Just research what alignment specs you want, for the use of the car, your experience, and what you've done to suspension (ability to get to spec). The factory alignment specs, are for a very broad spectrum of drivers, their ability, road conditions etc. These specs don't necessarily yield the best response/handling/feedback/, but they are the most compliant, fairly even tire wear, and have the least detriment to "non-drivers". You specs aren't very aggressive, and you still have room for a bit more, if ya decide to change them. Even if your above what would be optimal for RS carriers, you MAY still be low enough, that bump steer is still present. May be reduced, but still has some impact. If your tie rod sits level with the ground (from inner/steering rack, to carrier, it may still have some bump steer. If the tie rod sits higher on the carrier end (while on flat surface), you'll most likely experience bump steer. Just try to imagine the tie rods plane of travel (vertically) as the carrier traverses changes in road. If, the tie rod loses "travel/play" as it goes beyond any compliance, that's where it becomes "input" to your steering, as it acts as a solid arm. If the tie-rod starts below neutral, it has that much more room to avoid inducing bumpsteer. Hope it makes sense.

 

By about 4mm both times, but I only drove it a couple miles. I plan to take it for a longer drive tonight, measure one more time, and have the alignment shop raise it more tomorrow if I find that it's still settling. These PSS10s are lightly used though so perhaps they won't settle as much as new ones.

 

Yes that makes sense, thanks. I looked at my tierods when measuring ride height and they are close to level once I've used some fuel and I'm at 1/2 tank or a bit less. At full tank they are a little higher on the wheel carrier side.

I did quite a bit of research on alignment before going in and decided to go more aggressive than M030 but not too aggressive. I considered more camber but then decided to give RS specs a shot and see how that felt, since I figured it would give me reasonably calm street manners.

Here's the instructions I gave my alignment shop:
- Use Euro RS alignment specs
- Maximum front caster within spec
- Minimal cross-caster
- No cross-camber
- Ride height should be set to RoW M030. I would prefer a slight downward rake, up to 1 degree max, so the front can be closer to 135-140mm and the rear 130-135mm, as necessary to get the specified rake but without going below 135mm in front since that’s the point at which bump steer starts to become more evident.

 

Good to hear the KT is correct. I'm not experienced enough with alignments to recommend anything specific aside from "make sure it's within factory specs." I leave any deviation from that to the real experts.

If I were in your situation, I'd probably leave it alone for now. If you have a chance to drive another 993 on the same roads you could at least make a relative comparison to a similar car.

I know I took a little while to get used to the relatively light front end of the 911 when I first got my car, so that could be it as well.

 

Where are you measuring from?

How much gas was in the car when balanced and aligned?

Assuming you are measuring accurately at the correct points and have the same amount of gas as when the car was balanced and aligned, the front is out of spec.

 

Thanks for the input mpruden. I also want to make it clear that I'm not really complaining, the car is brilliant, it handles amazingly well and is inspiring on twisty roads.

I guess I'm a typical Porsche owner and I want to be sure its perfect! Especially since I just put a lot of time in the suspension and I don't want it to be compromised by ride height or suspension settling that may upset the balance and keep the car from reaching its full potential.

 

I'm measuring at the correct frame points according to the workshop manual. The outer frame bolt in the front and the small line that sticks out of the bottom of the subframe between the rear a-arm legs.

It was balanced and I measured with nearly full tank - probably 7/8 since I had to drive from the station.

When you say the front is out of spec, what do you mean? What's out of spec and what would you expect it to be?

 

Sorry, in that post I was referring to ride height, ROW M030 is 144 +/- 10, which i know you know, but the rear is within spec so I would say the front could come up bit.

 

Gotcha. Yeah the front is low by 1 or 2mm.

 

My understanding is if you go much below ROW Sport height you will need some added parts, offset arm bushings or a wheel carrier or adjustable arms to bring the car into factory street alignment. Also, you describe driving the car on public roads. If you go too low you will have problems with aprons, steeply inclined driveways and parking blocks. These things can cost you a bumper cover or two. My experience is that the 993 likes a good alignment and if off a little the feel of the car is influenced greatly.

Here is a chart of comparative spring heights you may find interesting for comparison:

 

Thanks for all the input folks.

I'm going to keep driving it but I'll get it to my mechanic, talk to him about the suspension settling and probably get the car raised up ~10mm to bring it more into the middle of the spec height.

 

Do you have the fractions in degrees/minutes?

Front camber for RS is expressed as -1*27' +/-30' so does -1.3 equal -1*30'?

 

I don't and I'm not sure how to do the translation...

BTW - All measurements are in degrees (camber and caster) except for toe which is in inches.

 

Agree.

 

I don't either....