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Suspension getting replaced - what else?

Discussion in 'E30 (1984-1993)' started by az3579, Dec 9, 2008.

    • Member

    MGarrison

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    Yup - you guys are right - for camber to change, all three attachment points would have to move. If the middle or either end of the 'L' is in a fixed position, the other end of the 'L' moves perpendicularly to the opposite end. Never had a reason to think that specifically about it!
    • Member

    az3579

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    I don't want to change the specifications much. The lowering is all I want, along with a firmer suspension so the body doesn't roll as much. I don't want to change camber and castor specs if possible. I still haven't mastered my car on the track yet, but I just couldn't live with the bounciness on regular roads any more. Besides, my suspension is shot and my brakes are on their way out, so it's time.

    I can live with my camber and caster set the way they are now. I'll change that stuff down the road when I understand more about my car on the track and how certain things change the characteristics.
    • Member

    az3579

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    Alright, purchased some missing items from my "project":

    All from Bavarian Auto (since they're really close to where I live):
    * (2) Front upper strut tower bearings
    * (2) Rear shock mounts (convertible)
    * BavAuto rear shock installation kit
    * (2) Rear shock mount gaskets
    * (2) Shock tower bearing caps

    Not going to do control arms and tie rods just yet. I'll do that after the new year when I start getting paychecks again...
    But I KNOW that I'm going to have to do something soon about the front. It just started making a kind of crunching noise (only the automotive kind...) every time I go over a bump. It made this sound last year when I had to replace either the control arm or tie rods, I don't remember what the hell I had to replace.
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    Brian A

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    • Member

    az3579

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    $47.85 to be exact. :(


    But if I'm going to do this, I'm going to have it done right!
    • Member

    Brian A

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    Best wishes. (ie I hope they don't find anything expensive that also needs to be fixed.)

    I am going to start installing virtually the same stuff beginning New Year's Day (plus swaybars, plus control arms, plus tie-rods). I have never installed springs or shocks before. Gulp.

    Apparently the reinforcements are particularly important if you're going to autocross or track the car.

    ... Tire Rack currently has a great deal on E30 Eibach swaybars BTW. (Thought I'd let you know just for the torture value.)
    • Member

    az3579

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    [storymode]

    And so with the help of fellow BMW enthusiasts (pronounced en-thoo-zee-aasts for the sake of the story), the red E30 finally received the long awaited and long deserved suspension and brake replacements. Red E30 was overjoyed for becoming a fresher automobile, one that rivaled new vehicle handling, and Red E30 greatly thanked its owner and fellow enthusiasts for the TLC it so longed for.

    The day the replacements were made, Red E30 was eager to try out the new hardware, and was unable to wait to do so. Unfortunately, duty called, which meant that Red E30 would have to wait till another day to try out his new toys, but the wait was worthwhile, and another day wouldn't hurt.


    In the mean time, Red E30 slept comfortably on its be... err, parking space on the street and dreamt of corners to come the following day.



    The End

    [/storymode]



    Will post pics tomorrow.

    Autohaus guest

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    z31maniac guest

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    Actually, I've been thinking about this some more and M3 bushings should increase caster, camber, and track width.

    Think about this, the control arm is essentially shaped like this > (obviously less angle, but stay with me). The CAB moves the mounting point for the "lowest" for purpose of using this drawing (but the farthest back in real life), now for the caster to be able to change the middle mounting point where its mounted to the strut assembly has to move forward, correct?

    OK, since the Subframe mounting point remains the same when the CAB mounting point changes, the strut mounting point has to move "out" (away from the car) along with moving forward (otherwise the CA itself would have to bend or the angle of > would have to change.

    So, since the bottom of the strut mounting point moves out and the top mounting position stays the same, that is how you get the additional camber and track width along with the additional caster from the mounting point moving slightly forward, which in turn also slightly lenthens the wheelbase.

    Pretty crazy what a simple bushing change accomplishes.
    • Member

    MGarrison

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    I don't think the strut mounting point moves out, though -

    In the attached pic, the fixed pivot point represents where the control arm mounts to the subframe (the base of the 'L'). If you move the one end, the opposite end moves correspondingly, in an arc. (Actually, both ends move in an arc, but for illustration's sake...)

    That being the case, and the pivot point being fixed, it would seem camber & track width are reduced, while caster is increased (in the instance of installing and properly orienting an M3 offset bushing). I would have to guess that whatever is gained by the increased caster would more than offset the reduction in track width & camber, or else BMW wouldn't have done it, and that therefore the track width/camber loss is either nominal, or otherwise insignificant.

    Where's a race-team suspension engineer when you need one! :p
    • Member
    • Technical Service Advisor

    mooseheadm5

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    Because it depends on the exact positioning of the outer ball joint to determine the changes in track width and camber, it is also possible that in addition to a tiny increase in wheelbase (which is required if all other points stay the same and we increase castor) that you actually lose a tiny amount of track width and camber. If, for instance, the stock bushing puts the arms with the ball joints at their furthest point from the center line, then any change in the bushing position will cause a loss of track width and cause more positive camber. If the stock bushing has the position of the outer ball joints back from max track width, then you gain some track width and more negative camber. If in front of max, then you simply lose track width and gain a little positive camber. There is one situation where it is possible that only the castor changes: the outer ball joint is ever so slightly behind max track width and the offset CAB will move it ever so slightly forward of max track width. This would leave you with the same camber and track width. Who knows, this could be the case. Only way to find out is with a completely computerized alignment that would track these changes before and after.

    z31maniac guest

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    Hmmm, you make an excellent point, and looking at a diagram of the suspension what you're saying makes sense. I had the mounting point for the subframe and strut mixed up in my head. :eek:

    [IMG]

    But there is this mention on the TMS site:

    E30, E36 Offset Front Control Arm Bushings (pair)
    Part #: 31129064875 (31 12 9 064 875)
    Applications: 1984 - 1999 (E30 E36)
    Anytime that you replace your front control arms (which should be often), you must replace your control arm bushings. The reason is because it's hard to tell if you're bushings are really bad and they are often destroyed when removed. These bushings have the hole off-center to give your car a little more track, caster, and camber. They are a solid rubber bushing that is great for the street. These came as standard equipment on E30M3s (8/89-later) and 1995 E36 M3s but will work with any E30 or E36.


