Question about alignment.
 

For a couple of years now my '84 Carrera car has been...darty and pointy... (for lack of a better way to describe it) to the point of being a little unnerving at speed when the road gets bumpy.

It has very, very quick reflexes on turn in and will take a set beautifully, and hold it steadily. While in the turn, the car feels really good. However, during the transition phase from a turn in one direction to a turn in the other direction while at speed, the car seems to exhibit a little tendency to want to over-do the initial turn in, which I have to correct a little before the car finally settles down and takes its set. It's not a confidence inspiring feeling. It almost feels as if it would want to snap around if I weren't careful with it. Again, this is only during the transition from turn to turn (or during quick lane changes at speed) and is most noticeable at high speed (like 70 mph+. At slow speeds, I don't really feel any of these tendencies. It feels good from side to side).

It feels great while established in the turn, just not so good in transition at high speed. Also, the car really wants to move around a bit while at speed on anything other than a smooth road and if I apply brakes at speed it becomes a handful again. Also, I have the factory tail and front spoiler. The tires are fairly new S03's rear and older S03's front. They're all in good shape.

I hope I'm making sense here. The suspension was (mostly) rebuilt back in the Spring of 2005 with new bushings, ball joints, 22/28 mm t-bars, Bilstein Sports, turbo tie rods, Rennline strut brace, good wheel bearings, bump-steer kit, etc. (the trailing arm bushings were not replaced due to the difficult access to the mounting bolts on the torsion bar tube, but they looked OK from what I could see). The steering system is tight as a drum with no slop whatsoever.

So, I'm guessing it might be my alignment settings. Could the front or rear toe be set a little too aggressively? Would toe adjustments make a difference in stability for this car?

Here are my corner balance numbers:
LF - 501 RF - 504
LR - 814 RR - 814

Alignment settings:
Camber:
LF -1 3/8 degrees
RF -1 3/8 degrees
LR -1 1/4 degrees
RR -1 1/4 degrees

Toe:
Front - +15'
Rear - +20'

Caster is all the way back, I believe.

Ideas?

I'm sure they checked it during your corner balance but is there any preload in your sway bars? From what I understand they are disconnected during the corner balance.

I can't imagine the shop you took it to wouldn't have mentioned it.

Scott,
I am not sure if you have the problem I had before (BMW, a daily car) when I had it aligned at a race shop years ago. This guy was famous among those racer guys. After he's done, I had wonderful oversteer, which made me smile at any corner. However, at high speed, it can get scarry, especially uneven highway surface. It jerks alot left and right. The tires were worn straight/evenly and nice but very quick. I brought it back there several times within 2 months. By 2 months, my 2 rear tires were bald and there are lot of "black mud" on my rear bumper corners every day. By that time, I knew that he had my rear wheels toe-in too much. I brought the car to another alignment shop, which is a normal shop with a hunter machine (not specify for race). With couple adjustments, the car was back to normal and the next set of tires lasted over 2 years.
I am not sure if you are having the same problem but maybe you might want to look into your alignment.

Try less toe-in ( I guess "+" indicates toe-in, not toe-out ,.... right?) in the rear, and maybe check "thrust angle"... how "square" the the car is against all 4 corners. Make sure the chart with + settings truly indicate toe-in. If toe-out ... then that could be your problem right there.

Another hint ..... I also find spooky handling whenever new tires are put on...either in pairs or all 4. Usually takes me 700 miles ( ! ) for that squirrelly-ness to disappear. Try old tires in place of the new ones ( borrow rims/tires as a test ?) that are now on the rear.

Otherwise your settings would not raise a red flag of the symptoms you're seeing.

IMHO....

- Wil

Thanks guys. Wil, I assume that the rear toe settings are for toe-in. Is it even possible to get 20' of rear toe-out with these cars?

I'm not sure what the total allowable range of adjustment is for our cars, Scott.

But..if thrust angle is "off", then one side may truly toe-out ( relative to direction of motion), and the other side would be severely toe'd-in...even if spec was for toe-in for each side. Like those old Chevy Nova's that "crabbed" and looked like they were always turning...but actually going straight ...right in front of you along the highway as you followed behind.

You're probably too young ... LOL !

- Wil

I found a big difference when I replaced the tires, 10-15 year old Yokies with newer more all season compounding (same mfg/sizes)....found a bit of a tail wag but nothing too radical. Bought my tires at Discount and go there about 4k miles, have them demount the tires and swap left for right same as when I ran SCCA....

Prior to this I had had complete turbo tie rod assys installed along with the bump steer kit. The alignment following this found a LR broken sway bar bracket and a possible minor bend (according to the alignment tech) in the RR trailing arm (still on the car).

I've just done new shocks so hopefully that isnt too big a deal for 1300 miles.

Unfortunately, I'm in the process of moving to a small town in western Colorado on Monday...so am going to have to live with what I have until I can find the time and the money to drive over to Denver or some place where there is a decent alignment shop/dealer...hopefully someone that can do Pcar alignment and corner balancing...

How was it prior to these mods?

Joe

I've been having a discussion with Tyson Schmidt via PM and he seems to have nailed it. It all started when I replaced my worn out rear S03's with new S03's. He said it sounds like the back is steering the front a bit due to the softer rubber on the new tires not harmonizing well with the old, harder, worn rubber on the fronts. He said that's why he always tells people to replace all four tires at once, even if the fronts are still showing useable tread left. He said old and new tires, even if they are the same brand and model, don't mix well on 911's.

