Rear suspension setup, hooking on drag radials

[White90GT]

OK, got the new coupe on the track last night for the first time and had a couple things working against me.
New drag radials 325/50/15 (I did heat cycle them at home several hours before I took it to the track)
Crappy track conditions (Friday nights always suck because of the street car and radials).

Now, either the rear suspension isn't working well, or something just isn't right.

I picked up this coupe with all the current rear suspension on it. I put my strange 10 ways and 130 lbs springs up front, so I know I'm good up there.

The rear has solid bushing all around, double adjustable everything, and coil-overs with a 9" and 4.10 gears.

Problem is I don't know what spring rate the rear coil springs are and I'm pretty sure the rear shocks are not adjustable. The rear of the car is stiff as hell. The shocks I believe are something called Carrere or Carrera, something like that. They have a knob on the bottom, but I backed the knob out thinking it might be an adjustment screw and it just drained some fluid out, so I tightened it back up.

I have the pinion angle at -1 considering the solid bushings.

I had the drag radials at 15 psi to start. First pass on the footbrake was something like a 1.68 sixty foot spinning and getting out, getting in and spinning again. Basically all night was like that. First gear was about useless. I think that 1.68 was the best sixty foot all night. I tried pressures all the way down to 10.5 psi, but never more than the initial 15 psi. At 10.5 psi, they spun, but shook really bad. I'm betting they were spinning loose on the rim.

I was told drag radials like more tire pressure if you're not hooking. I've never run a drag radial with this much power, much less a drag radial this big.

Any advice is appreciated.

This motor/tranny combo in my white car went a 1.43 sixty foot on the t-brake on a 28x10.5 ET drag on a 15x8 wheel with 3.73 gears and about 200 lbs heavier then this coupe. If it hooked last night, I was expecting high 1.3x sixty foots and a decent wheel stand.

As it was, the car never went faster than a 7.17 last night, but did pull 103.8 mph on two passes basically spinning most of 1st gear. The white car went 1.43, 6.49@105.8 in the same weather and again, 200 lbs heaver with less gear.

[gray86hatch]

Unless the housing is a team z the ears on it are most likley way to high and the rear suspension is way off.

Rear shocks and springs are a place to look but you really need to plot the rear suspension.

once the rear suspension is close the other 60% is in the front of the car.

Tim

[88gtguy]

Originally Posted by gray86hatch

Unless the housing is a team z the ears on it are most likley way to high and the rear suspension is way off.

Rear shocks and springs are a place to look but you really need to plot the rear suspension.

once the rear suspension is close the other 60% is in the front of the car.

Tim

X2

A standard bolt in 9in housings put WAY too much bite in a car with the upper bar angles. Also look at what your lower bar angle is, you don't want the front end of that bar pointing down.

[TC86GT]

More pressure as well. Mine like 16-18psi and held a transbrake launch spraying 200hp out of the hole on my old 408W going 9.40's with a 1.34 best 60'. I've had passes when it came up and shook violently, bumped the pressure up a single pound and dead hooked next pass. I never had to run them much lower than 16psi on a 10" rims to hook. I found the track has to have some decent level of prep as well, no prep was almost a waste of time.

[NUTTSGT]

I'd start at 16 as well.

[White90GT]

Originally Posted by 88gtguy

X2

A standard bolt in 9in housings put WAY too much bite in a car with the upper bar angles. Also look at what your lower bar angle is, you don't want the front end of that bar pointing down.

Someone had mentioned the lower ctrl arm angle to me yesterday, so I climbed under there and looked. The lower ctrl arms are angled upwards, not a lot, but today I'll go out there and see if I can get some kind of measurements of the angles of the bars.

One other thing I noticed. The rear coil-over shocks and probably springs are off a damn circle track car. They are Carrera shocks.

I know my white car liked the rear stiff on an ET drag when the track was good. If the track was bad, I would loosen up the rear shocks to allow more/easier squat in the rear to absorb some hit.

[88OrangeLX]

The lowers need to be level with the ground. Try adding a little weight in the rear bumper say 80 pounds to start with.

[White90GT]

OK, I went out and took some measurements, hopefully these will be enough for you guys to plot it out or Kevin.

