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BMW E36 - What parts alter Caster + How much is too much?

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  • BMW E36 - What parts alter Caster + How much is too much?

    This came from a discussion with a customer's question via email, but it was a good refresher for us to put up these images and correlate the data together.

    The E36 chassis was made from 1992 through 1999 model years. It came as a 4 cylinder or 6 cylinder, and M3 models and non-Ms.

    This chassis came with three different strut mounts, at least three different spindles, and two versions of the lower control arms and three different LCA bushings.

    (This shows a 1996-99 M3 control arm and the "centered" LCA bushing - the offset version altered caster)

    These OEM parts can be mixed and matched get to a fairly extreme caster setting beyond what BMW or anyone else intended. The aftermarket options add even more variables. We have seen people get parts combinations together that can reach +8.5° caster, but that is beyond excessive. +7.5 caster is at the outer edge of what we shoot for.

    We tried putting E36 front suspension - control arms, spindles and struts - onto a BMW E30 and ended up with +12 degrees of caster. It was a mess!

    We then tested various control arms we had and found then measured some of the differences.

    The post above shows a good list of differences in the E36 model parts that had an effect on caster, and references some of our pictures.

    The non-M E36 uses a "centered" strut mount (which put the strut pin in the middle of the strut tower hole), the 95 M3 used offset (for added caster) strut mount, and the 96-99 M3 uses an extremely offset top mount that had a little negative camber built in, too.

    Our E36 camber/caster plate gets to the 95 M3 caster location - which itself is extremely offset. If we pushed caster back any further, you would have zero camber adjustment (due to the round hole in the strut tower). And camber is way more important than caster, when it comes to handling / performance / lap times.

    I raced this 1997 M3 for many years with the centered LCA bushing and our camber plates and +7 degrees of caster. Some folks try to mix and match the 1995 offset LCA bushing and the 1996-99 M3 strut top mounts to get to some "extreme" caster setting. This is neither beneficial nor necessary. If you try to go beyond about 7 degrees it will push the wheel into the front of the fender opening.

    Caster over +7.5 degrees starts falling into that range of "diminishing returns", quickly. There is a bit of corner jacking that occurs with "extreme" caster. It does not help tire wear or performance, which is the point of our camber/caster plates. What you want is enough camber to keep the tire flat while loaded up in a corner - that is what matters most.

    This is a E82 BMW 1M unit strut mount above, next to our E36/E90 camber/caster plate (this chassis uses the same camber plate). Notice how the center of the strut in the stock top mount is dead center of the bolt circle.

    That puts the strut in the middle of the strut tower hole - which is where most OEMs shoot for, and what we try to get into all of our camber plate designs. This allows for centered (usually "stock") caster and centered camber. Then we have adjustments for more positive caster and more negative camber from that starting point, as shown above.

    Compared to many chassis, the E36 has a large strut tower opening, which allows us room to add caster and camber.

    The E90/E82 chassis shown above has a smaller opening, which limits camber travel if you add a lot of caster - so we ship plates for those E90/E82 cars in the "Stock" centered caster setting.

    Just remember: like with everything, there is always a point of diminishing returns. On most McPherson Strut cars we try to shoot for +6 to +7 degrees of caster and call it a day. We treat camber 10x as urgently as caster, too! #CamberIsEssential

    Thanks for reading,
    Last edited by Fair!; 03-27-2020, 11:04 AM.
    Terry Fair -
    2018 GT / S550 Dev + 2013 FR-S / 86 Dev + 2011 GT / S197 Dev + C4 Corvette Dev
    EVO X Dev + 2007 Z06 / C6 Dev + BMW E46 Dev + C5 Corvette Dev