[mistersolo]

I was looking at the layout for SCCA SoloII A stock class and I think that the Supra could have a chance. The class layout is as follows.

A STOCK FOR 2002
Acura
NSX
BMW
M Coupe and Roadster (E36 motor, 240 hp)
Chevrolet
Corvette C4 ('84-'96)
Corvette ZR-1
DeTomaso
Pantera
Mangusta
Porsche
911 (993 chassis), non-turbo ('95-'98)
Saleen
Mustang, non-SC
Shelby
Cobra (all)
Toyota
Supra Turbo ('93 1/2+)

I was wondering what a good setup is. What kinds of shocks, tire sizes, front swaybar, wheel spacers, and alignment is necessary to make a well balanced car? Also, what is the lightest, most reasonably priced exhaust available for the supra. I don't have the money to go all out street mod this year, so stock class will have to work for a while.

Any input from experienced auto-x'rs is greatly appreciated.
Thanks,
John B

 

[jkbrauch]

John - I'm not up on the stock class rules, so I can't help you there. I'd recommend -2 degrees of camber all around, with 0 toe up front and 1mm total toe in for the rear. I think the tire sizes for stock wheels should be 255 front and 275 rear. I just happen to have a set of stock wheels, powdercoated black, with BFG G-Force R-1 tires, 255/40 and 275/40. 60% or more tread remaining. I used them in 3 autocrosses last year and have bought some lightweight race wheels. I run my '97 in Street Mod. The Koni shocks are good but are only adjustable off the car. People seem to go with the KYBs because they're externally adjustable. I had one autocross with the Koni/Eibach combination and felt the car had too much body roll for serious autocrossing. I would recommend a coilover setup if you'll be racing much, which would obviously take you out of stock. The Tiens I hear are good, while the HKSs I know are good, since I have them. The spring rate on the stock springs and to a lesser extent the Eibachs is simply not up to the task of racing. Per Kent Rafferty, who has won the Nationals in Street Mod (his wife won this year), people who are racing Supras seem to go with soft rear sway bars and moderately stiff front bars, with front spring rates around 1000 lbs. and rear rates 6-700. The HKS and Tiens are a bit less, with the HKS rates at 770 and 440, Tiens are 10 lbs. higher. The HKS setup is liveable on the street, but certainly a compromise. I'm guessing the 1000/650 spring rate would be pretty harsh on the street. Hope this helps and good luck - Jeff

 

[mistersolo]

Thanks for the help Jeff.
I know a few people that have run GAB 8ways for other cars than supra's, and have loved them. I don't think that anyone makes independent compression and rebound adjustments for the supra that aren't a coil-over. If I were going street mod I would probably run Tiens or Intrax. Unfortunately for stock class, I am only able to change the shocks and I must keep the factory springs, running at factory height. I can only change the front anti-roll bar, and stiffer is usually better, as long as the car can be reasonably kept away from too much understeer. I was hoping that larger front tires could partially eliminate the understeer. I am looking foreward to autocrossing something besides my MR2turbo. The S2000 and boxster are a little too tuff to beat in the new B stock class for next year. Anyone else ever run the Supra TT in stock class?
John B.

 

[jkbrauch]

John - Sounds like we're almost neighbors, with you living in OMA. Probably the biggest help for understeer will be the alignment (camber in particular), with larger front tires also helping. The Supra is undertired with stock wheels, so you'll have to contend with a lower grip level than what the car would like. The trouble people have had with stiffer rear sway bars is lifting the inside rear tire during cornering. I do not know of anyone running stock class in the Mkiv. The Supra does well in B Street Prepared or Street Modified. When you move up to a modified class, you'll probably want to run 285 in front and 315 in the rear. I just bought a set of CCW wheels, 18x10 in front and 17x11.5 in rear. Different sizing is due to what is available in tires. I haven't had enough race days yet to get my car dialed in, but on the open track day I did this summer, the Supra was one of the fastest cars out there, even running low boost. I'm the only guy in Denver running Solo 2 in a Mkiv, based on what I saw in the late part of the season last year. I wouldn't think you'd have too much trouble with an S2000, from what I've seen. The Boxter may be a different story. Jeff

 

[bwill]

