Caster Settings -- Post your results!

[tsunari]

Ok . . . I know the Caster on the eclipses isn't adjustable . . . but how are we to know if it's out of spec? And if it IS out of spec . . . what needs to be replaced?!?

FSM says that the Caster should be [ 3.2 deg <-> 6.2 deg]

Personally, mine is set at [3.2deg -- Left] [5.7 deg -- Right]

Now I've heard of having the caster offset to compensate for the crowned roads here in the US, but a difference of 2.5 degrees?? I'm wondering if perhaps I might have something bent.

So . . . PLEASE- post your Caster settings so I can compare

I realise I'm within the specs, but I just have a sneaky suspicion that something might be worn/broken

Thanks!

 

[jtmcinder]

5.7 is a tad high for the right. Most 97+ DSMs have about 3 degrees on the left and 4.5 degrees on the right. (If you have an earlier 2G with the left compression-arm bushing right-side up, then you should have about 4.5 on both sides. It's a pain to flip the bushing to being right-side up on both sides, but I've done it to my 97.)

How much faith do you have in the person who was running the alignment machine? If the answer is "a lot," then I'd be looking very carefully at your right front suspension.

- Jtoby

 

[tsunari]

so the ~3.2 degrees on the left side sounds about right then . . .?

As far as 'faith' is concerned, I guess I'd have to say 'a lot'

I've had a few alignments since I got the car roughly a year ago. Got a lifetime alignment plan from Firestone when I got my camber kits. The readings back then were:

*Installed Energy Suspension Bushings -- no camber kit*
3.3 / 5.2 Before Alignment
3.3 / 5.2 After Alignment

*Installed Camber Kit*
2.9 / 4.8 Before
3.6 / 5.0 After

*Todays Alignment*
3.2 / 5.7 Before
3.2 / 5.7 After

So looks like maybe the problem has been there ever since I got the car? Curbed perhaps?

Also . . . would you be able to describe the compression-arm bushing, or post a pic of what it looks like? Once I get this problem fixed, I'd like to try and flip mine if at all possible . . .

 

[jtmcinder]

It's really quite difficult to get exactly-repeated alignment values, even on a good machine (e.g., Beam + Visualiner), because it's so hard to get the darned things on the wheels the same way. But because the right-side values are consistently high, I'd take a look at the compression arm on the this side, to see if it seems OK, as well as the upper arm pivots, to make sure that they are all straight.

As to flipping the driver's side bushing, you remove the compression arm from the car (two bolts and a ball-joint) and press out the bushing and press it back in upside down (which will now make it match the right side). Be sure to mark it before you press it out so that you can get it in exactly reversed ... since these are vulcanized bushings, they act as a spring, so you want them to be the same on both sides. As soon as you're looking at the thing, it'll be clear why this works to add some left caster. The mounting bracket is offset. Starting in late 96 they installed it to take out caster on the driver's side, instead of add caster (as the other one does on the right). Flipping it equalized my caster at 4.6 degrees. Since I'm not big on NASCAR and turn right as often as I turn left, the extra caster on the left was useful.

- Jtoby

 

[TSiAWD666]

Prior to my recent accident damaging my driver's side front suspsension, I had 4.6 on each side. You can get some caster adjustment out of the camber kits on the front that replace the anchors for the upper a-arm, like the ingall's kits. With this my alignment guy got the caster equal.

After my accident, he could only get 3.9 and 4.6. Do I notice a difference? <shrug>

 

[jtmcinder]

If your alignment guy got a degree and a half of caster by moving the upper arm in or out (using either replacement pivots or eccentric bushings in the same), then he is a genius. Marry him at once.

After the honeymoon, crawl under your car and look at the bushings where the compression arms mount to the chassis. See if they are installed the same way or if they are mirrors of each other. My guess is that they are mirrors, since you have a 99, and that you never had matching caster. Another item to check if the set back that should be on the alignment print-out. See if it is zero. My guess is that it isn't.

As to whether you notice a difference ... I have no idea, but you should. You car doesn't turn left better than it turns right just because of your weight in the left front seat. In fact, it will still turn left better if you have a passenger. (That was my first hint that the mis-matching caster was an issue.)

- Jtoby

 

[TSiAWD666]

Pay attention. I didn't quote how much he gained in caster by fiddling with the eccentric bushings... however, since you're curious, it was approximately .8 degrees. I have the alignement printouts from before and after. What prompted his discovery was that after I'd received the car I felt it was driving a bit oddly... so I brought it back to the shop where he played some more since that was the only measurement uneven.

If we're going to assume the alignement sheet specs afterwards were correct, then they were accurate. WTF, did you think I guesstimated my alignement settings??

I bow to your ability to notice .5 degrees difference in your caster. Of course you're not driving in my car, on my suspension, on my tires... but whatever, be the know-it-all. Maybe once I get back to Virginia International Raceway I'll notice something strange, but haven't so far in my commute to and from work.

 

[jtmcinder]

Ah, so it's eccentric bushings; now it makes sense.

If you are silly enough to use eccentric bushings to adjust caster, then, of course the car will drive funny.

