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The ride height as measured from the fenders may vary. GM measures ride height from the rocker panel. In the manuals it it is referenced as the Trim Height measurement. The so called J and K measurements are taken at approximately the location of the shipping slots in the frame.
From the manual:
Incorrect trim heights can cause bottoming out over bumps. Incorrect trim heights can cause possible damage to the suspension components and symptoms similar to those produced when there is a problem with the wheel alignment. Check the trim heights when diagnosing suspension complaints and before checking the wheel alignment.
Perform the following before measuring the trim heights:
Set the tire pressures to the pressure shown on the tire placard. The tire placard is located on the driver's door.
Fill the fuel tank.
Place the front seats in the full back position.
Make sure the rear compartment is empty.
Make sure the vehicle is on a level surface, such as an alignment rack.
Close the doors.
Close the hood.
Close the rear compartment lid.
J and K dimensions are measured vertical to the ground. These trim heights should be within 6.4 mm (0.25 in) to be considered correct.
Measuring J Height
Important
The Real Time Damping system must be operative while taking measurements.
Lift the front bumper of the vehicle up approximately 38 mm (1.5 in). Gently remove hands. Let the vehicle settle.
Repeat this step two more times.
Push the front bumper down approximately 38 mm (1.5 in). Gently remove hands. Let the vehicle settle.
Repeat this step two more times.
Measure 88.9 cm (35 in.) from the center of the front wheel to the lower edge of the rocker panel.
Mark the spot.
Measure the J dimension (from the lower edge of the rocker panel to the ground). Refer to Trim Height Specifications in Wheel Alignment.
If the J dimension is not within specification adjust the Z height.
To adjust the front spring to correct the Z height. Refer to Trim Height Adjustment in Front Suspension.
Measuring K Height
Important
The Real Time Damping system must be operative while taking measurements.
Lift the rear bumper of the vehicle up approximately 38 mm (1.5 in). Gently remove hands. Let the vehicle settle.
Repeat this step two more times.
Push the rear bumper down approximately 38 mm (1.5 in). Gently remove hands. Let the vehicle settle.
Repeat this step two more times.
Measure 78.7 cm (31 in.) from the center of the rear wheel to the lower edge of the rocker panel.
Mark the spot.
Measure the K dimension (from the lower edge of the rocker panel to the ground). Refer to Trim Height Specifications in Wheel Alignment.
If the K dimension is not within specification adjust the D height.
To adjust the rear spring to correct the D height. Refer to Trim Height Adjustment in Rear Suspension.
Here the spec's referenced above.
Front Rear
Base, F45, Z51, Z06 J Height (Curb) K Height (Curb)
Service Preferred 152 mm (5.98 in) 157 mm (6.18 in)
And the drawing below was from lucky131969 from 2010. If there are others who published this information earlier, my apologies for not locating their information so they could be credited. Not specifically the measurement you are looking for but my understanding is this is how GM measures ride height so hopefully it will still help you.
See, here is where you're wrong. If you're running aftermarket wheels/tires with a different overall diameter than the stock wheels/tires then measuring using the method that route99 posted, which i understand is directly from GM, will do you no good. The ONLY way to get a consistent measurement for setting suspension height is measuring from the center of the hub to the fender.
See, here is where you're wrong. If you're running aftermarket wheels/tires with a different overall diameter than the stock wheels/tires then measuring using the method that route99 posted, which i understand is directly from GM, will do you no good. The ONLY way to get a consistent measurement for setting suspension height is measuring from the center of the hub to the fender.
Wrong, but you have it figured out.
Just one question, you think all the fender lips are square all the way around the car??
There is a reason GM measures from the frame. There is a simple way to figure it with different diameter tires.
Just one question, you think all the fender lips are square all the way around the car??
There is a reason GM measures from the frame. There is a simple way to figure it with different diameter tires.
Merry Christmas
Just one question, do you think every brand/model tire in the same labeled size actually measures out to be exactly the same size? This would make it hard to get a good number just by adjusting for different tire size, although I’m more than capable of doing the theoretical math. The fenders should be REALLY close to the same size from side to side. I find it hard to believe there is much variance there.
Just one question, do you think every brand/model tire in the same labeled size actually measures out to be exactly the same size? This would make it hard to get a good number just by adjusting for different tire size, although I’m more than capable of doing the theoretical math. The fenders should be REALLY close to the same size from side to side. I find it hard to believe there is much variance there.
I would say that wheel and tire sizing would be very consistent, much more so than bolted on fenders.
And holding a frame to ground dimension would be much more critical as far as handling is concerned. Fender to wheel center more for aesthetic purposes.
One of the reasons the fender height method is not used as trim height is the inconsistent dimensions of fender location from side to side. When the C5 first came out our club had stock ride height as one of the pure stock requirements for our club autocross points. Having numerous GM tech engineers in our club we used ride height checking at the rear of the jacking points as the criteria. The front measurement was 6" and the rear was 6.25. After we allowed lowering on stock bolts for that class we only checked for the 1/4" of rake front to back. Everyone who lowered there car to balance the fender heights almost always was off by 1/8" or more side to side.
01-01-2018, 02:02 PM
Stock ride height measurement