The car handled perfectly before I changed out the rears. I simply forgot that it had becuse it was a while ago.

+ toe out in the rear is a recipe for disaster, though it appears you just have a tiny bit of static rear toe out.... whos knows whats happens with the rear toe when the rear is loaded from braking or acceleration.

Scott,
I am with Tim and other about rear toe. The explanation makes sense but does our car really that sensitive, maybe I am too naive. If you decide to throw them out, I'll take them and will enjoy them :)
Another thought, might not be related at all. Once I flipped the front tires (inside edge to out side edge) because the inside edge worn more do to too much negative camber. THe result was expreme tramlinning.

RE: +20' toe: Yea, I noticed that too. I wonder if my alignment guy actually meant -20'. That would make much more sense. I don't even know if you can get +20' toe out in back.

time to spend 1/2 hour to set up string method at home. Just a reminder, tomorrow is saturday if you forget :)

Yea. Time to learn the method, I guess.

It'll have to wait until next week though. I work over the weekend.

sure you can.. you can F$#% up the rear alignment to the nTH degree...have a touch of toe in dialed in, or better yet have it set to spec, which I dont remember off the top of my head

On edit: set a touch of toe in, and then adjust camber.

I'd definitely get clarification on the toe. If it is 15 minutes and 20 minutes toe out, then there is your problem.

Thanks guys. They offered to throw it up on the laser alignment rack and check the settings.

Just look down the side of the car and line up the leading and trailing edge of the rear tire with one eye shut - with a bit of comparing side to side front to back you will see quite quickly if the wheel is toed in or out.

Although Tyson's suggestion to replace all 4 tires is sound...do recall I said this within 3 answers of starting this post--->

"Another hint ..... I also find spooky handling whenever new tires are put on...either in pairs or all 4. Usually takes me 700 miles ( ! ) for that squirrelly-ness to disappear. Try old tires in place of the new ones ( borrow rims/tires as a test ?) that are now on the rear."

- Wil

Yes you did. However, the rear tires have well over 700 miles on them now. Probably more like 2000-ish. The spooky handling is still there so I initially discounted the rear tires as a cause because it never dawned on me that mixing old and new tires could cause a problem like this, considering that they are the same type. I was mistaken.

Thanks for all of the info guys. I really appreciate your input.

Thanks! :)

i'm no expert but if you can create equal width, front and rear, w/strings your figures will be correct.

(This is a copy from another one of my threads dealing with the same issue. I've included this to give this thread some continuity)

Well, well. So, after bringing the car to the shop I use, Hergesheimer, here's the deal - the back end is indeed steering the front around. However, the reason isn't due to my alignment settings after all, it's actually being caused by my very worn and sagging trailing arm bushings.

The car was driven by Jim this morning and he confirmed that the car is squirrelly indeed. He said "Whoo yea, if you're not careful with that car the back end feels like it really wants to snap around!" Spooky for sure. Uh huh. I'm not dreaming then (he knows what old 911's are supposed to feel like. He drives a '77 Targa as his daily driver, and his is not spooky like mine).

He put it up on the machine, checked the settings and all was good. He took a good look at the trailing arm (sometimes called the banana arm) bushings and through-bolt alignment and found the bushes to be a little worn. When I came out there to see it, he put it back on the alignment rack and showed me the problem.

While we were under there he took a marker pen and outlined the spring plate's positions relative to the trailing arms and marked all of the adjustment bolts so I can at least get the alignment settings close to where they are now.

I'll have to wait for a month or two before I tackle this job because my wife needs a breather from me spending large sums of cash on this car - I just plunked down $4,000 for a bunch of other work that needed to be done so she's a little shell-shocked right now. Once I start on it, I'll go with the monoballs back there. Might as well do it right. I'll do the work myself and bring it back to them to have it re-aligned when I'm done.

Hey, now at least I know what the problem is (maybe).

use a press.

I think you can get away on the (relative) cheap. Those monoballs are about $300 from Elephant. You might need to replace some hardware along the way. I did not need a press. I was able to use my bench mounted vice. In fact, when I put the new monoballs in, the interference fit was not tight enough so I used a bearing retainer product made by loctite.

While I had the trailing arms off, I check the emergency brake shoes and cleaned years of $hit from the arms. I didn't polish them, but did use 90 degree die grider with an Aluminum cleaning wheel (often used to clean sealing surfaces like water pumps, cylinder heads, etc) to clean them up. Mine now have a machine swirl marks as if you used 150 grit sand paper.

Good luck! Glad you found the problem.

Doug

Doug

I thought removal of the old was a few slaps of a baby sledge and maybe some torch. It eventually came out that way but it was more work than i figured.

Thanks guys. Yea, I'm looking forward to having a car with a back end that doesn't shift around like this one does.

I'll tackle this in a month or so.

Come on it is fun having the back end sliding all over the place but my excuse is tires but that should be remedied real soon.

Ha Ha, Chris! Your car is the same year as mine. Are you sure your trailing arm bushings aren't worn like mine? ;)

I can't wait to see your wheels on the car, Chris.

I just quickly read through this thread.

Just want to point out that + toe is "toe-in" not "toe-out", so your alignment settings are fine.

Yea. I slowly figured that out. I'm learning. ;)