Rolling radius

[HEKTOR]

I am considering fitting a new set of new wheels to my rs4. The fronts are 8" wide the rears 9" wide. Will i have issues if i run 215/35/19 on the front and rear? I am happy to run a stretch on the rears in an attempt to keep the rolling radius the same.

 

[aragorn]

215's are surely far too narrow?

Especially on an RS, they run 255's as standard?

running the same tyres front and rear is fine, but 215's is just going to look silly on a RS.

245/30r19 or 255/30r19 might be a shout?

 

[HEKTOR]

I think they will be to narrow, but i was using that size as an example as those are the size of the tyres currently fitted to the wheels.

I think that might be a good shout, so there doesnt have to be to big a size difference to keep the rolling radius in check?

 

[aragorn]

the rim width doesnt effect the radius a huge amount, so as long as the tyres are the same size front and rear i recon it'll be fine.

 

[murran]

when going up or down in wheel size.... its the profile/aspect ratio that you change to keep the rolling radius the same or similar. not so much the width, but it can be juggled around within reason to get near the original rolling radius.

205 55 r16

the 55 is a percentage of the width. 55% of 205.

always go a little under the original rolling radius rather than over. nothing wrong with your speedo under reading, but over reading can be a problem for obvious reasons.

 

[HEKTOR]

Is there something like a calculator that can work this out? It would make getting the correct tyre size easier

 

[aragorn]

Googling "tyre calculator" finds a few options.

I've used this one before:

Tire size calculator

 

[HEKTOR]

Googling "tyre calculator" finds a few options.

I've used this one before:

Tire size calculator

Thanks, I will give that a try.