James Bailey

But Kibort's way is perfect......for Kibort I take mine to a bodyshop guy with the $$$$$ machine as I want to get caster around 6 degrees. He check it after I change the upper A-arm and had the lower ball joint adjusters undone. Charged $20 since it checked out as I wanted it 3 1/2 to 4 negative camber. He knows to not lift the car and rolls it back and forth off the pads if he has to adjust anything.

dr bob

I'm sure it's perfect for mark, but that doesn't suggest that it might be even minimally acceptable for anyone else. For an adjustment that is easily responsble for the way a car gets around the track fast or slow, I'm constantly amazed that Mark proposes doing it the way he does. It's better than the calibrated-eyeball sighting from the doorhandle, but barely.

FredR

Jeff,

When you say "you found some 45 sidewall tires" what exactly do you mean? Presumably you mean that you found a shop somewhere that had them in stock and not on a scrap heap!

Do you know how old they are and did you find two of these for the rear wheels or "4 of them". I presume you are talking about a 245x45x16 section. Did you fit two of these on the front wheel rims by any chance or did you stick with stock 225x50x16 on the front wheels? A stock front rim probably would not like a 245 section on it but then your tire shop shouldahe pointed that out to you as they fitted them- apologies for the question but this is just elimination of the possibilites I see.

WRT to alignment all kinds of weird and wonderful things can be done at home but there are so many quid pro quo's that unless you are really very competent [and patient] and have the turnplates, a completely flat surfaces, 4 pairs of hands, the patience of Jobe and can crawl and work under a 5 inch gap beneath the car then it is probably not worth it.

Clearly you understand the importance of having the car settled but unless you know and trust the alignment shop implicitly never leave the car with them to do the job in your absence. Always watch what they are doing and tell them specifically what alignment settings you want within the allowable range [or even outside the range] and probably most important of all, ensure the settings are very accurately balanced side to side and well within the tolerance range specified in the WSM. Alignment shops may well try to fob you off with something that is "permissible" if they have a queue of cars on the ramp as fine tuning generally takes iterative steps.

Cars with widish tires have a tendency to tramline anyway and particularly so on raised road markings and there is probably nothing that can be done about that but I would not describe the 928 behaviour as "crazy" so clearly something not right.

I run 265 fronts with 2 degrees camber and minimal toe in and I have no problems of this kind. If the tire sizes are OK, your alignment OK then look for a tire fauly or some kind of compatibility issue- a laser alignment shop should be able to tell you if you have any slop in your steering system linkages- dodgy rack mounting bushes not so sure of that one but they would probably see soemthing.

Feathering on the outer edges can be caused by inaccurate toe setting [and if the car was aligned at incorrect height then the wheels will toe out as the car settles- no doubt about that]. With little or zero toe the car will feel very "nervous" and turn in like a demon but I would not call this tramlining.

Do not forget that wear on the outlet edge can also be caused by agressive cornering !

Regards

Fred R

jon928se

I may be being a dunce here.

At the correct ride height the tie rods are parallel to the ground ?
Thus if the car is aligned at the wrong ride height (normally too high because it has been lifted and not allowed to settle) The tie rods will be angled down from rack to hub carrier while it is being aligned.

As the car settles the tie rods will become parallel to the ground again and the horizontal distance between the joint on the rack and the ball joint on the steering arm increases.

This pushes the rear of the wheel further out because the steering arm where the tie rods connect is on the rear of the hub. This causes more toe in not toe out.

mark kibort

Hey, it is surprisingly accurate. when it comes to toe and camber, im very close to what the machine prints out. I have compared my settings the day I did the hunter, and I told the guy my settings. when it was measured with the lasers, it was near right on to my settings. well within specs, but actually much better. near MY specs!!

why do you think its not accurate? a magic marker against the level on the ground is pretty solid. its not the width of the marker its the side that hits the level that is repeatable. lke I said, a spray can would do the same job as a marker.

mark kibort

actually, if the tire is involved, as long as it is the same on both sides it wont matter. my car tires use only the rim surface and you can use spacers to counteract a bulging tire.

picture using the straightedge, straight down from the front of the tire and wheel area and the rear . the marks are about 18" apart. (almost straight down, but slightly angled forward using the straightedge. then the 71" is the distance the front of the tires are apart from each other. the rears , if they are 71.25" means you have .25" of toe in. its very easy to detect a gross problem with toe. when i got hit at sears point last year, I was toed in .75" . just the drive home carved out some tread on the outer 3rd. when I adjusted it on that siide to be 1/16" toed in, it was perfect. I also did this when i changed tie rods. no issues. on the machine, after 7 years of not being on a machine, it as just as I wanted it, and measured it.

