Project Evo X, our 2008 Mitsubishi Evo GSR, has seen its horsepower steadily increased, but that doesn't mean we've been ignoring the rest of the car. On the contrary, we've had other goodies simmering for some time now.
Chasing our GT-R around the Streets of Willow roadcourse is going to require some serious grip to go with its grunt. Sticky as the Evo's stock 245/40/18 Yokohama rubber is, the GT-R brakes harder and turns faster.
To take the first step in addressing this, we gave Project Evo new shoes.
And, boy, it was time. Click the jump.
Rubber is critical. So is maximizing that rubber's potential. That's why we mounted the RE-11s on a set of forged monoblock Volk Racing RE30 wheels from Mackin Industries, the US importer of Volk Racing wheels. 
We received a set of Bridgestone's newest extreme performance summer tire, the Potenza RE-11, from www.tirerack.com. The RE-11 is slated to replace the popular RE-01R. Our size? 265/35/18, or 20mm wider than stock.
At 18x9.5 inches, these RE30s are the same diameter and one inch (25.4mm) wider than the stock Evo wheels.
They're also lighter. Our RE30s each weigh 2.1 pounds less than the forged BBS wheels that come on the Evo X MR, and 4.1 pounds less the cast Enkeis from the Evo X GSR. That's pretty impressive when you consider the additional inch of width on these RE30s.
You can install wider tires on stock wheels and see a net gain. However, you can see even greater gains in grip and steering response by increasing the width of the wheel, too, as we have here. 
This was the worst tire. No tread on the shoulder at all and minimal everywhere else. The wear observed among the four tires was fairly uneven, so it's possible our alignment is off. We'll do performance testing of the new duds as-is, then tweak the alignment and test again.
So how's the fit, you ask? Good question. When we first bolted up the wheel to the Evo's hub, there was clearance everywhere.. except the spokes cleared the caliper by less than 1mm.
The last thing I want in the middle of the bowl at Streets is a unfortunate confluence of hub flex and heat-induced brake expansion that winds up machining the inner surface of the spokes and trashes the caliper face. In short, 1mm is not enough clearance. We neeeded wheel spacers.
Mackin agreed and sent out a set of 3mm spacers. This would be enough to gain appropriate clearance to the caliper without adding a ridiculous amount of offset.
Speaking of offset, these RE30s are 35mm offset. Stock Evo Xs have 38mm offset. We're close to stock offset, and that's important.
Smaller numerical offsets increase the suspension geometry's scrub radius.
In layman's terms, scrub radius is a lever that increases torque steer and steering effort. Just stay close to stock offset and you're doing great.
A word of caution regarding spacers: they eat up thread engagement. By spacing the wheel out, your lugnuts have less stud to grab onto. You want a minimum of four turns of thread engagement, and that is definitely a minimum.
Another word of caution regarding spacers: cast universal ones can and do break, and usually at the worst possible times. I consider the cast ones we have now a temporary solution. You know what they say about those...
The new rolling stock went on this week, so impressions so far are limited but good--having actual tread has reduced road noise, and we've observed no rubs or ill effects due to the offset. Heck, maybe we should have tried to fit even more rubber...
We'll have hard numbers for you soon.
Jason Kavanagh, Engineering Editor @ 18,020 miles.
huyracing says:
04:00 PM, 03/26/09
you guys spent way too much on wheels not to have the right fitment...
felonious says:
04:34 PM, 03/26/09
$$$?
subytrojan says:
06:15 PM, 03/26/09
Great post, Jay! Is there any way a comparison of tire weights may be provided as an addendum?
tsy says:
06:46 PM, 03/26/09
"you guys spent way too much on wheels not to have the right fitment..."
I agree. About $650 per wheel, + $300 per tire? They should fit correctly, unless you got a screaming deal on them.
Nice wheels though, they look better than the stockers! Would be nice to hear how the RE-11s are too.
gibot says:
10:09 PM, 03/26/09
wow. makes me wanna buy this car once it's decommissioned from the long term fleet
opfreakx says:
06:38 AM, 03/27/09
tsy, they probably dont come in a 38mm offset. Which is both stock, and what edmunds effectly ended up with by adding a 3mm spacer
But I did find online that the wheels come in a 40mm offest
personally, I'd rather have wheels that fit perfect (esspically when your spending 800+ bucks a wheel), or get an offest on the wheel that does not require a spacer,(within reason) spacers are for possers.
technov says:
07:26 AM, 03/27/09
You guys really need to lower the car some more. With the new wheels it looks like a raised 4x4 truck.
catalystgod says:
09:17 AM, 03/27/09
I might be wrong here, but these wheels have a POSITIVE offset. which means, greater the offset number, the closer your outside wheel surface is to the hub. In other words, by including a 3mm spacer, you decreased the offset to 32mm. Am I completely wrong here ?????
