I have a 2008 mini cooper S convertible with the JCW engine package. It has the normal 205/45/17 tires. They simply don't have enough rubber on the road for the engine's power.... does anyone know how wide I can go before I start getting into trouble with the tires rubbing the suspension or causing turning problems? I am thinking I want to go to 235/40/17 which have almost the identical diameter / sidewall but are an inch wider...anyone have any experience?

 

Queue the 'do a search' comments.

235 is pushing it, but people are running that width. 215 is the safe width when lowering from what I've read.

 

If your tires aren't already Extreme or Maximum Performance Summers, maybe it's mostly the tires' rubber compound that is limiting grip.

As Taz suggested, and from what I've read here, 215 is safe (and appropriate for the OE wheel width), 225 is usually okay (unless lowered), but 235 runs a significant risk of rubbing. Spacers might prevent rubbing toward the inside, but a slightly wider wheel with a somewhat shorter offset would be advised for the really wide rubber.

 

Frankly, I don't see how a wider tire is going to improve traction during acceleration. It will improve grip during cornering. The contact patch doesn't grow larger with a wider tire, it just becomes wider and shorter. Shorter means less grip for braking and acceleration.

And Jim is spot on. Stickier tires provide the best bang for the buck. A limited slip differential provides the ultimate improvement.

 

I have the limited slip with the JCW package so that isn't the issue..... and I do currently have summer sport tires that were just replaced right before I bought it...I am a bit confused how a wider tire with a bigger contact patch wont provide more rubber on the pavement during acceleration? I have to admit that I am very surprised that I have not found a lot more experimentation with various tires with all the minis that are out there and such an active community... I have spent quite a few hours going thru the forums here and elsewhere to no avail on people actually using wider tires... using a tire chart, the 235/40/17s are identical in every dimension except width, which increases 1.18 inch, or 5/8 per side. I would think that would be doable, and worse case I have to put a small spacer on... I was just hoping to get confirmation from someone who has already done the trial and error.... my next step is to go to the dealer tomorrow, but my bet is that they say stick with the 205s.

 

The 235 width tire will have a wider contact patch on an 8" or 8.5" rim, but you would be giving up some of the tire's available contact patch if you mounted them on 7" wide rims. The 235 is designed to fit at least an 8" wide rim, and is actually molded to fit an 8.5" rim. The 235 would have to be "pinched in" to fit into a 7" rim, leaving less car weight resting toward the outside edges of the tire tread.

See hsautocrosser's post #4. A wider tire means a wider, but shorter (front to rear) contact area or footprint. The contact area remains the same because the car is placing the same amount of weight down on the tires as it would with a narrower tire. Narrow or wide, the car's weight compresses the tire the same amount to support the same weight. At least that's what I think I know.

 

The JCW "limited slip" is actually an electronic device that applies the brake to the wheel that is spinning. I have it on my Justa and it sucks in autocrossing. What actual symptom is it that you are trying to cure?

 

Interesting all - thanks for the advice... the problem I find is that there is simply way too much power for the available tread - it is way too easy to spin the tires and I can catch rubber in 3 gears which seems nuts.... not to mention that the torque steer is a handful but thats a different issue...I guess the real solution would be all wheel drive like the countryman........

 

wicked grip in street tires:

Bridgestone RE-11
Dunlop Star Spec
Hankook Ventus R-S3
Kumho Ecsta XS
Yokohama AD08

 

True, but one could always lower the tire pressure just a bit. Bottom line, though, the difference between a 205 and a 215 is going to be minimal. I only made the switch to the 215 because doing so gave me more options to choose from.

 

Not true on the '08 cab that the OP has. The cab did not become a second gen car until '09, so the OP does, indeed, have a true LSD. Same as on my '06 JCW cab.

 

Thanks. I missed the fact that it is a first gen convertible.

 

Slacker!

 

i normally run a 215/45/r17 with no issues. When i put the 225/45/r17 i get issues and here is where they are

I have megan coil overs and have it lowered a little. -2.0 camber on the front. Which makes no difference on rubbing

225s rub on the coil over perch nut on the front.

on the Rear they have to be above the lip of the wheel well or they will rub inside at the top.

The solution to this was i put a 5mm spacer on the front. this cleared.

the rear i just had to adjust the ride height up to clear

Stock springs, and shocks nothing rubbed anywhere on running 225/45/r17

Hope this helps

 

Bottom line is that it's a front wheel car. You could go up to a 300 wide front tire and you'd still spin. 'Nature of the beast. I'd stick with 215/40's.