ratt_finkel

Not to derail the thread. But no, 275's are not too much. I run 285's on a 9 that weighs 2950 and I am considering going to 315's. If had a X I would be looking at 335's on 11" or 12" rims.

As far as the OP goes. I too run 18x10.5's. I have the worst combo of +15 offset. But I was still able to make them work in the rear with lots of pulling and eventually cutting/grinding. There are numerous threads in this sub forum covering this.

Just search 18x10.5". There is not a huge advantage IMHO running these over 10's or even 9.5's performance wise. The fronts are easy, but the rears will take some serious work.

Also of note, most of us are running a 285/30/18. Even though it's wider than the 275. The 275/35/18 Hoosier is significantly taller. So you will have even more issues in the rear clearing.

e_kobz

iTrader: (36)

Not to get off topic from the OP's post but what would the benefits be of running 12 inch wide rim with a 335 on a Evo X?! That's adding so much rotational mass to an already heavy car. Wouldn't you get similar performance results with say a 10.5 rim with 285's or 295's?!

ratt_finkel

The additional rotational mass would be negligible for the increase in grip. As you said, it's already a heavy car. An extra pound or 4 per corner is not going to kill you. I'm also assuming a X with at least 350 whp. Preferably 400+.

e_kobz

iTrader: (36)

I get what you're saying, I was just trying to figure what kind of X you were talking about. but I would love to see a evo rockin some 335 meaty tires. And I would love see a evo 9 with 315's. Make it happen

ratt_finkel

My good friend Jeremy Ault runs 315's on 18x10.5" +15 Enkei RPF1's. Personally I think 315's should be on at least an 11" wheel. But I have driven this car and it has a LOT of grip.

http://srwphotography.smugmug.com/Au...7754&k=gt2vrzJ

http://srwphotography.smugmug.com/Au...2966&k=VpxSHZX

http://srwphotography.smugmug.com/Au...4168&k=JkgkkBw

http://vorshlag.smugmug.com/Racing-E...1496&k=HKmTDML

http://vorshlag.smugmug.com/Racing-E...1836&k=4PcvPV7

Back to the original OP point again. There is very little performance difference between 9.5" width and 10.5" width. And technically, no one has proven which width is the fastest.

nollij

iTrader: (21)

Does this sound right? (T is torque)

Taccel = Teng - Tlosses - Tback
where:
Tlosses are engine losses
Tback is the back torque from friction, wind resistance, etc.
Teng is the torque the engine produces on the crank. The combustion cycle applies the torque to the engine. This is a set value per combustion (@ rpm).
Taccel is the torque put into accelerating the crank (leftover torque from the engine after the losses and back torque have been accounted for)

Taccel = MOI*alpha
where alpha is angular acceleration and is inversely related to the overall MOI of the drivetrain.

I am not sure if the dyno measures the angular acceleration of its inertia (I believe so) or what it is exactly doing.

Depending on how a dyno works, the MOI reduction may be accounted for in the dyno measurement and as such, shows up in the measured horsepower of the car for classing.

The classing weight-to-power ratio uses the overall mass of the car.

Reduction in MOI would result in a greater dyno horsepower for a set Teng (depending) but would not result in a significant reduction in the mass of the car.

A faster car in a set weight-to-power ratio (ie: NASA) would take advantage of lower Tback but a reduction in MOI would have to be "tuned out" to only make the power necessary for the class.

Hence, as long as you make rated horsepower for a wide powerband for the class you are racing in, MOI reduction is not terribly meaningful.

Or have I bungled this all up?

RJones

iTrader: (5)

Aww man, I missed the 10.5 party! Here's my stock body w/ 10.5 +30 NT03s (+5 front) and 285 BFGs



I have fender spacers in the front and a pretty big pull in the rear. I haven't relocated the bumper bolt (yet)

eeweeks

Are those the g-Force R1? Not slicks, but I'd love to see what a 295/35/18 Rival looks like on an Evo and on these NT03's.

285 R1, Section width: 11.4"
Diameter: 24.9"

295 Rival, Section width: 11.9"
Diameter: 26.1"!!!

Based on what I've read, the height will make this very difficult.

ratt_finkel

Um yeah. That is a HUGE tire. And it will be slower on top of that.

eeweeks

You'd gain about 3.5mph at the top of second and a little bit of contact patch. The two tires aren't comparable, but the sizes are.
Just thinking aloud...

Meathooker

iTrader: (2)

275/35r18 hankook's

a LOT of pulling in rear. did not have to remove rear bumper bolt. 2.1-2.2 camber in rear.

front - 4 camber with 20mm spacer. used washers to space fender out approx .375"



minimal rubbing on rear when cornering and hitting a bump. not bad though.

ratt_finkel

That's also 3.5mph of boost lag you loose on the bottom end. While the extra speed in 2nd would be nice. Ultimately the lack of grip would be far from worth it.

eeweeks

These two tires aren't comparable. But a 295 rival vs a comparably sized direzza? I'll have to wrap my mind around the 3.5 mph of boost lag statement when I'm not so coffee deprived.

eeweeks

Well, maybe I've got it. Boost correlates to airflow and engine speed, not vehicle speed. Power band obviously stays the same, effective gearing changes.

honda-guy

iTrader: (55)

Fyi, 255/35/18 R6 and 275/35/18 R6 have the same thread width. Only difference is 255 has shorter sidewall. They are considers a 275 tires in most clubs.