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Thread: spacing a crossmember down - how low can i go???

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    Senior Member J0RD0's Avatar
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    Default spacing a crossmember down - how low can i go???


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    Just wondering what is the maximum I can space a crossmember down before running into problems with steering etc
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    the way it works is that the further you go down the disproportionally more out it gets. So anything you add is affecting it, however.... this can be completely offset with running taller roll center adjusters. Dave from AJPS sells a type of steering ball joint that has no grease nipple on the bottom. This allows for much more room before the bottom of the outer steering joint hits the rim of the wheel.

    Here's the formula for you:

    Height of roll center adjusters needed = Lowered height from unsagged original ride height + crossmember spacer thickness
    Last edited by Sam-Q; 8th January 2013 at 01:25 PM.
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    Cheers for the reply Sam
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    Senior Member KE70GT's Avatar
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    Quote Originally Posted by Sam-Q View Post
    the way it works is that the further you go down the disproportionally more out it gets. So anything you add is affecting it, however.... this can be completely offset with running taller roll center adjusters. Dave from AJPS sells a type of steering ball joint that has no grease nipple on the bottom. This allows for much more room before the bottom of the outer steering joint hits the rim of the wheel.

    Here's the formula for you:

    Height of roll center adjusters needed = Lowered height from unsagged original ride height + crossmember spacer thickness
    with that formula will that give you the best lower control arm angle with stiff suspension or will you benefit from having the control arm closer to level cause the movement of the arm will be reduced by lowering the car I’ve never run rca’s before but I know that I get no bump steer at standard height and a lot when the control arm sits level when lowered

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    it effectivly the effect on the front geometry same as lowering your car

    just moves the other side of the lca down instead of up.

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    dont forgot your sump will hang down lower
    dose

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    Quote Originally Posted by KE70GT View Post
    with that formula will that give you the best lower control arm angle with stiff suspension or will you benefit from having the control arm closer to level cause the movement of the arm will be reduced by lowering the car I’ve never run rca’s before but I know that I get no bump steer at standard height and a lot when the control arm sits level when lowered
    Sorry off topic but ^ this is interesting, have thought about this.

    The natural angle of the LCA is to work in the most effect range, but with standard boat suspension, nearly all cornering would bring the outer LCA (LCA taking all the load) near level anyway?

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    That's an interesting viewpoint Deeken although I don't think the stock suspension would lean bad enough to get the same angles many of us are seeing in the suspension.

    Speaking of all this I have wanted for some time to get some real long RCA's made up, pity I don't have the time to do it.
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    Quote Originally Posted by KE70GT View Post
    with that formula will that give you the best lower control arm angle with stiff suspension or will you benefit from having the control arm closer to level cause the movement of the arm will be reduced by lowering the car I’ve never run rca’s before but I know that I get no bump steer at standard height and a lot when the control arm sits level when lowered
    this will give you the original geometry that Toyota thought was the most ideal for the vehicle when they designed it. How critical this is and how it still suits a sports suspension is the big question.
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    Quote Originally Posted by Sam-Q View Post
    this will give you the original geometry that Toyota thought was the most ideal for the vehicle when they designed it. How critical this is and how it still suits a sports suspension is the big question.
    The angle that the LCA sits at is something manufactures rarely screw up. They tend to ruin the suspensions ability to perform by messing up other angles that are more difficult to change.

    What I'm curious about is why anyone would want to space the crossmember lower in a car, aren't you just raising the minimum height the rest of the front end can sit at?

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