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Wider rubber IT-S

Old 02-24-08, 09:30 PM
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Wider rubber IT-S

Since I've also started running track days with my second Gen IT-S car I was thinking of getting yet another set of rims specifically for this. Considering that I wouldnt need to keep with the IT rule of no larger than 15x7 rims I could move up to something wider. With the limited power of my IT-S car do you guys think it would be worthwhile jumping up a couple of tire sizes. If I were to remove my spacers I figure I could get some pretty decent rubber under there. What are the EP guys running tire width wise?

Do you figure it would be beneficial for lap times, or would I be putting on more rubber than the car will be able to heat up to operating temps?
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Old 02-24-08, 10:45 PM
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EP guys are mostly running 23x9x15 Goodyear, or 23x9.5x15 Hoosier slicks (very sticky, fast wear, probably not good track day tires due to the cost of running them when there's nothing on the line. They're very similiar in size, and require a widebody (at least in front, I don't know about the rear, but most/all run a widebody back there too).

Maybe just some 15x8's and 225/45/15 or 225/50/15's would be a better compromise. It'll give a little better grip and feel than with the 15x7's and not require any ITS illegal fender mods. If you go up to something like a 16x8 you might fit some 245/45/16's, but that's a bunch taller. If you want even bigger then maybe 235/40/17's or 245/40/17's.
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Old 02-25-08, 06:59 AM
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ep cars run 15 x 7 wheels but the offset is much different than stock.
thats why the cars run flares front and rear.
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Old 02-25-08, 07:18 AM
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I'm not sure you can squeeze much more rubber under there with stock fenders. I know I can't on mine. The 15 x7 is fine, and as stated above what EP runs. The 225/45/15 Hoosier R6 is fast. If you aren't up to the 175-180 rwhp I'd spend the money to get there before buying wider rims/tires for track days.

If you want drop times during track days, lose the ballast if you have any (I had 150lbs). That's free, simple, quick. If you really wanted to mess around, put on a lightweight flywheel. Going from +/- 22lbs to 8lbs makes a huge difference... but it won't be IT legal if you leave it on for the race.
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Old 02-25-08, 10:01 AM
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Thanks for the input guys. The engine is strong and totally IT legal (had it built by Mike at ISC last year), but the people that show up at track days all bring some big guns with tons of HP, so its a little embarrassing. Its kinda bad when Im running around in a race suit, trailer in my car with tons of spares all badass looking, and then some kid in a souped up civic and a tshirt that drove to the track is tons faster than you .

I've removed the IT ballast....but then I replaced it with a passenger seat so I can give students and girlfriends rides. Im just brainstorming at this point to try to come up with some options of getting the car to be a bit quicker.

I have to get under it with a tape measure to look at my clearence for sure, but Im running (if I remember correctlly) 12mm spacers all the way around. With the spacers Im tight but not critically tight, so if I took them out I think I might get an easy 20mm of added wheel clearence....16x8 perhaps?
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Old 02-25-08, 11:23 AM
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Keep in mind that wider rubber, while it gives you a better launch onto the straights, it hurts your acceleration from having a greater flywheel effect (more weight), from higher rolling resistance, and for anything wider that'd be appropriate, it'll be taller, hurthing your gearing, all contributing to making it slower on the straights. The taller rubber also raises the car off the ground a little more, raising the CG, hurting cornering a little.

Here's what I'd suggest: get more power. Maybe run nitrous, get a second manifold or piece of one and install a wet nitrous setup, maybe 50hp and use it to pass those more powerful cars that'll be holding you up in the corners. Seriously. You will need to completely remove it for racing though, as the SCCA bans all forms of nitrous and I don't even think they allow it on site at all (not that you'd cheat like that, but it's best to leave as little remains as possible). Another option might be to get an individual throttle body setup. Make it so that it converts easily so you can swap it in for track days. You should probably be running an FPR and standalone already to get the most ITS power, so it'd be pretty easy to swap the manifold and load a new program, and then you've got instantly more power. You can do it in a downdraft setup like a Weber IDA, or sidedraft like a Weber DCO (puts the TB closer to stock location, so stock throttle cable might work). You'd need to fab up an air box and an ambient air intake, but it shouldn't be too hard to do. Should add maybe 10hp or so and not be too hard to convert it back and forth.
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Old 03-04-08, 09:17 AM
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Too bad most sanctioning bodies refuse to allow nitrous on the track. But if yours does, it could be a good idea.

Maybe run on tracks with more turns and less straights?
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Old 03-04-08, 09:42 AM
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If it's run by NASA or the SCCA or some other racing group, then probably not, but if it's run by a group that does HPDE's as its main thing then it's probably allowed, for sure check first. It's not my preffered way to get power, but it's cheap and would allow the car to remain ITS legal with some minor swapping parts in and out.
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Old 03-04-08, 11:56 AM
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This is a very timely topic...I've been looking into what it would take to be able to run the Hoosier 275/35-15 on my '89 for CSP auto-x, so I have many of the same questions as the OP. Is there any chance at all that the 275s will work up front with only fender rolling and the right backspace wheels? I currently run 225/45-15s on Mustang wheels (+24 offset, which is 6" backspace if I'm calculating right), and there's a ton of room up front. I may buy a 5.5" or 5.75" 15x10 Diamond just to see if the dimensions work...
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Old 03-04-08, 04:43 PM
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I highly doubt it since the EP guys with similiar tire diameters and widths and are running something like 2" wider fenders up front typically on 0 offset wheels. If you keep the height way up and run stiff enough to keep the tires off the fenders then it could be possible, but that's probably not what you were wanting. Maybe if you just trim the fenders to make more clearance?
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