928 ALIGNMENT MISCELLANEOUS RAMBLINGS 10/10/03

PERSONAL BACKGROUND

When I bought my '88 928 S4 four years ago and found that the car sits so low that you can't use a tape measure to check toe-in, I converted to string. String works fairly well, but takes a long time to set up and I usually trip over it and ruin the setup before I get done. That's when I developed the laser system. The custom laser adapter and magnetic spacer for the caster camber gauge allowed the alignment of 928's with Porsche wheels. I later found that some racing wheels don't have provision for Porsche center caps, but by using a laser level that rests on the rim edge, solves that problem.

When I tried to write this procedure for everyone to use, the major stumbling block was cost. The QWIK-EZEE gauge is still available for ~$700 and turnplates for ~$1400. That stopped me until Harbor Freight came out with ~$160 turnplates and ~$20 lasers. This - in my opinion - made home alignment economically feasible for 928 owners.

CORNER BALANCING

CASTER ADJUSTMENT USING A CAMBER GAUGE

Caster is the one adjustment that is not too critical. I doubt that you could tell the difference between 3 degrees and 5 degrees caster. But, if the cross caster (the difference side to side) is too different it may cause some pull. Porsche specification is 20' or 1/3 degree difference between left and right.

Using turntables, turn the wheel out 20 degrees and check camber. Add this reading to a reading taken with the wheel turned in 20 degrees. One of the readings will be negative and the other positive. Ignore the signs when you do the addition. Multiply by 1.5 for your caster.

Example: minus 1.4 plus 1.2 = 2.6 X 1.5 = 3.9 degrees caster. If you started checking caster with the caster eccentrics at the minimum, then increase the caster on the wheel that has the least caster to match the other wheel.

CAMBER ADJUSTMENT

Be careful when you check camber. The 928 has way more caster than most other cars, so when you check camber, if the wheel is not pointed straight ahead, the camber reading will be incorrect. If the alignment was fairly close when you started, then having the steering wheel straight ahead is probably good enough. If in doubt, point wheel straight ahead using laser and toe-in gauge before checking camber. If you have turntables, zero the degree indicator, and, after adjusting, be sure you are on zero before re-checking camber. Also note that when you adjust camber toe-in is drastically changed.

TOE-IN ADJUSTMENT

The method I use to check toe-in has some advantages compared to other methods. Shooting a Laser from axle to axle is 98.43 inches or 2500mm (the 928 wheelbase), far enough to get very accurate measurement. In "the olden days", toe-in was measured from the front of each tire to the back of each tire, so the distance was ~25 inches and considered accurate enough. Measuring this way is impossible on a 928 since the car is so low. You could drop a line or Laser to the floor, but still have only ~25". Shooting the laser to a wall or the floor means that you would gain accuracy but lose repetability and thrust angle and steering wheel centering. Assuming that you have turntables, the first time you turn the tie rod and watch the Laser move to the mark on the toe-in gauge and know that you are done, and your thrust angle and steering wheel centering is correct, you will be convinced of my methods.

STEERING RACK REPLACEMENT

If you replace your steering rack, or tie rods, how do you adjust toe-in so that it is close enough to not affect tire wear too much until the suspension is settled and you can do a proper adjustment?

This is a good question, posed by a neighbor and fellow 928 owner. In the past, we counted threads on the tie rods. This is probably inaccurate. Try this. Put car on jack stands. Install rack centering bolt. Mount laser on wheel and shoot and mark a spot on the toe-in gauge. After installing parts, adjust to spot on gauge. Drive far enough to settle the suspension, then do a proper toe-in adjustment. If the initial spot is not on the gauge, make a longer gauge or shoot to a Post-it on the floor near the rear wheel. Measure the distance between spots on Post-its and record, (in case the dog eats a Post-It before the parts are installed!)

928 S4 BELLY PANS AND RACK CENTERING BOLT

Normally you have to drop the front belly to install the steering rack centering bolt. There is an air scoop rivited into the pan under the rack where you need access to install the centering bolt. Drill out the 4 rivits and install self taping screws. Then just remove the scoop when you are aligning instead of the complete belly pan. I don't know if this applies to early cars.

GENERAL

Porsche adjustment values have tolerances, usually +or- xx. Except for height or caster, I recommend that you align exactly to spec. If you adjust using tolerances, like the local alignment shop, your tire wear will probably be tolerable. If you adjust exactly, and there is some error in your equipment, at least you will be close. The main reason is, with an exact alignment, the car feels good. When a car is adjusted to be just within the tolerances, the car feels numb. If you are going to turn the adjustment, then why not make it "right on." The 928 has a very robust suspension, and it would take something pretty drastic to "knock the alignment off". You will find that you will probably be aligning your 928 more often because you are adjusting ride height or replacing shocks or worn parts than because you "hit something to knock the alignment off".

ALIGNING YOUR "BEATERS"

I wrote this procedure so that you could do alignment on other cars. Just change wheelbase, caster, camber and toe-in values in the formulas and recalculate to match the car. When you make your toe-in gauge, pick a spot in the center of the hub and use that same spot for both plumb bob track calculation (offset) and laser height calculation. Caution, the calculations on the toe-in gauge chart were made for the 928 with positive toe-in in the front and rear. You may have to change the signs. If you are not familiar with trig, use a ~$8 scientific calculator. Where the calculations have "tan", just hit the "tan" button on the calculator. Use the 928 calculations for practice.

LASER CALIBRATION

After you assemble your laser level/carpenter square you can check for accuracy by mounting on a long straight board. Place a ruler a few inches in front of the Laser and record laser level height on toe-in gauge chart. Place ruler at end of board and if the laser hits the same spot, it is accurate. If it doesn't, the laser may be off or the board may not be straight.

Two other supplies that every 928 owner needs.

SUPER LUBE This is a waterproof Teflon grease that is the consistency of Vaseline. Excellent for greasing slip plates as well as sunroof and seat cables and window regulators etc. Also can be used as a dielectric grease. I used this grease on my sailboat wind vane steering pivots that I drug through salt water for months without it coming off. WWW.buySuperLube.com. ~$5 for a 3 oz tube that will last years. Just got an email from them. Take 20% off all Super Lube Products......The Best Multi-Purpose Synthetic Lubricants Available! Simply go to www.buySuperLube.com , place your order online and enter "20% OFF" in the comments field at the bottom of the order. Your order will be shipped immediately!

CORROSION BLOCK OR CORROSIONX.(www.corrosionX.com) Either of these products sprayed on electrical contacts will eliminate corrosion forever. I think, if we could dip the whole 928 in this stuff that we would never have an electrical corrosion problem again.

Most marine stores sell the above products. SuperLube grease may be called winch grease. I think it is the same.

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