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setting up an SN95 rear suspension for road course competition

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152
120
Exp. Type
Time Attack
Exp. Level
Under 3 Years
Greenbrier, TN
Just when I've got my S550 IRS figured out, I do something stupid and buy a '94 for NASA Time Trials. I've set up a few straight axles for the drag strip but I know nothing about setting one up for road course. The car will just barely squeeze in ST/TT3 with 340 rwhp and Toyo Proxes 266/40/zr17.
I've been reading " WATTS vs. PANHARD " until my head is spinning.
I'd sure appreciate some thoughts on it.
 
6,345
8,135
look into the "junkyard dog" build, there is literally tons of info there on an SN95.
As I'm sure you've figured out, the "triangulated 4 link" is a disaster, it also promotes serious snap oversteer on corner exit. Go view that article, and see what you find.
 
152
120
Exp. Type
Time Attack
Exp. Level
Under 3 Years
Greenbrier, TN
My head hurts! All of this “3l vs. phb. vs. ta vs. 5l, vs wl “ The SN95 is almost 30 years old. I can’t believe someone hasn’t come up with a “Beats all“ solution or a complete bolt in IRS system by now.
 
6,345
8,135
I've swapped the IRS into my 99, try to find an 03 or 04 out of as Terminator, they are the best gear ratio and the strongest. If you do that, make sure when you buy the IRS you get the brackets that replace the "quad shock" mount, they are not the same, and the IRS brackets are almost unobtainable.
I've put those IRS units into everything from Mustangs to Fairmonts (a Fairmont wagon at that), if you ever see the guy that tracks it, you may not want to call him out, it's a sleeper.
One of the builds is here... https://www.tamparacing.com/forums/projects/758828-johnny-cash-mustang-project.html

Basically, it comes down to this..
What do the rules say?
I had to run your exact setup in NASA autocross. back in the day against a crapload of Honda S200s, I finished 2nd for the year, so it can be done.
Go back to my article and visualize what is going on with those links, the bottom 2 are parallels, the upper 2 are in bind ALL THE TIME, this is why the rear goes into snap oversteer coming off the corners, those upper inks are fighting to center the diff, and are wreaking havoc. In NASA, the rules did change, they allowed a non spec material in the upper trailing arms, this allowed you to run urethane bushings in one side, and Styrofoam in the other, you were also allowed to run a Panhard bar. So think about that, you've negated one of the upper trailing arms, and are using the PHB to center the diff. This works, it works amazingly well. If you use a PHB, without negating one of the upper arms, you now have introduced ANOTHER binding arc in the suspension, so much so, that you can actually raise a corner of the car by cranking on the PHB... an utter disaster, you might as well weld the diff to the frame.
If your rules package is not specific, the install a truck (torque if you are from up north), arm and be done with it, or an IRS, but they are getting pretty pricey, at least the good ones are.
If you have to run the stock suspension in it's entirety, you are pretty screwed, you can use softer upper bushings (I used to soak mine in kerosene) and use urethane bushings in the lower trailing arms, this will kind of ease the whole snap oversteer thing, because the lower arms will be more "forceful," for lack of a better term, and will do some of the work centering the diff. If you have to do this, just try to soften up the upper bushings, mess with the sway bar, and adjust on the shocks, and walk away from the rear suspension, there is no future for you there.
The front, however, is a different story, use at least 4 degrees of caster, this will allow a phenomenon called "camber gain" when you turn the wheel, which is a good thing, Steeda 2x ball joints and a bump steer kit are mandatory for these cars. I ran the Steeda competition springs, I forget the part number. Basically, the whole car was Steeda. These cars are pretty flexible, so if the rules allow, install some weld in sub frame connectors and a firewall/ shock tower support (known as an export brace).
Some place, I have a pic of my car, hanging the inside front tire in the air, just like the S197 cars, and that was with the crappy 4 link.
One last thing, as lousy as the triangulated 4 link fs for road racing, it's actually pretty awesome for drag cars... well except it will put a rip in the floor pan eventually, but that's another story.
There, everything you need to know about Foxbody/SN95 cars.
 
