ride hieght WHILE aligning??

[AlphaE]

If you have ever seen or done a alignment on a BMW they always have you load the car w weight. In our (e30) case its 150lb in each of the seats and like 46lb in the trunk. This seem goofy to anyone else? why align for max load, and least often acheived? why not align according to most commonly drivin load? ( me, the misses and maybe a 3rd in the back seat). I swapped i a 5spd but remember that the auto would squat when you put it in gear.

Can someone with a auto and stock suspension measure the regular ride height and then the ride height when you put it in gear ( when it squats down) please?

Are they trying to figure in that squat when i align it??

any idea????

[jlevie]

The suspension geometry changes with ride height. Since the car is always driven with some load in it BMW chose to specify the alignment numbers for a specific ride height achieved by ballasting the car. On later BMW models where both front and rear are adjustable this is more important than it is on an E30 where only front toe is adjustable.

[AlphaE]

i fully understand how height effects camber and even toe depending on suspension/bushing design. I will be doin my own rear camber/toe kit, (picked up camber bolts this weekend). This little car is eatin tires w/o any spring yet. My toe and camber are bad in the back when i put it on our alignment rack.
So why did they decide on so much weight in the little car? It'll never ride at the height that its aligned at. See what im sayin? Id like to know the squat height in drive so i can add that into the vehicle height equation (me+ the girly + squat inherent in suspension when torque is applied to diff/axles/ground) BMW seems like they want tons of rear camber even stock. From what ive read and been to school for, you want a relatively flat contact patch. What are people runnin for alignment numbers w adj rear toe/camber?

[mlytle64]

that squat is only there when the car is stopped and in gear. pointless to align to that height.

yes, align to whatever load you drive with commonly. the bmw fully loaded spec is the "worst case" scenario.

"flat" contact patch, or zero camber, is great if you only go in a straight line. if you turn the contact patch changes with side load and suspension geometry. since you can't dynamically change alignment for every turn, settings are a compromise for all driving conditions. keep reading and going to school to learn even more about susp dynamics.

[taiden]

I did the alignment on my car today. Every time I do it, the wheel is biased very slightly to the left. I'm going to try putting ballast in the drivers side next time and see if anything changes.

[AlphaE]

so the car unloads/ raises as u let off the brakes? I mentioned a "relatively" flat contact patch. Obviously some camber is needed. Just tryin to get a feel for what guys are running for actual alignment numbers and the weight, if any, that they put in their cars during the alingment.

Note on sterring wheel to left- we always favor an ailgnment thrust angle to the left a liottle because of road crown. There are no flat roads especial old 2 lane roads. Cars/steering wheel are straight despite road crown.

[jlevie]

i fully understand how height effects camber and even toe depending on suspension/bushing design. I will be doin my own rear camber/toe kit, (picked up camber bolts this weekend). This little car is eatin tires w/o any spring yet. My toe and camber are bad in the back when i put it on our alignment rack.

Toe and camber errors on the rear wheels with stock springs suggests bad trailing arm bushings, possible bad subframe bushings, or bent trailing arms. In a like manner camber errors on the front wheels implies bad control arms or damage to the struts or front of the car.

So why did they decide on so much weight in the little car? It'll never ride at the height that its aligned at. See what im sayin? Id like to know the squat height in drive so i can add that into the vehicle height equation (me+ the girly + squat inherent in suspension when torque is applied to diff/axles/ground) BMW seems like they want tons of rear camber even stock. From what ive read and been to school for, you want a relatively flat contact patch. What are people runnin for alignment numbers w adj rear toe/camber?

The squat that occurs with an automatic transmission has essentially noting to do with rear ride height while the car is being driven. So it makes no sense to account for that during an alignment.

BMW had to pick alignment numbers that were the best compromise for how the car would be loaded. They are arguably not perfect and will be somewhat off for less (or more) load in the car.

When I align my SE30 I do it with a mid-race tank of fuel (~13gal) and my weight in ballast in the driver's seat. to some degree even that is a compromise, not quite right at the beginning or end of a 30 minute race.

The Bentley manual has numbers for an E30 in stock configuration, which is what you should aim for. Since the car is tuned for good handling, the outside of the front tires and the inside of the rear tires will wear faster if the car is in alignment. Which suggests that front to rear rotation will extend tire life.

[AlphaE]

I got new rear trailing arm bushings to go w the camber toe kit. Jlevie thanks fo the solid input.
Not to argue about the squat thing just for the sake of technicalities: The rear ends on these cars squat when under load correct? some guys say they'll get rear tire rub under hard eccelaratin in like 3rd even. So more load=more squat=more camber?? no sense in try to guess on the actual ride height under heavy load since thats a smaller % of driving condtion. our Hunter alignment rack calls for -1.5 to -2.5 fo the rear of these cars. But thats w max load, so average conditions should have less camber due to less weight=higher ride height. Yes no?? thanks

[lonestar22]

I did the alignment on my car today. Every time I do it, the wheel is biased very slightly to the left. I'm going to try putting ballast in the drivers side next time and see if anything changes.

my e30 and my e90 both do this when i align them. on the e90, the DSC, Brake, and TPM lights would all come on if there was an issue because the steering angle sensor would be reading improperly. which make me believe this is ok. if the steering wheel is biased to the right, which has happened before. all those lights come on.

ive used ballasts before, and it makes about a hundreth of a degree difference usually. not very much to worry about

[AlphaE]

We just got the update for our hunter rack. It comes w a steering wheel angle sensor calibration thing. U gotta make sure the sensor is readin straight when it really is. makes aligning these things even more fun.