Setting Front Ride Height After Suspension Refresh - What am I Doing Wrong? - Page 2

wrxnofx · wrxnofx's Garage

I've considered this exact point, javadog. I am not going to get to the rear until next winter because I've never done it before. I can't really tell for sure because I'm not entirely sure what I'm looking at, but it appears the eccentrics on the rear are adjusted all the way down, so I can only go up on height adjustment without re-indexing the rears.

I think I'll bring the front back up to what it was until I can do all 4 corners next winter. Thanks for the input.

javadog · 03-23-2016, 06:59 AM

Keep in mind that the rear height for your car was 4mm higher than earlier cars. Not a big difference, but worth noting. Rear torsion bars were also slightly larger. The later cars kept getting heavier, especially the '87-on cars that had the G50 gearbox, so Porsche modified the suspension settings to suit.

Whatever you do, corner balance and align the car before putting a lot of miles on it. Yes, you'll get to do it twice, but it will most likely be way off if you don't. You'll wear your tires unevenly, reduce your braking capability and have a lousy handling car if you don't.

Porsche got hip to the fact that owners in the US liked to lower their cars (especially back during the years when the US cars were higher than ROW cars to meet DOT regulations) and so when they made the spring plates adjustable, they set them at the factory at the lowest point of the adjustment range. This allowed the height to be corrected if the car settled a little bit after delivery, but prevented easily circumventing the correct height. Yes, you could still lower a 911 at the rear, but it took a lot more effort and expense, which probably kept some people from doing it.

JR

KTL · 03-23-2016, 07:40 AM

Quote:

Originally Posted by wrxnofx

No, I didn't, which would explain it. I put the caps and adjustment screws on AFTER connecting the ball joints to the struts.

That's full droop. When you install the caps and adjuster screws at full droop, you're setting the height near its maximum. When you set the car down on the ground, the suspension compresses a bit as the t-bars are loaded. You have to account for that compression/travel by jacking up the suspension a bit before you install the cap & adjuster screw.

Comparatively speaking, if you were to install larger t-bars, let's say a fat 23mm front bar for racing, and installed the cap & adjuster screw at full droop? When you set the car on the ground it would look like a SUV. This is because the stiffer t-bar reduces suspension travel. So in the case of a larger t-bar, you have to jack up the suspension quite a bit more to get the height where you want it (be that desired height right or wrong).

As JR aluded to, most importantly you must do an alignment. The front end of these cars are ultra sensitive to ride height and I can guarantee your front toe is all out of whack. It may feel OK but it'll handle like crap and eat your tires.

The rear end is not nearly as sensitive to height. You can adjust the rear height, even if your spring plates don't allow for it & you have to disassemble the spring plate. You can get the alignment close by marking the toe & camber eccentrics (reinstalling them as you marked them) and your alignment will be somewhat close. Still, it's very foolish not to do an alignment after futzing with the height.

wrxnofx · wrxnofx's Garage

Quote:

Originally Posted by KTL

That's full droop. When you install the caps and adjuster screws at full droop, you're setting the height near its maximum. When you set the car down on the ground, the suspension compresses a bit as the t-bars are loaded. You have to account for that compression/travel by jacking up the suspension a bit before you install the cap & adjuster screw.

This is the part that's confusing to me. When you say, "jack up the suspension a bit before you install the cap and adjuster screw", do you mean compress the shock by rotating the A-arm upward? If you do that and then put the adjuster cap and screw on, then when you put the car on the ground I would expect the car to be even LOWER because you've compressed the shock (bringing the wheel further up into the wheel well), and the torsion bars STILL have to load up, thereby dropping the car even further.

When I put everything back together, A-arms in full droop, and put the cap on and set the adjustment screw to what it was before taking things apart (3 threads exposed between the top of the cap and the stop on the top of the aluminum crossbar), the tires were up into the wheel well it was so low. If I jacked the car up, removed the cap and screw, compressed the shocks (by rotating the A-arms upward), put the caps and screws back on, then the car would be even lower I feel like.

KTL · 03-23-2016, 10:02 AM

You understood me correctly and you understand correctly what's going on with how the suspension behaves depending on the positioning of the A-arm and the indexing of the t-bar cap.

What I didn't recognize is that you already did it at full droop and it ended up with the height too low. In that case I would remove the nut on the top of the damper shaft and push the suspension down to have more droop before you index the t-bar by installing the end cap. And you can't do that if you have the sway bar connected because it'll be resisting you from the other side of the front suspension.

Driven97 · 03-23-2016, 10:10 AM

Don't, for the love of god, pull the swaybar, or you'll be disassembling EVERYTHING again to get it back in.

I seriously dread installing that thing.

KTL · 03-23-2016, 10:36 AM

Agreed with Matt. You should leave the swaybar in the A-arm and disconnect at at the rear where the U-tab fixes it to the body.

1000000% agree with Matt that I HATE the front sway bar installation. That thing is a mofo to wrestle with. It laughs at you and begs you to cross-thread the bolts as you struggle to get the belly pan and U-tabs to line up and let the bolt into the hole

brianlay · brianlay's Garage

To maintain the intended nose-down attitude (about 1 degree) your fender lip measurement should be about 1/2 inch higher in the front compared to the rear. I know it's counterintuitive.
So your front should be 27 1/8
If it were my car I'd lower the rear.
A good target would be 25 1/2 front, 25 rear.
That assumes you haven't got some unusual wheel/tire combinations on it.

wrxnofx · wrxnofx's Garage

Hahahaha, oh man, I thought it was just me with the sway bar!!! I think my body is still sore from pushing and pulling on it to get the U clips to line up and get the bolts in.

I finally understand everything completely. This being my first time redoing the suspension, this site is invaluable, thanks so much. I literally would have been incapable of doing this myself without your help.

Just think - the front was the easy part and I struggled with it. I can only imagine how difficult the rear is going to be...

Matt

Driven97 · 03-23-2016, 03:44 PM

The rear is easy, though I admit I haven't done the trailing arm bushings. Just mark everything before you take it apart, measure the spring plate angle, line it all back up with the marks and you'll be darn near the right height and close enough on alignment to drive safely to the alignment shop.

KTL · 03-24-2016, 07:47 AM

A trick for the rear spring plates is have some longer M10 bolts handy. Turns out the bolts for your CV axles are perfect because you have an '87 with the larger bolts that have the same thread pitch as the mounts for the spring plate bushing brackets. You use the bolts to "press" the cover plate & bushings into the chassis. Using the power of threads (make sure they're lubed with oil or antiseize goop) is WAY easier than trying to whack them into the chassis with a plastic mallet.