Just because it was not crying in pain wouldnt really mean it wasnt being damaged. I think any distance at any speed would be harmful. If one wheel is spinning quicker then the other because it has a smaller circumference its putting strain on the diff.

Shame i dont have my car, i could of gone to your house with a complete set of 16's/18's, put them on and gone to get new tyres.

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Honda Hannspree Edition CBR 600 RR - SOLD
Yamaha FZ1N - Purchased