FredR

Hi John,

Clearly one of us is a bit of a dunce here and I most certainly would not discount myself!

When the 928 settles the camber increases and the spacial distance between tie rod end connections needs to increase to retain the same toe setting. The tie rod length itelf is fixed thus it pulls on the back side of the wheel and the result is a toe out effect. If one is lucky the car will go to neutral toe but if you have spent time on an alignment rig you will know that if you increase camber ythis de-facto reduces toe quite markedly and thus need to correct.


I'm pretty confident that what I say is correct but stand to be corrected if I am wrong.

Maybe things work differently in down under land like the vortex in your bath tub spinning the other way compared to up here land. !

Best wishes

Fred

Best wishes

jon928se

DOH.

Thanks Fred.

I forgot all about the fact that the upper and lower a arms also should be parallel-ish to the ground at the correct ride height. Because they operate over a shorter radius than the tie rods, they push the wheel further out as the car settles than the tie rod does - hence the net effect is to induce toe out.

My initial example would only be true on something like a Morgan with sliding pillar suspension.

jon928se

I get it - you have the straigthedge vertical so the longitudinal marks on the floor are somewhere between 18 and 25" apart. And your measurement of 1/16" total toe is an at an arbitary but repeatable measuring place on the tyre/rim that you know translates to a toe angle that works for you.

It doesn't answer the question about the Beissbarth machine - where is there figure of Xmm of toe actually measured

I thought you meant this


Also in the diagram I show a more accurate way of measuring as I tried to describe in my earlier post. Total toe is just INVTAN ((71.75-70.25)/65)

Numbers chosen at random.

jeff spahn

Fred- Found as in they are hard to find new and this shop sells them new. Just not in Goodyear or Michelin. Had to go with an off brand and wait for a bit for delivery.

The tires are now stock size from the factory. 225/50/16 in front. 245/45/16 in rear.

Car is never lifted before or during the alignment process. They are the only place in town I could get to understand the requirement of the 928 to remain unlifted. They get the bushing issues and why it won't settle. Last time I went in they spent 2 hours aligning the car.


Thanks

Larry Velk

I started a geometry tutorial some time ago - here are some diagrams as examples of what can go wrong...
Some stuff is missing as reference to the letters is in the text.
As far as using string and such, I've seen Formula 5000 cars aligned this way at Elkhart Lake in the 70's and I've done my cars like that before I made the fancy set ups. The rig we had at the Chevy garage back in the 70's/80's was not as good as a craftsman with a ruler if you ask me.

Bob Rouleau

Jeff,

I claim no expertise on the 928, I'm a 911 guy. So your car may be different. My experience is that wear on the outside edge of a tire is caused by TOE-OUT. A car with enough toe-out to cause premature wear will have unstable steering and tram lining is a virtual sure thing.

Cars with excess toe-in wear the inside edges of the tires (at least on any 911 I've owned) and toe in gives the car more straight line stability. Toe-out tends to reduce under-steer at the expense of straight line stability.

Maybe the 928 behaves differently but I doubt it.

Best,

dr bob

Toe out on the 928 chews the inside ribs. These cars are way less driving-sensitive to toe errors v 911.

mark kibort

this is actually an advantage i have found. as the suspension compresses with huge bump steer, more toe out occurs. it desentitizes steering, and the opposite wheel scrubs alittle under droop. (toes in) But, with a competition suspension or performance shock set up, its not bad at all because droop is not much. i bet my car is at stock ride hight under full droop.

mark kibort

this is certainly not true on all cars I have worked on racing and street cars. toe in is clearly outside edge of the tire, toe out is inside tire wear. like I said, with 1/2" of toe in after a hit, my race tires were skinned clean on the way home from sears. toeed the car back out to 0 and the wear stopped. toe in issues, have worn the inner 1/3rd of the tire, stopped with a slight amount of toe in. I do agree, with toe in, its a little more stable in a straight line and dont know why that is. any unloaded wheel will give the other side a sterring effect to the extent of the toe in or out. (when you hit a bump on one side, etc)