Righto, the current steelies I have don't fit. They are 4x100, but it won't fit on the hub, as it's not 57.1mm. Pissed, yes, very. Now, I need to change said rims, as nobody has proper spigot rings and I have been told that it's stupid to fit them. So I'm on the hunt for new steelies, but the imperial system isn't quite clear to me. I guess that 175/70R13 means 6Jx13 right?

175/70/r13 is how the tyre is measured

6j x13 is the wheel measurement

Hmm, how can I know which one fits which one? Or are there some standards about? I've never been too clear on the whole tyre/rim mesaurements. So confusing!

The wheels are imperial. The tyres are metric width,but obviously have to be imperial diameter to fit the wheels.

So a 6in wide wheel is 150mm's wide. Theoretically,a 145 or 155 wide tyre is correct for the wheel,but you have quite a margin - theoretically then,they'll take 135's or 185's and that's about your margin.

But the wheel is measured from the inside of the rims,the tyres are measured across the tread. So the tyres need a slightly higher measurement than the wheel - so for a 6in wide wheel,you really want a 155-195mm tyre.

The aspect ratio is the profile in percentage to the width - so 195x50 means the tyres are 195mm wide and the sidewall is 50% of that.

Example then - I have 185x60x13s on a 5.5x13 rim. So both the tyres and wheels are a match at 13ins,the wheels are 5.5ins wide and the tyres are a touch wider at 185mm wide.

But of course they look the same width,due to the reason stated. The profile is 60% of 185mm.

The wheels are imperial. The tyres are metric width,but obviously have to be imperial diameter to fit the wheels.

So a 6in wide wheel is 150mm's wide. Theoretically,a 145 or 155 wide tyre is correct for the wheel,but you have quite a margin - theoretically then,they'll take 135's or 185's and that's about your margin.

But the wheel is measured from the inside of the rims,the tyres are measured across the tread. So the tyres need a slightly higher measurement than the wheel - so for a 6in wide wheel,you really want a 155-195mm tyre.

The aspect ratio is the profile in percentage to the width - so 195x50 means the tyres are 195mm wide and the sidewall is 50% of that.

Example then - I have 185x60x13s on a 5.5x13 rim. So both the tyres and wheels are a match at 13ins,the wheels are 5.5ins wide and the tyres are a touch wider at 185mm wide.

But of course they look the same width,due to the reason stated. The profile is 60% of 185mm.

You sir, are absolutley awsome! Thank you!

I wish I could give you some sort of forum prize.

Why thank you very much

The wheels are imperial. The tyres are metric width,but obviously have to be imperial diameter to fit the wheels.

So a 6in wide wheel is 150mm's wide. Theoretically,a 145 or 155 wide tyre is correct for the wheel,but you have quite a margin - theoretically then,they'll take 135's or 185's and that's about your margin.

But the wheel is measured from the inside of the rims,the tyres are measured across the tread. So the tyres need a slightly higher measurement than the wheel - so for a 6in wide wheel,you really want a 155-195mm tyre.

The aspect ratio is the profile in percentage to the width - so 195x50 means the tyres are 195mm wide and the sidewall is 50% of that.

Example then - I have 185x60x13s on a 5.5x13 rim. So both the tyres and wheels are a match at 13ins,the wheels are 5.5ins wide and the tyres are a touch wider at 185mm wide.

But of course they look the same width,due to the reason stated. The profile is 60% of 185mm.

people should have to read that as a condition of joining the forum! Would save so much time and confusion for wheel/tyre novices - throw in offsets and you're onto a winner!