Whilst checking my tyres at the weekend I was surprised to find that the rear threads (or is it treads?) are down to 2-3mm, the fronts are at 4-5mm. My surprise is because my last set of tyres wore more quickly on the front, albeit a different make of tyre and I have changed the tyre pressures I use on the fronts. All 4 tyres were changed at the same time.
It seems that shortly I will need at least 2 new tyres. My manual recommends changing all 4 tyres at the same time (standard advice on 4 wheel drives I believe). However the front tyres clearly have some good life in them yet, it seems foolish to unnecessarily change them. Therefore I have these options:
2 new tyres for the rear, changing to the front when the fronts need replacing. Cheapest option.
Or
4 new tyres. Best all-round except on the wallet.
And
Consider rotating tyres every 6 months? In future to even out tyre wear.
The car is a Toyota Celica GT-Four
Any opinions or advice on the best choice?
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As it is permanent 4wd I presume it'll have a centre differential. If the rolling radius of the wheels is different ,as through different wear on the tyres, the diff will operate continuously and therefore wear out quicker. A good analogy would be driving contantly round a slight bend, the diff on a 2wd car would wear quicker.
So in answer to your question, ideally replace all four tyres with the same make tyre and switch front to back on the same side at a regular interval (say 5000 miles) to even out the wear. This is what I have done ever since owning a Subaru.
Nice car, BTW.
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it would be better to change all four from a grip point of veiw and have 4 tyres with the same handling perfomance .
I would disagree with nick in that the rolling radius wont be as different as do any harm ,that is what the diff is for and a few turns per mile wont hurt it because of worn tyres on one axle ,it would maybe do damage if the profile was different but even then it would probably be ok from a mechanical point of veiw however unsafe it made the handling
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I would disagree with nick in that the rolling radius wont be as different as do any harm
May be so for a GT-Four, and I have no idea if any of its (likely three) diffs are free, semi locking, or fully locking, but there are some cars with limited slip diffs that most certainly suffer from exactly this problem. Mk I Discos and AWD Mk 1 V70s (850 facelift) spring to mind as two examples.
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I know the GT-Four has a limited slip diff, but thats as far as my knowledge goes. However it would be foolish to risk damage for the sake of trying to squeeze a few more miles out of the tyres.
My garage have always said that it's not worth rotating tyres, but then perhaps they would do, if it means more business for them. I think 4 new tyres and having them rotated every 6 months is probably the way to go.
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SjB Mk1 discos certainly dont have problems with this unless the vehicle is run with the centre diff locked which it should not be unless traction is poor in which case it should be manually locked by moving the range lever to the left
wear on tyres is not enough to cause mechanical problems ,if this was the case cars with LS Diffs would never be safe going round a roundabout without locking up ,I cant remember the % of slip figures but its certainly more than 5% and 4mm of wear would equal much less than 1% on the vehicles you mention . Changing the profile by 5% for example would be 195/65x15 instead of 195/60x15 would only make a 3% difference in circumference and tyre wear is much less than that
as in my first post it may affect handling and grip though
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