Alignment Spec Recommendations? - Info Inside

[Cinnabar325is]

Okay, I'm just about finished buttoning up a 100% suspension overhaul and upgrade on my '89 325is. Quick aftermarket specs:

Complete GC Coilover kit with SA Konis front and rear 535lbF/750lbR
GC Hybrid Front Camber Plates/GC RSMs
Converted to E30 M3 style adjustable front sway links
M3 FCABS
ST 22/19 sway bars
AKG 85A subframe bushings
AKG 75D RTABs
OEM M Roadster/Coupe diff bushing
AKG rear camber/toe plates with eccentric E39 bolts
Reinforced everything plus front strut housings shortened 1"

At the moment, the only set of wheels for the car are 16x7.5" et20 with 205/45 tires. That will change when I can afford to go with 15x8 or so and wider tires.

So the car serves a dual purpose, nice weather daily driver and weekend autocrosser and hopefully some track days.

Obviously the front camber plates give me some ease of adjustability between the street and auto-x course, but I don't want to have to play with the rear settings for each auto-x. And a confession: thanks to my 2.8 M20 and big cam, I'm relegated to Street Modified anyway, so I'm really not very competitive and for now, I'm okay with that.

I would like some advice on a sporty, but not too aggressive street alignment. And also perhaps, what to do with the front camber plates for an autocross weekend. I understand that this can be rather subjective, but it shouldn't be too hard to recommend a good baseline to get me started.

Thanks!

BTW, I hope this was a good place to post this, I debated a bit.

[nrubenstein]

Up front, align for slight toe in on the street. You'll want -3.5-4 degrees for conepacking. (Likely just slam the camber plates in.)

In the rear, as absolutely much toe in as you can stand. Half an inch total toe would be fine. Realistically, you're probably going to want 1/8-3/16ths.

[Cinnabar325is]

And for caster in the front? The plates are also caster adjustable.

[bmwguy325is]

As much caster as you can get. You will most likely trade camber for caster.
I daily drove on 3 degrees of camber front and rear for a long time. With toe settings similar to the above sugested.

[jlevie]

For autoX caster is far less important than camber. How much to use depends on the tires run, but you probably want to be in the 3-3.5deg front and 2-2.5deg rear. About 1deg less rear camber. Front toe can be set to zero or about 1/16" total toe out. Rear toe should be about 1/16" total toe in.

The toe setting (front and rear) can be left there for street driving, but camber needs to be pulled back for 1.5deg front and 1deg rear to reduce tire wear.

[Cinnabar325is]

I just found this info for the stock specs:

Camber(degrees) -.069 +/-.050 Front
-2.00 +/- .050 Rear

Caster(degrees) 8.75 +/- .050 Front

Toe(inches/degrees) 0.16 +/-0.05 .031 +/- 0.09 Front
0.19 +/- 0.06 0.38 +/- 0.13 Rear

Should I just shoot for the stock front caster? About 9 degrees?

Also, this is saying the rear camber from the factory is a full 2 degrees?! Is that correct?

[Cinnabar325is]

Anymore thoughts? Alignment is tomorrow.

[Cinnabar325is]

For autoX caster is far less important than camber. How much to use depends on the tires run, but you probably want to be in the 3-3.5deg front and 2-2.5deg rear. About 1deg less rear camber. Front toe can be set to zero or about 1/16" total toe out. Rear toe should be about 1/16" total toe in.

The toe setting (front and rear) can be left there for street driving, but camber needs to be pulled back for 1.5deg front and 1deg rear to reduce tire wear.

What is the conversion to translate a toe measurement in inches to degrees? The rack I'm using does not give me the option of inches.

So, for example, when you say a total of 1/16" toe out in the front, I know that would be 1/32" per side. But what is 1/32" translated to degrees?

Thanks.

[SmokeE30]

i simply went for as close to stock m3 specs as i could get obvioulsy having much more camber though because of bing lowered and unable to adjust the rear

[Cinnabar325is]

Ok, I want to bump this up again with some new info and knowledge on my part. I never was able to complete the alignment last time (I'm doing this after hours at a friend's shop with a brand new top of the line Hunter Rack, but we needed a modified wrench to reach the rear camber/toe adjustment and we ran out of time).

We're taking a second shot at this tomorrow night after work. I now have my new auto-x wheels and tires, which may affect thoughts on the alignment. I'm running 15x8" et15 wheels with 225/45 BFG Rivals.

Now keeping in mind that everything is basically adjustable on the car:

Front
Camber: -2.5* as a good street/auto-x compromise?
Toe: tough one, everyone seems to think differently. Nrubenstein says toe-in, jlevie says toe-out
Caster: About 8.8* right now, basically stock. I understand caster is not so important for auto-x.

Rear
Camber: Maybe -3* as a good street/auto-x compromise? These cars are -2* STOCK according to my findings
Toe: 1/16 toe-in per side?

[jlevie]

Zero or slight toe out in front makes the car "want to turn". The disadvantage is that the steering won't be as self correcting and will be more twitchy. Not a problme on the street, but does require more attention from the driver (like all the time).

Rear camber should be 0.5-1 degree less than front, depending on how much front camber you dial in. If you go with 2.5 front, set the rears to 2.

[Cinnabar325is]

Ok, here's what we ended up with after playing for 2 hours. Granted, it isn't exactly what I wanted, but the trouble was thanks to the rear subframe I used (came in the car) that was worn/abused and led me to weld the rear camber/toe plates in not exactly the right locations. I should have sought out another subframe in hindsight. For now, it is what it is.

Front
Camber: -3* each side
Toe: 1/32" out each side (~.07* for a 24" wheel/tire combo)
Caster: 9.5*

Rear
Camber: -3.5* each side
Toe: -.46* Left / +.46* Right

So you can see that the total rear toe is 0*, but the wheels are both pointed to the left. I can only assume this is thanks to the beat trailing arm mounts on the subframe I used. The rear of the car will likely get loose more easily in a right hand turn....

I couldn't get anything less than -3.5* camber in the right rear, so we chose to match it on the left side. I know jlevie said to run 0.5* less camber in the rear than front, but that would have meant -4* up front on the street, which is too extreme. So I went with -3*. I still have a ton of room on the camber plates to gain more negative camber for an auto-x.

Steering wheel is perfectly straight now and I have to say just from the drive home that the car feels 100 times better than before. It may not be ideal but I'm still pleased with the improvement.

[jlevie]

You really need to fix the the rear toe problem. My guess is that the subframe is bent, or more likely the right trailing arm is bent. It won't be bad at AutoX speeds, but the car will be a handful on a track at higher speeds.

[Cinnabar325is]

You really need to fix the the rear toe problem. My guess is that the subframe is bent, or more likely the right trailing arm is bent. It won't be bad at AutoX speeds, but the car will be a handful on a track at higher speeds.

Agreed, it's on my list now.