Help setting up Speedtech torque arm for more traction

[joeelutz]

I've got the SpeedTech Torque arm system in my 67 Camaro and have been very happy withe the overall performance of the system. It rides well and handles the corners great. I would just like to get a little more forward bite. The car has a lot of carbon and light weight goodies. It weighs 3140 lbs with 48% rear, 52% front and a half tank of gas, no driver.. With me in it, it weighs 3330 and is about 49% rear, 51% front.
I'm running an LS7 with approx 650 hp at the flywheel, T56 magnum trans and a Strange 9" that came with the torque arm kit, with 3.90 gears and tru-trac. The tires are fresh 335 KDW's I realize that's quite a bit of power to put down with street tires, but in first gear at any speed if I roll into it, it almost sounds like a free rev it spins the tires so fast. In second gear, if I ease into the throttle at a low boggish RPM, it will try to hook till the engine gets to where it starts making power and then it just lights them up. This pic pretty much shows where I have the links and shock mounts. Lower links are in the middle hole. Shocks are up one hole from the bottom.
Can I get any suggestions to try to get more forward traction with suspension adjustments?

Thanks.
https://static1.pt-content.com/images/pt/2012/12/resized_DSCN4126JPGpsid1-1.jpg?psid=1

[MonzaRacer]

Generally I tell people to dial in more pinion angle, On that set up I might fathom a guess, are the holes where lower arms multiple holes in kit, if so move them up or down, This will let the suspension work from different angles.
Generally if a car takes off good but then UNLOADS the tires its trying to lift the front too much. The intersection points of the suspension delineates where the rearend is trying to "lift" the car, try to take too big a bite and the rear end lifts instead.
What most people miss is letting the suspension separate, like use index finger and second finger like scissors, then open them short finger is upper "link" longer is lower link. Rearend is attached to both. what you need is the lower or longer one being forced INTO the road more.
This plants the tire and allows it to give maximum traction, stiff rebound on shocks can als cause tires to break loose.
Good Luck
Lee

[SR71]

dropping your lower control arms to the bottom hole will put more antisquat into the car. if you have adjustable shocks, loosening up the extension on both ends will also help. however, with that kind of hp, non drag radial 335 bfg's are not going to work. they simply are not soft enough to let the car get up on the tire in the first two gears. you will need a softer compound tire to make use of that kind of power down low.

[GeoffP]

Yep definitely drop the control arms to the bottom hole. Third gen Camaros are plagued with the traction problem if they're lowered. After you lower the arms, check the angle of the arms. Make sure you have some incline in the arms - the front of the arm should be higher than the rear. Check out www.thirdgen.org in the suspension section for some good information on torque arm suspensions.

[exwestracer]

I'd be a little bit careful about putting TOO much pinion angle in it. I believe the Speedtech arm has the 2 tie rods from the top of the housing down to the arm itself? That's your pinion adjustment. You want the rear U-joint close to straight under full power. Unfortunately, unlike a drag 4 link, the torque arm doesn't allow the pinion to "climb" under hard acceleration, so what angle you dial in stays there. When it DOES hook, I'd hate to see your traction problem become a U-joint through the floor problem... Drop the lowers as suggested above.

How much air pressure are you running in those tires? That's a lot of square inches of tire supporting approx. 1700lbs... If my math is close, those 335s should hold the car up fine with about 20psi in them. Air down a little and see if it helps.

[joeelutz]

Thanks for the advice. That makes sense dropping the lower arms to the bottom hole for anti-squat. I'll do that. exwestrace, I'll also take your advice about airing down the tires. I'm at about 28psi right now with very little sidewall flex. Running the 1350 U-joints so they are pretty stout. The torque arm bolts to a bracket welded to the bottom of the 9" housing and there is a bracket that bolts to the pinion support that comes down to the arm. You shim at that point to adjust pinion angle. That rear U-joint is pretty straight and stays that way through the travel since the driveshaft stays parallel to the arm. I realize that there is no way to really hook a street tire, I'm just looking to improove it some.

SR71, I'm not sure I follow "loosening up the extension on both ends" They are adjustable QA1 coilovers.

[diesel25lrs]

Joe,
Keep us posted- i'm having the same issue with almost same exact setup... I did notice a bit traction gain when i dropped mine to bottom holes but still mega spinouts... I'm almost to the point of trying different shocks with better adjustability...not sure if that will help?

