LCA Relocation Brackets
 

Has anyone used these, and if so did they improve traction?

I tried a set on my street car. On a couple of marginal tracks, it hit hard than caused the tires to unload. Didn't improve times due to this. On a better track, may have helped. Have since went with a 9", so they're off now.

Which ones specifically,have seen several different ones?

Bret P.

These are the ones from Quick Performance for the 9". They have several adjustment holes. I have not installed them yet. I have been having tration problems with the 4.56 gear. I have installed adjustable uppers, I have boxed lowers, Moroso springs, Summit adjustable shocks, and control arm braces. I changed tires from a 26x11.50x15 to 27x10.50x15. Brand new tires. I took the car out this weekend for the first time since the changes were made and had horrible 60' times. Spinning all the way through first gear, had to peddle a couple of times. I was hoping the taller tire would help some. Only made 4 passes though. Would the pinion angle help with traction. What is the best way to set it? I have heard several different suggestions. At 97 MPH I should be 7.0's. Thanks.

Sounds like you are shooting in the dark.

You need to understand where your rear suspension Instant Center is with respect to the center of gravity of the car. I recommend finding an Alston Chassis manual or Dave Morgan's doorslammer book and doing some more reading.

This may bring some naysayers out of the wood work but pinion angle has nothing to do with 60' times. It can't - based on the physics of the rear suspension. It can only pass or hinder the transmission of torque through the driveline.

My $0.03.

K

Thanks. Can you describe how to find the ideal IC? I am sure it changed when I went from the 10 bolt to the 9" rear.

A little but the above references are your best bet. The answer will be a target range and then you will home in to your optimal setting by experimentation.

It varies based on vehicle platform, rear suspension type and transmission (manual vs automatic) so we need to know this detail before continuing.

K

The car is a 1980 Grand Am (G Body) Ford 9" with stock suspension bolt ons. Trans is TH350. Thanks for your help. I am really trying to learn all I can on tuning my suspension.

TH350 (2.52 gear) x 4.56 rear axle ratio sounds like a lot of first gear. That might be part of the problem.

Nonetheless, here's the deal on suspension:

Alston refers to the relationship between the Instant Center of the rear suspension and the center of gravity as "Percentage of Rise". Some people also describe only the instant center point, in terms of how far forward and up (off the ground) of the rear axle.

You will need to scale the car to determine front end weight and rear end weight. From this you can determine the CG location fore/aft; you can assume the CG height to be the distance of the centerline of your engine camshaft above the ground (it's a good approximation).

You will now also need to measure the suspension attaching points at the front and rear of the rear axle control arms. What you are going to do is "imagine" the control arms extending foward to an intersection point; this is the imaginary point around which the rear suspension rotates as it moves up and down in it's travel.

You can do this by measuring the location of the upper control arm rear attachment and front attachment; plot those as a line (either on a piece of paper, or by duplicating the measurment with string/masking tape on the garage floor). Do this again for the lower control arm (measure the forward attaching point and the rear attaching point, and plot that).

Report back with your findings.

To summarize, what you are going to try to do is move that IC point rearward from it's production location, either by raising the rear of the upper control arm or by dropping the rear of the lower.

K

Thanks. I think I get the general idea. If I can move the instant center closer to the rearend, the tires should plant harder with more rear end seperation from the body. Am I correct? Again thanks.

Correct.

K