Sportmod trailing arm questions

[Sportmod Rookie]

Im new to sportmods. I have some questions on the effects of moving the trailing arm. If I move the trailing arm up or down on the frame how does it effect the car? Will the change only help under acceleration? Any info will help. Right now my car pushes on corner entry. Which bar should I move?

[dirttrackrocker]

Up at the chassis puts more roll steer in the car

[burnerdaddy]

Need to kno more whats your scale numbers and bar location now

[Sportmod Rookie]

Even on the right side it puts more roll steer? I was looking at a post on a different forum but he had the same problem. Push on entry. He had his right side bar to the top hole. Someone told him to lower the right side. Is that bad info? I will post my scale weights when I get home. I run IMCA northern sportmod.

[racinjj]

Assuming you have an IMCA type 3 link:
With the lack of horsepower and rear suspension adjustment sportmods tend to be very tight if not setup correctly. The biggest thing I can tell you is take rear weight out of your car get down to at most 54% full of fuel. In general adding trailing arm angle to either side will increase roll steer. However either side effects things differently beyond the roll steer effect.

Lowering the right side bar will make your problems worse.

[Sportmod Rookie]

Right now I have a 650 LF 650 RF 200 LR 175 RR. I have seen on setup sheets online that a stiffer RF spring will help loosen the car on entry but I have also seen setup sheets say go softer on front springs. Thoughts?

[dirttrackrocker]

Lots of things you can do. More stagger, trail RR, More rear brake, stiffen LF

[washeduptoo]

Are you on the throttle when it pushes? Springs on top of rear end and solid pull bar? Is pull bar centered on rear end bracket? Just some questions to help with your problem. Good luck.

[Sportmod Rookie]

Off throttle. Centered Solid pull bar. Springs above and centered on the axle. Thanks for all the help everyone. This is my first post and this forum is great.

[Sportmod Rookie]

Weights.
LF 492 RF 519
LR 695 RR 595

Rear % 56.1
Left % 57.5
Cross % 52.6

Left side trailing arm. 20 degree
Right side trailing arm. 10 degree

Panhard bar 14 degree mounted about 2" below centerline of axle

1/4" toe
-2 caster +3 camer LF
+5 caster -3.5 camber rf

About 1/2" stagger front and 1 1/4" rear

2" lead

[Sportmod Rookie]

The chassis is a DW8. Was thinking maybe of taking some angle out of the panhard bar and raising it an inch. Open for suggestions.....

[Hagen14t]

-200 pounds of bite? Sounds like a problem to me.

[Sportmod Rookie]

I must have wrote down the wrong weight for RR. Cuz car doesnt weight that much. Had to be about 595. Figuring that by total weight and what I had for rear %

[GUARDRAIL]

I don't think that LS% is right. Looks more like 51.5% or so. Get about 30-90 lbs on the LF. That will help hold the car down.

[Sportmod Rookie]

I was going to put a stiffer front right spring in. Would that actually make it worse then? If I want more weight to the front left where should I take/put turns in? Is 14 degree on the panhard bar way to much?

[dirttrackrocker]

I'm not up on 3 link, but, 2" of lead/trail??? Which side are you leading?

[TS3g]

I agree with Guardrail, you're LS% has to be wrong, and is likely low based on your numbers (I'm too lazy to do the actual math). Get it around 52.0-52.5%, and the only way to do this is to physically mount weight on the car.

And also the 2" of lead is not good. I'm assuming you are calling lead 2" back on the LR compared to the RR? If so, you need to flop that and trail the RR some, 1/2" is a good starting place.

[Sportmod Rookie]

No, I'm trailing the RR 2" measuring from the motor plate.

[dirttrackrocker]

No, I'm trailing the RR 2" measuring from the motor plate.


Then something is TOTALLY effed up!!!!! It should spin out on the straight away with that much RR trail.

[Sportmod Rookie]

haha....well i know that. Anyone have an idea what? or have a good setup sheet for a DW8 to start from? I have called Dirt Works. They dont seem to care.

[CHRISTINE]

On the dirt works i have worked on, the 2x3 tubing in front of the trailing arm mounts is what we used to sqaure the rear end with.

[burnerdaddy]

Put a lighter rf spring in and run lf heavy will help on entry. 3/4 of inch of trail 60lbs of bite 50% cross leave the rear.

[RadRacer211]

2 questions:

Does it matter where the springs are mounted on the rear end, as far as closest to the tire, or closest to the pinion. They are on top though and centered.

Does it matter if the shock is in front of the axle on drivers side and behind on passenger, or vice versa?

Thanks.

[rrcmotorsports]

Spring- If the springs are closer to pinion you'd have to increase spring rates because less spring force is put on that tire do to leverage and vice versa if you put spring closer to tire. And with massive rearend movement we're doing in todays racing i'd have to say putting the springs closer to pinion would be more beneficial do to the less travel in that spring and which that spring would store more energy.

Shocks- I've heard both ways to mount rear shocks. I mount LR behind housing and RR in front of housing. My theory is that when you get off throttle to enter the turn, that LR shock is helping push the housing into an opposite rotation then what the pinion is doing thus damping the shock to the chassis if using a solid pull bar. This tends to help if you use an aggressive compression shock.