Quote:
Originally Posted by Byhlinder
Hmm, was thinking about going 245 PS4S Front and 275 Rear. Is that too wide then? On the 444 turbine wheel i might add.
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well, in order to find out which width and profile (tire height from the wheel) you might choose, its time to learn how this website works and why. it's pretty easy, once you get past how busy it looks.
https://www.willtheyfit.com/index.ph...8-5&offset2=40
you type in your stock wheel and tire size is on the left. You type in what you "think" you want on the right. Then look at the chart called "Your Results--Old, New"
you want to compare wheel diameter and speedometer error. (even for front tires, it might mess with the ABS sensor) Almost never will going from one tire to the next, give you the "exact" same diameter or speedometer results. That's hot-rodding. Nothing you can do about it. We all live with it. So, how much discrepancy are you willing to go with?
on this website, it only compares one size to your new choice. It cannot do fronts and rears, so open another window and do the rear tires, for instance.
what you may find is, (I have not tried this, this is for the sake of argument) instead of say a 275/40, you might need to go to a 275/35 to get the right size, and one 275 is too large in diameter compared to stock and one is too small. So, then you play with 265s (if they are available, 265s are not very standard) and see if you can get closer.
now, to answer your question directly. Once you have found a tire diameter that looks OK, will that 245 fit on a 7.5" front rim, for instance.
245 is in mm, and the rim is measured in inches. There is a rule of thumb which people might break, but generally you do not want to go a whole lot more than 1', maybe 1.5" at the very most in tire width over your rim width. on a 7.5" I would not want a tire much wider than 8.5". 215mm / 25.4= 8.45". Its right at that 1" oversize mark I mentioned. BMW did the right thing.
A 245/25.4 = 9.64" tire you are trying to put on a 7.5" rim. more than 2". Have guys done it? Maybe (probably using spacers, see below). Would I do it? no. Also, if you read above, the post with the pictures there is only 12mm or so clearance between the stock 215 tire and the front suspension. if the 245mm tire is sitting on the rim as centered (which it is) that only gives you 12mm to stick out on each side, and it will touch the suspension. 12mm+12mm is about an inch of tire width. You want to add two inches to your width.
unless you get custom rims that set the tire out towards the fender, or buy 1" spacers (or bigger!), I imagine your 245 would not fit on a stock front rim because it will not just rub, but seriously interfere with the stock suspension upright.
one word of warning:
when I shop for aftermarket wheels and tires I have my own priorities: 1] losing weight on each corner, to help with acceleration, in all situations, (and handling) 2] the tread wear rating, to get less slippage and cornering (the lower number the better, but---they die quicker and need replacing--I am looking for something below 180. stocks are 280) and for me, 3] then, maybe extra wide rim and tire for looks and cornering, and maybe some traction capability.
bigger, wider tires on the same stock rim weigh more. They will look cooler, but they weigh more and they "will" effect your acceleration, especially on a car with a 228 hp rear motor and 141 hp front. Dragy can prove that out. And the track guy will point out, heavier whees and tires effect the way the car reacts on bumps and in corners. If all you care to do is cruise and pose, then who cares, right? I am not judging, here. Its a valid reason to own the car.
you can easily verify the weight by looking up your stock tire on tirerack.com and clicking into the information and finding it, then comparing to your proposed choice and comparing the weight. And compare the tread wear rating, while you are at it.
You could end up with a heavier, and less high-performing tire. Looks cool? maybe. Slows your car down? in that case, for sure. You can measure it with Dragy and if it's more than a few pounds each tire or tire and wheel, I have had cars where I actually feel it, as well. I know this because I have done all this, more than once, and there's plenty of write ups on it, and physics to back it up.
to solve that weight issue I am looking at having some forged or flow-formed rims made. if you made custom rims that are the exact same size as stock, you could stand to lose 3-4-5 lbs per corner, which is huge(!!) if you stick with the same tires.
problem is you can't have those made, at least, not in front: most forgers do not have 7.5" billets to cut into a rim. They start at 8.5". And, most people, me included (I like to pose sometimes too), are not going to pay $300-600 minimum to have someone custom make a 7.5" wide 20" rim, even if the company had billets that size.
Now you have a wider, somewhat lighter, but (dang it!) not AS much lighter rim, because it has more metal on it. You could have lost 3-5 lbs going forged for 7.5"x20, but an 8.5"x20 might weigh 1-2 pounds more than a 7.5x20 forged. Couple that with a wider heavier tire? You would need to do the math. Might be lucky to lose 1 pound, maybe 2, or hopefully not go over the stock weight.