CoreyZ06

lowered my car, i need to measure the rake. when i bought the car it was maxed out tall on the stock bolts and it was obvious it had been tampered with, uneven tire wear, wrench marks etc. so i didnt have a reference point to get it right.

so. where do i measure to get the prescribed 1/4" rake front to rear? (i deduced 1/4" thru a search, if that is wrong please correct it)

my fenders do reflect what im measuring under the car, but im tired of guessing. i need to get this right so i can get the car aligned before i start ruining my tires from more extreme negative camber. i want each side to measure the same, and have proper rake front to rear.

in doing a search i found this statement from aungel: Measuring from the ground to the lower control a-arm mounting to the frame is the correct place.

that just doesnt have enough information for me to be able to stop guessing. from the ground to the lower A arm bolt? to the frame? to where the cradle bolts to the frame? see my point..?

i dont know squat about aerodynamic stability, and would rather leave that in the hands of GM engineers. as a rare case lol.

bumble-z

Measure @ the puck slot locations

CoreyZ06

okie dokie, pretty sure i know where those are after doing my frame slider research.

leadfoot4

According to the factory shop manual, the "ride height" is measured from the control arm bolts to the ground.

Gideon's_Test

Procedure

Trim Height Adjustment
Tools Required
• J 42743 Trim Height Adjustment Tool
• J 42854 Trim Height Measurement Gauge
Important
When adjusting either the right or left front trim height the opposite side trim height will be affected.
Trim height should be measured with a full tank of gas and no passengers or cargo.
An alignment hoist should be checked periodically to assure that both runners are the same height off the ground, side-to-side and front-to-rear.


1. Place vehicle on an alignment rack.
2. Set the tire air pressure to the proper pressure.
3. Manually lift the front of the vehicle up approximately 38 mm (1½ in) then, gently remove hands and let the vehicle settle.
4. Repeat the above step two more times for a total of three times.


5. Use J 42854 to measure the distance between the lowest point of the ball joint and the center of the front side of the lower control arm mounting bolt .
6. Manually push the rear of the vehicle down approximately 38 mm (1½ in) then, gently remove hands and let the vehicle settle.
7. Repeat the above step two more times for a total of three times.
-Measure both the right and left sides of the vehicle.
-The true Z trim height on each side is the average of the high and low measurements. Refer to Trim Height Specifications in Suspension General Diagnosis.

Important
When adjusting the spring adjuster bolt, J 42854 must be used in order to prevent damage to the rubber shear pad on the end of the bolt.
One complete turn of the spring adjuster bolt is equal to 2 mm (5/64 in).
8. Using J 42854 , adjust the Z trim height by turning the spring adjuster bolt.
9. Lower the transverse spring back onto the lower control arm and remove J 42854 .
10. Perform the jounce procedure again and remeasure the Z trim height.

Important
Do not exceed the maximum difference between the right and left spring adjuster bolt gaps.
11. Measure and adjust the front spring adjuster bolt gaps (1) to 2 to 24 mm (0.078 to 0.944 in). Refer to General Specifications .

CoreyZ06

thanks for the replies.

thank you gideon for the extensive info on how to do it correctly. i dont have access to all that, but ill try and adapt as much of it as possible to get it as close as i can. thank you.

CoreyZ06

if i measure at the puck locations, im dead even. 4.5" at all 4

if i measure at the control arm bolts, after the last adjustment my fronts are within 1/8th side to side

the rears are off side to side a good 1/4", even though i have 1/4" more bolt showing on the passenger side rear, and no bolt(no threads at least) showing on the drivers side. at the current adjustment, its still off.

as it sits, the front is almost a full inch lower than the rears, but my car doesnt look like it has any rake, it looks level. the tire gaps are about the same, with a slightly larger in rear. very slight. i dont want to lower the rear to the point of only 1/4" disparity between front and rear measurements.. my car would be stink bugging like crazy. i'd look like one of those douchebags with the lowered trucks that drives around with the front end 2 foot off the ground and the rear throwing sparks.

i still feel like i am missing something, in what seems like it should be very simple in straightforward.

voda1

Not quite - it's the 'difference measurement' between the grd to ctrl arm bolt(ctr) and grd to btm of ball joint. Special tool needed because the ball joint is tucked up inside the wheel and can't measure directly.

The 1/4 is not spelled out in service manual. Someone probably measured a stock vehicle at the puck slot locations.

CoreyZ06

made some more adjustments. i am now satisfied. the guy thats gonna do the car said he'd tweak it more if needed once he gets it on the rack.

as far s the control arm bolts, i am within 1/16" side to side, and have the 1/4 rake front to rear. this is in my driveway which is very unlikely to be perfectly level. but i have checked it on 3 different stretches of concrete same results.

if anyone else is measuring at the fenders (on my car they happen to translate perfectly from under car) i am getting 1" higher in rear than front BY THE FENDERS. at the control arm bolts i am getting the 1/4 inch.

my puck locations are dead level to the ground, maybe ill crank the rear bolts one full turn up.

thank you all for your input/advice/help

Bill Dearborn

Here are the measurement points from the frame and what the measurements should be. Some of the early Service Manuals had this info. It was incomplete in the 97 manual (didn't have diagram) and dropped altogether toward the end of C5 production.




The Z and D heights are the measurements taken at the control arm.

Bill

CoreyZ06

awesome info. thank you