Tightening A-arm bolts??
02-12-2010, 01:26 PM
#1
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Tightening A-arm bolts??
I'm having a tough time being able to get anything up inside the frame to tighten the nut onto the bolt. Where the bolt goes through the bushing and into the frame. Any suggestions?
02-13-2010, 02:25 PM
#2
AudiWorld Senior Member
Re: "up inside the (sub-) frame...
Try an off-set box-end wrench (see photo). Sometimes these are available in a "deep" version. You know you're to have the weight on the wheels before tightening these, correct?
Last edited by Lago Blue; 08-24-2015 at 07:19 AM.
02-13-2010, 07:05 PM
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Thanks
I ended up using a gearwrench socket. It worked out great. I torqued them to 30 ft/lbs with some weight on the tires, as i'm too big to get under the car with it fully loaded. Think this will cause problems?
02-15-2010, 08:11 AM
#4
AudiWorld Senior Member
Re: "torqued A-arm bushings..with (only) -some- weight on the tires,.cause problems?"
It may and here's why:
a.) It's the factory recommended procedure to put the <b>full</b> weight on prior to, and while tightening.
b.) Note they're also quite happy to sell you more bushings the sooner your current ones are toast!
c.) The normal operation (winding-up & unwinding) of the bushing during suspension travel can be seen in the graphic below. Since the bushing wants to return to the "at rest" position, it is therefore critical to bushing life that the "at rest" position for the bushing be made to correspond to the "at rest" position for the car. Hence the factory reco'd procedure for normal weight on wheels.
d.) The normal failure mode (as you may know having replaced yours) is tearing. So even if installed properly, they tend to fail by the shearing or tearing of the rubber inside the mount, and/or outright failure of the bonding between the rubber and the metal core and/or outer sleeve.
e.) Each A-arm is held to the sub-frame by these two bushings, most of your tire's lateral loads are transmitted to the car through these, and they need to share the load, more or less. As one begins to fail (usually the rear one fails first) the remaining bushing is simply not positioned correctly to transmit the load, let alone strong enough to function by itself. It too, will distort and fail in short order.
f.) By not fully weighting the suspension prior to, and while tightening the subject bushings centre-bolts; upon lowering the car totally onto it's wheels afterwards, you have wound-up the cores of the bushings relative to their exterior shells. This means that even in their most relaxed position, the bushing's thin rubber sections are never fully relaxed, but are pre-stressed and set up perfectly to wind-up even farther during normal suspension travel, beyond the design limit, and tear early, if not immediately.
Considering the benefits of proper installation (reduced maintenance and improved drive-ability, etc.) I wouldn't risk fudging this procedure. In fact, keeping these bushings in good shape is probably one of the simplest and best things one can do for your car, period. Strut mounts get a lot of press, and their replacements can be almost sexy; but A-arm bushings are just as basic if not more so, to the proper functioning of the car, but perhaps because they are hidden; they get little respect. That they often get overlooked and abused is just wrong. To properly locate and suspend all your tire's loads with pin-point precision in the wheel-housing, you need at least three near perfect fixed position chassis attachment points, two of which are these.
If you had just installed "Pro-Mounts" and realized you did it wrong, would you hesitate?
You can see a cross-section of the mounts here (open the audi 90 front control arm bushing "pdf" below):
http://www.meyle.com/EN/Service/Tech...formation.html
The other thing to realize is that the rubber is <i>not</i> captive in that assembly, <i>except</i> by being bonded to the metal parts. They have only a limited axial and radial envelope within which they can operate without over-extending and not be able to bounce back; unharmed. Even a partial failure of that bond will degrade your suspension's performance. This will result in geometry inaccuracies, tire misalignment and wear etc. Note there are three metal parts and the rubber is very thin. Thin like an elastic band.
I suspect that many who have been in a hurry to "lower" their cars have either ignored or not even thought of this critical OEM instruction, and whether they realize it or not, they suffer as a result.
