WSM Confusion - Lower control arm bolt torque
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WSM Confusion - Lower control arm bolt torque
Reassembly after doing the oil pan gasket.
Volume IV
Page 40-5
Bolt #19
From the manual:
"Screw in until only 2 threads are visible. Do not tighten to 120Nm (88 fltb) until assembly is completed and springs have settled"
Ok, I did not remove or disassemble the strut - so when it says "springs have settled" do they mean after driving it a few miles to settle the front end? I dunno driving around with these loose seams odd so I must not be understanding something.
Volume IV
Page 40-5
Bolt #19
From the manual:
"Screw in until only 2 threads are visible. Do not tighten to 120Nm (88 fltb) until assembly is completed and springs have settled"
Ok, I did not remove or disassemble the strut - so when it says "springs have settled" do they mean after driving it a few miles to settle the front end? I dunno driving around with these loose seams odd so I must not be understanding something.
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Whoa! I've been doing this wrong. I read a chart earlier in the WSM on page 40-02 incorrectly as 62 ft lbs for the front axle control arm bolts - both sets (19 and 22 in the chart on 40-2 for early suspension; bolts 23 and 26 in chart on 40-7 for 86+ suspension). Don't ask me to explain how I did this.
Table 40-02 clearly says that the bolt materials are different between the sets on the front axle and the torques are different. Eeek! OK, looks like I'll be going out to the lift tonight for a little checking. Fortunately, I have not done this to anybody else's car.
I'm guessing this means you lower the car to the ground before you torque, although it only makes this note for bolt 19 and not 22. I suppose with only 62 ft lbs on 22, it settles without being left loose, but they want the clamping force on the other end with bolts 19 to be much higher.
Others have commented that they LOOSEN these bolts after the car is on the ground and this allows the car to settle to the correct ride height. I've never done that, and the car settles eventually the same as when you lift the car and let it down. When I have loosened the bolts later, the car did not settle any further. That's because I didn't do bolt 19 to 88 ft lbs.
So, I guess they intend there to be a differential in that way the bushings are held at each end of the control arm, with one end pinched tighter than the other.
Table 40-02 clearly says that the bolt materials are different between the sets on the front axle and the torques are different. Eeek! OK, looks like I'll be going out to the lift tonight for a little checking. Fortunately, I have not done this to anybody else's car.
I'm guessing this means you lower the car to the ground before you torque, although it only makes this note for bolt 19 and not 22. I suppose with only 62 ft lbs on 22, it settles without being left loose, but they want the clamping force on the other end with bolts 19 to be much higher.
Others have commented that they LOOSEN these bolts after the car is on the ground and this allows the car to settle to the correct ride height. I've never done that, and the car settles eventually the same as when you lift the car and let it down. When I have loosened the bolts later, the car did not settle any further. That's because I didn't do bolt 19 to 88 ft lbs.
So, I guess they intend there to be a differential in that way the bushings are held at each end of the control arm, with one end pinched tighter than the other.
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It is an interesting topic as I did tighten my front control arm with the proper torques, but evidently not the correct way.
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I'm sure most people just torque them down, I'm being very careful with this job. Parts falling off is not a habbit I'm looking to start.
I like the "with two threads showing" What? Showing where? Between the coupler and the chassis? I tried that, the bolt was very loose (no, didn't lower the car to "see what would happen").
Not to mention this is giong to be one hard bolt to torque down with the car on the ground. Not only will access be a bitch, my torque wrench will be upside down!! I do not use the click wrenches on anything but the wheels and crank bolt (non-click wrench at that size is mucho $$$, page has one).
I like the "with two threads showing" What? Showing where? Between the coupler and the chassis? I tried that, the bolt was very loose (no, didn't lower the car to "see what would happen").
Not to mention this is giong to be one hard bolt to torque down with the car on the ground. Not only will access be a bitch, my torque wrench will be upside down!! I do not use the click wrenches on anything but the wheels and crank bolt (non-click wrench at that size is mucho $$$, page has one).
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I agree this is a bear to reach on the ground. A 4-post lift helps. Talk to your SO about that. Or just roll the front up on ramps.
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Originally Posted by Bill Ball
I agree this is a bear to reach on the ground. A 4-post lift helps. Talk to your SO about that. Or just roll the front up on ramps.
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I think the concept on these is that the fastener locks the bushing material into its' "resting" orientation, so that when the wheels move up and down on the road surface the bushing material is twisted within its designed range of movement.
I found this out on my 968 which has the same requirement ... there are voids in the bushing rubber which are designed to permit movement a certain number of degrees in either direction. If you were to tighten the bolts with the car on jacks and the A-arms hanging down, then when you set the car on the ground the bushing would be twisted away from the neutral position and the bushing would no longer function as intended.
I found this out on my 968 which has the same requirement ... there are voids in the bushing rubber which are designed to permit movement a certain number of degrees in either direction. If you were to tighten the bolts with the car on jacks and the A-arms hanging down, then when you set the car on the ground the bushing would be twisted away from the neutral position and the bushing would no longer function as intended.
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Thanks, Tom. It's interesting that the two ends, whcih seem identical, have different bolt hardware and torques and the precaution only deals with the high-torque end.
I rechecked today that I had not swapped the bolts, and I loosened the high-torque end and resnugged it to spec.
I rechecked today that I had not swapped the bolts, and I loosened the high-torque end and resnugged it to spec.
Last edited by Bill Ball; 08-18-2006 at 12:33 PM.
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So, to be sure, the corrective action is, to simply loosen the nuts in question with the weight on the wheels, allow the bushing to adjust itself and retighten to spec? I wonder if they will find their position if it has been 9 months and a thousand miles since the mistake? Not much else I can do. Glad to catch this thread.
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Originally Posted by SteveG
So, to be sure, the corrective action is, to simply loosen the nuts in question with the weight on the wheels, allow the bushing to adjust itself and retighten to spec? I wonder if they will find their position if it has been 9 months and a thousand miles since the mistake? Not much else I can do. Glad to catch this thread.
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Note added - The front bushing on the lower control arm is FIXED to the control arm and its solid fitting that is bolted up to the body. The rear bushing is clamped down with a separate bracket. If the bushing on the front fitting rotates at all, it is broken and the whole arm needs to be replaced. This is not new knowledge. It's just not in this thread. So, the rear is free to move when the bolts are left loose and the car is settled. The front should not be able to rotate unless the bushing is no longer bonded properly.
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If the front cannot rotate at all relative to the attachment point to the chassis, then the control arm, itself, cannot rotate either. And it must.
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On the original subject of this ancient thread: I always hand-tighten the rear LCA bolts, back them off two turns, settle the suspension and then torque them to spec. With the rear bolts loose the suspension will settle very quickly: two 360's in my driveway, one each way, a drive up the street with some heavy brake application and it's done.
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Whereas the rear saddle can be clamped down onto the bushing with the bushing and arm in different positions - with the arm drooping (most likely) arm straight (shouldn't take much settling) or arm pointing up (highly unlikely) You are effectively preloading the suspension one way or the other, hence the need for settling. In the worst case if the arm was at an extreme angle when the saddle clamped down putting the weight of the car back on it's wheels could deform the bushing far enough to tear the rubber.
Hence leave the saddle loose until the weight is back on the wheels so that the bushing can rotate in the saddle without deforming the rubber.