[SR71]

a traction inducing set-up is very different from a corner burning set-up.

loosening up the front extension will let the nose rise easier to transfer weight rearward. loosening up the rear extension will allow the rear suspension to seperate easier and apply the tire to the pavement harder.

the trick is to find the right balance. you want the nose to come up a tiny bit sooner than the rear. if the rear seperates too soon or too quickly, it will throw weight on the nose and cause even worse tire spin. once you get the car applying the tire properly, you can start dialing in the compression little by little to keep it applied.

[David Pozzi]

& soften shock settings front & rear.

[joeelutz]

I realize that most everything chassis related is a compromise and us in the PT crowd would like to have our our cake and eat it too as far as handling and straight line acceleration goes. I realize this may be a ridiculous question. That being said, I have to ask. How detrimental to handling is running a drag radial in the rear with a fairly short sidewall such as would be used on an 18" wheel? Has anyone tried autocrossing such a tire?

[SR71]

if you are going to use a soft compound competition tire, why not something like a toyo proxes r888? it comes in the 335/30/18 size and has the same treadwear rating as most drag radials...but it doesn't have the softer sidewall. the only downside is that, if used only on the rear, the car is going to plow like a john deere on the auto-x course. but then again, judicious use of the throttle and excessive power from an ls7 should help with that problem. :)

[David Pozzi]

What tire pressure are you running?

[Payton King]

Too lazy to look up the rear. Does it have a watts or panhard bar? Whichever one you have, if you will drop it down (watts or panhard) it will lower the roll center and give you a little more forward bite. What spring rate are you runnig in the back?

[diesel25lrs]

It's a panhard bar. So does it matter if its parallel to the ground or @ an angle?
I believe the rear springs are 350#?

[dontlifttoshift]

I know Payton and several others run big springs like that , but it seems like a lot of rate when you are trying to put power down.

[exwestracer]

It's a panhard bar. So does it matter if its parallel to the ground or @ an angle?
I believe the rear springs are 350#?

A quick note on the shocks... Long torque arm setups are not prone to wheel hop, but keep in mind that if the wheels are spinning, the suspension is not loaded as hard as if they are hooked up. It is possible to go TOO soft on the rebound (extension) as you start gaining forward traction. That is a LOT of spring rate for pure straight acceleration. The shocks have to keep up with the spring frequency.

The bar angle doesn't play as important a part in straight line traction as it does picking up the throttle coming off a corner.

Not that it's something you can change easily, but how far out (from rear axle centerline) and up (above ground) is the front mount on the torque arm? Also, how high above the ground is the centerline of the camshaft?

[Payton King]

Ray is going to know way more than me on this stuff. I would follow his reasoning and advice.

My 69 ran 550's front and 325's rear and my watts was a little above axle centerline when I autocrossed the car and I woulld drop it about 2.5 inches below axle centerline when I was at the strip and soften the compression on my shocks (like most are suggesting above). I could feel the difference in straight line hook on the street even before I changed the shock setting. Softer rear springs would have been better still...say 250 or 275 lbs. All the old drag tricks would apply when going to the strip or you could leave it the way that it is and pedal it mid way through 2nd gear and then let it eat.

[joeelutz]

A quick note on the shocks... Long torque arm setups are not prone to wheel hop, but keep in mind that if the wheels are spinning, the suspension is not loaded as hard as if they are hooked up. It is possible to go TOO soft on the rebound (extension) as you start gaining forward traction. That is a LOT of spring rate for pure straight acceleration. The shocks have to keep up with the spring frequency.

The bar angle doesn't play as important a part in straight line traction as it does picking up the throttle coming off a corner.

Not that it's something you can change easily, but how far out (from rear axle centerline) and up (above ground) is the front mount on the torque arm? Also, how high above the ground is the centerline of the camshaft?

It's been a little crazy at the shop this week, so I haven't had a chance to play with the Camaro. I'll try to get some measurements tomorrow. Cam centerline?? Are you trying to estimate CG height?
Thanks,
Joe

[exwestracer]

Yup.

[killer69]

sounds like your biggest issues are HP and Traction, the BFG's are so hard it will be almost impossible to get them to hook wit 650 hp. My Nova has 315 35 18 Falken 615 on it and 500 hp, and if i roll into it in first i can get the tires blazing. there is just no way to hook on the street, My camaro with a 750 hp bb and 325 50 15 nitto Nt555R on it didnt stand a chance and that is a full drag race 4 link with 130% anti squat and 8" of front travel. so the Bfg's just are not going to cut it.
but did you notice no wheel hop ??? kinda nice to be able to do 100 foot long straight burn outs don't you think lol

[joeelutz]

Absolutely no wheel hop.

