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Front LCA eccentric bolt tabs- Question
Trying to make a long, complicated story short-
I found that the sub-frame on the end that locates the eccentric bolt head end of the driver's front LCA (rear bolt) is bent back. It was found when I went to replace all of the eccentric bolts after a shop performed an alignment and gave the car back to me stating "the bolts are toast and need to be replaced". So I ordered the new hardware, crawled under the car and started replacing them. Upon getting to the driver's front, just looking at the rear LCA/sub-frame, my attention was immediately caught that something was very wrong...and documented/took pictures of everything before even thinking about touching it. When I attempted to put a socket/ratchet on the nut, the head of my ratchet would jam into the body of the car before the socket even came close to fitting on the nut. That's when I noticed a bunch of dings/marks in the undercoating in the same area, leading me to the conclusion that the person who performed the alignment ran into this same situation. Replaced all hardware successfully and took the car back so the alignment could be finished to the desired specs. Later that day, I was told they were done, but the specs still couldn't be reached. This was done by the shop foreman (not the original alignment tech) and the service manager. When I dropped the car off, I had a conversation with the service manager about finding the bent sub-frame, the eccentric head not making contact with both tabs on the sub-frame, and how all of those areas had very fresh scoring on them before I put any tools on the bolt/nut, possibly indicating that the hardware had taken far more force to turn than it should have. He was very adamant that the tabs are not needed/critical to the range of adjustment, and said he didn't see any problem with the position of the end of the sub-frame and that what I was pointing out on a picture would not cause any problems with adjusting/aligning the bolt. Also, a small, but irritating detail- I got the car back and the steering wheel is clearly off-center to the left.......and the service manager "couldn't see" this....even went for a test drive with him, let him drive...and he still denied seeing any issue with steering wheel not being straight when driving in a straight line.....gave me a bunch of BS about how "they center the steering wheel by measuring various points of the wheel and the column cover to determine that it is straight". In all the years I've watch cars be aligned, the tech does it by sight, making sure left/right play is even, then putting locking device on the wheel to hold it in place. I've attached a picture of the steering wheel upon driving dead-straight into my garage. Given how much I've worked on cars, and understand why things are designed the way they are tells me that those 2 tabs are fulcrum points/points of leverage for the head to push off of in order to rotate the bolt within a designated range. Am I wrong? I simply cannot understand how the tabs are not critical to the designed range of motion of the bolt....that the tabs are spaced slightly narrower than the head to hold it in a specific location...and not let it turn without moving the bolt/changing the point of rotation from making the bolt move vs. the bolt being the "center of rotation" and not moving/adjusting the LCA.......if that makes sense. Apologies if my terminology is off. It seems to me that the tech didn't put a wrench on the head side when loosening the nut, and when trying to loosen the nut, the head of the bolt spun and bent/pushed out the sub-frame/tabs.... rendering the purpose of the tabs useless. That, coupled with the angle of the bolt being wrong (causing the problem of the ratchet to contact the body), leaves me unable to come to any other conclusion that all of those points are designed to be in specific locations and have a mechanical function. Can anyone confirm the design/location/function of the tabs? Can anyone provide me with any kind of documentation stating the function of the tabs and/or how critical their location(s) are, and that the eccentric head must be in contact with both tabs to maintain the designed range of adjustment? Here are some pics...including a side-by-side picture I took of the same location on another NB and how the sub-frame/tab is perpendicular to the eccentric head. https://cimg4.ibsrv.net/gimg/www.mia...0a905807e7.jpg https://cimg1.ibsrv.net/gimg/www.mia...e289c9f798.jpg https://cimg2.ibsrv.net/gimg/www.mia...288add77cc.jpg https://cimg3.ibsrv.net/gimg/www.mia...b7cc196e3c.jpg https://cimg9.ibsrv.net/gimg/www.mia...94819b9f59.jpg https://cimg2.ibsrv.net/gimg/www.mia...c0fed8dfac.jpg https://cimg5.ibsrv.net/gimg/www.mia...70bef1c7bd.jpg https://cimg0.ibsrv.net/gimg/www.mia...7b25812928.jpg |
Tabs locate the eccentric shim; and obviously are critical, as without theme there's nothing to resist lateral movement of the bolt inside the hole. It is the basis of how alignment adjustment works in a miata.
