Hi all. New to this website but already have learned a great deal, Thanx. I put bilstein/eibach coilovers all around on my 88 s-4 originally equipped with boge's. After having the ride height and alignment done by a reportedly reputable P-car shop it has settled (sagged) a great deal. (No they didn't raise the car) I'm going to adjust it myself but the factory recommended 180mm is not for bilstein/eibach's right? That is out of my adjustment range.
1. Should the fronts be set to 180mm-25mm=155mm
2. Should the rears be set to 173mm-25mm=148mm

Thanx, Brian

 

This one ranks up there with venturis and wingnuts for number of different opinions.

The factory ride height recommendation is made with consideration for the suspension geometry, road clearance, and ride quality.

The Eibach spring package has a higher spring rate (simplified to in pounds of load for each inch of spring deflection) so it might be OK to use a slightly lower initial setting. Your comfort in this is that when you hit something that causes the suspension to compress before the alternator/AC compressor/oil sump/spoiler crashes into the ground, you'll be OK. Think about wide dips in the road as maybe a good example.

The downside is that there is a list of things that are tall enough to catch those same items on the car without ever even twitching the springs. Stuff like rocks, or even a narrow dip or pothole, a parking lot bumper, or (my personal favorite) a 24-pack of beer that fell off the boat on the trailer onthe freeway ahead of you.

So that fact that you can leave the car a little lower doesn't mean that you have to.


Oh yeah, the suspension geometry--

The ideal geometry has a minimum of side-to-side tire movement as the suspension is compressed or extended in normal driving. That equates to a position where, at normal drive attitude, the two control arms are as close to level as possible. As you move away from that attitude, the track and the camber both change more rapidly for any given change in suspension height. Bottom line is that tires will last longer if they don't get scrubbed sideways as much in normal travel.

On your car where the alignment was set with the car at a certain height and then it sagged after that, you need to get the car back to the height it was aligned at, or get it aligned again at the new height. Changing the ride height changes the toe and the camber directly, so your tires will take an extra beating.

I live in southern California, where we have no freezing ground and therefore few potholes. My car arrived with sagging original springs, and deserved a ride height improvement just so I could cruise through the raingutter dips in my own street. The factory-recommended height looks kinda funky after I was used to the lower raked look of the car as it arrived. I compromised on the lower end of the factory settings at the front, without that extra 10mm they give you for aging spring sag. It still looks tall, especially when parked next to some fellow SoCal928 member cars. There are three fingers plus of space at the top of the front tire to give you an idea. Meanwhile it rides better, the spoiler is still intact, no crashing into the rain gutters at 25 like it used to (I can blast through at 40+ now with not a hint of problems)and the tires are lasting pretty well (30k from the last set).

Use your best judgement on this, and consider that your location includes potholes and frost heaves that my car never sees.

<img src="graemlins/yltype.gif" border="0" alt="[typing]" />

 

i have the Bil/Eibachs on my car, only about 1000 miles on them. LOVE'M. I have only just started to really tweek my ride hgt...I cant recall...Im not at home right now, but when i get back and i remember i will snap a picture of the number of "threads" i have below showing on the back and the front adjustment rings. If i recall its a good inch in the back and appx 1/2 inch in the front. Im refering to the space were you can see the threads below the adjustment ring.

TIP: get a marker and mark the adjusment collar that you put the wrench on. This way you can track the number of turns you have given it. Also before you start, take the same marker and drag it down the threads below the adjustment ring so you can see how far you have changed it.

I made a trick little ride height gauge from 2 small pieces of aluminum tube. The OD of one basically nearly matches the ID of the other and i slide one iside the other..I get under the car and telescope the tube, extending it from the ground to reach the ride hgt ref. points. When it touches i pull it out and measure it! Very easy to make and do. I have all sorts of pics, just havent had the time lately to add a few pages to my website.
<img src="graemlins/yltype.gif" border="0" alt="[typing]" />

 

the dr's way-scientific ride height gauge set is a series of progressive lengths of precision-formed metal sections, with the final length of each section adjusted with handheld shear-type lever-action soft-handled tooling. The actual material is a ferrous compound that includes a protective gold-colored coating to prevent corrosion and to help avoid any discoloration or staining of the white gloves required during the measurement process. Each section is identified for length using a waterproof ink application device, applied to a length of self-adhesive cellulose acetate material that is then precision-applied to the gauge section to make the markings readable from either side of the gauge while it is in use.

That's the mil-spec description.