Sidenote: many here like myself have even back-stopped the OEM bushings with low-friction plastic "stop" (or thrust) -washers to preserve that brand new feel and function of properly installed OEM A-arm bushings with great success.
Finally, as to access, to make room under the car to do this job, drive onto a wide plank. I do at least two things prior, to prevent it from possibly rolling, such as; park in gear and block the tires at the opposite end of the car. If doing only one side with the wheel off, I jack the car with a hockey puck on the jack to give it a soft face to the chassis. I then block <i>under</i> the car with some wood so it can't fall. This gives me a secure space to proceed. Please work safely.
a.) It's the factory recommended procedure to put the <b>full</b> weight on prior to, and while tightening.
b.) Note they're also quite happy to sell you more bushings the sooner your current ones are toast!
c.) The normal operation (winding-up & unwinding) of the bushing during suspension travel can be seen in the graphic below. Since the bushing wants to return to the "at rest" position, it is therefore critical to bushing life that the "at rest" position for the bushing be made to correspond to the "at rest" position for the car. Hence the factory reco'd procedure for normal weight on wheels.
d.) The normal failure mode (as you may know having replaced yours) is tearing. So even if installed properly, they tend to fail by the shearing or tearing of the rubber inside the mount, and/or outright failure of the bonding between the rubber and the metal core and/or outer sleeve.
e.) Each A-arm is held to the sub-frame by these two bushings, most of your tire's lateral loads are transmitted to the car through these, and they need to share the load, more or less. As one begins to fail (usually the rear one fails first) the remaining bushing is simply not positioned correctly to transmit the load, let alone strong enough to function by itself. It too, will distort and fail in short order.
f.) By not fully weighting the suspension prior to, and while tightening the subject bushings centre-bolts; upon lowering the car totally onto it's wheels afterwards, you have wound-up the cores of the bushings relative to their exterior shells. This means that even in their most relaxed position, the bushing's thin rubber sections are never fully relaxed, but are pre-stressed and set up perfectly to wind-up even farther during normal suspension travel, beyond the design limit, and tear early, if not immediately.
Considering the benefits of proper installation (reduced maintenance and improved drive-ability, etc.) I wouldn't risk fudging this procedure. In fact, keeping these bushings in good shape is probably one of the simplest and best things one can do for your car, period. Strut mounts get a lot of press, and their replacements can be almost sexy; but A-arm bushings are just as basic if not more so, to the proper functioning of the car, but perhaps because they are hidden; they get little respect. That they often get overlooked and abused is just wrong. To properly locate and suspend all your tire's loads with pin-point precision in the wheel-housing, you need at least three near perfect fixed position chassis attachment points, two of which are these.
If you had just installed "Pro-Mounts" and realized you did it wrong, would you hesitate?
You can see a cross-section of the mounts here (open the audi 90 front control arm bushing "pdf" below):
http://www.meyle.com/EN/Service/Tech...formation.html
The other thing to realize is that the rubber is <i>not</i> captive in that assembly, <i>except</i> by being bonded to the metal parts. They have only a limited axial and radial envelope within which they can operate without over-extending and not be able to bounce back; unharmed. Even a partial failure of that bond will degrade your suspension's performance. This will result in geometry inaccuracies, tire misalignment and wear etc. Note there are three metal parts and the rubber is very thin. Thin like an elastic band.
I suspect that many who have been in a hurry to "lower" their cars have either ignored or not even thought of this critical OEM instruction, and whether they realize it or not, they suffer as a result.
Sidenote: many here like myself have even back-stopped the OEM bushings with low-friction plastic "stop" (or thrust) -washers to preserve that brand new feel and function of properly installed OEM A-arm bushings with great success.
Finally, as to access, to make room under the car to do this job, drive onto a wide plank. I do at least two things prior, to prevent it from possibly rolling, such as; park in gear and block the tires at the opposite end of the car. If doing only one side with the wheel off, I jack the car with a hockey puck on the jack to give it a soft face to the chassis. I then block <i>under</i> the car with some wood so it can't fall. This gives me a secure space to proceed. Please work safely.