    --------------------------------------------------------------------

    So then it would seem that depending on where the "L" is in the circle, or curve, of its motion path, that moving it could reduce these parameters (this would assume that its already at the furthest point out in the curve, am I making sense? Or it could move it the furthest point out and gain a touch in these parameters.
    • Member
    • Technical Service Advisor

    mooseheadm5

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    If TMS is correct, then the outer ball joint is behind the point of widest track and you would indeed get negative camber and wider track by using the offset CAB to move the rear mounting point outboard.
    • Member

    az3579

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    Alright, as promised, I went out, got a car wash, and drove to a good spot for a photo.

    The difference is MASSIVE and I have to admit, worth every penny. The car drives like it's brand friggin new!

    Yes Chris, I got a car wash just before just so you wouldn't complain about how dirty the rims were. Naturally, the photo place wasn't nearly as close to the car wash as I wanted it to be and if you look at the car now, looks like it has never ever seen a wash before.


    Here is a photo of it before lowering:

    [IMG]



    And AFTER lowering:

    [IMG]





    And I couldn't resist the panoramic view, which came out well enough for the full-resolution version of the photo to become my new desktop wallpaper:

    [IMG]



    And by the way, the grayish building on the very left corner of the last picture houses an E38 740iL. :D
    • Member

    MGarrison

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    In addition to the camber/caster Wiki articles mentioned several posts ago is this thread, a link from the Wiki discussion -

    http://www.ozebiz.com.au/racetech/theory/align.html

    "The tilted steering axis has another important effect on suspension geometry. Since the wheel rotates about a tilted axis, the wheel gains camber as it is turned".

    I'm going to assume that statement is correct, which explains how camber is increased. That might also account for the increased track - perhaps the track increases as the wheel is turned as well.

    Ok - well, given what's fixed in place for the control arm (the pivot point of the 'L'), the only way the outer ball joints/end of the control arm wouldn't be placed at the furthest distance from centerline would be if the stock bushing holes are not centered. That could be easily measured if anyone had a stock bushing in hand, and if not centered, the offset direction can be ascertained by knowing how the bushing is oriented in the bracket. I believe there are arrows on the bushings and brackets to show how they are to be oriented and installed.

    The outboard position of the control arm is determined only by the inboard/outboard placement of the bushing end, as the bushing end of the control arm is not permanently affixed to the bushing, and able to move through the bushing as the control arm is positioned left or right (even though it is a very tight fit).

    btw Botond, nice picture, very scenic. I think you could make it even more scenic if you could take roughly the same shot earlier in the day with more sun behind you to light up the side of the car and the buildings, parked a bit further back from where you are now, and taking the shot further from the left of where you were, so that the tree would appear to the left in the picture, so the trunk's not blocking the larger building. Sorry, just my college photo-class re-emerging. ;)
    • Member

    az3579

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    I was actually thinking of going back to take another few pictures because the spot was better than I expected. I set out with this place nowhere in my mind and ended up here. Best part is, I know exactly how to get back here, which involves a very nice windy road which is way too short and is ruined by people actually going the speed limit, but you didn't hear that from me. :)

    I like the darker lighting and prefer not to have the sun light everything up.
    Besides, I don't know what the "sun" pattern is there and cannot just sit there all day to see where the sun's path is. :rolleyes:



    But anyway, is the rear supposed to have less lowering than the front? It appears to me that the rear is more raised...
    • Member

    MGarrison

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    It looks fine to me, at least from the picture - probably varies from mfg. to mfg. depending on what they do w/ rear springs.

    I like your pic as it is too, but was also thinking the dark red facades of the buildings would make an interesting complement & contrast to your car's red, which would take some light, as the red on the building barely shows in the low light. I wouldn't recommend sitting all day to check the light pattern either, unless you're getting paid for it! Since the horizon in your pic is lit up in the background, I would guess you're more-or-less facing west when you took it, and the sun would light up that scene from about 10-11:30am as it's rising from what's presumably east in the late morning.

    But - the snow, buildings, woods, & car; really the whole scene - very nice choice!

    Autohaus guest

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    Pics of the E38 740iL? Just kidding man, nice! I knew that the sport setup would eliminate the fender gap. Your car sits just like my E28 and E39. You should come up next weekend so I can see how different your car feels. Now are you planning on going all out and getting sway bars, strut bars front and rear, roll cages, this and that? If you get hired and work for your company with full benefits and such, you should get either an E36 or E46 as your DD and keep the E30 as your track rat/weekend fun tool.
    • Member

    az3579

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    Nope. It belongs to someone we know, but I didn't want them to know I was there!

    Not unless you have a kickarse route planned. I'm not gonna drive all the way up there just for you to oogle at it. :p

    Maybe sway bays and strut bars, but it's not going to become a full track car. I don't have space for a 2nd car and I would gladly have two and keep this as the fun/weekend car, but I cannot afford to maintain two cars and don't have storage for two either.
    Besides, this one is destined for an M/S50. :)

    Autohaus guest

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    Oh, so you are gonna go full throttle with that then. Great! Did you ask Kamal how much he will charge you or are you going to pay a visit to Paul and help him work on it?

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