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Discussion Starter #1
For the 91-96 Bbody, has anyone tried different alignment settings other than stock? I'm thinking about going with 1/4 degree negative camber while keeping the caster closer to the negative side of the stock setting. I'll also keep zero toe since you lose straight line stablity if you dial in some toe-in. Not sure what the stock setting is but if I had to guess, it would be zero toe, zero camber with maybe a few degrees of positive caster.

If you've tried something other than stock alignment, what specs did you dial-in your suspension alignment and how did your car behave?
 
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Discussion Starter #2
Toe-in will give you increased straight line stability. So dial some in. Also, something to note about how caster and camber affect tracking - the more negative camber you have, and the less caster you have, the more the car will tramline in the dual ruts often found on truck-traversed highways. Toe-in will also help reduce tramline.

Dial in only as much negative camber as you think you need from a handling perspective (put another way, excessive inside tire wear is NOT the only downside to negative camber). Caster will use the weight of the car to center the wheels while rolling forward, and impart a feeling of solidity to the steering. You can also dial in some cross-caster to get rid of a steering pull.

So my recommendation for alignment specs comes only with an answer to "What do you do with the car, and how much do you value tire life?"
 
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Discussion Starter #4
I am running about 4.00 left caster; 4.25 right caster; and 3/32" toe in. I was just surprised last week to find that going from 1/16" toe to 3/32" had a pretty noticeable influence on my car, since 3/32" is a little more than ordinarily recommended. But if it costs me a little extra wear, I don't care at this point. Also, I am thinking about biasing the caster to the right (lowering the right number or raising the left, which will cause the car to pull more towards the right) because it turns out that the freeways in the Los Angeles area are actually crowned in toward the center. Most normal alignment specs call for a higher caster number on the right, which causes the car to pull left, to make up for the "crown" designed into roads that allows water to drain off to the side. But for some reason they are now making the freeways lower in the center here in L.A., and I find the car tending to head naturally towards the center rail. So I'm thinking about adjusting a little to compensate.
 
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Discussion Starter #5
Originally posted by SSSSnyder:
I am running about 4.00 left caster; 4.25 right caster; and 3/32" toe in. ... Also, I am thinking about biasing the caster to the right (lowering the right number or raising the left, which will cause the car to pull more towards the right) ...
Alignment shops love to raise that right caster value but my car needs some pretty noticable compensation in the passing lane as a result. And I drive in the passing lane a lot of the time (due to my....passing other cars). I think the biggest thing to remember is, give the car what it wants - try out an alignment setup, then go back and make adjustments to how the car is setup (not to how it was supposed to be setup). On my car, that will probably end up being more caster on the left, but so what, if it tracks how I want. And I agree on the toe thing - it helps your straight line stability, right? I'll have some added next time around...what's your camber set at?
 
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Discussion Starter #6
Pretty straight up - less than 1/4 degree each side. I've had no noticable wear on the insides and I'm also thinking about adding some more camber, even if it costs me a little wear. Frankly, I have been thinking that the stock BFG's suck (original style on the back and KDWS on the front), so I'm figuring that if I can gain some handling improvements and it wears the fronts out a little faster at the same time, all the better. Then I can look around for something else in tires.
 
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Discussion Starter #7
I thought I'd bring this post back to life. A few months ago I got a wild hair and on my break at work, I added shims to give me more pos caster and more neg camber (It was set to IGBA specs before I messed with it). I didn't have my alignment tools but I just moved the shims to see how the ride would be. I noticed right away on my way home, I could go about 3 mph faster on my two favorite turns (about 35 mph turns). It still tracked straight as an arrow and generally feels good. I definitely like it better. This was during the summer and I never bothered to check what my #s were until tonight. Found out I now have 4.5* caster both sides, -1.6* camber left, -1.4* camber right. I love it. I'm curious to see how fast the tires will wear with that camber. I don't care, I'm leaving it! :D BTW suspension is stock other than what's in my sig.
 
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Discussion Starter #8
Originally posted by Kevin Moore:
...excessive inside tire wear is NOT the only downside to negative camber
So what are the other downsides?
 
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Discussion Starter #9
Other downside to excessive negative camber is longer braking distance

With reasonable toe (i.e. 1/16" toe IN.....and yes, your toe did change when you changed camber/caster) you should do OK on tire life (reduced life, but not horrendous) with that much neg camber. But if the car is toe out right now, your tires will be short for this world. It'll be a FUN tire life, but a short one :D
 
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Discussion Starter #11
Just for the sake of argument I'm running about 1/4* camber both sides and 4* caster. That's about all I can caster with the lowered springs without getting into some funky caster curving. As it is, jounce steer is pretty fun to say the least. The future calls for 1) thoroughly reading Milliken's Race Car Dynamics, 2) seeing if a taller spindle is in order, and 3) getting some rear springs that work better.

Ed, you had mentioned taller spindles in the tubular A-arm thread. Are you sure they need to be taller? I though we were pretty cool on that area. Aren't our camber curves pretty optimized from stock? I thought that was our one good parameter
 
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Discussion Starter #12
Curtis : while it is definitely better than the "shorter spindle" cars (i.e. G-body), there is still room for improvement with an even taller spindle and re-configured upper A-arm.

And one of my "suspension secrets" I'll let you in on is that my rear springs are still stock SS springs ;) . About the only stock parts left.....
 
