The time is coming to put together a summer wheel / tire setup for the E38 740. Stock, it runs 18x8s with a 235/50 up front, 18x9.5 with a 255/45 in the rear. The stock rears end up looking kinda stretched which I don't like.
Currently, I've got 4 18x8s with 235/50s on them for winter. For summer, I have the stock rear wheels (which need tires), so I have a pair of 18x9.5 wheels to work with. I've got nothing for the front. The M parallel wheels I've got also come in a 3rd size of 18x9. So I'm thinking of picking up a pair of those and running 18x9 with 255/45 up front and then the 18x9.5s with 275/40 in the rear.
What does the hive think? Any better suggestions or am I probably on the right track?
Slightly smaller diameter but not much on the rears.
In reply to iceracer :
Yeah, the setup I'm thinking of is 27" front, 26.7" rear. About 1/3" shorter than stock all around but the same front / rear diameter difference (stock fronts and all 4 of my snows are 27.3", stock rears are 27"). The cars that came with 16" wheels stock had 27.1" tall tires all around.
I did contemplate 285/40 for the rear (27" tall to match the fronts), but I think it might be getting to a little bit wide for the 9.5" rear wheels and for the tires I'm looking at (Conti Extremecontact Sport) it's an extra $40 / tire over the 275/40.
I've found BMW speedometers are a bit optimistic(5% or so) on all the 90s BMWs I've driven. On my e36 I went slightly taller than stock tires hoping to correct the error.
I can't remember the threshold where the ABS and DSC+T starts wigging out due to tire size differential. Dink around with Tire Calculator
Strike_Zero said:
I can't remember the threshold where the ABS and DSC+T starts wigging out due to tire size differential. Dink around with Tire Calculator
It should be safe with the 0.3" difference front / rear, as the car left the factory with that much difference and no issues. IIRC, the limit is 3%, so a little over 3/4". I'd love to stay a little taller, but unless I go 255/45 and 285/40 (both 27" tall), the only other ways to get 27" or more is a 235/50 or a 265/45 (both about 27.3"). And the 265/45 has very few tire choices (would be fine if I had a desire to run RE-71Rs on this car). Well, there's also a 295/40 (also 27.3", RS-4 available, but also just silly).
I guess part of the question is whether going from the stock 235 / 255 stagger to 255 / 275 (and adding an inch of wheel width up front) is the right choice. Or should I be looking to stay a bit closer to the stock setup? Or spending up the extra $$$ for 285/40 in the rear? (but then I have to worry about how the 285s sit on the 9.5" wheels)
Why not just go with a square setup? Performs better, easier to match tires, zero diameter difference, and you can rotate easier.
And it looks cooler.
ProDarwin said:
Why not just go with a square setup? Performs better, easier to match tires, zero diameter difference, and you can rotate easier.
And it looks cooler.
My default thought would have been square fronts for winter, square rears for summer. But this car is an exception to that. If I needed to buy 4 wheels, I'd just run square 255s on 9" wheels and be done with it. But I've already got a pair of 9.5s to use. I could get 2 more and run square 9.5s, but then I get into the problem of 255s on 9.5s look stupid and I don't want to go wider than 255 up front. I feel like 275s on the front would probably induce too much tramlining, etc. and take away from how well the car cruises. Plus, 275s up front would be a tight fit (fenders are rolled, so they would clear, it would just be tight).
Huh. I think 255s are pretty much perfect on 9.5s
ProDarwin said:
Huh. I think 255s are pretty much perfect on 9.5s
I'll have to grab a picture of the (very old all seasons) 255s on the rear wheels I've got. Maybe it's just how those tires sit or something.
Found a picture of a 255/45 on an 18x9.5. To me, it looks stretched. I think it's mostly an issue of too high an aspect ratio for a 255 on a 9.5" wheel (higher aspect ratio usually means less tread width for a given overall width). I've found pictures of the same on a 9" wheel and it looks much better IMO.
