Wheel alignment by Earl Gillstrom (http://members.rennlist.com/captearlg/928%20DIY%20ALIGNMENT.html )
If you are unfamiliar with automobile wheel alignment, go to the library or a book store and learn the theory. It can be found in some older Chiltons and Haynes manuals as well as some of the new suspension books (~$18). Also read WHY 928 SUSPENSION IS DIFFERENT and MISCELLANEOUS RAMBLINGS and QUICK CHECK OF 928 ALIGNMENT
ALWAYS use proper safety procedures. ALWAYS use jack stands on cars that are jacked up. To jack the front of a 928 I use two garage floor jacks under the front jack pads and then put jack stands under the inner frame members for safety. Caution, do this only for safety. These frame members are not made for holding the car up. They are usually bent from unknowing mechanics using them as jack points. If a jack should fail they will get bent, somewhat, but may save my life.
TOOLS AND SUPPLIES
You should be able to assemble all of the Special tools necessary to do home alignment on your 928, as well as your "beaters" for less than the cost of one "professional" alignment. You probably have many in your tool box already. You should refer to the 928 shop manual (section 44) to identify the adjustment eccentrics etc., you will be adjusting.
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.
With either choice you will have to mount ~1" thick wood spacers where the level contacts the rim to space the level out far enough to clear the tire and center of wheel bulges. The sliding adapter for the HF level shown is a modification of Jay Kempf's design. This has the advantage of adjustability for different size wheels.
TURNPLATES. Harbor Freight (harborfreight.com or 1-800-423-2567)is selling turnplates (item number 45742) for ~$150 a pair. You need these for the front wheels if you are going to adjust caster. If you are not going to adjust caster, you can make a set of 4 homemade slipplates (the slipplates that I use for the back wheels are shown in several of the photos) out of 3/8" minimum Plexiglas (not polycarbonate) 2, 12"X12" for each wheel, and Teflon grease. Chassis grease between the plates is not slippery enough. Super lube with teflon is great, (WWW.buySuperLube.com). Drill a hole in each outside corner for a holding pin, so you will be able to drive on without slippage. After alignment, the holes won't line up, so you can't put the pins back in. I usually push the car off of the plates while holding the hand brake handle to stop the car. If you have to buy the plexiglass, you may find that it does not cost much more for the HF turnplates. I recommend two sets of HF turnplates, or if you want to save a little money, make plexiglass slipplates for the rear wheels and use HF turnplates for the front. Or use 1 set of HF turnplates and align the front and rear separately.
CAMBER GAUGE. Harbor Freight sells a camber gauge (strut alignment level item number 42496 ~$10) that you may be able to use instead of the level and shims (drill bits), although it may not be as accurate and you would probably have to make an adapter to fit 928 wheels. See MISCELLANIOUS RAMBLINGS for using this as a caster gauge.
HF also sells a toe-in gauge for ~$40 that is impossible to use on a 928, due to the low ride height. It is also very inaccurate compared to the laser system.
LEVEL GARAGE FLOOR. Most garage floors look level, but very few are. Use a water level and 2x4's and tapered wood shims (horse-feathers)to check. Drive your car to where you are going to do ride height checks and alignment. Mark on the floor where the wheels sit. Back car out. Put down four 2x4's,about 1' long on edge. Lay a piece of clear vinyl tubing filled with water between the 2x4's and shim until the top of the 2x4s are level. For accuracy test diagonally as well as front/back and side to side. Now measure the thickness of the shims at each wheel location and make 12" square plywood shims to go under the turnplates/slipplates. If your front and rear turnplates/slipplates are different thickness, compensate with plywood shims so that the front and rear wheels sit at the same level. Mark the floor to be sure the car will be aligned at these spots and mark each plywood shim with it's location.
Ramps. My front turntables are 1 1/2" high and the rears are 2 1/2" high (to level my floor). This is probably the minimum car height to be able to reach the adjustments laying on the floor. The rack centering bolt is a long reach. It would be nice to build ramps to raise the car 3 or 4 inches, but you would still have to lay on the floor (I use a 3' X 6' piece of carpet to lay on.) If you build ramps, make the center between the wheels removable, so that the car sits on 12" X 12" pads. This will make adjustments easier. You could make them out of 2x12 planks, and if you want them higher add 2x3 spacers under the 2x12's. Be careful, if you are using homemade greased slip plates, you could have the car fall off during spirited adjustments, so don't make them too high.
