after i ran the calcs, it turns out the harmonic issues were legitimate. the front ride frequency and rear ride frequency were only 3% apart. this is horrible for low speed ride quality.

as for the zip tie trick, haven't tried it yet. good idea! what do i do, just tighten a zip tie around the shafts, trim the excess, and go for a ride?

Correct! With the suspension in full droop, place a zip tie on all 4 corners. It is the *cheapest* form of data acq I can give you.. :) put it through some twisties!

I'm now wondering if having the rear mounts that protrude UP into the tub, would have also cured your issue with harmonics (by lengthening the shaft travel) and not changing the ride height.



B

shaft travel wasn't the problem; the issue was a genuine harmonic frequency issue. i calculated the natural frequencies of the front & rear suspensions based on spring rate, motion ratio, etc. They are only 3% different front to rear. what this means is that at lower speeds when a bump is encountered, the front is compressed while the rear is extended. this causes excess pitch / dive motion. this is cured in road car suspension design by running a rear ride frequency that is between 10% and 20% higher than the front. this allows the rear of the car to 'catch' the front over bumps so the car stays flat.

This has been a great thread.

Insite, are you of the opinion that if I raise the rear of my car a half inch my ride quality will be better?


Thanks
Gary

that really depends on some things. if you tell me the height of the front of your car to the fender, the height of the rear of your car to the fender, and your spring rates, i'll calculate a good setup for you.

I will get the fender heights tonight and the springs are the springs that came with the Ksports.

Thanks for the help.

Gary

Insite (or anyone else with the knowledge to help me here):

I was going to bring all my suspension parts to my mechanic this morning after I swapped the springs out on the rear Ksport coilovers.

However, the top nut (19mm) is on very tight and the shock spins with it.

I attempted to tighten down the spring to put pressure on the pillow top thing and remove it, but it didn't work.

Another thought I have is to lower the adjustment rings to the bottom, slide the spring down, and grasp the shaft of the shock with a vice grip at the very top where it would not travel (probably).

However, I thought I'd just post this here and ask anyone to give me some quick advice on what to do. My mechanic has time to get this done and I don't want to miss my window of opportunity!

NOOOOO! Don't do that! it might be a good idea to let the mechanic do this since he'd be on the hook if he screwed up. here's the PROPER way to do this: look inside the shaft (in the center of the nut where the adjustment knob goes); you will notice that you can fit an allen key into the shaft. use a 19mm box wrench on the nut and an allen socket to hold the shaft. this will do the trick.

so it loosens from the inside?

disregard the PM I just sent you...

Randall:

You can also use an air wrench on it. It pops right off. K-sport had told me this was the preferred method of removing the nuts.

Randall, it sounds to me like you're trying to get the nut off the shaft of your KSports, right? I just had a similar problem with my JRZ adjustables - how to hold the shaft from spinning to tighten the top nut down. What I did (since I had enough exposed thread to do this) was put two more nuts on the shaft above the nut to be loosened or tightened. I then snugged those two nuts up real tight to each other. This kind of locks them onto the shaft. Then you can hold these locked nuts with a wrench (which then holds the shaft steady from spinning) and loosen or tighten the main nut you're trying to get to. Worked for me and no need to bung up your shock shaft with vice grips.

Kirk

Der Geist wins the prize. My mechanic took his impact wrench out and three seconds later, they popped right off. I swapped the springs, added the skinny ones below on the rear, and put them back together.

He's planning to work late tonight and have the job done by tomorrow. 19 hours is what he quoted me to do all four bearings, the trailing arms in the rear, three lower control arms, install the Ksports, and the track arms (toe links)... $1500.

He's also thrown in a four wheel laser alignment he's doing at the dealership on his own time and nickel. Not bad considering the hours required to do all this work.

I am expecting a totally different car when I pick it up.

Insite, your instructions did not have a measurement on the rears from the ground to the top of the wheel well. Is there a recommended height?

BTW, I noticed something very interesting on the freeway out to his place today. I had the ksports in the rear trunk, adding about 45 lbs to the rear of the car. The front was really squirrelly at 75 mph and unstable. Almost like I had a flat tire. I do hope that was just the extra weight in the back with nothing added to the front to balance it out. Weird indeed.

rear ride height should be a little higher than the front ride height; something in the 25.25 - 25.75 inch range. FYI, M030 RoW is 25.75 and bone stock is 26.25.