For those thinking of trying this at home, fear not! Take some coathanger wire, cut it to length in 5mm increments between about 140mm and 180mm, and mark the length with a pen onto some masking tape flag labels that you wrap around the wire. I used pair of handy linesmans pliers for the cutting and trimming task. They live in a ziplock in the tool box, rubber-banded closed, in case I need to use them again. Takes 5 minutes to make them and two hours to use them.



Cheers! . <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

 

my trick ride height gauge is courtesy of the ace hardware bin and is a long screw with rounded head and a bolt that is approx 2" long. a millimeter measuring stick is a must (doh!).

 

oh yeah...oh yeah..well..uh...im going to get mine made out of Titanium to save weight so

 

Just wanted to send thanx for the replies. I was on vacation for a few days and came back laughing out loud <img src="graemlins/a_smil17.gif" border="0" alt="[blabla]" /> to the replies! Funny stuff! Thanx! I have a good measuring instrument sort of like a scissor with the ends turned slightly outward with an axis about 12" from the tips. I just take a reading then measure the distance, my problem is......do I add spacers to enable the eibach/bilstien to reach factory specs, or do I leave the car lowered expecting the new springs to make-up the difference? I am now thinking that I will add a spacer to bring the front and rear to about 170mm. I guess trial and error will tell. Dr Bob's reply about the potholes in my area is a big part in my decision. Although I live out on Long Island where the roads aren't that bad, I'll still catch an occasional crater! But, I also thoroughly enjoy taking high-speed raking turns and do not want my car higher than it has to be. I'm gonna shoot for 170mm and see where it takes me.....

 

Tony's measuring device prompted me to think of using one of those telescoping pen pointers for taking measurements.

 

Hang on. Wouldn't things like wheel diameter, different brands of tires, and amount of tire wear affect the ride height? Even tire pressure could affect it, right? If you measure it from the ground to part of the suspension, there can be at least a centimeter of ride height change just from wheels and tires, couldn't there? So how is it even possible to set the ride height precisely? Or is the ground clearance the primary issue addressed by ride height alterations and the suspension geometry secondary? I'm confused here.

Bryan

 

Telescoping pointer.....good idea! Bryan, as far as I know, if you change wheel/tire configuration from oem you should always shoot for the same outside diameter of the tire so all of your readings don't get screwed up enroute to the brain like your actual traveling speed. (If you go from a 16" rim to a 17" rim you should be looking at a lower profile tire to keep the total diameter the same, not too familiar with this subject as I am still riding on oem 16" manhole covers!) Correct me if I am wrong. And yes, it is important that all of the tire pressures are checked prior to adjusting or measuring anything to do with the suspension. I usually keep mine @ 40psi all around. (slightly negates understeer) Anyway, my thing is although I like the way the car looks since it was lowered by the bilstien/eibachs, my steering tie rods are level to the ground when standing still. This means when the suspension travels upward at all, they're travelling upward with it, and heading away from the prime angle. My feelings are that they should have a slight downward inclination while standing still so that when the suspension travels upward they are at the best angle. Not to mention all this while under some body roll and the Weissach rear doing it's thing! One of the other posts here gave a good description on the ride height procedure and stated to set each corner to 175mm, I'm gonna put some spacers in mine and bring them all to 170mm and see how it works out, should be an improvement seeing that I'm now about 153mm in the front and 145mm in the rear.......we'll see. <img src="graemlins/beerchug.gif" border="0" alt="[cheers]" />

 

Just found this on Greg Nichols' page: <a href="http://ourworld.compuserve.com/homepages/nichols/tips.htm" target="_blank">Greg Nichols 928 page</a> [quote] 4) Personal Opinion
Set your car at the factory ride height. This is where the suspension was designed to work. My car was lowered by the Previous Owner. Raising it to standard height very noticeably improved both the ride and handling. Low may look cool, but it doesn't work well!

Wally Plumley
928 Specialists <hr></blockquote>

 

All,
Couple of things.
1.If I were to mount a new set of tires... is the order: mount the tires, adjust for ride height, angular distance between the tires, castor, camber, toe in?
2.If Brian diddles with his ride height... he does have to/should get a re-alignment, right?
Is there an acceptable balance - no re-alignment necessary - if the ride height is adjusted for example, 10 - 15mm off of the prior height setting?

 

Changing the ride height changes the camber and the toe, but has little or no effect on the caster. This is good, because you can set the toe and camber at home, but caster is difficult to measure.

I am about to do the same routine on my '90 GT, and the plan is to:
Measure the ride height before jacking the vehicle;
Install the tires and adjust the ride height;
Drive the car for two or three miles;
Recheck the ride height, and toe, correct if necessary, drive the car if necessary, repeat until ride height is correct with approximately correct toe.
Measure toe and camber;
Adjust the toe and camber;
Drive the car for two or three miles;
Recheck ride height, toe and camber.