Check explanation here:
http://www.tirerack.com/wheels/tech/techpage.jsp?techid=101
catalystgod says:
09:18 AM, 03/27/09
Basically, If you had cone with a 30 or lesser offset wheel, you'd not have had clearance issues.
catalystgod says:
09:22 AM, 03/27/09
Basically, If you had gone with a 30 or lesser offset wheel, you'd not have had clearance issues.
jkavanagh says:
09:32 AM, 03/27/09
Yes, the spacers effectively make our offset smaller by the amount of their thickness (3mm). These wheels are 35mm offset, so we have:
35 - 3 = 32mm offset currently.
32mm is much closer to the stock 38mm than the typical Evo fitment of 22mm offset wheels. It was important to me to stay as close to stock offset as possible since we've added a LOT more torque.
Yes, the spacers are not ideal. I'm trying to work on a more elegant solution than the cast spacers + plastic hug ring arrangement we have now.
subytrojan, sorry, no tire weights. Weighing our worn-out stock tires wouldn't be representative of a new stock tire anyway.
t10 says:
10:04 AM, 03/27/09
J,
I run a 20 ofset on a X GSR and subjectively it seems like the steering feel is a bit more dead on center than stock offset. I assume,however, going from 38 to 32 is to miniscule to be noticed ? Also, I assume if the wheel with the same offset had been 18X9 (vs 9.5) the spacers probably would not have been required(?). I'm also curioous if you just migrated the tpms sensors or went with a second set. It is intereesting to see cases of wheel/tire implementations since it sort of hit or miss buying remotely wheel /tire combinations.
jkavanagh says:
10:09 AM, 03/27/09
t10, yes, dead on-center steering and more sluggish turn-in are telltales of small offset wheels. Yet more reasons I wanted to stay close to stock offset...
Not sure about the 9-inch wheel.
Yes we migrated the TPMS sensors.
catalystgod says:
11:12 AM, 03/27/09
I am not sure if using offset alone to determine if you are going to have sluggish turns is correct. With a decrease in positive offset, if wheel width is increased such that the distance between the hub surface and inner edge of the rim is maintained close to stock, why would the steering get any sluggish or quicker? This is of-course assuming that sidewall hardness and all other parameters are kept constant. I can understand if steering effort increases, but why would it behave differently? I am just trying to understand here.
For eg: in stock setup, distance between hub mounting surface and inner rim lining is 50% of 8.5 plus 38 mm = 145.95
if a 18X9.5 with +22 offset is used, the same measurement leads to 50% of 9.5 plus 22 = 142.65.
Assuming that tire widths are equally greater than the widths of the wheels in the respective cases, This would be a very close to stock setup in terms of distances between the two fronts or the two rears.
So if you are dealing with high torque figures, I am assuming you are concerned about offset because it is likely to place more strain on the drivetrain/axles if the wheels are too far apart. And, if you want a close to stock setup, assuming that is what is best, why would this place any greater strain on the system as such. Lets not forget that you just reduced the rotational mass by almost 4 lbs per wheel by using the Volks. Even if the bigger tire penalty is 2 lb per tire, you are still 2 lbs lighter on each wheel.
Please explain, I would love to understand this better.
huyracing says:
12:20 PM, 03/27/09
the increase in tire width alone will cause more stability and less responsive turn in... but it really comes down to alignment settings. people do not realize that stock settings are not ideal anymore, even in terms of tire wear, for something as simple as a wheel and tire swap. it is likely you can run more toe out to compensate for the reduced turn-in response, while optimizing tire wear at the same time. i saw this on my WRX when i went with wider (lower offset than stock) wheels and tires.
jkavanagh says:
01:23 PM, 03/27/09
When you accelerate, that force is applied over the entire contact patch but in terms of how this force interacts with the suspension geometry, it effectively acts at the center of the contact patch.
Reducing offset moves the center of the contact patch outboard, but the steering axis doesn't move with it. The distance between these two points (at the plane of the contact patch) is the scrub radius.
Torque steer is amplified when the scrub radius increases (due to smaller wheel offset), even at stock output levels. And when you've got more torque than stock, well, you know what happens...
huyracing, increasing toe out should only reduce tire wear if you had toe in to begin with, and went closer to zero toe. But your point is valid that alignment settings play a role in all of this scrub radius talk, especially camber and caster.
subytrojan says:
02:53 PM, 03/27/09
No worries about tire weights, Jay. I suppose people could compare the weights of new tires with numbers from the Tire Rack or other reputable source.