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Discussion Starter #13
Along with what Ed mentioned, a potential downside to extra camber is poor straight line stability, and it's generally a bad thing to do something that would make our cars worse in that department. That said, if you are happy with the tracking and "on-center feel" of your steering, good for you! I personally think that lots of caster is the way to go. Speaking of which, I was reading one of the many recent articles about the C6 and I learned that they're now using 8 degrees of caster!!!

Also, I think some of you (Curtis, Ed) were hinting at something like this:

http://www.pro-motorsports.com/store/product.asp?id=66

Rob, the reason all that negative camber likely feels good is because of our back-asswards dual A-arm camber curve. If you had something like this in your car, you could get away with a LOT less negative camber. In fact, if our negative camber actually increased with roll, we would probably need less than that giant HA rear bar on our cars for "neutral" handling, because the front end would bite so much better.
 
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Discussion Starter #14
In fact, if our negative camber actually increased with roll, we would probably need less than that giant HA rear bar on our cars for "neutral" handling, because the front end would bite so much better.
Yep, one of the side benefits when I went to -1 deg of negative camber (along with Torsen T2R, better shocks, better control arms, etc) is that I do NOT need the big rear bar any more. My car is fairly neutral right now, and I am running only a 30mm rear bar!

I'm seriously thinking about trying those spindle spacers that Bill pointed out, even though I won't have the "ideal" upper arms for them. Should let me back off on the camber some in the static state while still having the "in cornering" camber I want.

BTW Kevin, I know some of the Silvias in Japan (think of it as an old Nissan 240Z on steroids) run around 7 deg of caster. And I know some of the GM FWD stuff runs over 5 deg of caster.
 
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Discussion Starter #16
I was thinking about it kinematically and I think I have a rough idea how it could work, since the upper control arms' sole purpose is to locate the spindle during suspension travel (not load bearing).

Picture the front suspension in full compression. Upper A arm is past parallel with the ground and is pointing upwards, some angle. This kit says it lengthens the spindle by 2 inches, on the top. Now picture temporarily disconnecting the upper BJ from the spindle and lifting it up enough to stick a 2 inch spacer in there. In order to line up the spindle hole for the stud, the spindle will have to tilt inwards, which is less positive camber/more negative camber. So that means at full compression we'll have some amount more negative camber than before (actually, I think we have positive camber at full compression, so having any negative camber is an obvious improvement).

Next, picture the other extreme, full extension. Full extension is defined by when the upper A arm contacts the frame via that rubber stop (the shocks shouldn't limit travel). Our suspension normally has more negative camber at this point in suspension travel. Now disconnect the upper BJ again (from stock) and insert a 2 inch extension. The LCA is going to have to come down some in this case (since the UCA is already on the frame). This means that the bottom of the spindle is coming in closer to the car, which translates to positive camber.

I think this is how it works. Someone correct me if I am wrong. I can draw what I tried to explain if necessary...
 
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Discussion Starter #17
The only bad thing I can think of is that with the taller spindles, the upper control arm stop probably won't come into play and thus the shocks will limit travel...if you're not careful when lifting the car up on jackstands then you could cause shock damage...and if you're interested in your car enough to try this mod, then more than likely you are the type of person who has it jacked up and is crawling around underneath it all the time. I also wonder how it would be for wheel clearance. I've read that some people have had problems with specific wheels and the lower balljoint with drop spindles, because they effectively move the lower balljoint further from the center of the wheel...this mod would move the upper balljoint further from the center and I wonder if it would clear stock Impala SS wheels. I think it's safe to say that if you put on 9C1 rims for snows in the winter like I do, then you'd probably need to remove the spindle extensions...but I haven't measured the clearance between the upper balljoint and the wheel as is with the stock configuration.

I think that a different way to say exactly what Kevin is saying, is this. Think of a line parallel to the ground coming out the side of the car from the upper control arm bushings with a vertical line perpendicular to it through the upper balljoint. If you move the upper balljoint up in relation to the center of the spindle, at full suspension compression, the imaginary horizontal line is shorter than it was before, so the spindle is pulled in closer to the car. Since the lower balljoint remains where GM put it, the spindle has to tilt inwards...negative camber. Now at full suspension extension, that imaginary line is longer, so following the same logic, positive camber. Even if there wasn't a complete reversal of negative and positive camber, less positive camber at full compression and less negative camber at full extension would still be beneficial to the handling characteristics of the car.
 
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Discussion Starter #18
Mike : taller bumpstops are available for the upper arms to limit extension and thus prevent shock damage. And I agree, it'd be something to watch out for.

As for wheel clearance, I'd be surprised if this would clear (spindles with extensions) on anything less than 17" wheels.
 
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Discussion Starter #19
Considering the clearance with a 15" wheel is basically just enough, it makes sense that adding 2" to the spindle would raise that minimum wheel diameter to 17".
 
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Discussion Starter #20
Originally posted by Kevin Moore:
Considering the clearance with a 15" wheel is basically just enough, it makes sense that adding 2" to the spindle would raise that minimum wheel diameter to 17".
And since that 17" wheel is only adding 1" (in theory) of radius versus an extra 2 inches of radius needed for these spacers.....even a 17" wheel may not be enough!

In other words, it'd be BIG wheels time (not good from a handling standpoint since most "dubs" are really freakin' heavy) OR time to get taller springs with drop spindles, then pray you can align it all afterwards :D
 
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