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Thread: Measuring front LCA angles

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    Measuring front LCA angles

    I should probably start a build thread or something......


    I was wondering if you guys had some suggestions on easy ways to measure the angle of the Front LCA. I'm trying to get it flat and level with the ground and adjust the tie rods to match. I'm sticking my digital angle finder on the flat machined surface where the sway bar brackets bolt to. Its the only flat spot i have access to on the LCA, but in taking a second look it might be a bit different than what the actual angle of the LCA is. Suggestions? In just looking at the pic, i'll probably have to lower the car more.

    I already measured the flatness of the garage floor and placed a stack of vinyl flooring tiles under each wheel to bring the whole car level. I'm comfortable in knowing if the gauge is reading .1 degrees, its probably an actual .1 degrees. The ride height is set. L & R are within a mm or two of each other.


    So everything is fitted up, just tweaking suspension alignment a touch before i start cutting into my widebody kit for wheel clearance on turns.... I'm going to have to chop a decent amount off the side skirts and front bumper. Hopefully i don't touch the oil cooler, but its looking like i MIGHT. Definitely going to have to do some aero add-ons to make up for all the stuff i have to cut off.

    IMG_20180611_232217.jpg


    Oohh, mods are megan ball joints on tallest setting and racefab tie rod ends.
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    Im assuming that you want to minimize lateral movement of the wheel as the suspension travels up/down? And to make sure that the LCA and the tie rod is parallel to eliminate bump steer? that machined surface looks like the best place to measure, although i am not sure that it's parallel to the line running thru the ball joint and pivot points.

    I've used the little digital gauge (just like yours) to set up my camber also. What i've found is that the length of the flat area of that gauge is simply not big enough to give consistent reading. It's always within .1 of a degree, but i think a longer level gauge would be more precise. I've now been using a 20'' harbor freight laser leveler and gauge. It may be too long for your needs, but they may have slightly shorter ones too.

    I like how you've leveled your car to compensate for uneven floor. I do the same with sheets of laminated paper and wood.
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    Quote Originally Posted by mityaz View Post
    Im assuming that you want to minimize lateral movement of the wheel as the suspension travels up/down? And to make sure that the LCA and the tie rod is parallel to eliminate bump steer?

    Exactly. Someone gave me the idea to mark a point on the LCA bolt and ball joint then measure its distance from the ground. The only problem is i cant stick an arm under the car while its on the ground lol. I'll see if i can get a straight edge, mark the two points, and use my gauge while holding the straight edge along the two points.
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    Know someone that has an alignment rack with floating tables/plates that you cna borrow/rent? Then you can get under it easily enough.
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    Anyone know what the angle is on the LCA's from the factory? Like with stock suspension and stuff? Is it level, or pointed slightly downward??
    Quote Originally Posted by Erik@MIL.SPEC View Post
    Technically speaking, modding cars is a "waste of money." But here we all are. On a car forum. Modifying our cars
    Racing cars makes a heroin addiction look like a vague craving for something salty.

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    Quote Originally Posted by HispanicPanic View Post
    Anyone know what the angle is on the LCA's from the factory? Like with stock suspension and stuff? Is it level, or pointed slightly downward??
    You will struggle to find an X at standard ride height to check

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    got some bump/toe data on the setup as it currently sits.

    MCS Remote 2 ways
    Perrin PSRS
    Vorshlag top hats on minimum caster & Maximum camber
    Minimum camber at knuckle
    Meagan ball joint on longest setting
    RaceFab adjustable tie rods.

    Static ride height is right at 2.5 inches. Don't pay attention to the actual value of the camber. It actually sits at -2.8 or so as it sits, but the corner is jacked in the air, that's why its reading higher.

    1.jpg

    22.jpg

    33.jpg


    Too tired to digest this data right now. I need sleep!!
    Last edited by HispanicPanic; 06-26-2018 at 08:03 AM.
    Quote Originally Posted by Erik@MIL.SPEC View Post
    Technically speaking, modding cars is a "waste of money." But here we all are. On a car forum. Modifying our cars
    Racing cars makes a heroin addiction look like a vague craving for something salty.

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    Ok here's my thinking. Let me know if you agree with my rationale.

    Front static height is at 2.5 inches of compression. Under braking, i'll estimate about 1 inch of compression. As i turn in, say it'll add close to .5 inches of more compression to the outside front, while the inside front bounds .5 inches. With 4 washers above the tie rod, This results in a situation where the outside front toes in slightly as weight transfers, and inside front toes out nearly an equal amount, of about .015 inches. The same scenario with 3 washers, leaves me with toe out on the outside front during weight transfer, and toe in on the inside tire, working against the corner. Toe change seems to be slightly less during weight transfer of bout .01 inches. Less change is good, but the tipping point of where the toe goes from positive to negative is closer, leading to the tires working against the weight transfer.

