Going Stupid big on wheels - Racecar

HarrisRacing · 05-21-2009, 04:33 PM

Ok here's the dilemma and I want to see if anyone has good input on a racing setup (heck any input will help).

My car is a 1991 gutted track car. real-deal caged-out racecar. Forged piston gen3 motor car on stock CT20b for now, APexi powerFC and lots of other go fast goodies - 2300 lbs finished. 12.1 @ 110 in 1/4 on pumpgas and only 15 psi.

Suspension wise, I am running Tein SS w/ camber plates and have the strut layed all the way into the car with the plate and then am pulling the spindle away from the strut at the bottom 2 bolts before tightening (can't remember which crash bolts I'm running here). I am only getting about 1.5 deg camber this way and am going to need a lot more soon.

I am running 16 x 7.5 +35 mustang wheels on the front and stock FD rx-7 on back 16 x 8 +50. 225 Hankook race tire on front and 255 on rear. I am now in a class where I need more grip to hang with the big cars (Vipers, Corvettes, Trans-am, Panoz etc). I am going to need quite a bit more grip to hang with these cars...and I can tell you that's honestly the problem right now. Camber will help if I put a spacer up front, but I would be chasing the back end then, and let's face it, Rubber meeting the road is the best solution to increasing grip.

SO...First, I was looking into getting some dirt track style 15" wheels. 15 x 10 up front and 15 x 12 out back steelies from Diamond Racing Wheels. Bad news is tires are hard to find it 275 and 315 15"s.

Yes I will HAVE to cut / flare fenders at this point - no problem there.

So I called some tire manufacturers and started talking about what's typical and of course in those widths most people recommended 18" wheels. I hate going from 15 to 18, but will if I have too. They all said that performance will be DRASTICALLY increased on a road course, so we will see. Plus more REAL road race slicks (as opposed to DOT R comps) are made for this size.

I looked at 18 x 9" Mustang wheels and 18 x 10" in rear and could fit with minor spacing in front. Getting pretty heavy for this setup and expensive to keep on ther car for something that's still not yet on the EXTREME side of sizing on the car. SO back to the drawing board. I could also go with the 17 x 9 mustang fronts and 17 x 10.5 rear with spacers and try that if I can find decent sized 17's in constant surplus.

Anyway, just give me some ideas on what you guys think right now.

Patrick

mr2nv · 05-21-2009, 05:19 PM

Well, I know for a fact that Hoosier makes 275/35/15 in R6's. I would maybe look at 16's. Probably a good amount of options with tires, less weight than 18's and cheaper. You also might want to try flipping your camber plates 180 degrees to get more camber. I did that with my tein flex and was able to get more camber along with crash bolts.

Sylvan · 05-22-2009, 07:40 AM

Well, Hoosier R6 is available up to 335's on a 17" wheel, so that's an option if you wanted to stick with R-comps instead of full slicks. Like he said above, up to 275 on a 16" wheel. If it were me, I wouldn't go much bigger or wider than the 275 on the 16" wheel. Your car is so light that you will feel more adverse effects from having a heavier wheel/tire package as opposed to on a 3,000 lb car. An 11" or 12" wide wheel is going to have a lot of inertia at the rim where it does the most damage to your acceleration. Obviously, wheel options are limited at these extreme sizes, so you may have to go custom with something from CCW for example. My opinion is that you don't have a lack of rubber, but rather the suspension isn't really up to the task of keeping that rubber planted properly, as would be the case with a more sophisticated wishbone setup. There's only so much you can do with struts, so you might have to find ways to get more static camber to begin with. -1.5 degrees isn't much, so I think your efforts could be better spent looking for suspension improvements.

EL PAALO · 05-22-2009, 11:08 AM

hack up the fenders.
SCCAForums.com - FS: SM2 MR2 -- 3rd and 4th at 2008 Nationals -- Beat the RX7s! ($19,000 obo)

kbrew8991 · 05-22-2009, 01:42 PM

I would copy Randy Noll's wheel setup if it were me and I had $$$$$ to burn on 18" tires

17s would be a good comprimise

mr2greasemonkey · 05-22-2009, 05:23 PM

YouTube - mr2 V6 zia backing up to dyno

Big but I can still smoke 'em. I suggest the suspension suggestion as noted above.

