Rolling radius mismatch; your opinions on possible harm

[svxistentialist]

My Jersey Girl came with very poor tyres, perished rubber and generally in very poor condition.

These I have replaced with the tyres from Black Betty, which are Dunlop Sport 2000E standard fitment 225/50 ZR 16. Betty had recently passed an MOT and two new tyres were mandatory, so effectively I have four tyres the exact same fitment, two are brand new, two are part worn, possibly half worn I would say.

The way they are fitted is with both new tyres on the right side, and both worn tyres on the left side. I did not want the front and rear axles having different rolling radii.

This is my question; does anybody think this difference in rolling radius left to right will cause detrimental effects at the gearbox?

The actual measured radii in cms is 31.6 on the left side and 31.8 on the right side. [The rolling radius figures will be lower than these once weight is applied, but there should be the same ratio proportions]

My own opinion is it should be OK, as it will be the same to the gearbox as if the car is turning right all the time [the left hand wheels make more revolutions that the right side do, just as when turning, and the diff should be able to cope with the difference]

I would like your opinions. Am I being naive? There are two solutions;shave off half the rubber on the new tyres; or buy two new ones and throw away the half worn ones. Either solution involves throwing out about €160 worth of rubber [$240 in your money] and I would rather not waste if there are no ill effects.

Joe

[Hocrest]

Will the side/side mismatch cause an issue with the rear LSD???

[svxistentialist]

I don't know Dave. That's one of the reasons I asked the question and quoted the actual radii. I thought perhaps one of the engineers on board here that understood rotational forces would venture an opinion.

Joe

[oab_au]

Originally Posted by svxistentialist

I don't know Dave. That's one of the reasons I asked the question and quoted the actual radii. I thought perhaps one of the engineers on board here that understood rotational forces would venture an opinion.

Joe

I think it would be better to fit the two new to the front, the worn to the rear. The VTD won't be as worried about the difference as the rear diff that will heat up due to the difference. We have had a few rear end fires.

Harvey.

[svxistentialist]

Would you think so Harvey?

It's doing very little miles at present, so I have not managed to check temperatures at the LSD.

It would mean swapping the tyres around on the wheels, but that would not be too difficult, I suppose.

Thanks

Joe

[TomsSVX]

Harvey is right. I have heard fire stories from the rear diff but it is really only possible to get the rear that hot by overworking the LSD w/ mismatched tires... So no diff fires please Always keep equal diameter tires on the axles

Tom