Last edited by Lago Blue; 11-06-2015 at 08:18 AM. Reason: just the usual, clarity, punctuation, spelling and emphasis.
02-16-2010, 05:45 PM
#5
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Get Some...
Ramps! Or make them out of wood (never cinderblock). The quattro system makes it easy to drive up onto them. Also, your basic open-ended wrench works for these, albeit at a weird angle. With the right bolts and some anti-seize, the nut doesn't really want to turn that bad anyway, so it doesn't matter if you don't have the perfect leverage.
In an emergency, you might be able to use a loading ramp in a deserted warehouse district (DAMHIK) to get enough room under the car to do this kind of thing. Some oil change places use a pit, so the car has weight on wheels while still having room under it to work.
Torque them down with the full weight on, or you'll get seriously reduced life from them. PITA, maybe, but better than doing it over all again in a few months.
Lago Blue: A question: where do you put the washers to bolster the control arm mounts? I have a new set under the car right now waiting on camber bolts so I can tighten everything up with weight on it, and I'm seriously interested in something that does for the control arm bushings what Mount Savers do for the strut mounts (got some of those, too.)
In an emergency, you might be able to use a loading ramp in a deserted warehouse district (DAMHIK) to get enough room under the car to do this kind of thing. Some oil change places use a pit, so the car has weight on wheels while still having room under it to work.
Torque them down with the full weight on, or you'll get seriously reduced life from them. PITA, maybe, but better than doing it over all again in a few months.
Lago Blue: A question: where do you put the washers to bolster the control arm mounts? I have a new set under the car right now waiting on camber bolts so I can tighten everything up with weight on it, and I'm seriously interested in something that does for the control arm bushings what Mount Savers do for the strut mounts (got some of those, too.)
02-16-2010, 09:59 PM
#6
AudiWorld Senior Member
Re: A-arm stop-washers; and where to put them...
Into the void.
IMO on each A-arm, the rear-most bushing's "share" of the load is greater, and is greater simply because braking force typically trumps what acceleration could offer.
The later cars have the lovely front OEM forged steel wish-bones with the larger than previously sized bushings. Interestingly, some of those forged arms have different sized bushings, fore vs. aft. In those rare cases, it is always the aft one; that is larger.
Have a look at an early A4 sometime with it's "improved" front suspension (you might already know it shares it's rear legs with our B4s). The rear-most joint on it's lower front A-arm is also way enlarged vice the forward one.
They wouldn't be doing all that for nothing. Clearly the best place to put a thrust-washer is on the rear side of the aft bushings. The rear side of the forward bushing (properly installed, it is pointing the other way), doesn't lend itself nearly so well to the task as the relatively broad flat rear face of the aft bushing. By also installing a 2nd pair of thrust-washers on the front side of the forward bushings, any forward A-arm movement is also prevented, the arms are now captive fore and aft between the "stops", and the the interface between bushing faces and stop-washers is now positively kept closed helping to keep debris out. Further, despite that I think most of the work is done by the just the washers installed on the aft side of the rear bushings when the car is travelling in a straight line, cornering is perhaps another matter.
In the photo above, the washers are going to fit around that metal centre-core's O.D. and extend outward sufficiently, such that they fill the void between bushing's flanged face and sub-frame bracket face. Like book-ends, together they will now limit the A-arm from any fore-aft movement, removing this task from the bushings themselves and in my view, prevent the damaging fore-aft over-extension of the bushings that would otherwise take place.
The significance of this axial movement was made clear to me as follows. I had spray-painted white, my A-arms after replacing the subject bushings, reinstalled and drove the car. Later working under the car again, I noticed that the white paint was partially worn off the rubber faced bushing flange where it <i>must</i> have been both touching and turning, at the same time, the sub-frame!
Ergo, plastic stop-washers.