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Yea, but it should still work. And unless you’re on track with Hoosiers it won’t slip if properly tightened. I’ve seen plenty that aren’t touching. Neither of you should be tightening any of that with a ratchet and socket, just two long wrenches. You may not be engaging the bolt head if you’re on at any angle. If you’re really worried about it, you can try to bend that tab with a pry bar against the control arm or something, you might just move the bushing though. if the wheels off a little bit, turn the tie rods equal amounts to turn the wheels in the same direction as the steering wheel is pointed. Won’t affect your front tow significantly, but will cause you to counter the other way, therefore straightening the steering wheel. You’ll need next to no adjustment to fix that though. |
At the end of the day it sounds like you need a different alignment shop.
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Originally Posted by curly
(Post 1517362)
Yea, but it should still work. And unless you’re on track with Hoosiers it won’t slip if properly tightened. I’ve seen plenty that aren’t touching. Neither of you should be tightening any of that with a ratchet and socket, just two long wrenches. You may not be engaging the bolt head if you’re on at any angle. If you’re really worried about it, you can try to bend that tab with a pry bar against the control arm or something, you might just move the bushing though. if the wheels off a little bit, turn the tie rods equal amounts to turn the wheels in the same direction as the steering wheel is pointed. Won’t affect your front tow significantly, but will cause you to counter the other way, therefore straightening the steering wheel. You’ll need next to no adjustment to fix that though. My concern is that if the points where the big, round head of the bolt contact are not in the correct location/not even being touched, then would that not change the rotation point of the bolt, or allow the head to rotate around the body? Would allowing the head to sit lower change the designed location of the bolt's body? Furthermore, if the head/contact point of the head is not perpendicular to the axis of the control arm, would that not change the location of one end of the control arm vs the other? Given the inability to get the cross-caster adjustment problems they had, it seems logical to me the two are related. As for the steering wheel, well, I know it's a mostly simple fix....but no reputable should let a car leave like that. Whatever the outcome, the car is definitely NOT ever being worked on there again. |
Originally Posted by Doppelgänger
(Post 1517381)
I'm not worried about it slipping or coming loose, and the reason I had such tools on there was to remove the bolts and lightly snug them down enough to drive it back for a re-alignment.
My concern is that if the points where the big, round head of the bolt contact are not in the correct location/not even being touched, then would that not change the rotation point of the bolt, or allow the head to rotate around the body? Would allowing the head to sit lower change the designed location of the bolt's body? Furthermore, if the head/contact point of the head is not perpendicular to the axis of the control arm, would that not change the location of one end of the control arm vs the other? Given the inability to get the cross-caster adjustment problems they had, it seems logical to me the two are related. As for the steering wheel, well, I know it's a mostly simple fix....but no reputable should let a car leave like that. Whatever the outcome, the car is definitely NOT ever being worked on there again. Practically speaking, you should either fix your tabs or replace your subframe. Although it is the clamping force of the bolts that keeps everything in place, the bolts will slip more easily with messed-up tabs. They already slip too easily as it is. A better alignment shop would also be nice, but everyone always wants a better alignment shop :dunno: The bend appears to be outside the slots, so it shouldn't affect the actual clamping faces. That's almost certainly why it bent so easily. |
As always you’re heavily overthinking this, many miatas can’t reach advertised numbers. How a bolt sits doesn’t significantly alter the geometry, like deflection in rubber bushings is probably much more. As long as the numbers are good after tightening, it’ll be good. As afm said the real answer is a new subframe but I’d consider that overkill |
Original alignment Tech did that with an air impact on the nut side and no wrench on the bolt side. You can't prove it now.
You're going to have to try to bend it back to make it functional. |
Originally Posted by sixshooter
(Post 1517567)
Original alignment Tech did that with an air impact on the nut side and no wrench on the bolt side. You can't prove it now.
