out wear. For example:

Front left --> Rear left
Rear left --> Front right
Front right --> rear right
Rear right --> Front left.

If you want to incorporate the spare tyre in there too, you can do.

Click to expand...

Yeah Paul,

I agree 100% in the RR case but permanent 4WD can only account for maybe 1 or 2% of cars. BMW even recommend replacing all 4 together most of their motors.

What I'm getting at is a piece of advice, given freely to the general populace, that to me is founded on dangerous logic. I'd like to hear what you guys here think on it.

depends on the 4wd setup. i wouldn't put the rear tyres on the front, and the front tyres on the rear on a freelander, coz this may damage the diffs if the diameter of the rear tyres were greater than the front ones. must always have equal size tyres or slightly smaller on the front.

If you think of physics its not the front, but the back you need to control. Stamp on the brakes, all the weight goes to the nose, therefore the rear is light and most likely to skip out.
In the case of a landy its not going to be warp factor 'brown trouser' and to keep control you need to stop the rear overtaking the front...hence i'd rather have more tread on the rear tyres.

but the front tyres control the direction of travel from the steering

I didn't say let go of the steering wheel!!

yea but need tread on the front to grip when steering.

i sort of assumed the front tyres were road legal...

howardo said:

but the front tyres control the direction of travel from the steering

Click to expand...

Are you sure?

if we are ignoring vcu issues, the front tyres will get most of the power and have to steer aswell , so will want newer tyres on the front.

Braking in the dry is more to do with the coefficient of friction of the tyres rather than the tread depth i.e. compound / age etc. Tread depth only really comes into it when it's wet with standing water. In the dry, a 'slick' tyre would have more braking effect than a treaded tyre due to more rubber being in contact with the road. The same goes for cornering for the same reason. Obviously this only counts for dry tarmac though.
I agree with the principle of changing both tyres on one axle at a time but it's not always possible due to cost or availability. Also, if you have a (unrepairable) puncture in one when the other is only half worn, are you seriously going to change both? You'd have to be pretty flush to do that each time, especially if you have expensive tyres (or run-flats as on BMWs).

Taking things to the extreme..to prove a point....if you were driving a hgv (not a trailer type)...and you had to choose, where would you want the better tyres..front or rear?

hgvs have alot of weight behind the cab though

I'm just saying, if i have the choice i'd like to be able to control the back of the vehicle as much as possible..if all the weight shifts to the front its easy to control that bit..imo.

i personally would only put new tyres on the rear of a permanent 4wd vehicle if it had a vcu anyway.

storm99 said:

If you think of physics its not the front, but the back you need to control. Stamp on the brakes, all the weight goes to the nose, therefore the rear is light and most likely to skip out.
In the case of a landy its not going to be warp factor 'brown trouser' and to keep control you need to stop the rear overtaking the front...hence i'd rather have more tread on the rear tyres.

Click to expand...

See, this where I differ completley in opinion.
You are of course entirely correct that the weight transfer is to the front but thats where we part company. The physics IMHO are that the back can't start to come round unless you introduce a rotation moment around the front wheels. Braking in a straight line is not going to do this unless you've a big difference in grip between the front wheels. Braking around a bend will cause the front to wash out before the back gets out of line in a car whose natural tendancy is understeer (which as per OP is over 80% of motors on the road today).
I've had more 'hairy' moments than most thanks to a mis-spent youth behind the wheel and speed of rotation as you enter a spin is much lower and catchable than the speed at which you are approaching your imminent demise. I'd much rather have as much stopping power as possible under those loaded front wheels and steer into any precipitent slide.