Eccentric bushings change the effective length of the upper arms. If you set them differently in order to change caster - something for which they were not designed to do - then you have changed the lengths of the two upper arms by different amounts. So there is no longer a single axis of rotation for the upper arm; there is one axis for one arm and a different axis for the other arm. Problem is, the two arms are parts of a piece that doesn't flex. So you've created a nasty binding in the upper half of the suspension. So, of course, it drives funny.

Let me back up and explain the assumption that I made that caused you to think that I wasn't paying attention.

You car started with more caster on the right than the left. You reported that after installing a camber kit, you had matching caster. I made the assumption - for which I apologize - that no-one would be silly enough to try to fix caster using a camber kit. I will try to avoid this mistake in the future and I will be sure not to bury the fact that doing this would be silly in a humorous paragraph.

Thanks.

- Jtoby

 

[TSiAWD666]

hold on...

Ugh, last time jtoby. Alignement was done. Drove car and felt funny, drifted, just didn't feel perfect. Returned car immediately. Tech noticed castor difference was only difference in the across the sides, but didn't think he could adjust it. Tech played with alignment finding that with the already in-place camber kit he could adjust things so as to address the castor and keep everything else the same, and in his test drives he says he noticed the improvement. Alignment sheet confirmed that castor was now equal with no modification to the other settings. My driving confirmed that the car drove well in my mind... no odd drifting, no odd turning, "felt" right.

As for this being a silly or detrimental solution... maybe it is, and maybe it isn't. I understand the geometry involved, but am willing to see how this left-field solution works. So far no problems and my recent alignment confirms no abnormal wear on the eccentric bushings. While your basic understanding of the suspension geometry seems to absolutely not allow this sort of fudge, perhaps there are tolerances at play here that will allow this sort of solution. It's ok, we all bench-align (or race) from time to time.

In short, I'm saying some adjustment was made to castor using my eccentric bushing camber kits succesfully. Jtoby states this is a bad idea for so many reasons. I say in my real-world experience it's working... so far. I won't be surprised if I notice pre-mature failure somewhere, and have been watching it since the changes of course, hehe.

 

[jtmcinder]

Given the new info, I think that it's more likely that the eccentrics were installed unevenly before you took the car in. The reason that it pulled was that one wheel was binding. The messing around with the eccentrics may have freed things up enough to eliminate the pull.

The problem with this is that it leaves unanswered why your caster matches, when 97- DSMs all seem to have mismatching caster from the factory. I'd seriously consider looking at the compression-arm bushings to see if, for some reason, yours are both installed right-side-up.

As to the idea that there's slop in our suspensions that would allow for some interesting and non-suggested tricks to getting the alignment values to be the same ... I'm in 100% agreement. In fact, because of this I'm much less interested in the raw values (on my own car) and more interested in how it drives. I never paid any attention to the mismatching caster until it because clear that the car turned left better than it turned right. Then, when I went looking for why this might be true, I came to the caster issue.

Put another way, if you like the handling and the tires aren't being ripped on the street, who cares what Visualiner prints out, right?

- Jtoby

 

[TSiAWD666]

I should've realized this possibility... I obviously was under the assumption that the bushings were adjusted evently prior to my complaint, but perhaps not.

You state that the castor is uneven on the cars you've seen. Are these measurements taken with or without weight in the driver's seat? My alignment tech pointed out a few times on my previous cars that the castor on them changed noticeably from uneven to even/matching once he got in the car. This logically makes sense, and of course I chastised him repeatedly for his stunning grasp of the obvious, hehe, but of course make a point to remind anyone doing my alignment to do so with weight since it can be easily forgotten.

Ditto... the only time I really cared was when I noticed a weird driving feel.

Well put.

 

[jtmcinder]

The bump-caster curves for a 2G are almost flat. (I have a complete set of graphs for our cars.) There is no way that a non-broken car can have caster change by more than a few tenths of a degree due to the weight of the driver. Camber, sure; but not caster.

No, we have a mystery on our hands. Seriously, I gots to know (as the perp in Dirty Harry said) ... are your compression arms bushings both in there right side up? Yours would be the first 97- DSM that I've ever heard of on which this was true.

- Jtoby

 

[TSiAWD666]

Certainly can't write-off something being "broken" as loose as that term is. All my cars have been bought used.

Next time I take things apart I'll drop you a line from the dsmtuning list.

 

[tsunari]

This is all very interesting . . . and brings up another question . . .

I have the ingalls camber kits on front and rear. What are the effects of getting an alignment done and only one of the adjustment points on each tire being moved (as opposed to both of them being moved equally) -- 2 adjustment points on each tire- right?

Most likely from a lazy technician . . . Would this have thrown my caster off? or (since the #'s are so high) is more likely something bent?

 

[jtmcinder]

Yes, when the camber adjusters work on the pivots, you must adjust the two to be equal or (1) caster will be affected and (2) the suspension might bind, because of the non-parallel axes.

- Jtoby

 

[tsunari]

*grrrrrr* Guess it's BACK to the shop again then . . . lazy people. . . they see two adjusters for one tire and think- hey! I only need to use one of these!

I'll keep this thread updated with whatever I find out is wrong. Thanks for all of the info