Alignment problem with Adjustable LCAs
Alignment problem with Adjustable LCAs I have on-car adjustable LCAs. And when they were set to equal lengths (~19.25" IIRC) the wheels looked pretty centered in the wheel wells.
I got an alignment today and two different alignment racks said the thrust angle was around .35. So it got adjusted.
Afterwards i can tell the LR wheel is set back atleast half a finger width (my rough measurement). So my question is how crooked is my car? Why is my thrust angle straight but it looks so bad?
I have pics.
I got an alignment today and two different alignment racks said the thrust angle was around .35. So it got adjusted.
Afterwards i can tell the LR wheel is set back atleast half a finger width (my rough measurement). So my question is how crooked is my car? Why is my thrust angle straight but it looks so bad?
I have pics.
Moving one forward and one back would have given the same results, the difference would be the same, except one would be slightly in front of where it used to be and the other side vice versa. Thing is, i'd have alot more fender beating to do if one had to move forward.
By adjusting both of the LCS instead of just one, you're splitting the difference, therefore the outcome isn't as noticible. For example, if you had to move one side of the car a 1/4" to get the thrust angle to zero, you'd get the same net result by moving each side 1/8", which would be less noticible.
Also, keep in mind that any variation in the way the front K-member sits in the car will affect the thrust angle. So, if for some reason your K-member isn't "dead nuts" to the rest of the car, the rear axle will have to be slightly "skewed" with respect to the rear of the unitbody, in order to line up with the front. This will also show up in your rear wheelwell gaps.
Having said that, did you notice any difference in the way the car drives? A couple of years ago, I had some "down time" at work, and during that period I was able to mess around in the machine shop. I got some steel tubing and fabbed up a set of rear LCAs. My mission was to make something stronger than stock, yet able to use the rubber bushings, as this is strictly a street driven car.
A few weeks ago, I got the car on a brand new Hunter "Hawk-Eye" alignment rack, and found that the thrust angle, while "within spec", is somewhat off. I was considering buying a set of adjustable LCAs to remedy this, because now that I know it's off, it's bothering me. However, I don't want to spend the $$$ if it's not really going to make a big difference, seeing as I spent a few $$$ to fab my tubular replacements....
It does drive better but this was a full alignment (Thrust angle, camber/caster on both fronts, and toe) so who knows how much of an impact it makes. Everything was slightly out.
I really never thought thrust angle mattered much on a street car because you set the front wheels to go straight based on the thrust angle anyway.
This is making more sense now, i might have to eyeball it though. And just move the axle forward an equal amount of threads on both sides. I'm running out of free seat time with the alignment rack.
I really never thought thrust angle mattered much on a street car because you set the front wheels to go straight based on the thrust angle anyway.
This is making more sense now, i might have to eyeball it though. And just move the axle forward an equal amount of threads on both sides. I'm running out of free seat time with the alignment rack.
I have a question though. I understand adjusting them on the slip plates allows the axle to move. Does that mean if i adjust them at home i should adjust them with the axle hanging? I figure if its on ramps weird **** could happen.
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I was considering buying a set of adjustable LCAs to remedy this, because now that I know it's off, it's bothering me. However, I don't want to spend the $$$ if it's not really going to make a big difference, seeing as I spent a few $$$ to fab my tubular replacements....
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as to slip plates take two pieces of plywood about 24"x24" put a garbage sack beween the two and add a spoon of oil presto you have slip plates, becarefull do not let ti slip sideways and fall off your jackstans
as to rear thrust line I suggest +/- 0.013 or less , my car likes +0.003, leaves hard and tracks stright
check my wed site to better understand alignment
and I am only posting for info, I want no work as I have retired two years ago
just my .02' Johnny
Along that line, however, do you know a source for those "adjustable rubber ends" that you speak of? I was considering the "Johnny-Joints", and dreamed up a way to modify my "custom" LCAs, but have to get a lathe that I can use, to make a couple of the parts....
The ones I used for mine were the Howe Rubber bushings. With one rubber end and one rod-end, it actually was pretty quiet, until the rod-ends would begin to wear.
It was actually this design: http://www.jonaadland.com/Z28/Mods/L...minumLCAs.html
EDIT: This is the FRRAX thread that goes into discusses it: http://www.frrax.com/rrforum/index.p...inum+LCA's
I can tell you already that I've actually tried both Howe rubber bushings in both ends (with reducers) and there was WAY too much bind! I then reinstalled the QA1 rod-ends on axle side only and then it felt "normal".
The only other thing I could suggest would be to see if you or someone could fabricate your own threaded bushing "cases" to accept the moogs.
It was actually this design: http://www.jonaadland.com/Z28/Mods/L...minumLCAs.html
EDIT: This is the FRRAX thread that goes into discusses it: http://www.frrax.com/rrforum/index.p...inum+LCA's
I can tell you already that I've actually tried both Howe rubber bushings in both ends (with reducers) and there was WAY too much bind! I then reinstalled the QA1 rod-ends on axle side only and then it felt "normal".
The only other thing I could suggest would be to see if you or someone could fabricate your own threaded bushing "cases" to accept the moogs.
Last edited by Foxxtron; Jul 14, 2009 at 11:45 PM.
I can't find the threaded rubber bushings, but I know they're out there. I've found them before, but I can't remember how I found them.
Another idea is to buy rod-ended ones. Get the rod ends with 3/4" holes. Then, buy a delrin sleeve that has a 3/4" outer diameter and a 5/8" inner. Then use a 5/8" bolt to hold it, with the sleeve inbetween the rod end and the bolt to absorb vibrations.
Oh, and just a point of clarification - QA1 XMR rod ends are NOT the best out there. They are what I use, but not the best. Aurora ends are the best I've heard of. But, at $75 for a 3/4"-3/4" rod end, a little rich for my blood.
Another idea is to buy rod-ended ones. Get the rod ends with 3/4" holes. Then, buy a delrin sleeve that has a 3/4" outer diameter and a 5/8" inner. Then use a 5/8" bolt to hold it, with the sleeve inbetween the rod end and the bolt to absorb vibrations.
Oh, and just a point of clarification - QA1 XMR rod ends are NOT the best out there. They are what I use, but not the best. Aurora ends are the best I've heard of. But, at $75 for a 3/4"-3/4" rod end, a little rich for my blood.
EDIT: I still think that this is all best done with accurate measuring tools (e.g. an alignment machine at best)
Last edited by Foxxtron; Jul 15, 2009 at 08:40 PM. Reason: Additional comment
