Just bought some 18" alloys...

[Cally]

and need tyres as the rims will be here tommorrow. Bought some ultralite taka\'s in 18" - 8.5" fronts and 9.5" rears.

Does anyone know what tyre size I am best to run as I dont know what width etc is needed for an FD. Cheers.

[G@NDY]

I would have thought 235 and 255 matey

[ace-rx7]

it seems that
235/40/18 front and 255/35/18 rears is the norm.

[Cally]

yer thats what I thought but was unsure on the right profile so I dont have any problems with rubbing etc

[mikeyh]

is the car lowered or anything cally?
im running 265 40/17`s the now but its standard hieight

[Cally]

yeah its lowered, about 40/50mm

[n4bes]

MikeyH and myself were discussing this...........................:xconfused

Why have 35 profile rear but 40 profile front.........??

I have 235/40 front and 265/35 rears, but dunno why not 40 or 35 all round.

[d-king]

if you have 235/40/18 on the front you should really have 265/40/18 on the rears because otherwise your rolling radius will be incorrect :0)

[n4bes]

if you have 235/40/18 on the front you should really have 265/40/18 on the rears because otherwise your rolling radius will be incorrect :0)

I have done the calcs and you are only 1.25mm of difference................

Wonder if it\'s a cost and availability thing....?

[Archbish]

the 35 is a percentage of the width of the tread.  So you would need to have 35% of 265mm to match 40% of 235mm tread.

[Rixio]

As D King said the rolling radius what be off...35 at the front will equal out to 40 atr

[n4bes]

As D King said the rolling radius what be off...35 at the front will equal out to 40 atr

Don\'t think it\'s that bud. If you matched the wall size on the rears with the front the rolling radius would be out by 12mm. It is only out by 1.25mm at the moment.

If anything the reason is to componsate for the width of the rear as Arcbish said.....?

[d-king]

i was told when i bought my rims that if i had 255/40/18 on the rear the rolling radius would be off but with 265 it was almost spot on to the front , ive no idea as i failed maths bigtime so only going bt what i was told lol

[Archbish]

bit more info here...

http://www.tyres-online.co.uk/techinfo/aspect_ratio.asp

[n4bes]

i was told when i bought my rims that if i had 255/40/18 on the rear the rolling radius would be off but with 265 it was almost spot on to the front , ive no idea as i failed maths bigtime so only going bt what i was told lol

The size of the tyre is as follows bud.............

The wall is determined as a % of the width i.e

265mm wide 40% of that is 106mm
235mm wide 40% of that is  94mm

Hence 12mm rolling radius difference

265mm wide 35% of that is 92.75mm

Hence 1.25mm rolling road Difference

HTH mate.