Hello there and welcome to the BMW Car Club of America.

If you are a BMW CCA member, please log in and introduce yourself in our Member Introductions section.

E30+S50+Auto-x=*mm swaybar?

Discussion in 'E30 (1984-1993)' started by az3579, Jul 28, 2010.

    • Member

    az3579

    Post Count: 3,270
    Likes Received:3
    I already posted this on Bimmerforums, but I'd like as wide range of responses as possible, so I'm going to repost this here:

    Currently the car has Bilstein Sport shocks and H&R Sport springs. I'm not looking to change the springs, though if it comes down to it, I will. What I'm looking for is to buy a swaybar kit that would significantly reduce body roll and perhaps help a little with the slight understeer I get around tight turns on the auto-x course.

    I understand that the S50 is about 60lbs heavier than the M20 I had in there before. This probably contributes in a small part to some of the understeer I get.

    If I remember correctly, the swaybars I have stock are 19 or 20mm front and 12mm in the rear. I know there are kits out there that are adjustable, with a fixed size. How do the adjustments affect the car? Where are these adjustment points (i.e. is it easy to adjust just by jacking up the car and tweaking with the settings)? What thickness am I looking for front and rear? Does anyone have any experience with certain thickness bars and setups?

    Finally, what brands and thicknesses are recommended for auto-x, track, AND daily driving? I'm content with the "jarring" associated with thicker swaybars when going over potholes/bumps, so I understand that getting swaybars means sacrificing a little daily drivability for performance, though I would like to know how much worse is it?



    Thank you for any help that can be provided.
    • Member

    Brian A

    Post Count: 657
    Likes Received:7
    Swaybars won't "significantly" reduce body roll: that's mostly a function of stiffer springs. They do help a (noticable) bit.

    Generally, stiffening the rear and/or softening the front causes the rear outside tire to take more load relative to the front outside causing the car to exceed the traction limit in the rear first and therefore increasing oversteer. There is voodoo out there though; some E30 owners have removed their rear swaybar to increase oversteer (I don't know how this could work).

    There are several systems, but the simplest is the one where the swaybar has several mounting holes for the connectors to the control arms. Using a hole nearer the end of the swaybar reduces the stiffness of the swaybar. There are other infinitely adjustable systems (clamp systems) and even ones ("blades") which can be remotely adjusted from inside the car.

    Stiff swaybars don't add much: its mostly stiffer springs that add "jarring".
    • Member

    MGarrison

    Post Count: 2,842
    Likes Received:144
    • Member

    CRKrieger

    Post Count: 1,616
    Likes Received:20
    ... and here's why I don't get the rep points. When I tell people what they don't like to hear, they get annoyed. I'm still willing to take that chance in the hope you'll learn how to make your own choices instead of blindly and ignorantly following the questionable advice of others who may have no more of a clue than you do.
    You seem to misapprehend the primary functions of springs and anti-roll bars. It is springs that have the primary effect on body roll. The anti-roll bars, despite their proper name, are only secondary. If your goal is performance, then it doesn't really matter how much the body rolls; it matters if it handles well for you. At low speeds, there's hardly any way of avoiding understeer without making the car an ill-handling pig at high speeds. Learn to drive around that shortcoming with paraphrased advice from Bobby Rahal. Slow corners are slow corners. You can't make them fast.
    That and the normal tendency of any E30 to understeer at low speeds ...
    This tells me that you need to read a lot more about suspension theory before messing around with yours.
    1.) It varies.
    2.) I don't know. Neither does anyone else.
    3.) Of course they do; but it's not likely to be very relevant because almost no one else has your engine and suspension setup to start with.
    Different ones; or adjustable ones.
    This is what actually motivated me to reply. It tells me that you hardly have any idea what an anti-roll bar does, how it works, and how it affects the suspension. This book is out of print, but you can still find copies. It is one of the best I've ever read. Track it down. Read it. Learn. Then think for your self. Don't expect it all to get handed to you.
    • Member

    granthr

    Post Count: 1,583
    Likes Received:2
    And there you have it! :) Boy Botond you really should go to O-fest buy CR a beer and then give him hell. :D I am sure it will be lots of fun. :)

    All I will say is that I have H&R sway bars on my 318i front and rear and on my 325ix in the rear (they don't make one for the front). They are much stiffer than stock and was most noticeable in the 318i b/c it is such a light car and the fact that it did not come with a rear bar from the factory. :eek: Most sway bars are adjustable. I have Dinan's on the E36 but I bought the car that way and have no idea how it handle before, I just know now that it handles great.
    • Member

    CRKrieger

    Post Count: 1,616
    Likes Received:20
    I'm doing all I can to **** off enough folks to set a new attendance record ...
    That is not all that unusual. In fact, the running change from the 1977 US spec 320i to the later E21s was removing the rear anti-roll bar and using heavier front springs. The 320i, like the predecessor 2002, had a habit of lifting the inside rear wheel when it had a bar back there. With an open diff, this allowed the inside wheel to spin wildly - and ineffectively. The car would slow until that wheel hit the ground again. When you remove the rear bar and stiffen the front springs, it does two things: the inside rear wheel doesn't get lifted by the bar and the front doesn't lean as much, helping the rear wheel stay on the ground. Net result is better (faster) cornering.
    No; they're not. Most are non-adjustable.

    So, how many beers are you buying me before you kick my ass? :D
    • Member

    az3579

    Post Count: 3,270
    Likes Received:3
    Unfortunately, I won't be buying you any beers and won't be kicking your azz because I won't be at O'fest this year. =(
    • Member

    granthr

    Post Count: 1,583
    Likes Received:2
    Well CR I wish I was going to Ofest too to give you a hard time! :D

    When I said most sway bars are adjustable, I meant aftermarket ones like H&R, Ebach, etc. Most of those are adjustable.

    That is interesting about the E21, I had no idea that is what people did to reduce the rear wheel lift that they are infamous for.
    • Member

    CRKrieger

    Post Count: 1,616
    Likes Received:20
    Well, not many people. Only a few owners of '77s would have bothered before the car rusted itself to oblivion. It was BMW that changed them for '78. Unfortunately, they did nothing to improve body integrity.:(
    • Member

    Brian A

    Post Count: 657
    Likes Received:7
    Going Faster by the Skip Barber Racing school and published by Bentley is mostly about driving technique ("The Line", braking, etc), but includes a huge amount of technical information about vehicle set-up. If you can't find CR's, this one is good too. It also includes an excellent bibliography for further reading suggestions.

Share This Page