I suspect balance means the tyres were balanced.

The worn tyre would have had a lower rolling radius than the new one, and as far as recall the RX8 is RWD, which would have meant the diff was working all the time to balance out the different sizes, which would not to it any good.

Be thankful you don't have one of the more fragile soft roaders with an all wheel drive system made of cheese because you could have been looking at changing all 4.

It can be good practice to change tyres at 3mm anyway, under the circs i would have got both changed but kept the good one as a spare just in case of a puncture that couldn't be repaired at some point in the near future when the tyres were approaching half worn.

This wouldn't have been a thread at all if the spare wheel had been full size, just swap over and keep the out of shape for emergencies.

Edited by gordonbennet on 07/06/2017 at 14:35

I have always ensured I have the same make/type of tyre on both tyres per axle - I understand this isn't a legal requirement, but is best practice. However, when I once damaged one front tyre I simply replaced just that one.

So without knowing more it's difficult to judge whether you have been ripped off.

By the way, I assume the word "balance" doesn't refer to the new tyres being balanced, in the sense of weights attached to avoid vibrations, does it?

Edited by FP on 07/06/2017 at 14:36

I feel I may have been sold a tyre I didn't need, which has resulted in a hefty total bill – does this sound like the case to anyone else?

Yes.

Please also note that the treads for both rear tyres were noted as being 62% worn with 4mm on the outers of the tyres and 5mm on the middle of the tyres.

Loads of wear left. New tyres are around 8mm. Legal limit 1.6mm. While different sizes are not ideal I suspect for your type of driving it would be irrelevant. The tiny difference in diameter would put virtually no extra strain on the differential pinion which would just very very slowly rotate in a straight line. They probably sold your tyres to a back street second-hand tyre specialist ( I have known one for years who has occasionally provided me with excellent service). And to add insult to injury, I bet they charged for disposal!

Edited by John F on 08/06/2017 at 13:50