Which tyre size?

cr5000462

Junior Member
Messages
32
Hi All,

What's your recommended tyre size for wheels which are :
Front wheels size: 21x8.5
Front offset ET: 44
Rear wheels size: 21x10.5
Rear offset ET: 45

The car is a Ghibli.

I don't like thin tyres, so something that fits (not stretched), and gives a little bit of comfort.
 

Zep

Moderator
Messages
9,110
Hi All,

What's your recommended tyre size for wheels which are :
Front wheels size: 21x8.5
Front offset ET: 44
Rear wheels size: 21x10.5
Rear offset ET: 45

The car is a Ghibli.

I don't like thin tyres, so something that fits (not stretched), and gives a little bit of comfort.

You need to match the original rolling circumference as closely as you can, a bigger tyre will mean that the speedo will under read, which will be a problem with speed traps.

For example, if you went from a 285/30/21 to a 285/35/21 your speedo would under read by 4.3%, this is a fairly big difference. If you want a bigger sidewall the best thing to do is buy smaller wheels, as you should really match use the OEM sizes.
 

cr5000462

Junior Member
Messages
32
Thank you all,

Currently I have 18s on it, but thick tyre walls.

I would like 21s with average (not skinny walls) so I’m wondering jus how thick the tyres can go without there being a rubbing issue

The Speedo will be a problem, however I imagine there is a way to have this adjusted somewhere?

Regards
 

Zep

Moderator
Messages
9,110
Thank you all,

Currently I have 18s on it, but thick tyre walls.

I would like 21s with average (not skinny walls) so I’m wondering jus how thick the tyres can go without there being a rubbing issue

The Speedo will be a problem, however I imagine there is a way to have this adjusted somewhere?

Regards

The aspect ratio will give you the sidewall height as a percentage of the tread width. So standard rear, a 285/30/21 will be 285 x .3 = 85mm. About 22mm of this sits inside the rim, so the height outside the rim will be about 63mm. This is pretty much the same for the standard front 245/35/21.

You could go up a size or two on the width which would give up to an extra 6mm which is barely discernible, for a significant increase you will have to up the aspect ratio at which point you will have to have it calibrated I would suggest.
 

outrun

Member
Messages
5,017

The Ghibli has a 21” wheel option from the factory, I had them. This is the factory sizes so you’d have thought this is where to look. One word of caution, if your car does not have skyhook, don’t buy Pirelli tyres in that size or the car will scare you when the tyres are cold.