Yes exactly, the stop (or thrust) -washers are complimentary to A-arm bushings, just as Mount-Savers are to strut top-mounts. Again MHO only, those three mounts, restrained, (note I only did this mod post-Pro-mounts); further transforms the steering. I could go on, IIRC, I did a write-up on this, if I find it later, I'll post a link (for others, you may have seen it) so I won't have to go on; now.
Frankly, I'm impressed that someone actually appears to get it.
Good points about the ramps too, I occasionally use a set of steel ones.
IMO on each A-arm, the rear-most bushing's "share" of the load is greater, and is greater simply because braking force typically trumps what acceleration could offer.
The later cars have the lovely front OEM forged steel wish-bones with the larger than previously sized bushings. Interestingly, some of those forged arms have different sized bushings, fore vs. aft. In those rare cases, it is always the aft one; that is larger.
Have a look at an early A4 sometime with it's "improved" front suspension (you might already know it shares it's rear legs with our B4s). The rear-most joint on it's lower front A-arm is also way enlarged vice the forward one.
They wouldn't be doing all that for nothing. Clearly the best place to put a thrust-washer is on the rear side of the aft bushings. The rear side of the forward bushing (properly installed, it is pointing the other way), doesn't lend itself nearly so well to the task as the relatively broad flat rear face of the aft bushing. By also installing a 2nd pair of thrust-washers on the front side of the forward bushings, any forward A-arm movement is also prevented, the arms are now captive fore and aft between the "stops", and the the interface between bushing faces and stop-washers is now positively kept closed helping to keep debris out. Further, despite that I think most of the work is done by the just the washers installed on the aft side of the rear bushings when the car is travelling in a straight line, cornering is perhaps another matter.
In the photo above, the washers are going to fit around that metal centre-core's O.D. and extend outward sufficiently, such that they fill the void between bushing's flanged face and sub-frame bracket face. Like book-ends, together they will now limit the A-arm from any fore-aft movement, removing this task from the bushings themselves and in my view, prevent the damaging fore-aft over-extension of the bushings that would otherwise take place.
The significance of this axial movement was made clear to me as follows. I had spray-painted white, my A-arms after replacing the subject bushings, reinstalled and drove the car. Later working under the car again, I noticed that the white paint was partially worn off the rubber faced bushing flange where it <i>must</i> have been both touching and turning, at the same time, the sub-frame!
Ergo, plastic stop-washers.
Yes exactly, the stop (or thrust) -washers are complimentary to A-arm bushings, just as Mount-Savers are to strut top-mounts. Again MHO only, those three mounts, restrained, (note I only did this mod post-Pro-mounts); further transforms the steering. I could go on, IIRC, I did a write-up on this, if I find it later, I'll post a link (for others, you may have seen it) so I won't have to go on; now.
Frankly, I'm impressed that someone actually appears to get it.
Good points about the ramps too, I occasionally use a set of steel ones.
Last edited by Lago Blue; 11-09-2015 at 10:27 AM.
02-17-2010, 01:04 PM
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Awww, shucks.
Since I just put in a set of Mount Savers, it made perfect sense. I still have the front control arms out of the car so this will be the perfect time to get some washers in there.
After autocrossing this car last year I had the same experience, the control arms had made wear marks on the subframe. That helped explain the loose sloppy feeling around the cones, and prompted me to start a suspension rebuild. I figured it was just because of the ancient worn-out bushings, but if they do it with good bushings, I definitely want something in there firming them up. Looks like it's time for another trip to Ace hardware.
Since I just put in a set of Mount Savers, it made perfect sense. I still have the front control arms out of the car so this will be the perfect time to get some washers in there.
After autocrossing this car last year I had the same experience, the control arms had made wear marks on the subframe. That helped explain the loose sloppy feeling around the cones, and prompted me to start a suspension rebuild. I figured it was just because of the ancient worn-out bushings, but if they do it with good bushings, I definitely want something in there firming them up. Looks like it's time for another trip to Ace hardware.
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