Wheel / Tire experts here?
 

I recently lucked out on a find from Craigslist.

Found 17" wheels for my snow tires that apparently used to be used on a BMW X5.

Center bore is a match, along with bolt pattern. (They are not BMW wheels, though they look similar to the early X5 model 17" wheels)

The differences are what I'm curious about. Instead of my stock wheel size of 17x8, they are 17x8.5 and the offset is et43 instead of et46.

The offset doesn't concern me, however the slightly wider wheel shows a noticeable decrease in my sidewall flex since it's stretched over slightly.

What I am curious about is whether this is a problem (though I doubt it is?) and whether or not my tire pressures should be lowered slightly for the increased sidewall stretch?

I tried looking through Google, but not sure how to sift through the wealth of hits to drill down to the info I want.

Check out:

http://www.tirerack.com/tires/tirete...jsp?techid=198

The 8.5" wide X5 rims are within spec. for 235/55/17 tires, but at the upper limit.

I don't think you need to run decreased psi.

During winter time you dont want a "wider" tire.

You could run a 235/60r17 size tire if you want more sidewall. This is the size I use for my summer setup.

I wouldn't go below 29 psi on the front tire pressures and 32 on the rear as per the BMW manual recommendation.

Even a 225/65 r17 can work for a skinnier and taller tire. This is the size I use for my winter setup.

I should clarify that I'm using 17"x8" wheels.

Also, if you search on Michelin's website for example, it will show the safe "rim width" for each size tire under specifications.
If I look at Michelin Pilot MXM4 in 235/55r17 size it shows the safe rim anywhere between 6.5" and 8.5"

Sorry, I wasn't asking about a wider tire. I was asking the effects of a wider wheel on a tire.

Duh, thanks Supercourse. I didn't think to look on tirerack for information about tire tech, I'm too used to shopping and leaving to explore the site. That helps narrow searches a lot better than just Google!

Thanks a lot everyone for pointing me in the right direction!

Cant go wrong with Tirerack and they stand behind their sales. I recently bought a set of Conti extremes and Wheels for just under $1500.00. They offered free balancing. Well the balancing wasnt right and I got hi speed wobble. Even though the balancing was FREE they still discounted my sale back to my card for the price I paid to have them re-balanced. Very impressive. I will recommend them any chance I get after that. Awesome CS.