offsets

cheers, i was getting a bit confused as different places say different things.

now the decision, do i get 17's or 18's ?????

im swaying towards 17" rs4's at the mo. i want whatever i get to look like it came on the car, dont want it to stand out to much (although its decked), just update the looks
 
Go for 18's m8, theye will be the same rolling radius as the 16's you have, At least thats what i want, nay NEED to do,lol
 
as far as im aware, and please correct me if i'm wrong, but doesnt the offset stay the same no matter what size of wheel ?
the offset is how the far wheel sticks out/sits in from the arch.
The tyre profile is the thing that changes, so 45 for 17's, 40 for 18's 35 for 19's, to keep the rolling circumference the same
 
Thats right, its just generally the width increases too, this can cause the tyre/wheel to foul the suspension or arch, therefore sometimes it is necessary to change to ofset to space the wheel accordingly.
 
This is all true but the profile should only change in relation to the tyre width in order to keep the same rolling radius since it is a percentage of the width itself.

For instance, my car had 225 x 45 x 17's on it as standard which gives a rolling radius of 63.43cm

45% of 225mm = 10.25cm
x2 [because there are two sidewalls] = 20.25cm
+ 17" [43.18 (17x2.54)]

Total = 63.43cm


For the 225 x 40 x 18's that I now have on there...

40% of 225 = 9
x2 = 18
+18" [45.72 (18x2.54)]

Total = 63.72cm


So as you can see the radius difference is within 3mm and tolerance is easily within that of the difference between a new and worn tyre.

/ubbthreads/images/graemlins/smile.gif

T
 
Offset is actually the distance between the back of the mounting hub and the centre line
of the wheel. Wide wheels can require a change in offset to avoid fouling.
 
Definately go with 18's. I made the mistake of getting 17's at first and they look too small, had to wait a couple of years before I could justify getting 18's
 

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