Quote:
Originally Posted by andrewwynn
I think you are missing the point of large rim diameter. It's how you run a lower ratio tire on the same tire diameter so you can get higher cornering performance and lower unsprung wheel / tire weight and all the helpfulness that comes with.
Consider this: BMW chose from all possibilities to use 285/35/21 on the front of their highest performance X5M. Do you think you will achieve a better solution with "seat of pants" engineering?
The combination you chose is about 6% larger diameter and I'm pretty sure you will find other problems than a large speedo error.
It's not an accident that all the BMW approved sizes are within 1% rolling circumference.
https://www.carbibles.com/calculators/
Use the tire size comparison calculator to find a size you'd be happy with that is within say 2% of the original circumference.
Example: 255/55/18 and 255/50/19 are identical diameter.
255/35/22 is the magic combination that nets you the same diameter.
265/35/22 is a decent match
255/35/22 is an exact match
295/30/22 is an exact match
305/30/22 is likely an ok match to the 265/35/22
If I was going to set up an X5 on 22" rims I would run:
255/35/22 front 295/30/22 back. They are within 0.2% the same size and very close to the design size for the car.
255/40/22 & 295/35/22 is about 4% bigger than stock. I would not recommend larger than stock by more than 1% though, your affect all dynamics of handling, for what purpose?
If you want a softer ride with trade off of lower cornering performance, the alternative set is:
235/40/22 & 265/35/22.
There just is no good reason to upsize the wheel and tire that I'm aware of.
If you are aiming for a lowered look and fill the wheel well for a "low rider" look with the trade off of performance, that's a reason but the trade off will be rubbing tires on the wheel wells and worse handling.
275/315 fits in the wheel wells of the X5.
Actually 285/35/21 & 325/30/21 were used on the newer M model. That's actually smaller rolling circumference than the base sport tire. |
Ok. I guess you are trying to help in your own condescending way. I guess that's how you need to be
At what point did I claim I am trying to achieve a better solution to BMW's engineering team on the X5M? Where did that even come from? Not to mention you're attempting to compare a wheel/tire size decision from a
completely different chassis.
I am aware that upsizing the diameter is going to reduce things in a lot of ways. Speedo? Not a concern of mine. Brakes, CV axles, bushings, bearings, etc are all going to wear faster. As for the trade off in performance, this isn't my performance vehicle. I have other cars for that and I'm fine with this decision, thanks for your input. Not everybody is using their SAV for time attacks.
I'm aware that the combination I suggested is increasing rolling circumference.
The front and rear sizes I'd like to run are well-matched. In your post are you suggesting I run a 235 on a 9.5" wheel? and a 265 on an 11" wheel? That's quite a stretch, which is not what I'm looking to do.
Again, what does the X5M matter when considering an E53? The 4.4i was offered with a 285/45/19, which is a 4.3-4.5% difference in circumference front to rear from the sizes I'd proposed. This is reasonable to me. Even within the 4.4i model range, BMW used wheel sizes that are 1.4%+ different circumference from each other.
As for whatever this was about, I'm not going for a "low rider" look, one would think I'd explained myself enough in my first post. On the contrary, "low riders" want slim tire profiles. I am doing the exact opposite.
So to reiterate, I was only looking to find out whether the taller diameter is going to cause issues rubbing/knocking on anything with my proposed wheel/tire combo. And the front offset is 20mm further out, so there should be a bit more forgiveness there.
I actually was able to find a couple of threads finally where some members used the sizes I'm proposing without issues of rubbing. But I would still like to hear any other input from people who have done something similar, more on topic input never hurts.
Edit: If anyone is wondering why I'd choose 22" wheels, it's because I couldn't find OE 20" style 168, but I did somehow stumble upon a set of the old 168 replicas in 22" locally. The style looks too good not to run them for a while.