ed devinney

I installed the time-honored RoW M030 + Bilstein HDs this weekend and have a q that I can't find an answer to, hopefully the massed minds here will know.

I will measure precisely tonight but my ride height in the rear appears about 122mm L and 120mm R. Do I need to pull apart the rear suspension again and even this out for a street car? Fronts are not identical, either but they're easy to adjust.

If I do need to reset the height, does anyone know how far the perch moves for each turn? I figure I can leave the top of the shock attached, loosen the droplink mount and rotate the shock body 1/2 or a full turn, depending on how far I need to go.

Thanks in advance!

MadMarkie

Hi Ed,

Since the ride height tolerances are +/-10mm, you probably don't need to worry about 2mm. If you are having the car corner balanced with the alignment, the front spring perches will be adjusted to balance the weights... which will probably change the ride heights in the rear a little as well.

I just replaced my PSS9s with Cross Comp coil-overs, and happened to measure the thread pitch on the Bilsteins at 1.5mm. In Jeff's DIY, he mentions a roughly 2:1 ratio between ride height and perch adjustment, which was verified as I dialed in my new stuff. So assuming the HDs and PSS9s have the same threads, to move your ride height 2mm you would turn the perch about 2/3 of a turn. Doesn't seem worth it to me...

Good job on the install, and post "lift kit delete" pics when finished!

Cheers, Mark.

Land Jet

I believe I read on the PCA forum that, after a couple of days and drives, some of this settles out. You may want to wait on this before trying to get it perfect.

ed devinney

Mark - thanks for the data. Someone else pointed out that corner balancing usually throws it off more than this, so I'm going to call it good and have the car aligned.

LJ - I did lose a couple mm after the 10 mile test loop, but for better or worse it was consistent all around :-)

InTheAir

Ed -

Did you get the car aligned yet? Do you plan on getting it corner balanced?

Nonetheless, don't worry about it too much. Heck, if anything, by adding your weight, the car will level out pretty well.

ed devinney

Yeah, I didn't phrase that very well. Alignment scheduled for Friday am, but no corner balancing for this street car. I figured being a little high on the driver's side is OK, too.

jimbo3

A few notes for clarification-
-The rear perches have to be turned in full turn increments when raising or lowering as it has to line up with the drop link and sway bar. Each turn on the rear is worth ~3mm in height.
-Corner balancing involves adjusting all four corners, not just the fronts. It is spec'ed in the service manual and needs to be done. Variance is <40 pounds between the left and right side on front and on back, IIRC. Now isn't the time to try to save a hundred bucks.
-The "+/- 10mm" spec isn't intended for side-to-side differences, but for a roughly equal overall height difference. i.e., if the height you are shooting for is -5mm, all four corners should be as close as reasonably possible to that spec. At that point, the corner balance can begin. (If you could imagine that spec being a side-to-side variance, the extreme would be a total difference of 20mm, would would be very bad, indeed!)

With the 2mm difference in the rear, I'd send it to the shop as-is for the corner balance and alignment. Your front chassis height should be ~140, BTW.

Good Luck.

-Jim

ZombiePorsche44

Ed,
My car sits slightly higher on the left until I mount up due to a correct corner balance and no matter what anyone says, all cars benefit from a corner balance and I wouldn't drive mine without, just remember to have them ballast the drivers side with your weight in the seat if you have it done.

ZP44

mkc4s

I once measured carefully my garage floor. It looks smooth and perfect flat, by in fact has ups and downs by 4-8 mm. So if you want to measure your suspension height with few millimeters accuracy, first you need to measure your garage floor. Also, the garage floor settles in new houses and my floor measurement with about 2 mm accuracy done some years ago may not be accurate now. It is somewhat tedious work.

jimbo3

The corner balance determines the final height on each corner, irrespective of minor garage floor inconsistancies. Get the car as close as possible to the ride height you've chosen and let the corner balance procedure take car of the rest.

Land Jet

Dumb question time: Once a car is corner balanced, how often does it have to be redone?

InTheAir

~Generally speaking~, it only needs to be redone when the suspension is altered, which includes ride height adjustments.

ed devinney

I should learn to read better, the answer is in the full table in section 44 of the shop manual: 5mm :-)