Hey Mistersolo,
Well to be competitive in A Stock you first are going to need another set of wheels and tires to run the DOT race rubber "A" compound tires. If you don't the other A stock cars are going to beat you (at least the ones with DOT race rubber). That will be your biggest way to knock off time. The toughest part for the Supra is that is weighs a lot which ain't good in Solo 2. The M coupe can be a very tough car in the class which weighs probably 300 lbs less than the Supra. The Boxster will be a bitch too because it doesn't weigh as much and is smaller. For alignment I do the "Lance" alignment that can be found at MKIV.com If you really want to go overboard you could dial in even more negative camber than those specs. Power really isn't the key in Solo 2. Hell our cars already have more than enough for this type of event. I would shove some 255s or maybe 265s on the front and put 275s or 285s on the rear. Others in Street Mod run more but I wonder at least on race tires if they are getting the tires up to temp with the bigger sizes. One guy who runs in my class (now Super Stock) soon to be A Stock who drives an M Coupe now runs 245s all the way around and says he is faster with it. He had been running 275s in the rear but after doing some skippad and tire pyrometer tests he found out he was not getting enough heat into the rear tires and that was why he was getting more oversteer than he wanted. I am still debating the springs issue. People either do Eibachs or teins coilovers but the coilovers take you out of stock. I have (somewhere) the different spring rates for the various brands but have not taken the leap on that yet. H&R makes a stiffer spring set that is progressive in the front and linear in the rear. It is a good bit stiffer than the eibachs. Sway bar? Mine is stock but then I am heading to a street mod class and have custom made sway bars being made now. If I were you, hell I would get the wheels and tires first. BIG DIFFERENCE. Probably make you two seconds faster on a 60 second course ONCE you learn how to drive with them. That usually means getting a trailer hitch and a small utility trailer to transport the wheels too. Good luck. I am doing a Solo 2 tomorrow.
Barry H. 94ttsupra 6sp.

 

[jkbrauch]

I think Andy B. has a spring rate table for different springs. Many people have 2 drivers run the same car in autox because the tires do get up to temp. better. As far as tire size, I would try what the winners have done - and they say bigger is better. This is not a reference to you, Barry, just a deference to guys like Kent and his wife Karen who have won National titles. I have heard, as well, that one can go too big with tires, but this doesn't seem to be the case with the Supra. Anyway, I'll be able to give some feedback once I have a few days on my new wheels and tires.

Here is some spring info-

Stock 430 front/219 rear
Eibach 370-510/180-263 progressive
H&R 470-495/250
Ground Control 950/600
HKS 771/441
Tien 780/450
Intrax 559/285

Jeff in CO

 

[bwill]

Hey Jeff in Co
Yeah I know Kent F runs 315s in the rear and275s up front. Actually I have been meaning to ask him if he had done the tire pyrometer check to actually see what temps he is getting his tires up to. The guy who (again this was an M coupe) went down on tire size in the rear is a regional winner who Solo 2s each weekend. He at least has a sound basis for doing it. Didn't mean that it is necessarily true for Supras. I am just curious as to whether Kent has done the same thing (probably). The point being that bigger is usually better but at some point in Solo 2, maybe not. A track event, certainly. As to having two drivers as a regular Solo 2 event, that doesn't work at least in my neck of the woods (Birmingham) and when I have gone to Atlanta. In Birmingham, two driver cars run in different run groups. If you know Kent personally ask him, I am curious. I see him on MKIV. I saw where Kent's wife got 1st this year and Kent got 3rd in Street Mod but I am not probably not tellling you anything new. I think the Lance alignment is 1.5 degrees negative. You are running 2 degrees negative. I would imagine it is better. What kind of tire wear issues if any do you have with it? I would like to go there if it isn't too darn rough on tires.
Barry H. 94ttsupra 6sp Super Stock

 

[bwill]

Jeff,
I forgot one thing. If Mistersolo is going to stay in what will be A Stock in 2002, a lot of people in this region "supersize it" on the tires by putting on what would appear to be too wide for the rim size such as a 265 front/285 rear if they are running Hoosier or Kuhmo race rubber. The rationale being the sidewalls are stiff enough for it to get some benefit from it. Just thinking out loud here. See ya.
Barry H.

 

[Grant]

Lance's specs are 1.0 negative in front. IMO you need more than this, outside tire temps were quite a bit higher than inside, don't remember the exact #s. My car isn't lowered so I couldn't get 1.5 in the front.

From what I hear, extra camber won't make that much of a diff on tire wear unless you go >2.0 degrees.

M coupes don't seem to be much trouble, but I haven't run into many. Watch out for the Z06s on hoosiers.... There were two ex national champs w/ Z06s at the FL state solo 2 here in Gainesville, and one got the FTD with 6 seconds better than me (I'm on street tires, and I could have shaved a second or two off with non-shitty driving, but still).

