M42club.com - Home of the BMW E30/E36 318i/iS
DISCUSSION => Suspension => Topic started by: Slowered318 on July 27, 2015, 08:21:46 AM
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I can't find adequate alignment discussion anywhere regarding E30's, maybe it's time we talk and possibly achieve something?
Looking for a "sporty" street setting for a slightly lowered and reasonably upgraded car (stock size wheels). Been driving e30's for 17 years, I don't need excessive understeer built in and I don't mind a little tire wear (negative camber) as long as it's holds nice on the highway.
This is mainly for those fortunate to have rear toe and camber adjustment kits (Ireland Engineering) along with front camber plates or the offset hats you can play around with.
I don't trust the suggestions some computer gives me at the alignment shop, my initial thoughts on ideal are listed below.
Front:
0 to 1 degree toe (total)
2.0 degree negative camber (each side)
Rear:
1 to 1.5 degree toe (total) "roughly 1/8 each side"
1.5 degree negative camber (each side)
This is based on my own general knowledge of the suspension geometry we are dealing with here. It appears that under load the rear trailing arms squat significantly and toe in slightly, the front is a little more linear so I gave 0.5 degrees less negative camber to the rears. I find toe in really eats tires and with poor quality roads it can become a handful to drive thought I want a slight toe in on the rear to help around town.
As it currently stands I had quite a bit of negative camber and toe out in the rear, only 2.5 degrees total front camber. Had to buy new tires! Plenty of of roll onto the outside shoulder of the tire and the rears are scrubbed off badly on the inside.
Please post your thoughts and correct me if I've made an incorrect statement.
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im no suspension guru but as far as camber goes -1.5-2 sounds good for daily driving with the occasional track visit from what i have been reading. im new to e30s but all my other previous cars had camber in that same range. i know that dedicated track cars will go as crazy as -3 or higher so this is a good in between.
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Well I'm new to this aspect of E30ism and BMW won't give me the factory alignment specs without putting the car on their rack.
So I have been studying the stance of other Bimmers and they all have considerable negative camber and slight toe-in on the rear wheels. Front is more or less strait and perpendicular to the road. I'm trying not to question the reasons for this but when the car is lowered things change quite a bit.
Moved my car up and down today and took some measurements of the effect on camber. It appears the trailing arms are far from linear, you get about 1 degree positive camber for every 2cm the car is moved up, center point seems to be slightly below where my car is sitting. By this logic on a hard corner I should be getting plenty of pitch and roughly 4 degrees negative camber on the outside wheels.
I'm thinking in light of saving tire wear I shouldn't exceed 1 degrees negative rear camber. Maybe dial in more negative camber on the front so I'm not rolling over so much on the outside of the tire.
I have a feeling this is going to be a lot of trial and error.
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I believe the Bentley Guide has the factory specs listed. Sorry, I don't have my copy handy.
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maybe run with 0 toe in for the front wheels for a bit more lively car (quicker reactions) .. but you also need zero bumpsteer.. what about your caster settings?
I've never driven an E30 .. but my gut says also little toe in the rear, it has not enough torque/hp to spin the wheel a lot.
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That's way too much toe to be running. Something around 0 in the front and 0.2 toe in total in the rear
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colin86325: I checked my guide books, both explain caster/camber/toe but no numbers.
E36-italia: I didn't get a caster reading but it should be slightly over stock. I installed M3 lower control arm bushings, they move the front wheels forward 1/2 inch.
How do I achieve zero bumpsteer? Swapped to an e46 steering rack and e36 tie rods, I have a some ability to shim it up or down but it's currently at the lowest position. Come to think of it I've played around quite a bit with the suspension, not entirely sure how a stock e30 handles anymore.
nickmpower: I think the car should have a neutral stance with the wheels pointed perfectly strait, but I have no idea exactly what happens when forces are applied. That's why I've been looking around for the factory specs.
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Interresting tread,juste post to follow sorry
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Found this in the Bentley service manual.
Not sure what unit of measurement they are using? Need to convert to a format I'm familiar with and then most likely adapt it to work with my suspension setup.
Problem with all of this is I can't easily tweak the alignment settings.
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I just searched for some alignment e-mails with my shop, looks like I run -2.5 camber up front (have m3 offset bushes) 2mm toe in - in front, 0mm toe in the rear. Car is used on track and street.
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E36-italia: How do I achieve zero bumpsteer? Swapped to an e46 steering rack and e36 tie rods, I have a some ability to shim it up or down but it's currently at the lowest position.
Theory is quite simple, yet difficult to do.. when your steering arms are moving up/down exactly parallel to your lower wishbones then you have zero bumpsteer.. but the moment you do steer.. that theory goes out the window, for the simple fact that they are no longer moving (up&down that is) parallel to each other.
To combat this you can do what streetracers do.. add superstiff antirollbars with solid springs so that the car has no body roll at all.. that gives you zero bumpsteer with the free addition of zero grip.
Or you can edit the rollcenter of the front axle (moving the inner wishbone mountings upwards, or the outer lower - do the same with the steering!) and mount a softer ARB.
since the car has a higher R/C, it will take more force to roll the body, hence the softer ARB, equals more grip!
( i plan to run my E36 with no ARB's.. but that has polyester bodypanels)
but that is a tad extreme for a daily car..
If you can get your car on a lift for a couple of hours, measure (height from floor/asphalt and distance from the center of your car.) the 'rotation points' of your front suspension, write them down and go figure out what happens...do this in 2 different set ups, one at full droop and one at static ride height.. then you have an idea what will happen with your car.
so.. that's your racecar 101 :P
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Found this in the Bentley service manual.
Not sure what unit of measurement they are using? Need to convert to a format I'm familiar with and then most likely adapt it to work with my suspension setup.
Problem with all of this is I can't easily tweak the alignment settings.
Degrees and minutes'
1 degree equals 60 minutes
Hope this helps
Cheers Rohan
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Thanks Rohan! It's so simple once you pointed that out.
I just searched for some alignment e-mails with my shop, looks like I run -2.5 camber up front (have m3 offset bushes) 2mm toe in - in front, 0mm toe in the rear. Car is used on track and street.
I assume the car drives fine with those settings?
How does it feel with the added front camber? I've always heard that reduces understeer. Anything strange happening with the back end without any toe... scrubbing the tires at all?
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Update:
Going to aim for these settings but it's hard to say what happens out in the road with a 25 year old car. Could be flogging a dead horse.
Front Toe: 0.3 degree, 1/8", or 3.2mm (total)
Front Camber: -1.3 degree (each side) ...can't change this at the moment
Rear Toe: 0.0 or 0.3 (total) ...if I can make up my mind
Rear Camber: 2.0 degree negative camber (each side)
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I assume the car drives fine with those settings?
How does it feel with the added front camber? I've always heard that reduces understeer. Anything strange happening with the back end without any toe... scrubbing the tires at all?
The car drives great with these settings, the shop I use is very performance oriented and know their stuff.