Full Report: Road & Track tests stickier FR-S/BRZ tires
 

http://www.roadandtrack.com/special-...transformation




As much as we love to drive the wonderfully balanced Toyobaru twins, we were displeased at how the BRZ stacked up against the Mazda Miata and Hyundai Genesis Coupe in a recent test (see “The Great New Hope... or Hype?” July 2012). Yes, the BRZ dominated our subjective ratings with its balanced chassis, but it lacked an edge around the racetrack. We theorized that the tires were holding it back.




The Subaru-Scion twins are shod with Michelin Primacy HP 87W GreenX summer touring tires. They have a UTQG treadwear rating of 240 and howl in the corners like a beagle strapped to the roof. Buy a Prius in Europe upgraded with 17-in. wheels, and you’ll get these same sad tires. That’s right, these sporty coupes have hybrid tires, tuned for low rolling resistance, not grip.

But what happens when you slap on some sticky stuff? Will it go quicker? Will it ruin the sublime handling? With those questions in mind, we ordered a set of autocross-winning Dunlop Direzza Sport Z1 Star Specs in the factory size (215/45-17) that retail for $146 each at Tire Rack. For good measure, we arranged another set in a plus-one size of 235/40- 18 at $192. Both are cheaper than the factory Michelins that sell for $214, and the Dunlops have a 200 treadwear rating for only a slight decrease in life.

We needed 18-in. wheels, and worked with Eddie Lee at Mackin Industries to find a set that would fit the FR-S without any modification. He set us up with a set of Advan RG II wheels, measuring 18 x 71⁄2 with a +48 mm offset. Although expensive, the 18-in. diameter Advans actually weigh less than the stock rims (an RG II weighs 17.2 lb.; the factory wheel weighs 20.4 lb.). Plus the Advans fit perfectly with no rubbing or clearance issues.

With our new tires, we headed to Spring Mountain Motorsports Ranch and our favorite test loop. We also brought along a Subaru WRX and Mazdaspeed3 for comparative purposes. All three of these cars can be purchased for around $26,000. On the track, the front-wheel-drive MS3 set the bar with a lap time of 1 minute, 27.6 seconds. The all- wheel-drive WRX was 0.7 sec. behind, and the FR-S on the stock tires was slowest, running another second arrears of the WRX. Interestingly, the MS3 and WRX come with high-performance Dunlops as standard equipment.

Install the Dunlops on the stock wheels, and presto-bingo! We have a new winner. The FR-S dropped 2.3 sec. with a simple tire swap. And not only does the car maintain its wonderful balance, it’s vastly improved. The FR-S’ sharp steering is enhanced by the tires’ grip, providing a dramatic increase in feedback—with the Dunlops’ greater forgiveness at higher slip angles, you can literally turn the steering wheel more. The rear rotates more gently on turn-in and the suspension easily handles the added grip. This is the way the FR-S was meant to run! I’m surprised the engineering team didn’t murder the bean counter who forced the low-rolling-resistance tires on them.

We were salivating at the thought of lapping with the noticeably fatter 235-width Dunlops. If the stock size does this well, this bigger tire should rock, or so we thought. The reality was that we gained a little in grip, but gave up some speed (a total of 1.5 mph on the back straight). Although the wheel/tire weights of the 18-in. Advan and stock setups were similar, weight concentrated farther outward on the larger wheel made it slightly harder for the car to accelerate. Also, the bump in overall diameter hurt a bit too; the smaller tires effectively offer shorter gearing. Handling behavior changed only slightly with a minimal decrease in steering feel and less willingness of the chassis to rotate. That said, the FR-S with the larger Advan RG II wheels still managed to tie the Mazda’s lap time.

If you own a BRZ or FR-S, you owe it to yourself to upgrade the tires and feel the way your car was meant to drive.

The key message of this video: no need to swap wider gripper tire. Just stay at the stock size.

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:eyebulge:

I would like to see someone test 16 inch wheels and lowering the car.

I'd probably do 225/45 all around, either 17" or 18"

That's cool. I want to know what kind of times they would see with a 17x9 wheel with dunlops or even hankooks. Keeps the wider tire but not the gearing issue of the 18s.

I also have a set of 225/45/17 dunlops and kooks that I autocross with.

So that -2.3second gain WOULD have beat the Mustang V6 GT with track package at Willow Springs? :D

This test is somewhat misleading. When they plus sized the tire, they changed the gearing. The new tire is about 20mm taller than the 17" size. If they wanted a more comparable comparison, they should've run 225/40-18s, which would still be 11mm taller. Also, this doesn't take into consideration the weight of the larger Advans.

So a TL;DW would be.......

225/+45/17? and for 18's the same?

For reference the Mustang V6 track pack comes with:

Pirelli P Zero P255/40ZR-19

220 AA.

A much closer tire match to the Star Specs they put on the BRZ.

TL;DW

There is improvement found on using stickier tires
Dunlop Direzza Star Specs are better than Michelin Primacy HPs
Video is not a helpful comparison between 215/45-17s and 235/40-18s.

Im rocking 245/40/17's on 17x8 rpf1's. Fastest lap time around my local track was 1.35.9 with the oem tires im hoping to drop at least two seconds in my next run this sunday. Videos will be posted for sure trying to confirm this.

I am happy w/ my oem size tire w/ grippy RS3's :)

Lol, I just posted this.

Say it with team: "Rolling Diameter"

Is anyone.. really anyone, surprised that stickier tires turned a faster lap time and "taller" tires affected gearing?