These measurements are taken center of bolt to center of bolt at each mounting point:

Passenger lower: Rear to ground 9 1/4", front to ground 9 3/8"
Driver Lower: Rear to ground 9 1/4, front to ground 9 3/8"
Passenger upper: Rear to ground 18 1/2", front to ground 16 1/4"
Driver Upper: Rear to ground 18 1/2", front to ground 16 1/4"

Driveshaft measurements:
Rear end U-joint center to ground 11 1/2"
Front trans yoke center to ground 11"

Crankshaft front measurement center of balancer to ground 17"

Coil-over shock measurement, rear coil-over bolt to bolt is 11 5/8" long
Coil-over spring is 7" front cap to cap

So the motor drops at a downward angle, 6" from front crank center to transmission output shaft center. I guess thats normal

I have about 2" of thread to drop the rear coil-over shocks, however, if I go more than 1", the tire will rub the outer fender.

Something to note, the upper ctrl arms look home made, they look like a box that is cut open on the bottom to mount up to the mount on the rear end. The bottom of the box appears to be hitting the rear end mount ever so slightly (barely touching). That said, I may not be able to raise the rear of the car at all due to it hitting and the stress it may put on the bolt.

Let me know if any other measurements are needed such as k-member to ground or a-arms to ground or both.

[White90GT]

I also just noticed, the bushings for the upper ctrl arms to rear end housing are rubber. At first I thought they were solid because I couldn't see the rubber.

That said, I need to bring pinion angle down at least another 2 degrees to -3.

With the lowers being double adjustable, I can just extend them a little to bring the rear back a little closer to the rear of the wheel well. It looks like its just a little closer to the front than rear right now. Its not a problem with tire clearance since the car is mini tubbed, just a matter or being more centered front/rear.

[feetfirst]

Originally Posted by 88gtguy

X2

A standard bolt in 9in housings put WAY too much bite in a car with the upper bar angles. Also look at what your lower bar angle is, you don't want the front end of that bar pointing down.

X3...........those ears are way to high. Did a quick plot, and ballpark without knowing arm lengths, your IC is around 30", with a 155%+ AS.
This is way to violent.
There is no fix other than moving the upper body hole up, or see if Baseline/TeamZ make an upper control arm setup for a 9".......Im assuming they do???

[gray86hatch]

$600 team z has a housing that will fix the issues. just reg control arms.

Tim

[White90GT]

Originally Posted by gray86hatch

$600 team z has a housing that will fix the issues. just reg control arms.

Tim

This isn't a home made housing, it was professionally built. There is remnants of a rear end order form wrapped around the passenger side axle tube.

oh, the car should be somewhere around 2600-2700 lbs with driver.

[gray86hatch]

Originally Posted by White90GT

This isn't a home made housing, it was professionally built. There is remnants of a rear end order form wrapped around the passenger side axle tube.

oh, the car should be somewhere around 2600-2700 lbs with driver.

It dosn't matter who built it. the upper mounts are too high. The Strange/Team Z housing is the only one that has the correct mounts. They are sunk into the housing to be correct.
I know that mosers is wrong, curries, strange was wrong untill Dave fixed it.

good luck

Tim

[White90GT]

Originally Posted by gray86hatch

It dosn't matter who built it. the upper mounts are too high. The Strange/Team Z housing is the only one that has the correct mounts. They are sunk into the housing to be correct.
I know that mosers is wrong, curries, strange was wrong untill Dave fixed it.

good luck

Tim

Well, I can't afford to drop cash on another housing right now, so lets figure out how to crutch it and get the car to hook for now.

[88gtguy]

Originally Posted by 88OrangeLX

The lowers need to be level with the ground. Try adding a little weight in the rear bumper say 80 pounds to start with.

"Need" is a strong word, every car will be different. But parallel to the ground is a good way to start.

90GT- Try not to use the coil spring threads to raise the car, if you can go up a bolt hole. When using the threads you are taking away for the shocks travel by extending it. Also, you might want to just re-drill the hole for the upper arm mounts. There's enough room, and will correct the problem. I know people who've done it and it works just fine.

[DeuceCoupe]

A few pictures might help.

[White90GT]

OK, I raised the rear of the car about 1" and have taken some new measurements. I did not touch the length of the arms.

Upper arm front 17.25 rear 18.5
Lower arm front 10.25 rear 9.5

This looks much better and I think brings the AS down to around 116%