I'm still trying to work out some alignment issues but have a question ... If I were to make the passenger side LCA longer than the drivers side would that make the Jeep pull left, right or have no affect?
Steering Geometry Question
- Thread starter CodaMan
- Start date
Lowers are for moving the axle back and forth. Extend or shorten both the same length to move your axle forward or backwards. Only reason that you would make them a different length is to square your axle to the opposite axle. If your axles are not parallel with each other then yes your jeep will pull to the left, right or be bouncing all over the road.
I’m a firm believer that parallel axles will really improve ride quality.
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OP
I squared my front axle to common points on the frame and have them within 1/16" I believe. So now I guess I need to check the front axle to the rear axle so I can find out why this thing pulls left.
what do you mean "pull to the left"? Is the steering wheel not centered or does it lit. veer to the left and under what conditions? What had you changed before it began to pull to the left?
Is it pulling hard to the left or tracking left??? I always thought that if you take your hands off the wheel and it pull fast to the left then it could be a different problem than it slowly tracking left. Toe in and tire pressure would be my first place to look
As for the control arms. Maybe it’s just me but I like to square the rear axle to the front of the skid plate. Then square the front to the rear. I think a lot of people confused the draglink and track bar angles causing bumpsteer. When it’s really their axles after a lift that aren’t parallel and they are fighting each other. Gives that same type of bump steer feeling.
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As for the control arms. Maybe it’s just me but I like to square the rear axle to the front of the skid plate. Then square the front to the rear. I think a lot of people confused the draglink and track bar angles causing bumpsteer. When it’s really their axles after a lift that aren’t parallel and they are fighting each other. Gives that same type of bump steer feeling.
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One of the more common myths out there, lowers set wheelbase, uppers set pinion and it just isn't true. You can NOT change the lower arm length to move the axle forward or back in the front or rear without also changing the pinion angle. The reason for that is the brackets are below centerline so if you push the lowers longer, the pinion will also lower front or rear.
You can NOT extend the uppers to fix pinion angle and not change the wheelbase. The LCA brackets are below centerline so as the pinion rotates upward, the axle moves to make the wheelbase longer.
Very first thing to do with any pull to one side is make certain the steering wheel is perfectly centered with the axle centered. The steering gear has to be centered or there will be some slight steering output because it thinks it is getting a slight bit of steering input. Start there and report back.
Dang dude. You mic dropped on me again. I’m goin to throw out some sound advice one and you better approve.
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My apologies sir, it is absolutely nothing personal and the vast majority of the time when I reply to something, I do not read who said it. In places that have signatures, my most common and favorite is "knowledge does not equal understanding".
That has to do with my experiences with a lot of products over the years that were designed by those who see something, make their copy of it but have no understanding of the nuance of the problem they are trying to solve with said product so they tend to overlook the things that make the product the way it is.
Most notable is M from a 3 letter company. I designed the Savvy aluminum trail door. There were many aluminum trail doors that have graced my driveway from several companies over the years and the three things they all had in common as problems I set out to solve.
They were all bent out of one piece of aluminum or one piece with a small welded in section at the armrest bend.
To understand the consequences of aluminum and the bending issue, you have to know that high strength aluminum alloy sheet will break if you try to bend it in a tight bend. Second problem is due to the top rail not being flat and rises up toward the windshield frame, there is a weld there or some goofy brace and it either looks like crap or the weld breaks. Third problem is the use of the crappy Bestop soft door latch.
So, since we play in the rocks, I made the door have a 6061 T6 main panel and I designed a separate bent top rail out of weaker aluminum that can be bent with tight corners and then I had a forming die built that put the bend in it to make it raise from flat under your arm up to the windshield frame. I used a commercial latch and mounted in only on the inside. (trail doors don't have uppers)
The design was "borrowed" except that they used 5052 which is a softer, weaker, and much cheaper alloy. But, they made a similar top rail and bolted the main panel to it. They fully missed the why of the two piece design by using the weaker lower panel. I did it because we need a stronger door when you get it against the rocks. If you don't do the stronger panel, there is absolutely no need to make a 2 piece door, just bend it up out of one piece since the weaker aluminum can be bent that way without breaking. Knowledge does not equal understanding.
