THSCC Forums

Ouch. That's why I work to avoid cars with larger than 17" wheels, or build that into the budget for ownership. I always chuckle when my friends who just bought new 991s complain about tire prices...

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Steve Carter
1972 Datsun 240Z-- resto pics at http://picasaweb.google.com/srcartermd
2007 GPW Honda S2000-- STR 86

Now you know why I drive a Miata and sold the Camaro, ~$500 tires are much more pleasant since they potentially only last a year.

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2017 Autocross Chief of Tech

2000 E Street Miata
2015 Focus SE EcoBoost 6 speed
2015 Fiesta ST (Wife's ride)
2012 Yamaha FZ1 sorta crotch rocket? All I know is 150HP and 487 lbs is fun!

For streets on a WRX with a 8.5" rim, a 255 should be perfect. As for rubbing, I would be shocked. On my 2010 STi SE (GR) I ran 295 Hoosiers on the 18x8.5" stock wheels without rubbing. Only 305's caused a rub. - AB

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'14 Toyota Sequoia Platinum 4WD
Super Westerfield Bros - '93 Integra - LeChump Du Jour
STX 93 - Scion FR-S

There you have it.

Also, what do your oe wheels weigh?
This thread
https://forums.nasioc.com/forums/showthread.php?t=2239019

is interesting because most STI wheels are in the same weight ballpark as the aftermarket wheels (~23ish pounds) that have been listed. I bet a used set of STI wheels could be had for a lot less. Alternatively, find a used set of 17x7 base WRX/impreza wheels and use those for DD/offseason with Conti DWS06s and save the 18x8.5s for summer.

Just a thought.

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Steve Carter
1972 Datsun 240Z-- resto pics at http://picasaweb.google.com/srcartermd
2007 GPW Honda S2000-- STR 86

Mark,
As you put wider tires on your car, you want to change the offset to maintain your tire within the wheel well. When I size my cars for wheels and tires, I run them up a set of ramps, get underneath and measure the distance from the tire to the strut or coilover. I also do the same measurement from the tire to the outer wheel well. Then I turn the front wheels to their extremes and measure to the nearest obstructions, usually the frame member. I guess at the width that the new wide tires will have on the rim that I choose and do the math to the strut and the outer wheel well. A good guide for mounted tire widths is on the tirerack site. Based on the result, I choose the wheel offset. Going form a -55 to a -50mm offset moves the tire patch towards the outside of the car. This is usually a good thing when adding wider tires. I used to run 235's on my Miata, but that was on a 48.5mm offset instead of the standard 55mm offset. That was .006” outside the SCCA rules at the time for tire class and I was teased by a club member for “cheating”. Since that time the rules have been changed from 1/4” to 7 mm because rims come in inch diameters and widths but metric offsets. Likewise, tires are inch sized, but dimensioned in metrics. What a screwed up world we have created.

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Mike Miller
AutoX VP 2016/2017
Just a C Stock Miata DD
Mazda Speed 3 Family Car
Corvette Z06 Toy

I think it's wise to consider the reason this rule was put into effect in the first place. Tire availability. The spirit of this law was to make the available the tire of choice to all/most cars.

In ES, my Miata came with 14x6" rims, but the RE-71Rs, and Rivals, and Proxes weren't available, maybe still aren't available, in 14" diameter. Now I can go up or down 1" in diameter to find tires.

Mark, in your case I think you have to stay at the 8.5" width, unless there was some way to get the 8" wide rim from the factory with the options you have. That said you can go up to 19" or down to 17" and remain fully SCCA legal. The 17" will be lighter and less expensive, and will likely have a better selection of tires.

Just my $0.02.