In over my head, wheels turning at different rate
So here's the deal, I've been doing a LOT of suspension work on my 4runner (custom steering knuckles, 4th gen lca's) crazy stuff. Now before anyone asks why, just know that my answer is going to be "cuz I can." The issue that I'm having is that when I turn the steering wheel back and forth one wheel will be facing further out than the other. When the front end is on jacks both wheels will be facing straight and turn with no problems. However when the wheels are touching the ground in my driveway and I turn back and forth one wheel eventually is much further out than the other. Is there anyone out there who has some kind of constructive advice?
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Read up a little on Ackermann Angle. You might not have a problem... The steering wouldn't work very well if the tires stayed parallel all the time.
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It's not that the tires become slightly out, they get WAAAY out. Out so much that I wouldn't even feel comfortable driving it. When I return the steering wheel back to straight, one wheel will be straight and the other is still obviously pointing out.
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Don't 4th gen LCAs require a bit of work to make them fit/work? My guess would maybe be something around there, perhaps with how/where the tie rods interact
Also generally interested in hearing about this LCA swap, iirc I've only read it once or twice on here Edit: skimmed over the part about weight on vs off the wheels. That's very strange. Maybe droop has something to do with it, but my money is still something to do with the steering rack. I believe @MStudt knows a little about this subject. |
“Correct” Ackermann steering geometry takes into account both the track width and wheelbase of the vehicle. So using 4th Gen LCA I’m assuming you are altering the width. Not sure of the details of the custom knuckles but the desired Ackerman angle is mainly achieved by altering the length of the tie rods and therefor the angle of the location they connect to on the knuckle. Also changing the location of the tie rod connection (making them not parallel) can introduce steering effects too.
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Put your steering wheel straight, loop the seatbelt through the bottom hoop of the wheel and lock it in place then measure each side of the the rack from the inner boot clamp to the outer tie rod end. 1/2" - 1/4" difference can make a big difference in steering angles. |
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I think pictures would help more than anything. Pictures of the spindles, steering rack, LCA's in place, and UCA's. If you have a custom spindle they had to have come from a 4th Gen 4runner or be 100% custom from the ground up. Obviously, the 4th Gen LCA will mount to the spindle in a different pattern than the 3rd Gen. The steering on a 4th Gen spindle is also in front of the suspension as opposed to behind like the 3rd Gen. That would mean you have a hybrid of sorts between a 4th/3rd Gen. Or, you have a 4th Gen steering rack that you somehow mounted in a 3rd Gen. UCA's are also going to be different, and so are the upper ball joints. Just did some T4R stalking. Are you also running the JBA 4th Gen UCA's you bought from the forum? If so you have 4th Gen LCA's, 4th Gen UCA's, and custom spindles. With no mention of a 4th Gen steering rack, I'll assume you have a 3rd Gen still. I'm betting you have done a lot more than what you're posting. Did you change the UCA mounts at all? Did you change the LCA mounts at all? What steering rack? Whose spindles? What CV's are you using? The 3rd Gen steering is known for not allowing wheels to return to normal if the guide bushing has been overtightened. Most of the time this happens when someone replaces the guide bushing and over tightens the cap during install. Mike |
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I guess I'll describe this build in a little more detail and start from the top down... you are correct about the uca's. Surprisingly they were fairly easy to mount, I had to add a couple of washers to each side of the inside of the uca to make up for the wider width. The spindles are a custom blend of 4th and 3rd gen spindles to accommodate the uca mount, lca mount and tie rod mount. I did my absolute best to not make them any longer than the original 3rd gen spindles and to keep the tie rod mount location as close to it's original location as possible, which I'll admit isn't exactly close to where it used to be. The steering rack is the original 3rd gen rack in its original location, which made mounting the lca's quite a p.i.t.a. Due to the wider width of the lca mounts I had to cut off the original mount locations and relocate them. Because the rack is in the same location that meant sending the front mount location about 2.5" forward from where the 3rd gen lca mount used to be. I'll definitely take some pictures and load them up at some point today to give you guys a better idea of that mess that I just explained. I should also mention that after turning the tires on the ground and them become not parallel with each other, and I jack it back up, the wheels return to being very close to parallel again. Any help and ideas you guys have is greatly appreciated and welcomed! |
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Mike |
Sounds like ridiculously large amount of bump steer, not an ackerman issue (yet).
The the lower arm and steering tie rod should be parallel. If not, you will get large changes in toe through suspension travel. -Charlie |
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