widest tires on '01 330ci

Hi All. What is the widest 17" tire I can use on the front and rear on a 2001 330ci? The car will be used for normal, everyday driving. Not racing or
on the track. I'd like to do a 225/235 in the front and 245/255 (maybe more if it will fit) on the rear. TIA!
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I think the 235/40x17 is the most you can get on the front rims, I would guess that the rear should be limited to the 255/35, give or take a little.
I have the 225/45x17s on all four corners of my car ('94 325i), but I am confident that I could have stuffed the 235/40s under it and been fine. The front rims are narrower than the rear, by an inch, so the rear rims will hold a wider tire than the front. If you get a wider (235, 245, 255, etc.) then you want a lower aspect ratio (50, 45, 40, etc.) to keep the overall diameter the same.
You can calculate the overall diameter by multiplying the Width X Aspect Ratio / 24.7 X 2 + rim size (17, in this exercise). So a 245/40x17 would have a diameter of 245 X .45 = 110.25 mm / 24.7 = 4.46 in. X 2 = 8.93 + 17 25.93 inches. (The division by 24.7 converts the metric measurement to inches. You have to multiply by 2 because the width X aspect ratio only gives one sidewall, but the diameter of the tire includes 2 sidewalls.)
I pulled a width and aspect ratio out of my ass to provide numbers that illustrate the formula. You can adjust the numbers as needed to find tire sizes that ultimately give you the same overall diameter as you have now. Work out the formula for your current tires, then adjust the width higher and the aspect ratio smaller to see where you end up. You want an overall diameter to be within a half inch or so of the stock tires or you will run into troubles with the gearing and speedo calibration.

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If the width of your mag is not different front to back, ie, if they are all 17" x 8" then all tires should be the same size. when you see staggered wheel sizes (like my 540i 235/255) it is because the wheels are also different sizes, 17x8 and 17 x 9" I would expect the car to handle poorly if you stagger tires when they should not be. go to http://www.bimmer.info/forum/forumdisplay.php?f  and get their input, that is the BEST site for BMW, 5 series in particular Sharkmanbmw

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Yes. I kind of already knew that but wanted to see what others thought of the idea. So, all four the same size. How wide can I go? TIA!

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I think the widest you can put on a 17 x 8 is a 235/40. I know for certain that the 225/45 fits well, but there appears to be plenty of room for a 235/40, and the overall diameter is equivelent.

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the stock mags on the 330 are 17 x 7"
whcich should carry no wider than 225/45 17's you need an 8" width to go wider
handling and comfort are better with 225/45 than with 235/40 anyway
snipped-for-privacy@canada.com

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If you are only looking for appearance, and aren't concerned with how badly the car will handle, or how terrible the ride might be, you should check out:
www.idiotsandtheirdumbtires.com

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I borrowed this from a Bimmer E46 M3 web site:
The M3 sits on 18-inch M-style alloy wheels (8.0-inch wide front and 9.0-inch wide rear), with appropriately sized high-performance tires (225/45 ZR - 18 front and 255/40 ZR -18 rear).
Will I be able to successfully install this combo on my 330ci? Is there a reason why it won't fit? ie different diff :) larger/smaller wheel wells, different suspension width? I'm not saying I want to run this combo, but since I will be buying these wheels and tires via mail-order, getting it wrong would be expensive. I don't have the luxury of trying out different sets. I have to get it right the first time! The E46 M3 runs different size wheels and tires in the front and rear. Is there a reason why doing this on my car would mess-up my handling and not mess-up the M3 (as another said earlier)?
I appreciate your indulgence while I get my feet wet with a BMW.

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An M3 also has wider arched to accommodate them. From experience on a host of 3 series the best combination for me was 225x45 ZR 17. Wider on rear lost traction in the wet and on the front caused tramlining.
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I borrowed this from a Bimmer E46 M3 web site:
The M3 sits on 18-inch M-style alloy wheels (8.0-inch wide front and 9.0-inch wide rear), with appropriately sized high-performance tires (225/45 ZR - 18 front and 255/40 ZR -18 rear).
Will I be able to successfully install this combo on my 330ci? Is there a reason why it won't fit? i.e. different diff :) larger/smaller wheel wells, different suspension width? I'm not saying I want to run this combo, but since I will be buying these wheels and tires via mail-order, getting it wrong would be expensive. I don't have the luxury of trying out different sets. I have to get it right the first time. The E46 M3 runs different size wheels and tires in the front and rear. Is there a reason why doing this on my car would mess-up my handling and not mess-up the M3 (as another said earlier)?
I appreciate your indulgence while I get my feet wet with a BMW.

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Thanks for the first, useful answers to my question. I know the M3 wheels/tires won't fit. I'm thinking the front wheels will be replaced with 18x7.5/or 8 using 225/40 Goodyear F-1s and the rears 18x9 45s using 255 or wider if they'll fit. And this was the question I had originally asked. Instead of real, practical answers, I was lectured as to why I shouldn't or specs for combos that the car came with. All I want to know is what width will fit in the rear without having to roll the fender. I will be buying new wheels to make this work. I'd like to hear from someone who has actually gone through this process as I am not in a position to try several combos until I discover the widest tire. Thanks to 330xi@ and sharkman for the useful suggestions.

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