Thursday, February 6, 2014

Winter 2014 Update

A couple of our fans have reminded me that it's been almost six months since I updated this blog, so here's a little run-down of what's new.

Bring it on
After running 255/40R17 Sumitomo HTR-Z tires through the warm months, I swapped back to the 215/45R17 Bridgestone Blizzak WS60 tires for the cold -- and boy has it been cold this winter!  With the winter tires, the BRZ has been a solid winter partner, with very good grip in the cold (sub-40 F temps) and wet.  On actual packed snow, the tires don't perform miracles -- this is a light rear-wheel-drive car, after all -- but we never worried about getting stuck or sliding off the road.  After experiencing the scary slithery feeling of driving this car with the stock Primacy tires in the snowy stuff, the winter tires are such a revelation.  I highly recommend them to anyone who lives in a place where it snows.

I had promised an update about tire sizes and different wheel fitment, so I'll get into that now.  First off, I am NOT in favor tire fitment solely for the purpose of appearance.  You might see this called "stance" or "stretch & poke" or other terms that basically imply pushing the wheels and tires out to as far (or farther) as they can go for the sake of looks.  What I am in favor of is larger tires for higher levels of grip.  More grip gives higher cornering speeds, better braking, and better control in all kinds of transitional maneuvers -- planned or otherwise.  I'm definitely not in favor of getting the tire to a point where it will damage the body (or worse) at full suspension compression.  If you can't use the car for its original purpose, what's the point of the whole exercise?

17x9" Mach V Awesome with 255/40R17
Note that for snow, you actually do NOT want wide tires.  Skinny tires will bite harder into the snow, whereas wider tires will tend to plane up on top and not grip.  What I'm talking about from here on out is warm-weather performance.

As I mentioned above, we've been running a 255/40R17 tire on a 17x9" +42 Mach V Awesome wheel at all four corners.  We also run Whiteline Com-C upper strut mounts, which give us extra camber by moving the entire top of the strut, rather than by moving the tire/wheel relative to the knuckle, lke eccentric bolts would do.  I mention this because a lot of BRZ/FR-S guys seem to run the eccentric bolts (or "crash bolts") to gain front camber, and this can lead to clearance problems as a wide wheel and tire can start to run into the spring perch on the OEM shock.

18x9.5" Mach V Wicked Awesome with 265/35R18
I also test fit some 18x9.5" +42 Wicked Awesome wheels with 265/35R18 tires.  This actually did fit okay in the back, but in the front the tire contacted the strut, so we had to use a 5mm spacer to get it to work.  With the 5mm spacer, the front tire was sticking out of the front body work, so without more camber I wouldn't advise running that size on the front of the car.

I could have put a 255/35R18 or 245/35R18 tire on the front 18x9.5" wheel, but those tire sizes would not be as wide as the wheel, and I'm really a big fan of having the right size tire for the wheel, and vice versa.  But if you DID want to run the 18x9.5" Wicked Awesome wheel on all four corners of your BRZ or FR-S, I'd probably do a 265/35R18 in back, and a 245/35R18 in front.

17" Awesome in front, 18" Wicked Awesome in back
Anyway, back to our fitment experiments:  Knowing that our slightly narrower 255/40R17 tire fit the front, I thought I might put the 17" wheels on the front with the 255/40R17, and the 18" with the 265/35R18 on the back.  Some sports cars (Acura NSX, Chevy Corvette) run a staggered front-back setup from the factory.  Why shouldn't we try it?  That actually fit pretty well, and the wheel size matched the tire size nicely.

Plenty of people run different tire widths on these cars front-to-back, but I haven't seen anyone else do two different wheel diameters.

One final question the fans asked me to address is gas mileage after installation of the Innovate supercharger kit.  On my daily commute, which is mixed driving, with a good amount of stop-and-go, I used to get as much as 28.5 mpg pre-supercharger.  Since the supercharger install, I have seen 26.5 mpg when I stayed out of boost as much as possible.  If I drive like a hooligan and flat-foot it every time I leave a stop light, I see more like 20 mpg.  (Of course, when I drove like a nut before the supercharger I would take a pretty big MPG hit, too.)  So basically, figure a 2 mpg penalty from the supercharger install -- a small price to pay for a 37% increase in horsepower!

Links: Mach V Awesome wheels, Mach V Wicked Awesome wheels, Innovate supercharger.

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