OP
Correction, it pulls right not left, and by pulling I mean that if I take my hands of the wheel at say 40 MPH, on a non-crowned road, I would be off the road in a couple of seconds.
History —-
— Been doing it since I bought this STOCK setup vehicle in May
— Installed +2" springs and longer shocks
— Installed .75" spacers in front to level
— Has new tires, balanced and set at 26 psi
— Replaced tie-rod with ZJ tie-rod
— Replaced drag link with TJ link
— Steering is tight
— Replaced LCA's with adjustables
— Steering wheel is straight until speed is increased
— Measured front axle to body mount bolts. It is withing 1/16" of being square
— Jeep has zero vibrations at any speed
— Swapped tires, first left to right then front to back ... no change
— Based off the below printout, which was from before the LCA's were installed, I plan on putting it back on the rack, make sure caster is even then clamp down the steering wheel at center and adjust the right side toe-in to .1, then adjust the left side to .1 to get a total toe-in of .2. That should center everything up, right @mrblaine? and then see how it drives.
Anything wrong with this plan or should I check other measurements first?
History —-
— Been doing it since I bought this STOCK setup vehicle in May
— Installed +2" springs and longer shocks
— Installed .75" spacers in front to level
— Has new tires, balanced and set at 26 psi
— Replaced tie-rod with ZJ tie-rod
— Replaced drag link with TJ link
— Steering is tight
— Replaced LCA's with adjustables
— Steering wheel is straight until speed is increased
— Measured front axle to body mount bolts. It is withing 1/16" of being square
— Jeep has zero vibrations at any speed
— Swapped tires, first left to right then front to back ... no change
— Based off the below printout, which was from before the LCA's were installed, I plan on putting it back on the rack, make sure caster is even then clamp down the steering wheel at center and adjust the right side toe-in to .1, then adjust the left side to .1 to get a total toe-in of .2. That should center everything up, right @mrblaine? and then see how it drives.
Anything wrong with this plan or should I check other measurements first?
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No apologies needed. I just just joking around. Nice story about the door and I totally understand about the CA’s. I can visualize exactly what your saying. Moving one is alway going to affect the other, so you have to find the sweet spot of what your trying to do by moving both. Trying to get me to explain that so someone can understand. Whole other ballgame.
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By that print out. Have you checked ball joints?? I would work on my toe and my thrust angle. Squaring the rear to the frame fixes the thrust angle. Then square front axle to rear.
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OP
Ball joints seem fine, but maybe the front right needs an offset ball joint?
Should I find the the rear is not square today, how would I square it?
Not for nothing but the TJ front axle has a few tenths of a degree cross caster in it so that it will ride up the low side of a crowned road since most US roads are crowned. If you run it on a crowned road and it goes fairly straight, then the pull is more related to a cross caster and not something inherently wrong.
I square my rear axle ( and I’m sure there are many ways to do it) by hanging plumb bobs off each end of the rear axle. Then I take a tape measure and hook it to the front of the skid plate facing the front axle. I measure each side then I make control arm adjustments until they are money. Then I hang plumb bobs on the front axle and measure between the front and rear. It’s a delicate process on which axle to move and how to make sure what your moving doesn’t mess up another item like pinion angle.
I chose to move the front because I can get away with the pinion angle not being dead on because of the longer drive shaft and caster. I wanted the rear pinion angle spot on. Make the adjustments you need your good. My thrust angle was all out of wack after my lift was installed. I fixed all that and got the front and rear axles dailed in, and the ride so much noticeability improved. I have good pinion angle and no inferences and full bump. I could probably even shave off some of my bumpstop extensions and still be find.
Let me know what you come up with I’m interested to see how it all shapes up
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I don't use a tape measure. I use a long stick and a framing square with a couple of clamps. Put the end of the stick (I use aluminum) against the forward edge of the rear axle tube parallel to the ground, lay square against stick, vertical end of square gets lined up in center of middle t-case skid bolt and clamped in place. Carry that over to the other side, check it and make both sides the same.