Hi all,

As the title suggests its that time when I need to change my tyres... and I am thinking about changing my alloys too, to some 18" BK 299s in Matt Black.
These alloys are 7.5J

Now, I am looking to get the widest possible tyre I can fit on the alloy and on my car. I have a 2007 plate (R56 model) Cooper S which is lowered on H&R Springs

I have been told that 225 is about as wide as I can go... is that correct?

I would like to go as wide as I can, for the go kart looks and also to get better grip down as my current 215s struggle to get all my ponies down!!

Thanks for any help
Nick

 

Check the wheel offset and calculate the scrub radius lest you end up with unpleasant behavior.

 

Sorry, I dont understand that last post at all?

The offset is either ET 38 or ET 45 (they do 2 different sizes)

What is scrub radius?

Cheers

 

To answer the original question, yes - 225 is as wide as you should go on a 7.5" wheel.

7.5" is 190mm, and 35mm wider is as much overhang as you will be safe with. Wider risks overheating the sidewall by excessive flexion, and even 225 on 7.5 will be less crisp on turn-in than it could be - an 8" rim would work better with a 225 tire, albeit not a realistic fit on a MINI.

 

Here is a definition of scrub radius. You can find many more.

http://www.ingallseng.com/terms.htm#Scrub%20Radius

Keep in mind that it changes with both wheel offset and tire height.

Do not accept wheel vendors' generalities about offsets not being important other than for wheel under fender clearance. Study the issue before you part with a lot of money for a set of expensive wheels and tires that may look good but degrade the car's handling and steering.

 

I'd stick to 215/45/17. Your wheel offset will play a factor.

Alex

 

I know most of the tirerack crew is pretty conservative when it comes to wheel/tire fitment. Do you know for sure that a 225/45-17 in the 39-42mm offset will rub on an R56?

Rob

 

See this other thread. I run 235/40R17 on a 7.5" +45 wheel. I would use 235/35R18, but there are very few tires made in that size and they're very expensive. So I put 225/35R18 on the 18" wheels.

17x7.5, 235/40R17:



18x8.0, 225/35R18:


--Dan
Mach V

 

Dan that looks really nice. What is your MINI dropped on in the second photo?

 

If you are going for looks.

225/35-18 fits rims 7.5-9" wide, perfect for 8" rim 24.2" tire diameter
Goodyear Eagle F1 Asymmetric

If you think that 215/35-18 is too narrow for a 18x7.5 rim it is not. In fact the limiting factor for traction for you is more likely in tire choice rather than in width of the tire itself. Softer rubber compounds and stiffer sidewalls would allow you to get better traction and handling and so I would suggest looking carefully at your tire choice.

If the OP was thinking of 17x7.5 rims then
215/45-17 Bridgestone RE-11 $182 each Extreme summer tire NEW!
225/45-17 like Yokohama S.Drive (small 24.8" tire diam)
but
235/40-17 fits rims 8-9.5" wide, perfect for 8.5" rim, 24.3" tire diam.
A good sized tire for 17x8 rims or wider.

If you are on a budget then
Dunlop Direzza Sport Z1 Star Spec in
215/45-17 for $133 each 200 treadwear. Very good handling and grippy tire for street use. Won't last as long but really fun while it lasts.
Another Extreme Summer tire.