    The scenario with the 2 washers has even less total toe change in the beginning, but the tipping point is a lot sooner and the outside will toe out a bit more (and inside toes in more) under full load in the corner. Looking at things a slightly different way.....

    4 washers: .06 maximum toe change through range
    3 Washers: .03 maximum toe change through range.
    2 washers: .035 maximum toe change through range.

    So the question is, do i want the toe change to work WITH my weight transfer, or against? I'm also making an assumption on maximum travel, which needs to be verified after a day on track. Perhaps an ideal situation is to use 3 washers plus one slightly thinner washer to achieve something in between 4 and 3?
    Quote Originally Posted by Erik@MIL.SPEC View Post
    Technically speaking, modding cars is a "waste of money." But here we all are. On a car forum. Modifying our cars
    Racing cars makes a heroin addiction look like a vague craving for something salty.

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    Quote Originally Posted by HispanicPanic View Post

    4 washers: .06 maximum toe change through range
    3 Washers: .03 maximum toe change through range.
    2 washers: .035 maximum toe change through range.

    So the question is, do i want the toe change to work WITH my weight transfer, or against? I'm also making an assumption on maximum travel, which needs to be verified after a day on track. Perhaps an ideal situation is to use 3 washers plus one slightly thinner washer to achieve something in between 4 and 3?
    Keep working on it. Get thinner washers so you can make smaller steps. You should be able to get max tone change from full up to full down to 0.020" or less per side. If toe change (full up to full down) is > 0.020", you're not done yet. Tjis is the pain=staking "setup" phase. And as long as you don't bend something, it will stay that way forever.

    Then you won't need to care which way the eror goes as it will be much smaller than the actual tyre scrub when under load.
    "BREAKING: 92% of Trump voters admit being aroused by the thought of shaving Mike Pence's head."

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    Quote Originally Posted by Yxd68 View Post
    Quote Originally Posted by HispanicPanic View Post

    4 washers: .06 maximum toe change through range
    3 Washers: .03 maximum toe change through range.
    2 washers: .035 maximum toe change through range.

    So the question is, do i want the toe change to work WITH my weight transfer, or against? I'm also making an assumption on maximum travel, which needs to be verified after a day on track. Perhaps an ideal situation is to use 3 washers plus one slightly thinner washer to achieve something in between 4 and 3?
    Keep working on it. Get thinner washers so you can make smaller steps. You should be able to get max tone change from full up to full down to 0.020" or less per side. If toe change (full up to full down) is > 0.020", you're not done yet. Tjis is the pain=staking "setup" phase. And as long as you don't bend something, it will stay that way forever.

    Then you won't need to care which way the eror goes as it will be much smaller than the actual tyre scrub when under load.
    You say from beginning to end...... But there's a peak in between. Are you saying i need to keep that peak smack dab in the middle of my overall travel? I don't think there's much i can do in terms of how much everything changes, only where the car sits within the two arcs that the LCA and tie rod make. Looking the graphs so far, perhaps the center of where those arcs deviate the least is somewhere around the 2 or 3 washer mark? I guess that's what i need to keep in the middle of my travel?

    I honestly don't think full up to full down being .02 or less is going to happen over 5 inches of travel. I can probably get points 2 and 4 nearly equal, but there will be a peak in between that will be a bit higher. The only way to lessen that peak is to change were the inboard points mount for LCA and steering rack.

    Speaking of which, anyone know how our steering rack mounts? Does it have rubber bushings or is it a solid mount to the subframe?


    Edit: Messing around with it again, it seems with 3 washers above the tie rod, the inflection point of the toe curve is sitting around 3.25 to 3.5 inches of compression. Me thinks i should tweak it to move this point to 3 inches. Based on the assumption of the front moving between 2 to 4 inches of travel. 2 inches under full squat, and 4 inches for the outside front during full cornering load after hard braking. Static Ride height is 2.5 inches. 800lb front springs and 1000 lb rear springs. What say you guys?
    Last edited by HispanicPanic; 06-26-2018 at 10:09 AM.
    Quote Originally Posted by Erik@MIL.SPEC View Post
    Technically speaking, modding cars is a "waste of money." But here we all are. On a car forum. Modifying our cars
    Racing cars makes a heroin addiction look like a vague craving for something salty.

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    Sorry for post spamming.... Made a few tests again back to back to ensure repeatability, and it seems with the 2 washers, the inflection point of the curve is about smack dab right at 3 inches of compression. Also increased my samples to get a little better resolution. Looking at nearly zero net toe change from static to what i assume is full front squat under braking, at 3.5 inches. Between 2 and 4, nearly zero net toe change, and approximately .033 absolute toe change over the entire range. I think this is about as good as its going to get at this ride height.

    4.jpg
    Quote Originally Posted by Erik@MIL.SPEC View Post
    Technically speaking, modding cars is a "waste of money." But here we all are. On a car forum. Modifying our cars
    Racing cars makes a heroin addiction look like a vague craving for something salty.

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