After you have completed your first alignment, leave the rack centering bolt installed and push the car out of the garage several car lengths (using care to stop car safely) Put a small dot of white paint on the driveway next to drivers side front and rear tires. The next time you do an alignment, line up at least your rear tires with the dots on the driveway and drive into the garage. You will be able to make slight steering corrections and the rear will end up in the right location.
928 ALIGNMENT AT HOME
1) Check and adjust tire pressure and fill the gas tank.
2) Check and adjust ride height. There is an excellent write up at www.928.org.uk/height.html except for the settling recommendation. It takes a minimum of 10 miles on the roughest road that you have ever seen or ~100 miles or more on typical highways.
3) Remove the front belly pan to provide access to steering rack centering hole.
4) Check and replace worn or damaged parts. The inner tie rod ends are usually the first to go. Don't forget to adjust your wheel bearings. Also, check your wheels for trueness on the rim edge. Curb rash or a bent rim will affect the laser level seating on the rim.
5) REMEMBER, IF you jacked the car in previous steps you have to settle the suspension by driving ~100 miles before doing the alignment.
6) Verify that gas tank is full and tire pressures are correct. Record depth of tire tread and ride height on the ALIGNMENT RECORD TABLE/TOE-IN GAUGE CHART.
7) Make your toe-in gauge.(see SAMPLE CHART AND GAUGE) Theory: The laser level is mounted on one wheel and projects the laser to a fixed spot on the toe-in gauge on the on the wheel at the other end of the car. The distance from the laser beam to the wheel center must be calculated and the difference in the wheel track must be compensated for (it is actually the location on the center of the wheel that the toe-in gauge contacts). To calculate the difference in wheel track, drive the car to the location that you will do the alignment and using the plumb bob stand off (wood stick with notch) held against the center cap or center cap flange or any other location in the center of the wheel that is convenient, stick a "Post-It" to the floor under the plumb bob. Hold the plumb bob on the wheel and carefully mark its location on the "Post It" on the floor. Repeat for each wheel. Remove car and measure and record front and rear track, on the TOE-IN GAUGE CHART ON THE ALIGNMENT RECORD TABLE. Subtract rear from front and halve the difference. I call the result "offset". This compensates for the rear track normally being less than the front (on some cars, the rear is wider, it also depends on the wheels). You divide the difference by 2 since you are doing one side of the car at a time. Post offset on the toe-in gauge chart (front wider or rear wider). Note that only one will be used, either front wider or rear wider, cross off the one not being used to eliminate confusion. CAUTION If the camber is really out of adjustment, then the offset may be incorrect. After you finish alignment, re-check offset and correct toe-in gauge and reset toe-in if far off.
To calculate total laser height, attach laser level to front wheel with bungee cord and measure from inside of level to wheel cap or recess or the location that you placed the plumb bob standoff and record on chart. Add laser level height to laser beam height (HF # 41895 or 54050 is 1 3/4") and record on chart. Repeat for rear wheel if rims are different (most S4 and later wheels are different).
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.If you are using a carpenters level with the laser level attached on top of it ,you will have to add the thickness of the carpenters level to get the total height. Record this data.Record the toe-in specification numbers. 928 front toe-in is 0.215" or 5.45mm (0.125 tan X 98.43" = 0.215)(0.125tanX2500=5.45)Rear toe-in is 0.285" or 7.24mm (0.166 tan X 98.43 = 0.285)(0.166tanX2500=7.42mm. (98.43" or 2500mm is the wheelbase of the 928.) Be careful to use the proper + or - sign when calculating. If you are NOT aligning a 928, be careful, the + and- signs are for the 928 which has positive toe-in on both the front and rear wheels.
Mark the total on your toe-in gauge measuring from the inner edge (see special tools). Put F on the gauge for front and R for back. Mark both sides of the gauge since the gauge is facing the other way when you use it on the other side of the car. This gauge, used to set the front toe-in, is attached to the rear wheel. The inner end must sit on the wheel measuring surface, and the gauge is held in place by bending a piece of wire that hooks onto the wheel and holds the gauge bar straight out from the wheel. You will adjust the front wheel until the laser dot rests on the F mark. Make a similar gauge for the rear toe-in, or mark the same gauge with an R. This time, you must subtract the track width offset and the toe-in from the laser height to get the total. Measure this distance and mark on the gauge, and mark it R for rear toe-in. Remember that the rear toe-in is set by attaching this rear toe-in gauge to the front wheel.
IMPORTANT NOTE All adjustments are sequence sensitive and must be done in the following order. Also, if you adjust caster or camber, you must adjust toe-in on that axle.
