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Author Topic:   Stock rear geometry question
Dirt Maniac

Total posts: 111
posted July 25, 2004 01:25 PM  
I bought the basic Steve Smith book 9 years ago. Just today graphed my rear end mounting points and need some input from those of you that have done this before. Stock full size GM. Stock mounting positions on rear end and frame. Lower arms tilt about 1 degree down in front. Upper arms tilt about 15 degrees down in front. When graphing this out according to the the Smith book, the roll center for this beast is about 25" above ground. The centerline of the axle is about 15" above ground.
I am adding a panhard bar to the rear end and removing the upper left arm. I graphed this to know how the panhard bar mounting would change the roll center.
Q1: Is a 25" high roll center one of the reasons I cannot get side bite. Is 25" abnormal for stock suspensions?
Q2: Where should I place the new roll center. I'm assuming I'll start with the centerline of the axle and adjust from there.
Q3: What should I expect out of the car after I add the panhard and lower the rear roll center?
Q4: Are there any concerns I should have with the extreme angle of the remaining upper arm? It would be a real stretch of my rules to move the mount, not to mention a pain in the *** .
Q5: Would it be worthwhile to lower the mount on the rear end lower control arm to get it level, or even up one degree?
Sorry for the long winded post, but I'm on my own here. You guys are my crew and we're running out of time to get that first win this year.

Dirt Freak

Total posts: 446
posted July 26, 2004 06:34 PM  
On Dirt.

Mount the panhard bar below the axle on the right side and have a 10 to 12 degree up angle to the frame mount on the left side...This is for starters.

Dirt Maniac

Total posts: 111
posted July 27, 2004 05:52 AM  

Dirt Maniac

Total posts: 179
posted July 27, 2004 11:25 AM  
I second PEDDLER's advice!



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