[joeelutz]

Not that it's something you can change easily, but how far out (from rear axle centerline) and up (above ground) is the front mount on the torque arm? Also, how high above the ground is the centerline of the camshaft?

Front torque arm mount center of pivot is 57 3/4" from center of rear axle and 5" off the ground. Waterpump center is 19" from ground. Hope that's close to cam center.

[Crazy Carl]

Listen to Blake/Killer69. He's the one who manufactures the system in your car. If you have more detailed questions, call him. He's in the US now so your phone won't have to figure out an exchange rate.

[exwestracer]

Front torque arm mount center of pivot is 57 3/4" from center of rear axle and 5" off the ground. Waterpump center is 19" from ground. Hope that's close to cam center.

I'll admit I took a couple of shortcuts on this, just using the desktop calculator. At 57 3/4" out, you are approx. 53 1/2% of the 108 wheelbase (assuming it's stock). Using the classic calculation for neutral line, and your measurement of cam height for C/G, 100% A/S should be about 10 1/8" above the ground at that point. So you are looking at approx. 50% anti-squat with the TA mount at 5" above ground. As I said earlier, there isn't much to adjust on it, but it does kind of clarify why the car won't hit the rear tires very hard.

I'm a firm believer in the torque arm as an excellent all-around suspension design (my own build uses one), but it does have limitations, especially trying to fit the mount around an existing subframe and floorpan.

[killer69]

I'll admit I took a couple of shortcuts on this, just using the desktop calculator. At 57 3/4" out, you are approx. 53 1/2% of the 108 wheelbase (assuming it's stock). Using the classic calculation for neutral line, and your measurement of cam height for C/G, 100% A/S should be about 10 1/8" above the ground at that point. So you are looking at approx. 50% anti-squat with the TA mount at 5" above ground. As I said earlier, there isn't much to adjust on it, but it does kind of clarify why the car won't hit the rear tires very hard.

I'm a firm believer in the torque arm as an excellent all-around suspension design (my own build uses one), but it does have limitations, especially trying to fit the mount around an existing subframe and floorpan.


Spot on Ray.
The advantages for street and road race/ auto x are apparent, but like you say not the "BEST" for drag racing due to the limitations with AS

[joeelutz]

I dropped the lower links to the bottom holes on the axle and it helped a little. I think I need softer springs in the rear and an anti roll bar. Reason is my car is a little lighter than most and it feels a little stiff in the rear, but when I come out of a hard left hander it really sits down on the right rear to the point of lifting the left front tire a couple inches.

[exwestracer]

Does the car try to swap ends when coming off the corner like that? The fact that the suspension is rolling over is not necessarily costing you traction. A rear bar that will counteract that much roll will definitely unhook the inside tire more. Also, keep in mind that when you dropped the lower links; the extra link angle means more roll steer, which will keep the rear tires at a lower slip angle in a corner. You are likely seeing more body roll because the rears are staying hooked up and loading the suspension and chassis harder.

Do your coil overs have the rubber travel indicator o-rings on the shafts? Make sure they are set against the shock body at ride height, then try to duplicate that left turn acceleration situation once. Get under there and see how much the RR suspension moved when it hiked the left front.

Your initial question (and our answers) seemed to involve straight line acceleration. Now, you are delving into a whole new area of tuning...and we'll have to look at things a little differently.

[joeelutz]

Your initial question (and our answers) seemed to involve straight line acceleration. Now, you are delving into a whole new area of tuning...and we'll have to look at things a little differently.

I completely agree. I was just thinking that softer springs in the rear would help with straight line accel at the expense of even more rear body roll. I could possibly counteract that with a antiroll bar.

Where I experienced this was a tight Autocross track at Goodguys (1st gear). This was my very first autocross experience so I learned a lot. I was only about 2/3 throttle when picking up the front tire, so with enough throttle, I could kick the back end out as desired, but it didn't really feel at all loose. I mostly had problems with a bad push entering through mid turn, but I mainly attribute that to having an old, hard set of front tires that I generally just use for mockup. I didn't have time to swap them before the event.

I don't think they have the O-rings, but I will check to see.

Just to clarify for those reading this, I really do like the Torque arm suspension. I'm just not experienced enough with chassis setups to know how to really tune it in.