Aluminum Ball joint question......
03-29-2003, 11:49 AM
#1
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Aluminum Ball joint question......
I have to change out the Aluminum ball joints in my '79 before I put her on the road.
I've looked at the drawings of the ball joint mounts and the adjustment cams and can't figure out why you have to replace the mount and both cams.
The only difference between the modified mount and the original one is that the mounting studs are a tad longer on the old ones. The 26mm cam appears like it should work as well on the new ball joint as the old one.
Can anyone think of a reason why I shouldn't; Obtain two 26mm adjusting cams, four 7.30cm + the thickness of the mount grade 12 bolts and locknuts, two steel ball joints. I can then remove the studs, replace them wth the short ones (tack weld 'em down), use the two old 26mm cams and reassemble?
Anyone else try something like this? Anybody think of something I'm missing here?
I've looked at the drawings of the ball joint mounts and the adjustment cams and can't figure out why you have to replace the mount and both cams.
The only difference between the modified mount and the original one is that the mounting studs are a tad longer on the old ones. The 26mm cam appears like it should work as well on the new ball joint as the old one.
Can anyone think of a reason why I shouldn't; Obtain two 26mm adjusting cams, four 7.30cm + the thickness of the mount grade 12 bolts and locknuts, two steel ball joints. I can then remove the studs, replace them wth the short ones (tack weld 'em down), use the two old 26mm cams and reassemble?
Anyone else try something like this? Anybody think of something I'm missing here?
03-29-2003, 04:49 PM
#3
Nordschleife Master
Instead of putting new studs on the bracket, why not put a good washer or lock washer on the thing? Can you obtain grade 12 bolts? the highest I could find was a grade 8.8, or something like that.
It's much easyer, to just add washers, and so far I haven't had any problems, or heard of anyone that has.
The old 25mm cam will work w/o a problem.
Btw, I tryed to put the nuts on without a washer. When I tryed to torque it up, I broke the bolt. The highest grade I could find at any parts store around was a grade 8.8. A grade 8.8 bolt worked for about 2 weeks before I replaced them. When I got them out, they were not bent, or mishapen in any way. The head of the studs is marked 10.8. I'm not sure if that means anything, but...
It's much easyer, to just add washers, and so far I haven't had any problems, or heard of anyone that has.
The old 25mm cam will work w/o a problem.
Btw, I tryed to put the nuts on without a washer. When I tryed to torque it up, I broke the bolt. The highest grade I could find at any parts store around was a grade 8.8. A grade 8.8 bolt worked for about 2 weeks before I replaced them. When I got them out, they were not bent, or mishapen in any way. The head of the studs is marked 10.8. I'm not sure if that means anything, but...
03-29-2003, 05:55 PM
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</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">Originally posted by ViribusUnits:
<strong> The highest grade I could find at any parts store around was a grade 8.8. A grade 8.8 bolt worked for about 2 weeks before I replaced them. When I got them out, they were not bent, or mishapen in any way. The head of the studs is marked 10.8. I'm not sure if that means anything, but...</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">You bring up a good point, for automotive uses, the highest strength metric bolt is marked 10.9 which is a, alloy steel, quenched and tempered. These have a tensile strength of approx 150,000psi as opposed to a grade 8.8 medium carbon steel tempered bolt with tensile strength of about 120,000psi.
Equivalent to grade 12 bolts are available in metric sizes, but inch ones can be gotten cheaper and easier. Sooooo......
I was planning on obtaining inch size grade 12 aircraft bolts. It happens that a 7/16" high strength bolt is a nice snug fit everywhere in the system. I can obtain these in a Nickel-Steel alloy that is compatible with both the aluminum alloy control arm as well as the rest of the steel components in the system. They have a tensile strength of about 150,000psi.
<strong> The highest grade I could find at any parts store around was a grade 8.8. A grade 8.8 bolt worked for about 2 weeks before I replaced them. When I got them out, they were not bent, or mishapen in any way. The head of the studs is marked 10.8. I'm not sure if that means anything, but...</strong></font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">You bring up a good point, for automotive uses, the highest strength metric bolt is marked 10.9 which is a, alloy steel, quenched and tempered. These have a tensile strength of approx 150,000psi as opposed to a grade 8.8 medium carbon steel tempered bolt with tensile strength of about 120,000psi.
Equivalent to grade 12 bolts are available in metric sizes, but inch ones can be gotten cheaper and easier. Sooooo......
I was planning on obtaining inch size grade 12 aircraft bolts. It happens that a 7/16" high strength bolt is a nice snug fit everywhere in the system. I can obtain these in a Nickel-Steel alloy that is compatible with both the aluminum alloy control arm as well as the rest of the steel components in the system. They have a tensile strength of about 150,000psi.