8) Drive car onto slip plates. Pull pins on slip plates. Adjust camber on rear wheels to negative 40' or - 0.66 degrees. Attach laser level or carpenters level with spacers to the wheel with bungee cord and check for 0.199" (#8 drill bit) clearance between the spacer and the rim at the top for 16" wheels (0.66 tan X 17.25" = 0.199"). For 17" wheels check for 0.210" (#4 drill)(0.66 tan X 18.25"=0.210"). This is the one adjustment that it would really be nice to have the car raised. I use every 1/2" extension that I own to extend out the back of the car and then a 4' pipe on a breaker bar to get the lock nut (22 mm) loose. Tighten to 200 NM or 146 Ftlb after adjusting. On most cars you have to drop the exhaust to get to the left side locknut, even if the car is raised.
9) Adjust toe-in on rear wheels. Use 2-19 mm box wrenches. With the toe-in gauge mounted on the front wheel and the laser level on the rear wheel, turn the eccentric until the laser is on the gauge mark for the rear wheels. Tighten the lock nut very tight (you can't get a torque wrench on it). This is a tough one, if you tighten it too tight it may strip. I have seen two of these stripped and they cost ~$50. If you leave it too loose it may allow the adjustment to shift. If it shifts, the steering wheel will no longer be centered because that rear wheel will steer the back of the car off center, (incorrect thrust angle and toe-in).
10) Adjust caster and camber on front wheels. Pull pins on slip plates or turnplates. Loosen lock nuts on both eccentrics (19mm). The eccentric is turned with an 8 mm Allen wrench. If you push the wrench all the way in it will catch on the lower control arm as you turn the eccentric and you will think that you have hit a stop. Put a piece of rubber tubing on the wrench to act as a stop so that it will only go in the thickness of the eccentric. It is almost impossible to adjust caster without calibrated turntables(see miscellaneous ramblings). I have found on the 17 928s I have aligned, that if you adjust the caster eccentrics to the minimum, then you usually have close to the maximum allowed caster. Turn the caster eccentric (inboard on steel ball joints) until the ball joint is all the way forward, the inner end of the ball joint carrier will now be all the way back. If the car has aluminum ball joints, STOP. REPLACE WITH STEEL BALL JOINTS BEFORE ALIGNING. ALUMINUM BALL JOINTS HAVE BEEN KNOWN TO FAIL, RESULTING IN SERIOUS DAMAGE TO SOME CARS.
Be sure wheels are straight ahead. Adjust camber to negative 30' or -0.5 degrees. Attach laser level or carpenters level with spacers and adjust for 0.151" (#25 drill bit) for 16" wheels (0.5 tan X 17.25" = 0.151") at top using the outer eccentric. For 17" (18.25") wheels use 0.159" (#21 drill bit). Note: Normally camber is adjusted before caster, but since we adjusted caster to the minimum and they are interactive we adjusted caster first. If you can measure caster, (see miscellaneous ramblings) adjust camber first, but you may have to go back and re-adjust camber, after adjusting caster, they are slightly interactive. Tightening the lock nuts (120Nm,88ftlb) may also slightly change camber, so re-check settings after tightening locknuts.
11) Install the rack centering bolt. Remove the plastic plug and eyeball the dimple in the rack and then install bolt while jiggling steering until snug. If the steering wheel is not straight, remove steering wheel and align correctly.
11a) This method can be somewhat of a PITA on cars that you can't use a rack centering bolt. Try tying the steering wheel down and use two toe-in gauges, one on each side, and then after each adjustment, make sure the other side did not move by moving the laser side to side.
12) Adjust toe-in on front wheels. Use a 22 mm open end wrench to loosen the lock nut on the tie rod. With the toe-in gauge mounted on the rear wheel and the laser level or special adapter on the front wheel, turn the tie rod until the laser is on the gauge mark for the front wheels and tighten lock nut.
>13) Using the above methods, the thrust angle is automatically correct. If you use anything other than the toe in gauge that you made in step 7 attached to the opposite wheel, (i.e. floor or walls) you may have to readjust until thrust angle and steering wheel centering is correct.14) Back car up several car lengths and put white dots of paint on driveway beside front and rear tires on drivers side for future alignments. When doing future alignments, line up tires on white dots and when you drive on turntables, you should be fairly well aligned. Remove centering bolt and install plastic plug and belly pan. (Remember, you can't steer the car while the centering bolt is installed).
15) Check tire tread depth periodically to assure that alignment is correct. If you started with worn tires from previous incorrect alignment, they may eventually wear even.