 

[jkbrauch]

Barry - I haven't had -2 camber long enough to tell what tire wear issues will occur, if any. I know there was a huge difference between -1 and -2 on handling on my car. My car understeered badly with the lesser camber. My tire temps at -2 were 5-10 degrees hotter inside than outside. I've been told that up to 10 hotter is good, over 10 means you need to take some camber out or drive differently. I can see where supersizing tires might be the best alternative for stock class, some of the sidewalls are so stiff they seem to tolerate less support from narrow rims. My guess is that one could run -1.75 camber in front efficiently. I haven't tried it though. I'm sure I'll be learning alot this coming season. I had alot of inside tire wear at -1 camber with Kumho tires. I was supposedly at 0 toe in front, but I can't believe the alignment was correct with the wear I was getting. I've started doing my own "string" alignments with a bubble camber/caster gauge. The local race shop guys tell me nothing is more accurate than that. Jeff

 

[bwill]

Thanks for the info Jeff. Doing your own alignment now that is the ticket. Yeah I am at 1.5 negative and think I will do 1.75 negative. I am running 0 toe and I guess I got a good alignment because I have noticed a pretty big difference in inside wear being a lot less. Do you find the rear end a little more "squirrely" in a straight line with zero toe. I have heard that can be one characteristic of zero toe. My car experiences more squirm or squirrel in the rear which I attribute to the alignment. Handles in a turn better though. I saw in Grass roots motorsports a smartcamber digital camber/caster device for about $275 but string and bubble has to be cheaper. By the way what sway bars are you running (if it isn't a secret)!
Barry H. 94ttsupra

 

[jkbrauch]

Barry - I'm currently running the TRD in front with the stock in the rear. I had too much oversteer with the TRD in the rear, which may be somewhat attributable to 0 toe. I'll have to change the rear toe to discover if that was the case. The balance of the car changed dramatically with the changeover to the HKS coilovers... Jeff

 

[Grant]

jkbrauch, Lance's alignment has less toe in back than the stock, which has quite a bit. But its still not 0. I have a hard time believing your car actually has too much oversteer for solo2, maybe its because of the toe? I haven't messed with it myself, just observed that other people with Teins and HKS coilovers still understeer a little.

Kent commented on the size vs. tire temps thing a while ago on the list, saying he thought bigger was always better.

 

[Eric]

My autox experience with the mkiv is somewhat limited, but I have a lot of autox experience with other cars and have spent a lot of time with my mkiv on the racetrack. The first thing you should do is get as much negative camber as possible up front. At stock ride height, you'll probably only be able to get about -1.5 or so, which isn't really enough, but will be a big improvement over the stock settings. I run -1.7 up front, and could stand to run a little more based on tire temps, but I'm maxed out. Autox usually requires more static camber than track use to boot. Tire wear with that amount of camber is not a big deal unless you combine it with a lot of toe. I don't have enough autox experience to suggest any toe settings. Also, don't give up camber to get more caster (you have to trade one off for the other to some degree with the adjustments built into the control arms). Max camber out first, then get as much caster as possible. Caster falls into the "nice to have" category, while camber falls into the "must have" category. I run -1.5 degrees of camber in the back, which results in good tire temps on the racetrack.


Bigger is almost always better when it comes to wheels/tires. Since you're limited to stock size wheels, I'd probably run 275s on the back and the biggest thing you can fit on the front wheels (not that familiar with the available sizes). The mkiv ought to be at least reasonably competitive in A-stock compared to SS, where it never had a prayer with well driven Corvettes and RX7s.

Eric

 

[jkbrauch]

Grant - It could be that 0 rear toe is a problem - although the recommended total toe in the rear is 1mm from what I've seen. It could be that there is a world of difference between 0 toe and 1mm. Interestingly, when I replaced the TRD rear bar with the stock, and left the rear toe at 0, the rear end felt stable again. This was on the street with street tires, so I don't know if that will be the same at the track. Kent told me most Supra road racers run a stiffer bar up front than rear, which is what I've been leaning towards based on my experience. I'll do some more testing with various rear toe settings and see what is fast. 0 toe up front seems to be good - turn in seems crisp.

Barry - Pole Position makes a Fastrax camber/caster bubble gauge which is used when the wheel is on the car. I seems to work well for me and is about $110. If you start doing your own alignments, get some slip plates to perform your alignment - they keep you from having to roll the car to unload the tire after making an alignment change. I set my car on a 6" high platform with the slip plates on it. This way I can align the car without jacking up each corner and having to reset the centerline reference each time. I have 4 platforms made up of 6x6 lumber.

Jeff

 

[carcnoid]

Grant,

When I upped the front tire size to 245 the car has a lot less understeer. You'll see when I get back. I can't wait to get racing.

Damn I miss my car.