Coulomb
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- MG4 Trophy ER
? There has to be considerable difference in tyre diameter between 17" and 18" alloy wheels.The spare wheel is the same even though the alloy sizes differ.
Are you saying that all the GS, HS, MG5 etc use the same spare wheel rim size? And there are different profiles of space saver tyres to fit that same to equal the diameter of the various main tyres? Is this a 17" rim for 125 mm temporary (space saver) tyres?
A centimetre difference in diameter might not look like much, but if you try to drive at 80 km/h, I'm sure it could be quite dangerous. You mightn't even be able to steer at all.
I guess that one inch difference in rim diameter is pretty close to 12.5 mm in radius, which is 10% of 125 mm, the width of the space saver tyre. So if the right size tyre for a ZS EV is T125/90 R16, you could get the same diameter from a T125/80 R17 (on a 17" rim, obviously).
There is also the offset to consider. But hopefully, all the MG models discussed have the same offset. For a temporary tyre, the offset probably doesn't matter too much, as long as the rim clears the hub.
How to read tyre sizes.