05-21-2009, 04:33 PM	#1 (permalink)
HarrisRacing Cage Fighter Join Date: Jun 2007 Location: Lafayette, La Posts: 214 Thanks: 13 Thanked 16 Times in 7 Posts My Google Map iTrader Rating: (0/0% )	Going Stupid big on wheels - Racecar Ok here's the dilemma and I want to see if anyone has good input on a racing setup (heck any input will help). My car is a 1991 gutted track car. real-deal caged-out racecar. Forged piston gen3 motor car on stock CT20b for now, APexi powerFC and lots of other go fast goodies - 2300 lbs finished. 12.1 @ 110 in 1/4 on pumpgas and only 15 psi. Suspension wise, I am running Tein SS w/ camber plates and have the strut layed all the way into the car with the plate and then am pulling the spindle away from the strut at the bottom 2 bolts before tightening (can't remember which crash bolts I'm running here). I am only getting about 1.5 deg camber this way and am going to need a lot more soon. I am running 16 x 7.5 +35 mustang wheels on the front and stock FD rx-7 on back 16 x 8 +50. 225 Hankook race tire on front and 255 on rear. I am now in a class where I need more grip to hang with the big cars (Vipers, Corvettes, Trans-am, Panoz etc). I am going to need quite a bit more grip to hang with these cars...and I can tell you that's honestly the problem right now. Camber will help if I put a spacer up front, but I would be chasing the back end then, and let's face it, Rubber meeting the road is the best solution to increasing grip. SO...First, I was looking into getting some dirt track style 15" wheels. 15 x 10 up front and 15 x 12 out back steelies from Diamond Racing Wheels. Bad news is tires are hard to find it 275 and 315 15"s. Yes I will HAVE to cut / flare fenders at this point - no problem there. So I called some tire manufacturers and started talking about what's typical and of course in those widths most people recommended 18" wheels. I hate going from 15 to 18, but will if I have too. They all said that performance will be DRASTICALLY increased on a road course, so we will see. Plus more REAL road race slicks (as opposed to DOT R comps) are made for this size. I looked at 18 x 9" Mustang wheels and 18 x 10" in rear and could fit with minor spacing in front. Getting pretty heavy for this setup and expensive to keep on ther car for something that's still not yet on the EXTREME side of sizing on the car. SO back to the drawing board. I could also go with the 17 x 9 mustang fronts and 17 x 10.5 rear with spacers and try that if I can find decent sized 17's in constant surplus. Anyway, just give me some ideas on what you guys think right now. Patrick

05-22-2009, 11:08 AM	#4 (permalink)
EL PAALO Wheels make the car. Join Date: Feb 2005 Location: San Marcos, TX Posts: 2,671 Thanks: 4 Thanked 86 Times in 82 Posts My Google Map iTrader Rating: (3/100% )	hack up the fenders. SCCAForums.com - FS: SM2 MR2 -- 3rd and 4th at 2008 Nationals -- Beat the RX7s! ($19,000 obo) __________________ WHEELSPECS.COM - a ridiculous number of wheel pics & links

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05-21-2009, 05:19 PM	#2 (permalink)
mr2nv Beams Owners Group Join Date: Mar 2007 Posts: 179 Thanks: 0 Thanked 10 Times in 8 Posts iTrader Rating: (1/100% )	Well, I know for a fact that Hoosier makes 275/35/15 in R6's. I would maybe look at 16's. Probably a good amount of options with tires, less weight than 18's and cheaper. You also might want to try flipping your camber plates 180 degrees to get more camber. I did that with my tein flex and was able to get more camber along with crash bolts.

05-22-2009, 07:40 AM	#3 (permalink)
Sylvan Bad Dude Join Date: Apr 2007 Location: San Jose, CA Posts: 878 Thanks: 22 Thanked 38 Times in 34 Posts My Google Map iTrader Rating: (10/100% )	Well, Hoosier R6 is available up to 335's on a 17" wheel, so that's an option if you wanted to stick with R-comps instead of full slicks. Like he said above, up to 275 on a 16" wheel. If it were me, I wouldn't go much bigger or wider than the 275 on the 16" wheel. Your car is so light that you will feel more adverse effects from having a heavier wheel/tire package as opposed to on a 3,000 lb car. An 11" or 12" wide wheel is going to have a lot of inertia at the rim where it does the most damage to your acceleration. Obviously, wheel options are limited at these extreme sizes, so you may have to go custom with something from CCW for example. My opinion is that you don't have a lack of rubber, but rather the suspension isn't really up to the task of keeping that rubber planted properly, as would be the case with a more sophisticated wishbone setup. There's only so much you can do with struts, so you might have to find ways to get more static camber to begin with. -1.5 degrees isn't much, so I think your efforts could be better spent looking for suspension improvements.

05-22-2009, 01:42 PM	#5 (permalink)
kbrew8991 gimme some turns Join Date: Apr 2006 Location: Houston, TX Posts: 1,685 Thanks: 76 Thanked 82 Times in 70 Posts My Google Map iTrader Rating: (5/100% )	I would copy Randy Noll's wheel setup if it were me and I had $$$$$ to burn on 18" tires 17s would be a good comprimise