Why not fit 205/55/13 to a 6J rim?

[green george]

I know the standard advice is that 175/55/13 are fitted to the 6J rims and that 205/55/13's are fitted to 8J rims.

However, it appears that the 205/55/13 and the current ZZS 215/55/13 tyres are within spec for a 6J wheel.

So why use a 8J wheel other than convention? Especially, as the 8J wheel can foul the rear suspension.

N.b. I have used the car bible "ideal rim width calculator" to check this.

 

[SteveA]

If I remember correctly it is something to do with sidewall deflection. When a tyre is suited to a rim the side wall will be almost vertical meaning lateral load will allow the tyre to shift around and keep the tread blocks in contact with the road more consistently (therefore maintaining temperature). When the side walls are bent in or out there is more tension on them reducing the amount of give. This can have the effect of lifting the tread blocks away from the road so the wider tyre won't necessarily mean more grip.

Plus you will have to find some nice tyre fitters because it is much harder to fit them and some might not have the patience or tools required.

[keybaud]

Or get a 7" wheel made up. 

[OliverSedlacek]

I run 205/60/13s on 6J rims as they are within spec. It kept my ride height and gearing where I wanted when I could no longer get 70 profiles. They needed some small wheel spacers (5mm from memory) tot clear the front wing stays.