Originally Posted by ecksreturns
LMB, I need your help again. I read every where that 305 is not a good tire size for the car and that it spoils the balance and will lead to rubbing. Can you recommend the ideal tire sizes for 20" rims ? 255 or 245 fronts? And 30 or 25? And for rear 285 or 295 with 30 diameter only , as 25 will worsen the ride quality on Indian roads.
Also, please note that the only reason I am changing the tire/rim combo is because I wish to install the 380mm all round brakes from Brembo. As recommended by Ilia/Nate , I need to change my 19" V710's as the brakes won't fit. Could you recommend 19 or 20" rims that go well with those brakes?
The majority of the problems associated with 305's rubbing, are frankly due to poor offset choices made by many multi-piece wheel manufacturers. Yes, it's a huge tire. And it's not one I would ever choose myself. (it makes little sense to me personally)
But this was the size you wanted, so I offered you the best tire size available in a 305 rear.
Many times, the offset of the wheels are usually driven by the size of the lip tsome wheel brands are trying to achieve. That is why the wheel ends up slightly askew from it's ideal position in the wheel well. (but that's separate issue for another time)
When you put such a large tire on a car like the M3, their will certainly be a penalty in regards to performance. I see that you are now second guessing your initial decision to go that wide.
It's good that you have decided to re-examine this NOW
...before you end up with a set of tires you didn't really want.
If you want something slightly smaller than the 305's, I would recommend a 295/25/20
tire as an alternative. This size will not rub anywhere if you get the wheels in the offsets I recommended earlier.
The 245/30/20's are a littler smaller as far as tire diameter is concerned, but the section width of that size does not offer you much rim protection against curbing.
Tire sizing is an art, and many times, there is going to be some type of compromise
made. (somewhere) When you go away from the stock tires sizes, there are fitment 'gaps' that will force you to choose one path vs. another. (to bridge this gap)
BTW: You seem to think tire sidewall aspect ratios are an 'option' you have to improve the ride quality of the car. You cannot do this if you don't have the fender or inner wheel liner clearance to make that change. You cannot simply upsize the sidewall from a 30 series to a 35 series at will. That will increase the diameter of the tire, and this will lead to rubbing issues.
You cannot always have a perfect
result, and it's important that everyone understands this basic truth.