Last edited:
152
120
Exp. Type
Time Attack
Exp. Level
Under 3 Years
Greenbrier, TN
I've swapped the IRS into my 99, try to find an 03 or 04 out of as Terminator, they are the best gear ratio and the strongest. If you do that, make sure when you buy the IRS you get the brackets that replace the "quad shock" mount, they are not the same, and the IRS brackets are almost unobtainable.
I've put those IRS units into everything from Mustangs to Fairmonts (a Fairmont wagon at that), if you ever see the guy that tracks it, you may not want to call him out, it's a sleeper.
One of the builds is here... https://www.tamparacing.com/forums/projects/758828-johnny-cash-mustang-project.html

Basically, it comes down to this..
What do the rules say?
I had to run your exact setup in NASA autocross. back in the day against a crapload of Honda S200s, I finished 2nd for the year, so it can be done.
Go back to my article and visualize what is going on with those links, the bottom 2 are parallels, the upper 2 are in bind ALL THE TIME, this is why the rear goes into snap oversteer coming off the corners, those upper inks are fighting to center the diff, and are wreaking havoc. In NASA, the rules did change, they allowed a non spec material in the upper trailing arms, this allowed you to run urethane bushings in one side, and Styrofoam in the other, you were also allowed to run a Panhard bar. So think about that, you've negated one of the upper trailing arms, and are using the PHB to center the diff. This works, it works amazingly well. If you use a PHB, without negating one of the upper arms, you now have introduced ANOTHER binding arc in the suspension, so much so, that you can actually raise a corner of the car by cranking on the PHB... an utter disaster, you might as well weld the diff to the frame.
If your rules package is not specific, the install a truck (torque if you are from up north), arm and be done with it, or an IRS, but they are getting pretty pricey, at least the good ones are.
If you have to run the stock suspension in it's entirety, you are pretty screwed, you can use softer upper bushings (I used to soak mine in kerosene) and use urethane bushings in the lower trailing arms, this will kind of ease the whole snap oversteer thing, because the lower arms will be more "forceful," for lack of a better term, and will do some of the work centering the diff. If you have to do this, just try to soften up the upper bushings, mess with the sway bar, and adjust on the shocks, and walk away from the rear suspension, there is no future for you there.
The front, however, is a different story, use at least 4 degrees of caster, this will allow a phenomenon called "camber gain" when you turn the wheel, which is a good thing, Steeda 2x ball joints and a bump steer kit are mandatory for these cars. I ran the Steeda competition springs, I forget the part number. Basically, the whole car was Steeda. These cars are pretty flexible, so if the rules allow, install some weld in sub frame connectors and a firewall/ shock tower support (known as an export brace).
Some place, I have a pic of my car, hanging the inside front tire in the air, just like the S197 cars, and that was with the crappy 4 link.
One last thing, as lousy as the triangulated 4 link fs for road racing, it's actually pretty awesome for drag cars... well except it will put a rip in the floor pan eventually, but that's another story.
There, everything you need to know about Foxbody/SN95 cars.
1) The NASA TT rules are a simple 'WEIGHT TO HP' ratio. So I can do whatever works best.
2) I've read a lot about suspensions & this is the first time I've ever heard 'camber gain' Awesome!
3) I finally know wtf a "truck" arm is.
Seriously though, I've got some funds set aside from selling my bracket racing foxbody and I'd really like the best set up. Is the IRS that much of a gain over everything else?
If so, I'm thinking about sourcing the needed parts and going that route.
Otherwise I'll just go TA & PHB.
I appreciate Your time and knowledge.
You two, blacksheep-1 & TMSBOSS , have been so much help to me this whole year. Thanks.
 