At this point, you can either drive the car, checking handling and tire wear (with a gauge, not just looking at them); or you can try to find a shop that will do a good alignment without lifting the car.

Toe is the most critical tire wear angle. BTW - I suspect that many 928s have incorrect toe settings. You can check this at home with string or with lasers.

 

Tony I can't help but think your Ti comment was in reference to my quest.

Anyway,

WallyP - Did you already write somewhere a proceedure more in-depth than the one here for aligning the front of the car? I thought I remembered something like that....

Also - Is there a place somehwere that has the explanation of the strings idea?


Thanks,
Brendan

 

Here is an earlier post on the subject.


To measure Ride Height:

1) What and Where.
Front: There is a small flat machined area on the bottom of the cast bracket that holds the rear of
the Lower Control Arm, between the ribs. This pad should be 180mm +/- 10mm from the floor. There should be a max difference of 10mm from left to right.
Rear: There is a small flat machined area on the aft bottom of the large u-shaped bracket that
holds the lower transverse control link (the large flat blade). This pad should be 173 +\- 10mm from the floor. There should be a max of 10mm difference from left to right.

2) How to Measure.
First, and most important: You CAN NOT measure, jack the car to change the ride height, lower
the car and remeasure! You MUST either measure, jack and change, then drive the car for at least three or four miles before you remeasure; OR measure, change ride height WITHOUT jacking the car, then remeasure. The 928 takes several miles of driving, or using special tool 10-222A to pull the front end down 60-70mm for one minute.
Yes, they are serious. Yes, if you don't do it one of these two ways, you will screw up your ride
height - and the same thing applies to front end alignment.

You will need a tool that you can use to measure the ride height points while manipulating it at
arm's length under the car. One possibility would be a pair of yardsticks, bolted together near the centers using a wing nut, making a kind of three-foot scissors.
Slip this under the car to the machined pad, put one tip on the floor and one tip on the pad, being sure to keep them plumb, tighten the wing nut, pull it out and measure the height.

3) How to Change the Ride Height.
Most 928 springs are adjustable. These have a round, notched, threaded nut around the shocks
under the lower spring seats. Ed Ruiz found a tool to adjust these nuts - a "Motion Pro Single Shank Nut Spanner, 08-029" at a motorcycle shop for about $16. (Someone bought one of these tools by mail order from a motorcycle dealer in Pittsburgh (tel. 800-860-0686). They refer to it as an "ATV Shock Tool" part no. P529. It's made by Motion Pro whose own part number is 08-029. Cost was about $14 plus shipping.)
Turn the front wheels all the way left or right, lube the nut area well with a penetrating spray lubricant, and turn the nut right to raise, left to lower. You can get to the rear (also lubed) with only a little stretching.

Adjust the height all the way around and remeasure. When you think that you have it right, drive the car for three or four miles and remeasure.

If your Spring Struts are not adjustable, the only way to change ride height is to change springs or
to disassemble and add a maximum of two spacers to the lower spring seats.

4) After you get the front ride height set, adjust the toe-in. Easiest way is to "string" the car, ala NASCAR. Use any four convenient objects to securely hold two strings that run beside the car, an inch or two from the tires. Warning! The track is rarely the same front and rear, so don't use the rear tires to set your string!

Measure the distance between the strings in front of and behind the car, and make these distances
identical. Make the distances between each rear tire and its string identical. Make the distance between each front wheel center and its string identical.

Straighten the front wheels with the steering wheel. (A better way is to pull the plastic plug on the front of the steering rack housing and center the dimple in the rack in the hole. If the wheel isn't straight with the dimple centered, take it off and straighten it. There is a Porsche tool that screws into the hole to hold the rack centered - you can use a bolt woth the end ground to a point.)

Measure the distance from the front of each front tire to the string and the distance from the back of each front tire to the string. Try to be very consistent on where you measure from on the tires. Do the simple math to get the difference between the front and back measurements on the front tires.

Adjust the tie rods on the steering rack to get the tires almost straight ahead, with the smallest amount of toe-in that you can measure. This will be close enough until you can find an alignment shop that will align your car WITHOUT JACKING IT UP. If your alignment shop can't or won't do the alignment without jacking the car up, find another shop.

4) Personal Opinion
Set your car at the factory ride height. This is where the suspension was designed to work. My
car was lowered by the Previous Owner. Raising it to standard height very noticeably improved both the ride and handling. Low may look cool, but it doesn't work well!