Rob Edwards

Not sure where to put this random musing, so I'm picking this thread.

I have ruined the mounting studs on my rear wing, and am thinking about how to fix it. I'd like of course to replicate the angle of the studs so I found an inclinometer app for the Ipad (Clinometer HD, it's free). Daily trivia, the rear hatch slope across the wing mounting area is 21.8 degrees.


The app also has a bubble level function. But it got me to thinking that perhaps one could use the app for alignments? No idea at all how that would be done.... Just a thought.

928mac

I do not know how Porsche dose it,
but everyone else sets all the cars on the assembly line to the same point.
as a matter a fact the first time you align a chev, ford, or dodge, you have to slot the car shock tower holes or punch out the hole knock-outs on the half tons.

If it needs to be adjusted then the dealer corrects it but most of the time they are to close to bother with.

Hilton

Rob, in response to your musing, I fixed one of my S4 spoilers a couple of years ago after breaking studs removing it from the car to replace the teflon stickers between it and the car.

To get the studs right, I made a wooden jig out of a bit of pine board, with a couple of 6mm holes. The studs themselves are parallel to each other, and from memory perpendicular to the mounting surface of the wing/spoiler at that point. Measuring the hatch at that point will just confuse you as its slightly curved, and picking the right tangent is just painful, so I focussed on the wing edge instead. I can't remember whether I ended up using the center-to-center measurement of the holes in the hatch, or the tip to tip measurement from the good end of another wing (still on car) - but either should work fine as long as you can drill parallel holes.

Once I'd removed the remainders of the original studs, including their pan-shaped head and the plastic spacer, I cleaned out the hole, and made new studs using a bolt, large washer, and bunch of plastic washers (to replicate the spacer). Then fill/pack every which way with urethane epoxy and use the wooden jig to make sure the studs were aligned correctly. Some careful wiping and then wax-paper between the epoxy and wooden jig, and clamp and leave it.

My repair worked a treat - that wing is still in use and has 5k+ miles on it since.

Of course, the better repair is to get your hands on a folding wing from an '87. No more messy studs, plus the ability to lift up the wing makes cleaning much easier

John Speake

The WSM page 44-2 etc shows a "pull down device" to get the front to the correct height. Maybe that's how they did the production cars ?

Tom in Austin

Just to join in the speculation here ... I suspect Porsche did the entire alignment process during manufacture and then checked it again after the road test. They were very particular about balancing everything to eliminate any vibration and I would think the same high standards would apply to wheel alignment as well. All that labor is why the car cost so much.

Meanwhile, in mass production environments like Japanese cars, the only adjustment in many cases is toe. That was true of my Lexus ... there were specs for camber and caster but all that did was tell you if you had a bent or damaged component ... assuming nothing's damaged, it's just "toe and go". That's part of the reason alignment shops are so reticent about doing a 928, their pricing and profit on the alignment rack is based on 'easy' cars and the average tech is really thrown for a loop when they try to do a 928.

AO

Rob-

That's a great find. This should work great for camber checks!

I remember when I was working on my DIY home alignment, I looked at the Harbor Freight angle finder tool, but it wasn't accurate enough and at the time I only had an ipod touch which also didn't have the accuracy I wanted.

The iPad is a perfect platform for this - and this app seems to be more than accurate (although I have not tested it against my current method).

The challenge is getting a flat surface to hold the iPad against across the face of the wheel. Luckily I built such a device for my alignments.



I need to check my rear alignment - particularly camber now that I replaced my eccentric bushings - so this will come in handy. I will report as soon as I can on it's effectiveness.

dr bob

I've been using the H-F digital angle gauges for caster adjustments, and they have adequate repeatability for the duty. I also tried them for camber, backed up by a bubble level and a drill bit spacer. The digital gauge is adequate but you have to give it a little time to settle. The ipad iPhone app using the g sensor in the devices is OK, but is missing a convenient way to attach the device while adjusting. Plus the iPhone is a liitle short on survival skills when dropped, even from just a foot or two. On mine, the screen broke the fall... \_8<0

Jerry Feather

Rob, I wonder if that is 21.8 degrees relative to the world or to the car?

brutus

I thought the studs are just square to the base of the spoiler and they mount to the sloped hatch. Nothing but a 90 degree to the base of the spoiler. But neat app !

Shark Attack

the cars were not hand made. There was attention paid to detail but the cars WERE VERY FAR from hand made.

I would be willing to bet they were jig'd or some kind of alignment tools right on the line and it took less than 5 min per car to do

AO

So I gave the iPad App Rob suggested a whirl yesterday and while is sounded good in theory, I think implementing it in practice is not viable. The issue is that the iPad seems to be be VERY sensitive to other axes of rotation. Furthermore, spec for the rear camber is between 0.5 and 0.8 degrees (if I remember correctly). The iPad app doesn't provide enough resolution to accurately discern between 0.5 and 0.6 especially coupled with the iPad's sensitivity to axial rotation - basically if you tilt it at all, the angle displayed goes into a tizzy - even though I did my best to keep it plum and calibrated the app.

If anyone figures it out, please let me know.

hacker-pschorr

You just descirbed most dealerships - yes even some Porsche shops.

SQLGuy

I used to have a '78 BMW 320i. That was the same story: no adjustment of caster or camber. If they were off, it meant something was bent.

For VW's, aftermarket adjuster bolts were needed to adjust camber, at least in the Golf II.

dr bob

My last 'murikan ride went back to the dealer twice when new for alignment issues. Said it was "within spec" each time. I twisted them a bit with the lemon law threat, to get them to share the actual alignment data from the car. Yes, both sides were "within spec" but weren't close to the same. Since they couldn't get reimbursement from Ford under warranty, there must not be a problem. Took it back to their contract alignment shop myself, where they adjusted camber/caster with a new eccentrics to get both sides the same. 15 mins, cost me about $75, worth every penny. They eventually covered it.

Podguy

Toyota's come with improper tow out. It is blamed on the strapping them down to the deck. I am betting porsche used the same adjustment on all cars. At least with the same components. How much can they be off. So many turns on each shock. So many turns on the tie rod. The concentrics set at the same place. It would be damn close for a car that had a machine gig welded frame and manufactured suspension components. An automatic may require different ride height adjustments than a five speed.