152
120
Exp. Type
Time Attack
Exp. Level
Under 3 Years
Greenbrier, TN
So I got the car home and here’s what she looks like. Adjustable uppers and lowers with coil overs. Subframe connectors and a cross braced Front K-member.
So, following the Junkyard Dog build I’m gonna loose the left side upper. Swap the right side upper rubbers for machined bushings and dump that axle bracing bar & sway bar in exchange for a PHB.

62AAA00E-4E1E-4C90-B9DF-7373660DC3DA.jpeg

13231FC0-30A8-4660-AAD9-64D3DE72113D.jpeg
 
Last edited:
152
120
Exp. Type
Time Attack
Exp. Level
Under 3 Years
Greenbrier, TN
I've swapped the IRS into my 99, try to find an 03 or 04 out of as Terminator, they are the best gear ratio and the strongest. If you do that, make sure when you buy the IRS you get the brackets that replace the "quad shock" mount, they are not the same, and the IRS brackets are almost unobtainable.
I've put those IRS units into everything from Mustangs to Fairmonts (a Fairmont wagon at that), if you ever see the guy that tracks it, you may not want to call him out, it's a sleeper.
One of the builds is here... https://www.tamparacing.com/forums/projects/758828-johnny-cash-mustang-project.html

Basically, it comes down to this..
What do the rules say?
I had to run your exact setup in NASA autocross. back in the day against a crapload of Honda S200s, I finished 2nd for the year, so it can be done.
Go back to my article and visualize what is going on with those links, the bottom 2 are parallels, the upper 2 are in bind ALL THE TIME, this is why the rear goes into snap oversteer coming off the corners, those upper inks are fighting to center the diff, and are wreaking havoc. In NASA, the rules did change, they allowed a non spec material in the upper trailing arms, this allowed you to run urethane bushings in one side, and Styrofoam in the other, you were also allowed to run a Panhard bar. So think about that, you've negated one of the upper trailing arms, and are using the PHB to center the diff. This works, it works amazingly well. If you use a PHB, without negating one of the upper arms, you now have introduced ANOTHER binding arc in the suspension, so much so, that you can actually raise a corner of the car by cranking on the PHB... an utter disaster, you might as well weld the diff to the frame.
If your rules package is not specific, the install a truck (torque if you are from up north), arm and be done with it, or an IRS, but they are getting pretty pricey, at least the good ones are.
If you have to run the stock suspension in it's entirety, you are pretty screwed, you can use softer upper bushings (I used to soak mine in kerosene) and use urethane bushings in the lower trailing arms, this will kind of ease the whole snap oversteer thing, because the lower arms will be more "forceful," for lack of a better term, and will do some of the work centering the diff. If you have to do this, just try to soften up the upper bushings, mess with the sway bar, and adjust on the shocks, and walk away from the rear suspension, there is no future for you there.
The front, however, is a different story, use at least 4 degrees of caster, this will allow a phenomenon called "camber gain" when you turn the wheel, which is a good thing, Steeda 2x ball joints and a bump steer kit are mandatory for these cars. I ran the Steeda competition springs, I forget the part number. Basically, the whole car was Steeda. These cars are pretty flexible, so if the rules allow, install some weld in sub frame connectors and a firewall/ shock tower support (known as an export brace).
Some place, I have a pic of my car, hanging the inside front tire in the air, just like the S197 cars, and that was with the crappy 4 link.
One last thing, as lousy as the triangulated 4 link fs for road racing, it's actually pretty awesome for drag cars... well except it will put a rip in the floor pan eventually, but that's another story.
There, everything you need to know about Foxbody/SN95 cars.
4B2F3554-C746-42F2-9EC6-1BF2CFDCA784.jpeg
 
6,345
8,135
you should be able to keep the sway bar with the Panhard Bar
It looks like you have a lot of good parts to work with.
Have you ran it yet? so you can tell the difference after the changes?
When you go to basically, solid upper trailing arms like you have, it binds the crap out of the suspension because there are no longer rubber bushings, so you have absolutely no give whatsoever.
 
