Tire size question
 

Iv done a search and found out that I can fit 305's on the standard Rays but I carnt find the exact answer to this.
Iv lowered the car on coilovers approx 50mm now the standard Tyres are
Front 245/40 diameter 678.6mm
Rear 275/35 diameter 675.1mm
Can I fit
Front 255/35 diameter = 661.1mm
Rear 305/30 diameter = 665.6mm

The difference is 3.5mm standard and 4.5mm new size

Iv heard wider rear and skinny front may sometimes create understeer but I don't drive my car like I stole it so this won't be a problem, I just want to know if I can fit these new sizes without the car bringing any warnings lights on thinking a tyre is spinning.
Thanks for any advice.

305 is too wide for the rim in my opinion. Bigger isn't always better, and that 305 will slow you down especially if you are N/A.

OK if it's too wide, what about
Front 255/35/19 diameter = 661.1mm
Rear 295/30/19 diameter = 659.6mm

This size there's just over 1mm difference?

Becareful, I put new rims on my car and the car shut down.
Speedo won't work, abs, traction and Ikey.
Tires must have at least 3% tollerance I heard

I definitely don't want that but the standard size is 0.53% from front to rear different and the 255/35 295/30 is only 0.23% different so I'm assuming this would be OK.
Are there any members that have done this as i need new tyres soon or is there a site that I can ask that will know the answer.

What sizes?

OP --- it'll work. I had the exact tire sizes on OEM sport rays before getting new wheels. Looked good with 20 mm spacers all around. No warning lights or anything like that.

If you go too wide of a tire on a narrower rim it's going to flex the side wall and even the treads themselves thus creating a danger. You might get away with some extra width but too much can be detremental.

http://rimringz.com/product_images/u...o-tire-fit.jpg

Here is a site I use to calculate what tire width you'll want for the width x diameter.

Tyre Size for Rim Size/Width Calculator - What's the best tyre size for my rim?

Stock rims get stock size tires , aftermarket rims get custom size tires imo