525iT Wheel Change Experiment (long) (archive)

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A friend and I got together this afternoon to perform an experiment. He owns a 735iL (E32) with 16" BMW OE rims (actually from a E38), and my wagon has 17" Mille Miglia MM11s. He's been toying with the idea of going to 17" and I was curious to see what my car would be like with 16" rims (it had the stock 15" bottlecaps with Continentals... yechh when I bought it).

Both our wheels had Pirelli P7000 Supersport tires with about the same amount of miles on them. The 16" OE package had 225/65-16s, the 17" Mille package had 235/45-17s. We both needed 5mm spacers on the front to keep the OE package from rubbing on the shock absorbers... there was about 1/2" 12.7mm) difference in the offset between the two packages.

So, how do the compare on the road? NOTE: I was running the 17" package slightly under pressure to smooth out the ride, but that reduced handling a bit too. The 525iT with the 16" package rode a little smoother, but not hugely so. Braking was not as good. Cornering was not bad, though there was noticably more noise and the car was not quite as tight. Overall, if I had to make the purchase again, I'd probably go with a 16" package... still handles pretty nicely.

My friend then drove his 735iL to get a feel for the difference. He said braking was much more positive, the car felt more predictable, overall tighter. The road noise and the texture of the road was more pronounced to the point that it may not be real nice on long drives unless the roads are smooth. He runs at higher pressures, 36/34 (f/r), so maybe that could be resolved by dropping a couple pounds in each.

What about appearance? Well, the wheel styles are VERY different. The OEM rims are the basket-weave and the Milles are the 5-spoke (very open). The 525iT when from being a seriously sporty looking car to a merely sporty, more refined looking car. His 735iL when from being a old-guy's sedan to a young-guy's sport sedan.

I put together a couple of web-pages that let you see the differences. One of the pages will change the wheels on the cars when you move the mouse over them... I had to Photoshop the pictures, got it pretty close but not perfect. The other page just shows the wagon in three different states of wheel change. I reversed two of the images to get the hood-tail orientation right... so the gas-door and steering wheel may surprise you :)

We're going to keep the wheels swapped for a week or two to get a better feel over familiar roads. If we're both happy with the change, we might work out an exchange.

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