Different spare tyre size

[ytt105]

I've just purchased a set of Bridgestone 697s

265/65 x 17

They look great!

However, my spare is 255/55 x 18 which works out at 38.6 mm smaller, some 5%.

Is this too much difference for the diff.

[TDV6]

Yes the difference is too great, I don't know what the tolerance would be but 776mm to 738mm but that's over 1.5 inches in the old money.

A good puncture repair kit ( ARB ) and compressor will get you out of most situations.

Ryall