Tyre size advice please

[Nogmeister]

Righto, im looking at some 18's to replace the 17" Avus 3's. Looking at 8.5" all round, 9.5" all round, or 8.5" fronts and 9.5" rears.

Can someone advise what size tyres to get for these combos? As the tyre price will be a factor in the decision.

Cheers

 

[ruffrida]

I am running 235 / 40 / 18's on mine (see my pics) and it is sounds, no hard bounce, but just enough tyre roll.

Decent new about £75 each

Budget new about £55 each

 

[Nogmeister]

Cheers dude, what rim width is yours?

 

[jcs356]

To maintain rolling circumference 225/40/18's are closer to the 225/45/17's you'll have previously had. They are also a more popular size hence tyres are cheaper due to the demand.

 

[Nogmeister]

Fair one, so 225/40's on a 8.5" seems ok, but on a 9.5" rim would be stretched a bit? Any issues with that?

I'd LIKE to go 9.5" all round, so maybe a bit of stretch will be needed...

 

[ruffrida]

Fair one, so 225/40's on a 8.5" seems ok, but on a 9.5" rim would be stretched a bit? Any issues with that?

I'd LIKE to go 9.5" all round, so maybe a bit of stretch will be needed...

Yeh you would have to go for the V-dub look with 9.5's, mine are 8.5 and look sweet.

The rolling circumference would only matter if you went to 225/35/18 or a 225/40/18, the 35 giving a lower and the 40 the higher. The width of the tyre has nothing to do with it, its all about your profile, 35, 40, 45.

I used to have 35's but the ride was to harsh on me rims and the speedo was out, put the 40's on and the speedo is nearly perfect, according to gps anyway

 

[aragorn]

The profile is a percentage of the width, so changing the width will affect the rolling circumference.

 

[ruffrida]

This is very marginal. a 235 vs a 225 is 2cm overall which is 0.4mph at 30mph, or 0mph difference at 60mph

Good little calculator - Visual Tyre Size Calculator | Kouki Tech

 

[aragorn]

yep, but a 195/40r18 is fairly different to a 255/40r18

The RS4 for instance runs 255/35R18's, which are the same rolling circumference as a 225/40r18.