Rolling Diamter

[ChrisKX250F]

Looking at buying 20" wheels for my VE SV6, the rolling Diamter for the standard 245/45/18 is 677.7mm, now my car has been to HSV to get a GTS steering wheel put on and they also fitted a HSV build plate under the bonnet, I am going to buy a HSV tyre placard from eBay genuine from GM that lists the factory fitted supersport 20" wheels that came fitted on Some VE SV6's from factory.( which I'm mainly buying to show that a load rating of 95Y is fine for the car) now my question is when calculating the rolling Diamter for the wider and bigger tires I'm putting on, do I calculate off the 18" size tire or the 20" supersport tire 245/35/20 size that the tyre placard says?? Thanks

 

[07GTS]

u will have to change the calculation to suit the new tyres, holden may have a setting for 20" factory tyres

 

[ChrisKX250F]

u will have to change the calculation to suit the new tyres, holden may have a setting for 20" factory tyres

Yeah so what I'm after anyway is I'm wanting 9.5" front and maybe 10" back depending, I was wanting 265 for the back but it 16% rolling Diamter being 1% over the legal limit... If I changed the rolling Diamter to suit the supersport 20" wheels to my new wheels it would be 14% (legal) hence why I'm wondering what calculation is okay to go off

 

[07GTS]

my ve gts has 275 rears standard so it should be fine if u are skinnier, whats this 16% rolling diameter..? width or tyre distance per turn..?

 

[Sean880]

Yeah so what I'm after anyway is I'm wanting 9.5" front and maybe 10" back depending, I was wanting 265 for the back but it 16% rolling Diamter being 1% over the legal limit... If I changed the rolling Diamter to suit the supersport 20" wheels to my new wheels it would be 14% (legal) hence why I'm wondering what calculation is okay to go off

1. Buying some tyre placard on Ebay and sticking it on your car does not make the load ratings on the 20 inch tyres you may want to fit compliant with tyre/wheel modification regulations in VIC any more than making a sticker yourself does.

2. As far as sizes are concerned, for a staggered fitment the closest rolling diameter in 20 inch to a 245 45 18 tyre are these which is a common fitment on VEs.
Front 245 35 20
Rear 275 30 20 (or 285 30 20)

 

[MYVESSV8]

as above, I run 275's rear, 245's front, no problems