While installing my Ksports, bearings, and other suspension parts, my mechanic found that my front right control arm (the one that extends from the chassis to the control arm with the ball joint) was bent and required replacement... Oklahoma Foreign sold me a salvaged one for $150 shipped overnight. I would have put in a brand new one or a rebuilt one, but I want to do both sides when I do it. This should be closer to the age of the existing one on the left side.

Here's a shot of the back driver's side, completed:

http://www.iwantaporsche.net/rearsetup.JPG

I picked up my car last night. Wow. Observations:

1. Much rougher ride. However, none of the dampering settings have been made and all four corners are not on the same place on the dial.

2. The car now handles as if it were bolted to rails on a roller coaster. Far less body roll and it's no longer sloppy. I did not feel any pitching front-rear either due to a problem with harmonic balance... but I'm fairly ignorant of all this and that may be to my advantage if it exists :)

3. I doubt I will ever drive across country with the wife on a vacation in the car again. She'll holler like a cat with it's tail on fire and ask me every five minutes why we didn't take the Lexus (or the BMW, which we'll probably have by end of year).

Kevin, what tire pressure do you recommend now? I can't seem to find it.

FYI for any 97 owners installing Ksports. You do not need new nuts and washers for the tops of the coilovers. The factory ones fit on our model year.

K Sport Coilovers
 

Hi, Insite. I was reading this thread but I am not sure you installed 300/400 or 400/500. Can you let us know? How is the ride on streets/ highways?
Thanks.

i've got the 400/500 and randall has the 300/400. the 400/500 are rough on the street for sure, but not unbearable. i actually don't mind the ride at all. my fiancee really doesn't mind it either. the dampers are actually not bad; they do a good job of controlling the car over bumps and dips. i would probably choose slightly different spring rates next time to deal with some harmonic issues inherent to the 400/500 choice; probably 350/500 or 400/550, but i'm not sure yet.

K sport coilovers
 

Insite, I thank you in prompt response. I appreciate your knowledge, analysis backed with calculation ( I remember " Dynamics" in Engineering class. Although I don't use it much at all ), and a fact that you track your car. Hats off to you and Randall. Thanks again. :)
Any word on the group buy, you mentioned in the past thread?

My 300/400 setup, set at the softest setting, is just a bit rougher than stock struts and springs.

I just sorted out the installation tonight, actually. My mechanic didn't tighten down one of the top nuts on the rear driver's side strut mount (loose a 1/4 inch) and the center nut was a little loose too. Tightened both and it stopped the rattle and banging I heard while going over every bump.

BTW, if you install these, double check clearance between the coilover and your rims and tires. Before I set my rears to 25.75 inches from ground to wheel well, they were rubbing my 18x10 aftermarket Carrera lights (from wheel dynamics) just a little. Fortunately it was only rubbing on the rubber perch base on the coilover, not the spring or perch rings. My 7mm spacers are now mandatory to keep the tires and rims from rubbing in the back. I suspect they're needed in the front too.

Then, because I replaced 3 of the 4 control arms (the ones with ball joints) and all four of the other control arms (that connect to the ball jointed control arms) and installed new rear adjustable toe arms, I had some serious rubbing problems with those stinking dust shields behind the rotors. Took me forever to get them out of the way so I didn't have a very loud, tinny, ticking noise when I made U turns (from metal whacking against the holes in my cross-drilled rotors).

Having all four wheel bearings replaced at once is a real treat! The car coasts silently and finally, oh joy! I do not have steering wheel vibration any longer! After buying new tires repeatedly and having road-force balancing done more times than I can count in the last four years, I solved a vexing problem.

Now, I must wait a week to get an alignment. My mechanic said he'd do it for free if I waited until next week, so I will be patient and save $$$ to let him do it when he has time.

The car feels so very different now, but I think I hear some noise coming from the springs clattering a bit over certain kinds of bumps. The adjustment knobs are really loose in the back and cannot be removed like the front ones. I might just tape them down to see if that's what's causing the clattering back there. Everything else seems to be bolted down nice and tight.