You're going to have to try to bend it back to make it functional. On the "prove it" issue, I feel I have pretty firm ground to stand on based on some key things: -Lack of any before/after specs documented from the initial alignment...to which the dealership admits that they should have record of, but don't. Likely due to them not having a printer connected to the alignment rack-/computer. The tech is expected to take a picture of the screen with their phone, email it to their work email, then save it in a specs folder. - A person who works on similar/focused areas of cars on a daily basis should notice if something is out of place. If something is wrong, the obvious protocol is to stop working, document/note all observations, bring it to a managers attention, then call the customer to inform them to see if they are aware of any issues and let the customer determine to proceed or stop working on the car. None of which happened in this case. - The scoring on the hardware indicates very recent forced contact/friction between surfaces that shouldn't take much effort to move if procedures are properly followed. |
Hit it with a BFH, touch up the paint. Don't get alignments there anymore.
The bolt is held by the clamping force though (which as those torques on a fine thread is in the 10s of ksi range). The tabs are not doing much as far as holding the bolt for the alignment. They are just there to push the bolt around for the alignment. |
Originally Posted by x_25
(Post 1517847)
Hit it with a BFH, touch up the paint. Don't get alignments there anymore.
The bolt is held by the clamping force though (which as those torques on a fine thread is in the 10s of ksi range). The tabs are not doing much as far as holding the bolt for the alignment. They are just there to push the bolt around for the alignment. Don't mind my craptastic paint skills, but this kinda represents in diagram of what I feel is the problem with the tab being bent off to the side...away from it's original location and how the bolts alignment is affected. I'm sure the tabs are, and need to be parallel to each other...being bent means they are no longer parallel. https://cimg1.ibsrv.net/gimg/www.mia...e4d628d51e.jpg |
The bushings are designed to take up angular slack like that. The 1-2mm over the length of the bolt are not going to do anything. (If the bushing section is 50mm long, and the bolt.is off 2mm on one end, thats a whole 2.3 degrees). All that is going to mater is that the car is in alignment, which they measure at the wheel and just finagle the bolt until it is. I honestly wouldn't even worry about it on my car, but your's looks in way better shape, so I can understand wanting it to be "right".
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I can understand that making sense. Unfortunately it only deepens my wondering of why the bolt is angled so much that the head of the ratchet hits the body when put on the nut...and why there is a 5.5* difference (negative?) in cross-caster...
I guess I was hoping to hear from someone else who has had their subframe/tabs out of place and what issues it caused/fix used. |
What are your current alignment specs? |
Originally Posted by curly
(Post 1517901)
What are your current alignment specs? Before is the "animated" picture, after is just numbers. Hell, the "before" was not far off of what I had asked of the tech on the initial alignment...that with 0* toe front and rear, -2* rear camber and even up the front camber with maximum achievable caster would have been fine, but the person who did the alignment pictured was so dead-set on getting the cross-caster even. I wish I knew what the numbers were the alignment tech set everything to the first time, but it sounded like he just gave up after "determining" the hardware was bad. The lack of before/after from that only leaves speculations. https://cimg1.ibsrv.net/gimg/www.mia...65ea797c5a.jpg https://cimg6.ibsrv.net/gimg/www.mia...a9143455b4.jpg |
4.2/6.6 caster indicates a problem. The tech was right to worry about cross-caster.
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Originally Posted by sixshooter
(Post 1517987)
4.2/6.6 caster indicates a problem. The tech was right to worry about cross-caster.
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A pothole or curb can bend things easily, too.
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And where are the eccentric heads of all four front adjusters? Every chassis and control arm can’t be perfect on everymiata, so at work I often max the camber and caster out, and adjust the high caster side down to match the low side, accepting whatever camber changes come with that. You’re more likely to feel a difference in caster vs camber side to side. Then of course for the front, zero the toe. |
Originally Posted by curly
(Post 1518012)
And where are the eccentric heads of all four front adjusters? Every chassis and control arm can’t be perfect on everymiata, so at work I often max the camber and caster out, and adjust the high caster side down to match the low side, accepting whatever camber changes come with that. You’re more likely to feel a difference in caster vs camber side to side. Then of course for the front, zero the toe. How you describe adjusting the caster and camber is exactly how I understand the procedure works, which is why I had told the alignment tech the first time a +/- target for those variances. Also, the tie rod ended were also replaced with new units at the same time as the bolts. I'm kinda surprised the shop foreman who did the 2nd alignment left the rears with those readings. The alignment he set makes for noticeable understeer/numbs steering input with weight transfer in hard cornering :( |
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