Space Saver Advice?

[V6Tom]

Good evening Gents,

I run 20 inch alloys with 255/30 R20 tyres. My space saver is a 19 inch with tyre 125/70 R19

So I did some calculations

so to my confusion my 19 inch space saver is bigger than my normal 20 inch wheel. so are space savers supposed to be larger than the full size wheels?

I had a blow out recently and I was told you cant run a wheel smaller on a quattro? messes up the abs or something

 

[joinerman]

It winds up the transmission

 

[Charlie Farley]

rim size and tyre size are not really the issue, well they are but its the " Rolling Circumference " that is crucial on AWD cars etc.
all wheel/tyres need to have the same rolling circumference otherwise you get adverse effects on the diffs etc, all wheels need to be travelling the same distance , there is a very small amount of variation , but it is small.
So how you get to the same data for the spare is up to you, just ensure you keep things all the same.

 

[jdp1962]

Good evening Gents,

I run 20 inch alloys with 255/30 R20 tyres. My space saver is a 19 inch with tyre 125/70 R19

So I did some calculations
View attachment 212364
so to my confusion my 19 inch space saver is bigger than my normal 20 inch wheel. so are space savers supposed to be larger than the full size wheels?

I had a blow out recently and I was told you cant run a wheel smaller on a quattro? messes up the abs or something

When you say your "normal 20 inch wheel", are you saying these are the OEM wheels the car came on from new? Or have you changed the wheels from the original and use "normal" in the sense on "not the space-saver"?

 

[V6Tom]

Sorry gents.

My car came with 19's at 30 profile and my 20's are 30 profile.