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Thread: Harley's 818S

  1. #361
    I had my rear lateral links parallel, as checked with a digital angle gauge. It wasn't enough. When I got a bump steer gauge and checked it, I had a fair amount of rear bump steer and it was making the car twitchy. I set it for just a hair of bump-in in the rear, mostly just to ensure that it never becomes bump-out under load.

  2. #362
    I've been working through one issue at a time, so now I'm ready to get back at the alignment.
    at low speed, its awesome, however at higher speeds, like 55mph and above, it is a bit twitchy like you say, or it seems to "hunt" to either side at the center position. You really have to concentrate to keep it straight.
    I was thinking now I will try to add the spacer in the LCA so I can adjust for a bit more caster, and I saw your comment about the rear bump steer in another thread. I'm not thinking that would affect steady state straight line twitchiness??? or does it?
    How did you adjust for a hair of bump steer? Slightly out of parallel biased toward the front lower, or rear lower? or do you need the bump steer gauge?
    I have been setting them parallel with the digital angle guage.
    Harley
    Bought 2002 Donor Jan 2014
    First Start Jan 18, 2015
    First Drive Feb 14, 2015

  3. #363
    Do you know how much caster you have now? I was able to get all I needed by flipping the hurricane bracket and cutting down down the rear tube nut on the upper a-arms a bit. I think I'm at like 5.5 degrees.

    So many things can cause twitchy handling. Having toe-out or zero-toe in the front, bump steer front and rear, and lack of caster, so it's important to check them all. And yes, rear-bump steer can make the car feel twitchy in a straight line as the suspension loads and unloads over bumps and ruts. It probably won't be as noticeable in a straight line as it is in corners, but I bet you could feel it.

    To get a hair of bump IN (very critical that it's bump-in and not bump out), you want the rear lateral link to be lower on the outside (toward the tire) end than the forward lateral link. The problem is, you can't really know how much you have unless you use a gauge. But in a pinch, I'd set them so your angle gauge reads maybe a tenth of a percent or two above 0. If you are laying the angle gauge across the two links toward the outside end of thinks, the front of the angle gauge should be higher than the rear.

  4. #364
    Quote Originally Posted by Hindsight2.0 View Post
    Do you know how much caster you have now? I was able to get all I needed by flipping the hurricane bracket and cutting down down the rear tube nut on the upper a-arms a bit. I think I'm at like 5.5 degrees.

    So many things can cause twitchy handling. Having toe-out or zero-toe in the front, bump steer front and rear, and lack of caster, so it's important to check them all. And yes, rear-bump steer can make the car feel twitchy in a straight line as the suspension loads and unloads over bumps and ruts. It probably won't be as noticeable in a straight line as it is in corners, but I bet you could feel it.

    To get a hair of bump IN (very critical that it's bump-in and not bump out), you want the rear lateral link to be lower on the outside (toward the tire) end than the forward lateral link. The problem is, you can't really know how much you have unless you use a gauge. But in a pinch, I'd set them so your angle gauge reads maybe a tenth of a percent or two above 0. If you are laying the angle gauge across the two links toward the outside end of thinks, the front of the angle gauge should be higher than the rear.

    I thought I dialed in 3 degrees of caster, but as you pointed out before, I measured it on the FFR weldment which may not be correct. I am going to do it again and measure the plus and minus angles you mentioned and divide by two. What did you set your angle gauge on?.
    When you say hurricane bracket what do you mean? flip the attachment of the rear of the LCA to the spindle? or flip the LCA rear mount with the squiggle down?
    And I didn't have to cut the nut to get my 3 degrees of caster, I just cut the thread, but if I go further, I will have to cut the nut as it is out of room.
    Thanks for your help, this is all new to me....
    thx again
    Harley
    Bought 2002 Donor Jan 2014
    First Start Jan 18, 2015
    First Drive Feb 14, 2015

  5. #365
    Senior Member RM1SepEx's Avatar
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    Re-check that the rear lower lateral links are parallel, you could be getting the rear steering the car, can be very sensitive to throttle on/ throttle off. I think the car would be easier to setup if they eliminated the eccentric adj for the lower rear lateral link, you should use a length adj rear link to adjust toe in the rear
    Dan

    818S #17 Picked up 8/1/13 First start 11/1/13 Go Kart 3/28/14

  6. #366
    You can come by and borrow our castor/camber gage, easy to use and super accurate. We set our race cars up with it, and could not be happier! We string every car we have on rotating pads and use toe plates for toe. To measure bump steer, we took out the springs, set jack stands to ride height all around, then jacked one wheel up at a time and measured toe. We were able to get set to zero bump steer front and rear with this method.

  7. #367
    Quote Originally Posted by Harley818 View Post
    I thought I dialed in 3 degrees of caster, but as you pointed out before, I measured it on the FFR weldment which may not be correct. I am going to do it again and measure the plus and minus angles you mentioned and divide by two. What did you set your angle gauge on?.
    When you say hurricane bracket what do you mean? flip the attachment of the rear of the LCA to the spindle? or flip the LCA rear mount with the squiggle down?
    And I didn't have to cut the nut to get my 3 degrees of caster, I just cut the thread, but if I go further, I will have to cut the nut as it is out of room.
    Thanks for your help, this is all new to me....
    thx again
    Yeah I would not measure caster like that. I tried it after I set it using a digital gauge and it wasn't accurate at all. Maybe others have had better luck with it but not me. I set my angle gauge on a little jig I made that resembles this:
    https://www.quicktrickalignment.com/...quantity-copy/
    You have to turn the wheel 15 degrees to the left, measure, then turn back to center, then 15 degrees to the right and measure again. You subtract the two. Go to youtube and search "quicktrick caster" or even just "DIY caster" etc and you'll see. You can use two floor tiles with grease in between them for the pivots, and use cardboard taped to the floor to set your lines for 15 degrees. I think I have pictures of my doing that buried in my build thread somewhere.

    On the hurricane bracket, I flipped the attachment to the lower control arm, but also had to ensure the squiggly part of the bracket was facing the same way as stock (I can't remember if it's up or down - I did it wrong initially and Bob noticed and corrected me as he has done for a number of other guys).

  8. #368
    Quote Originally Posted by Hindsight2.0 View Post
    Yeah I would not measure caster like that. I tried it after I set it using a digital gauge and it wasn't accurate at all. Maybe others have had better luck with it but not me. I set my angle gauge on a little jig I made that resembles this:
    https://www.quicktrickalignment.com/...quantity-copy/
    You have to turn the wheel 15 degrees to the left, measure, then turn back to center, then 15 degrees to the right and measure again. You subtract the two. Go to youtube and search "quicktrick caster" or even just "DIY caster" etc and you'll see. You can use two floor tiles with grease in between them for the pivots, and use cardboard taped to the floor to set your lines for 15 degrees. I think I have pictures of my doing that buried in my build thread somewhere.

    On the hurricane bracket, I flipped the attachment to the lower control arm, but also had to ensure the squiggly part of the bracket was facing the same way as stock (I can't remember if it's up or down - I did it wrong initially and Bob noticed and corrected me as he has done for a number of other guys).

    Thanks, I'll check the links and your thread. Sounds like I can switch the hurricane bracket. I know I have the LCA mount correct with Squiggly down because I had to change it once to get it right.
    Harley
    Bought 2002 Donor Jan 2014
    First Start Jan 18, 2015
    First Drive Feb 14, 2015

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