Alignment Question

[DonDavis]

I just had new rears put on the car, Bridgestone RE70s I think they were and the car's alignment was satisfactory and fairly non-agressive in that the front tires, after about 15k are still wearing evenly and not in need of replacement.

I asked the Honda shop (different one, as I'm not in Germany) to do a full alignment and to not align to factory specs as nearly all of my driving is straight line at autobahn speeds.

Unfortunately, the car's front end feels squirrely at anything above 80-90mph. The slightest movement of the steering wheel seems amplified in the car's reaction so that it almost wants to "jump" in the direction steered and even when holding it steady and straight, there seems to be some slight wandering... Before it felt like it was glued to the ground.

The printout of the computerized alignment, when I picked up the car, stated that specs for the front were and are as follows:

Toe was -0 degrees 15' and is now -0 degrees 10'.
Camber was 0 degrees 20' and is now 0 degrees.
Caster did not change.

From my limited understanding, they've reduced the negative toe-in and therefore the car should be LESS jumpy at speed. Also, to what amount will the rear alignment affect this?
Rear specs are:

Toe was -0 degrees 20' and is now +0 degrees 20'.
Camber was -0 degrees 30' and is now -1 degrees 20'.

I wish I knew the measurements in MM, but I don't.

My aim is to have the car as stable as possible at high speeds and to maximize tire wear. I don't track it, suspension is stock height with Koni yellows set to soft, and wheels are stock. The car is a '91.

Ideas/suggestions or recommendations as to what I should ask for to get the feeling back? Ken, can you weigh in on this one?

Don in Heidelberg

 

[Gerard van Santen]

Strange. The way you discribe the behavior of your car, you must have a very aggressive alignment. But the figures tell different story.

If I didn't know your alignment figures. I would say you have much more toe out than 3mm. 3mm is about 0.40 degrees. But you are way below that.

Perhaps the figures aren't right

 

[DonDavis]

alignment

Gerard, I guess they could be wrong, yes, but the shop is pretty good and has always done good work for me before.

Of course, I wasn't there to watch this, so who knows?

Don

 

[Gerard van Santen]

Re: alignment

Gerard, I guess they could be wrong, yes, but the shop is pretty good and has always done good work for me before.

Of course, I wasn't there to watch this, so who knows?

Don

For an alignment I always stick to my car to watch the technician work on it. To align a NSX properly it takes time, a good alignment system and skills.

 

[Barn Man]

Hey all,
Normally negative toe will cause the car to "wander" while driving on the interstate. The front wheels are pointed to the left and right slightly, and catch uneven patches of the road or crowned parts of the road and pull the front end one way or the other.
If you look at your toe specs from side to side in the front, you'll want zero toe on both sides to prevent any wandering. It's very important that both sides look exactly the same. If one side has 0 toe, and the other has negative toe, then you have negative toe on both sides. And more than likely your steering wheel will be off to one side. No matter what one side says, the other should match it. Negative toe will give you better turn in. Possitive toe on the front will give you a lesser amount of turn in, but it will not wander as bad until you get over 1/64 or so.
As far as camber goes, you have to get it as close to a low negative number as possible. If you find the side with the least adjustabililty, you can get the other side to match it and you'll have the least amount of negative camber possible. And again, you want both sides to be the same. If you have more than .50 degrees camber difference from side to side in the front, you'll more than likely have a drift or pull to one side. But I digress.
Keep it as close to 0 as possible on the toe and camber settings. Caster will not cause tire wear, but it can cause a drift or pull if the split (difference) between the front tires is excessive. The more caster you have, the better your car will stick in the turns, (to a certain extent), at the same time, too much caster isn't good. The NSX has a fair amount of caster in it from the factory. Caster will casue the tires to tilt on turns. For example, if you turn left, the caster in the front end will cause the left front tire to have possitive camber, and the right front tire to have negative camber. This helps the car make it around the turns a bit faster than a car with less caster.
And last but not least. Tires that have been worn down will cause the car to do strange things will a new alignment. The tires are coned (more wear on the inside than the outside) and thus act like a cone when they roll. They want to automatically turn. If you take a coffee cup, and spin it on it's side on a table, it will go around in circles. This is the best way I know to explain it. A tire will do the same thing. The wider the tire, the more noticable it will be. So if one of your tires on the front wheels have worn more on the inside than the other, it may cause it to pull / drift or a wander.

So, with all this being said, the only sure way to know if your alignment is a good one is with new tires and a good alignment. Only then will you know what to expect from a good alignment.
And always get a print out of your alignment if possible.
Make sure your toe is exactly the same front and rear from side to side.
Make sure your camber is no more than .05 different from side to side front and rear.
Make sure your caster is at least within .2 of each other. Caster will not cause tire wear, but will cause a pull or drift.
If you have all of these things, your tires may be causing the issue. Some cars can have a difference of 1 degree of caster and you'll never know it. But if you want your car to have balanced steering on the track, make sure your caster is as close as possible. I've spent 20 minutes just getting the caster to look good from side to side. It's by far the hardest part of an alignment. Also, after the caster is adjusted, (some cars don't have a caster adjustment), the person doing the alignment should do another caster sweep to check the actual change he made. I promise, after adjusting the caster, it will be different after another caster sweep. So you have to adjust, and sweep. Adjust, and sweep. You'll get the hang of how much to adjust the caster and how much it will actually change the caster after a few alignments.
I hope this was of some help.
Barn Man....

 

[Jeff A]

Barn Man -

As long as we're talking alignment here - I have a question for you. I'm about to install an R-type suspension package (dampers and springs). It's a simple bolt-on procedure, where none of the other suspension components are loosened. Do I need to have it aligned afterward? My bet is Yes, but wanted to ask someone who really knew.

Thanks much!

Jeff

 

[Barn Man]

You are correct! Anytime you change the ride height of a car, you need to do an alignment. The toe will go toward / further negative when the car is lowered. It doesn't take much at all to make a big difference in the toe.
Barn