Klepper

I know wheel offsets have been talked about a lot here, but it is a confusing subject to me and many others. I have done some math and have a few questions. What prompted me to calculate these numbers were a number of M5 and M6 take off wheel and tire packages that I see for sale on ebay. It would be so nice if the M5 and M6 tires would work on our cars

The front rims on my 2006 550 are style 124 which are 18x8 with an 18mm offset. The front rims for M166 and M167 rims are 19x8.5 with a 12mm offset. Using the wheel offset calculator on 1010tires.com (http://www.1010tires.com/WheelOffsetCalculator.asp), the M166 rims would have the exact same clearance on the inside edge of the rim, and protrude 12mm farther out (away from the car) on the outside edge of the rim.

The rear rims on my car are 18x9 with a 32mm offset. The rear rims for M166 and M167 rims are 19x9.5 with a 17mm offset (assuming M6 fitment rims without spacers, or M5 fitment rims with 12mm spacers). Using the wheel offset calculator, the rear M166 rims would be 9mm farther out on the inner side and protrude 21mm farther out (away from the car) on the outside edge of the rim.

The tire sizes that everyone seems to go with that we know work on the M5/M6 rims are 245/35/19 for the fronts, and 275/30/19 for the rears. These tires make an overall wheel diameter of 25.75? and 25.50? respectively. These tires are the same width as the stock tires on 124 style rims (which are 245/40/18 and 275/35/18) and work out to almost the exact same diameter (25.72? front, and 25.58? rear for the stock 18").

The OEM M5/M6 tires are 255/40/19 and 285/35/19. These tires make an overall wheel diameter of 27.03? and 26.85? respectively (or 1.31? taller on the front, and 1.27? taller on the back versus the 18? originals)

Therefore, compared to the stock 124 rims and tires, the accepted M5/M6 tire sizes of 245/35/19 and 275/30/19 would make the front tires stick out 12mm farther and the rears stick out 21mm farther. They are no closer than original 18" on the inner side of the wheels. The diameters are nearly identical to stock 18".

The OEM M5/M6 tire sizes of 255/40/19 and 285/35/19 would sit 5mm closer ?in? on the front wheels (0mm from the rim, and half of the extra 10mm of width of the 255 vs 245 tire) and protrude 17mm farther out on the outside of the front rim (12 from rim+5mm half the extra width of the tire). On the back, the tires would sit 4mm further out from originals on the inside of the wheel, and 26.35mm further out on the outside of the rim.

So finally to my question ? first, did I do the math correctly? If so, why don?t the M5/M6 OEM tires work? What makes them rub? Is it because of the extra 5mm protruding out on the front and back catching on the edge of the fender, or is it because of the taller wheel (the extra 1.3? of height) hitting up under the wheel well going over bumps? If it?s the extra height, how do people run 20? rims and then lower their car?

rsyed

There is nothing that rubs if you use the m5/m6 wheels, but it does stick out aggressively and I guess BMW has concerns with this respect. In some countries, the wheels may not stick out more than the body, and with the ET 12 in the front, we are very close to this border.

But the math you have done is correct - seems you have understood the math behind the two letters ET

cheers

EBMCS03

I didnt read all of your calculations and whatever math you did but going from what people have tried the front OEM M5 wheel offsets + stock 255/40/19 tires will rub the inner fender of a regular E60 during full lock turns and under close to full compression of the suspension.

patrick

I don't know why they don't work either, but my 545 w/M5 wheels would NOT support the M5 sizes. I went down a size after looking at Dinan's recommendations for the car - they still rub on occasion. I only installed the stock wheels with whatever offset comes with the wheels. I have sport suspension, but no aftermarket suspension items...

NY550i

I also wondered that when i saw the M5s and M6s running 40s and 35s in the rear... I would rather use those sizes to get a less harsh ride and more tire to protect my rims from NY streets.
I asked a few people who seem know something about this and they said the fender lining is different... there is more room inside the wheel well on the M models or so they say.

jet190rs

in that case can we overcome the problem by rolling our fenders?

vegastrashed

It doesn't matter if you roll the fenders. The problem is the sidewall height of the stock M5/M6 tires. I've highlighted it in red. Under compression you'll always rub. Remember, the M5/M6 have a different suspension set up than Sport package e60s.

From left to right: Stock 124 tire size, 166/167 non-M tire size, 20" wheel tire size (not correct, but most people use it; looking at the overall diameter compared to stock), 20" wheel tire size (correct, but "rubber bands"; looking at overall diameter compared to stock), 166/167 M tire size

Klepper

Ok, so if it's sidewall height, then anyone running 20" rims must be using 20 series profile tires or less. Anything bigger (assuming 245 and 275 widths) gets you to a taller wheel than the OEM M5/M6 tires on a 19" rim. And that also assumes no lowering of the car. Is that correct?

vegastrashed

People using 20" wheels run Front (245/35/20 or 245/30/20) and Rear (275/35/20 or 285/25/20) and lowered. Rubbing isn't only about tire and wheel size, it's also about offset.

Klepper

That's why in my original post, I did the math and figured out that with OEM M5/M6 tires and M167 offsets, it only moves the wheels 5mm different than with the recommended tires. I also did the math wrong regarding the 20" rims - 245/35/20 gives 26.30" radius, as compared to 27.03" for the 255/40/19's - just shy of 3/4" taller. So it's that extra height that makes them rub?