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2Addicts | BMW 2-Series forum Technical Topics Wheels and Tires -- Sponsored by The Tire Rack Best Combo for 18x7.5 Wheels

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      05-02-2019, 11:29 PM   #1
Nuckle
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Best Combo for 18x7.5 Wheels

I did a lookup of my vin and best I can tell I have a non staggered set up with 18x7.5 wheels. Trying to figure out the best set up from a performance perspective. I currently have Pirelli Cinturato RF 225/40R18 tires. Ride is ok but traction seems to be a place I can improve on. Looks like with that rim width the widest tire I should mount is a 235. I would assume that even in a 2WD car that a square set up would be best performance. Just curious if the general consensus is that 235's would work if not larger and what tire would be best for near max performance but also good as a daily. I live in the south so a winter setup is not really needed. I appreciate all comments and advice.
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      05-03-2019, 12:50 PM   #2
Maynard
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Most important factor in performance is the type of tire, not the size - a 215 extreme summer tire will grip better than a 245 all-season. I'm on Conti extremecontacts - those or the Michelin MP4s (factory option) are the current leaders, or you can go up a notch to the near-race tires (but you lose wet traction in favor of dry grip). There are also decent runflat options, but I don't think anybody really likes them as much as non-RFT's for handling performance and driving feel.

Square setup isn't really best for handling, but it does let you rotate tires and avoid buying new rims (staggered setup seems to be best handling, especially for RWD, but probably a very minor improvement). In terms of tire size, it isn't just width, it is also how it fits the wheel. 225 is about as wide as you can fit on a 7.5" and it will have softer sidewalls (looser is probably a better description). The improved tires are probably going to do the trick; trying to cram a 235 on that wheel will likely degrade steering feel some b/c it exaggerates the poochy sidewall (may even be out of spec or unsafe). You'd probably get tighter feeling handling if you dropped back down to a 215, but I don't know how noticeable it would be (you can get a similar effect by running higher pressures too). I'm on 7.5 fronts w/ 225's, and it isn't bad, but I'm likely going to move to an 8.5 with 245 square when I replace these.
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      05-03-2019, 01:07 PM   #3
Nuckle
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I really appreciate the advice and seems to make perfect sense. I think I will just replace all 4 with 225's and roll on for now. I like the black BMW wheels so I dont want to change that.

Thanks again.
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      05-03-2019, 06:02 PM   #4
MerlinMc
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8" wheel safer bet?

Quote:
Originally Posted by Maynard View Post
Most important factor in performance is the type of tire, not the size - a 215 extreme summer tire will grip better than a 245 all-season. I'm on Conti extremecontacts - those or the Michelin MP4s (factory option) are the current leaders, or you can go up a notch to the near-race tires (but you lose wet traction in favor of dry grip). There are also decent runflat options, but I don't think anybody really likes them as much as non-RFT's for handling performance and driving feel.

Square setup isn't really best for handling, but it does let you rotate tires and avoid buying new rims (staggered setup seems to be best handling, especially for RWD, but probably a very minor improvement). In terms of tire size, it isn't just width, it is also how it fits the wheel. 225 is about as wide as you can fit on a 7.5" and it will have softer sidewalls (looser is probably a better description). The improved tires are probably going to do the trick; trying to cram a 235 on that wheel will likely degrade steering feel some b/c it exaggerates the poochy sidewall (may even be out of spec or unsafe). You'd probably get tighter feeling handling if you dropped back down to a 215, but I don't know how noticeable it would be (you can get a similar effect by running higher pressures too). I'm on 7 .5 fronts w/ 225's, and it isn't bad, but I'm likely going to move to an 8.5 with 245 square when I replace these.
The fitment notes on the Apex website talks about 245s on 8.5" wheels. They say adjustments are necessary. See: https://support.apexraceparts.com/hc...-Fitment-Guide

There are some recent posts in this forum where 8" wheels were used with 245s and they fit without any modifications necessary to avoid rubbing. See this thread for one example with two different cars: https://www.2addicts.com/forums/show....php?t=1597122

Is the 8.5" choice driven by wheel preference or some other factor?
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