Last edited:
152
120
Exp. Type
Time Attack
Exp. Level
Under 3 Years
Greenbrier, TN
you should be able to keep the sway bar with the Panhard Bar
It looks like you have a lot of good parts to work with.
Have you ran it yet? so you can tell the difference after the changes?
When you go to basically, solid upper trailing arms like you have, it binds the crap out of the suspension because there are no longer rubber bushings, so you have absolutely no give whatsoever.
I’m going to Memphis next weekend for an initial run. Just some HPDE driving since I don’t know the car yet. It will be interesting to say the least!
The stiff 4 link should induce some real oversteer, but the big wing out back with a no front aero may bring about some light front end understeer. Add to that, the entire car is solid mounted with a braced k member and welded in subframe connectors... who knows? I wonder if I should take that wing off?

9E9073E9-B70D-482A-8DFE-82D48D7A3999.jpeg
 
6,345
8,135
I’m going to Memphis next weekend for an initial run. Just some HPDE driving since I don’t know the car yet. It will be interesting to say the least!
The stiff 4 link should induce some real oversteer, but the big wing out back with a no front aero may bring about some light front end understeer. Add to that, the entire car is solid mounted with a braced k member and welded in subframe connectors... who knows? I wonder if I should take that wing off?

View attachment 69930

It's not just oversteer, it's SNAP oversteer, very unpredictable.
So exactly what are you running for a rear suspension right now?
The solid upper links?
 
152
120
Exp. Type
Time Attack
Exp. Level
Under 3 Years
Greenbrier, TN
It's not just oversteer, it's SNAP oversteer, very unpredictable.
So exactly what are you running for a rear suspension right now?
The solid upper links?
Right. I haven’t been able to do anything yet. It’s got the Adjustable solid uppers with MM adjustable lowers. There are Koni Coil overs & a sway bar. Was hoping to get an MM PHB and a TA on it but they are backordered for 5- 6 weeks.
 
Last edited:
6,345
8,135
Right. I haven’t been able to do anything yet. It’s got the Adjustable solid uppers with MM adjustable lowers. There are Koni Coil overs & a sway bar. Was hoping to get an MM PHB and a TA on it but they are backordered for 5- 6 weeks.
well a phb with the solid uppers is the same as no suspension.
 
152
120
Exp. Type
Time Attack
Exp. Level
Under 3 Years
Greenbrier, TN
well a phb with the solid uppers is the same as no suspension.
Yea. that’s why I’m just doing some touring laps next weekend. I’ve only driven this car from the trailer to the shop. And I’d at least like to see how the rest of the car is. Since I can’t get my hands on a PHB I figured I’m better off not doing anything yet.
 
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110
132
Exp. Type
HPDE
Exp. Level
Under 3 Years
Nashville TN
Yea. that’s why I’m just doing some touring laps next weekend. I’ve only driven this car from the trailer to the shop. And I’d at least like to see how the rest of the car is. Since I can’t get my hands on a PHB I figured I’m better off not doing anything yet.
Hey, I'd love to catch up in Memphis. Nice new project! I have a '96 Cobra and am also planning to build a TT car with it, so would be great to compare notes. I'm guessing I'll end up in TT2, but MAY try to squeeze into TT3. Also trying to figure out where there's an actual field in NASA Mid-South so I'm not running a class of one. See you in Memphis!
 
152
120
Exp. Type
Time Attack
Exp. Level
Under 3 Years
Greenbrier, TN
Hey, I'd love to catch up in Memphis. Nice new project! I have a '96 Cobra and am also planning to build a TT car with it, so would be great to compare notes. I'm guessing I'll end up in TT2, but MAY try to squeeze into TT3. Also trying to figure out where there's an actual field in NASA Mid-South so I'm not running a class of one. See you in Memphis!
Awesome! I'll see you there. Are you bringing the GT350 this weekend?
 

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