FredR

After some 9 years since I last did an alignment and having had the elements of both the front and rear suspension systems off the car for some TLC I figured it was time to do the alignment and went off to my local friendly tire shop who have a nice laser alignment rig and an operator who knows what he is doing and is fully compliant with my needs.

It was interesting to see where the alignment sat relative to my eyeball alignment and following previous alignment marks I made. The front was actually not bad at all with a bit too much toe in [safer for the tires than too little or a toe out condition], the rear had too little toe but again not too bad.

On the rear I was hoping to see more adjustment range following my rectification of the adjuster pockets and whereas I was able to get the rear camber I was looking for this time -minus 1.3 degrees- this was the minimum I could get [previously it was 1.7 degrees] so it looks as though my dog bone bushes and the adjuster problem were part of the problem but not all of it- still I am happy.

My front alignment was also a bit of a mixed bag in that previously I set my 928 to run 2 degrees of front camber. For some reason I know not both my 928s exhibited some strange behaviour in that whereas I could get 2 degrees on the passenger side, I could only get 1 degree on the driver's side [LHD]. The solution to this problem was to use the earlier lower control arm and suspension bracket that shifts the range about 3 degrees higher. This time I wanted to reduce the camber to about minus 1.75 degrees as minus 2 degrees seems to be a bit more than really needed with Carl's lower frame brace fitted but to my surprise I found that 2 degrees was the minimum I could get with the longer lower arm fitted so I had to settle for that. For toe I set it to 0.1 degrees toe in both sides to give a total toe of 0.2 degrees. This is at the lower end of the stock range and this helps the car turn in a bit quicker and probably reduce the steering effort a bit given the wide front rubber I run. For caster I run at minus 5 degrees to help compensate for any twitchiness caused by the relatively small amount of toe.

I had hoped to do the alignment after fitting new rubber on the rear but I have not been able to get hold of anything. I thought I had secured a good deal on a pair of new Yokohama Advans that were in stock at the local dealers but I sat on the pot too long and found that someone with a Merc had just snaffled them up.

So, it looks like a trip up to Dubai to get some rubber is now on the cards but even there it is a bit of a hit and miss affair or so it seems. At least I have the Cayenne Turbo S rocket ship available for that trip given my current rear rubber is on its very last legs now. At least the Continental rubber lasted way longer than any other tire I have had on my 928's over the last 17 years of ownership but geez they have become so expensive running at some $400 per cover on the rear and about $350 each up front.

Hoping to try some Nitto rubber as per an earlier thread I started a while ago if I can get such in sizes that work on my wheels given they are aobut half the price of Continental, Michelin or Pirelli and tha tif they had any in stock which they do not and they are 18 inch! Nowaday they only seem to have 10 inch and 20 inch sizes would you believe?

The improvement of the ride quality on the way back home was well worth the effort even if i have to redo it after new rubber is fitted- hopefully not necessary but...?

Rgds

Fred

Adk46

I'm impressed that you know the in's and out's of this complicated business. I'm also impressed at how difficult it seems to be, even with a knowledgeable customer and service guy. And, of course, there are the many stories of woe.

Overall, the subject frightens me into inaction.

dr bob

Fred--

I'm interested in your thinking about how it will need to be re-done when new rubber is fitted. My most previous (and last...) commercial alignment included me sitting with the tech under the car as he dialed everything in on the machine. He then took the car for a drive, came in and did a little adjusting, another drive then pronounced it good. The second bit adjusting was done without the machine connected, and per him to compensate for road crown. It chewed through a set of tires in a very short time. This drove me to figure out how to do all the measurements myself.

Back to my thought question. It seems that we align based on the rims, so tire wear shouldn't cause any changes in alignment. It's hardware adjustments, not firmware, right? [Scratches head where hair used to grow...]

FredR

Bob,

I have been told various things about whether alignment should be done before or after new rubber is fitted and quite frankly I have no real world clue as to which version is correct.

The only thing I could think of is that when running with camber there is a degree of uneven wear on old tires and maybe that translates into an "error" when the new cover that is "more square" is on board as the rubber will sit sightly different. and bedded in.

Thus it may be of interest to revisit the alignment shop if nothing else but to check where the alignment sits as/when new rubber is eventually fitted. If camber does change slightly then toe will also change.

The truth is out there!

Rgds

Fred

FredR

Curt,

I suspect the trouble with most alignment shops in your part of the world is that time is money and they simply want to get you in and out of their premises ASAP unless you have a really special relationship with them. Today's session went reasonably trouble free but it still took over a hour to complete the alignment which is a bit of an iterative process given the way the different adjustments inter act. The alignment machines have a programme built into them for each make and model and they typically show green when the current set point is within the acceptable factory spec. As long the number drops into that zone most shops will call it a day I suspect.

I insist on getting the numbers bang on the same value on both sides and that is a bit more fiddly. I set my 928 up for optimal cornering to take advantage of the wider rubber and stiffer suspension capabilities I have. My mentor some 10 plus years ago was [is] one of the best known 928 personalities and his insights were most helpful. Even then some of his advice did not hold in my case and that was with rear toe. He advised setting a minimal figure but when I did this I found I could not get drive out of the bends. We put this down to the difference between the fast sweeping conventional circuits he drove on and the slow tight bends I was seeing in our autocross type events. The interesting bit was that I was able to know what was working and what was not and the old agage "The stop watch never lies" sure holds true.

I also had the added advantage that the technical manager for a major tire company was very excited about what I was doing and he helped me a lot by allowing free access to their laser alignment rig as long as it was quiet in the shop. He also got me some great [50%] discounts on their tires [how I miss him since he left].

Bottom line is when you understand what these changes do and can feel the difference [positive or negative] you learn rapidly. Then when you get really good you can set up a car for say Nascar racing and this is really interesting how they go about tuning the handling to go round left hand bends- those cars are a bag of crap in the straights but they go round the bends as fast as they do in the straights or so it seems. I would certainly like the opportunity to learn something about what those guys do.

Rgds

Fred