My New Tire Selection for the F...

4217 Views 4 Replies 3 Participants Last post by dsg03svt, Nov 23, 2010

SmokyStealthBomber

Discussion Starter · Nov 23, 2010

During the past 3 months, I have spent countless hours online investigating tire options for the stock F wheels. I read the posts on this forum and many others available on-line. I spoke to people from Lexus, Tire Rack and a tire expert at Sports Car Tire in Wilmington, Delaware. I know there is not just one solution for the stock rims, but I wanted to share mine.

First, the tires: I went with the Bridgestone RE050a Pole Position tires. 235/35R19 on the front and 275/30R19 on the rears. This tire looks very similar to the OEM Bridgestone RE050a, but this is newer technology and promises enhanced performance, response and wear which you can all read about at Tire Rack's or Bridgestone's website. I like the way this tire looks and feels on the car. The F really needs a tire with a stiffer sidewall and the Bridgestones deliver.

Now for the size selection: I started at the back to determine the largest tire I could (should) fit on the stock rim. I know some have gone larger than 275, and knowingly or unknowingly have "stretched" the tire to fit this rim, but the 275's are really the largest you should go on the stock rim. Given this, the 275/30R19 reduced the overall diameter of the stock size by .53 inches (only a 2% variance at 25.5) and increased the revs per mile from 774 to 791. Now that I found the correct size for rear, my next step was to find an exact match for the front (that being a tire with the same overall diameter and revs per mile of the rear). The 235/35R19 was nearly a perfect match with an overall diameter of 25.48 and revs per mile of 791. While a 245/35R19 should fit the front wheel OK, it does not match the overall diameter and revs per mile of the rears as perfectly as the 235's do. I hope this information is helpful for anyone considering new tires and/or upsizing on the stock rims. Here are some pics with the new tires just mounted today:

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lowrider

· #2 · Nov 23, 2010 (Edited)

I also did much research, and came to a different conclusion than you did. I was trying to match the OD of the stock tires as close as I could. On my stock wheels I have mounted 245/35/19 front and 285/30/19 rear. I considered the RE050A Pole Positions, they would have been my second choice. But I went with the Continental Extreme Contact DW tire. The rears fit fine, IMO. I see no tire bulge. I'm extremely happy with the improved handling and traction I have achieved with this change.

Edit - Added a third pict of the rear tire this AM.

Lou

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SmokyStealthBomber

Discussion Starter · #3 · Nov 23, 2010

The OD of those sizes are marginally closer to the original tires, but the problem is that the 285's call for a minimum rim size of 9.5". You may think the rears fit fine, but there is a reason every tire manufacturer's spec for that size tire is a 9.5" -10.5" rim. Staying within the approved rim width range helps assure that the tire's internal stresses are within its design parameters.

With regard to the tire choice (Continental vs. Bridgestone vs. everything else available), it's a personal preference. The only true way anyone will be able to determine which tire is the best on the F is to keep trying new ones for the life of each set of tires, but that could take a very long time to come to a final conclusion. Tire ratings/reviews on other vehicles are really not a guarantee, so it's always good to hear from those who are driving the same vehicle. Good luck with yours.

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lowrider

· #4 · Nov 23, 2010 (Edited)

SmokyStealthBomber said:
You may think the rears fit fine, but there is a reason every tire manufacturer's spec for that size tire is a 9.5" -10.5" rim. Staying within the approved rim width range helps assure that the tire's internal stresses are within its design parameters.

I know the tire fits fine. The tire side wall is not bulged and 100% the tread of the tire is firmly planted on the ground. I would not go with a larger cross section, however. Go to this site and try my combo. 285/30/19 is the widest size they recommend for a 9" wheel. I had the same trepidations as you until I did my research. When I was younger I managed a tire store and learned a lot about tires, wheels and fitments.

http://www.rimsntires.com/rt_specs.jsp

EDIT - One thing I forgot to mention last night is that it is never recommended that you replace a tire with one with less load carrying capacity. The front tires (235/35/19) ea. have 77 lbs. (5%) less load carrying capacity then the tires they they replaced. The rear tires you used have exactly the same load carrying capacity as the old ones.

Lou