04-04-2003, 10:15 PM
#5
Rennlist Member
My P.O. had to be cut from my '82 when the left side failed. STUPID, STUPID me, I did not figure out what happened when I rebuilt the car. 10 years later the right side failed. I feel lucky to have survived, but fortunatly it happened at about 5mph. Unfortunatly I was 500 miles from home and did not have my wheel lock key. Fortunatly I was near a good parts supplier who had the parts. I was able to change the joint without removing the wheel. I bought the plate, the joint and the eccentrics. When I got it apart I could not see any reason to change the plate...it looked just the same as the old one...and in my friends driveway with no tools and the wheel on I could not get the old one off. Perhaps it is a year model specific thing. If anybody know of any safety related reason to change the plate I love to know about it.
04-05-2003, 10:52 AM
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I'm in the middle of this job on the 78. I ordered new brackets, 4 used adjusters, new ball joints from 928 Intl. Tech spec book indicates a change in bracket for the steel joints so I'm not sure how you can 're-use' the existing bracket nor do I think I would want to. The whole point of the exercise is to correct a strength/reliability issue so any shortcuts would seem counter productive. Besides, the new bracket sure is purty and has to be worth a couple ponies.
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04-05-2003, 01:10 PM
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Erik Dvorak, you da man!
Not only high strength bolts, but everything else including the Kitchen sink.
They have a material perfect to make new fenderwell shields from.
Very cool!
Not only high strength bolts, but everything else including the Kitchen sink.
They have a material perfect to make new fenderwell shields from.
Very cool!
04-05-2003, 10:21 PM
#9
Nordschleife Master
There needs to be clarification here.
Apperently, there are 3 diffrent versions of the frount suspension. old, modifyed, and new: 86.5+.
According to page 40-20, the modifyed, and the new componets can't be intermixed.
The old commponets apperently included aluminum ball joints, longer studs on the clamps, and diffrent eccentrics. One thats is 21mm wide on the narrow part, and another that is 26mm wide.
The modifyed include the steel ball joints, a shorter clamp, and two of the same ecentrics. They are 26mm wide on the narrow part, and 45mm wide on the "circlurar" part. These are the parts that you should use to retrofit to the pre 86.5 cars.
The new parts include the steel ball joint, shorted bolts, on a shorter clamp (or bracket), and eccentrics that are narrower on the wide part. 39mm, rather than 45mm. The new bracket, doesn't have the indentions on the bend on each side.
The whole point behind the modifications is to replace the aluminum ball joint for the steel ball joint. The clamp is modifyed with the shorter bolts because the steel ball joint is thinner than the aluminum one. As such, the threads must be lower on the bolt. You should be able to do the same thing by adding a strong spacer under the eccentric. The whole point of the excersize is to correct a remature wear problem the aluminum ball joint experencs. There is nothing wrong with the clamp, or the eccentrics.
The post 86.5 cars have the ball joint turned over. Instead of being a trailing ball joint, ie the joint is mounted stud up, it's a upright joint. This places the weight of the car on the solid side of the cup, rather than the ring of material around the edge of the cup. This way the weight is pushing the joint together, rather than pulling it apart. It's pretty easy to see that it would be much harder to wear out the solid side of the cup, rather than the ring.
My information is from page 40-20, and 40-21, of volume 5 of the service mannual. It is also what I've figured out when I worked on my car.
I would be leary of welding anything in the set up. I have the feeling that most of the steel is some form of heat treated alloy, expecaly the bolts on the clamp. I would be worryed that even tack welding would screw up that critical angle between the head and the shaft of the bolt. Also, the tollorances are pretty tight, so you'd almost have to tack weld it with the bolts inside the clamp, and lower control arm. I would be even worryed about getting something on the lower arm screwed up. You'd probably be OK, but it would realy suck if it got screwed up.
Apperently, there are 3 diffrent versions of the frount suspension. old, modifyed, and new: 86.5+.
According to page 40-20, the modifyed, and the new componets can't be intermixed.
The old commponets apperently included aluminum ball joints, longer studs on the clamps, and diffrent eccentrics. One thats is 21mm wide on the narrow part, and another that is 26mm wide.
The modifyed include the steel ball joints, a shorter clamp, and two of the same ecentrics. They are 26mm wide on the narrow part, and 45mm wide on the "circlurar" part. These are the parts that you should use to retrofit to the pre 86.5 cars.
The new parts include the steel ball joint, shorted bolts, on a shorter clamp (or bracket), and eccentrics that are narrower on the wide part. 39mm, rather than 45mm. The new bracket, doesn't have the indentions on the bend on each side.
The whole point behind the modifications is to replace the aluminum ball joint for the steel ball joint. The clamp is modifyed with the shorter bolts because the steel ball joint is thinner than the aluminum one. As such, the threads must be lower on the bolt. You should be able to do the same thing by adding a strong spacer under the eccentric. The whole point of the excersize is to correct a remature wear problem the aluminum ball joint experencs. There is nothing wrong with the clamp, or the eccentrics.
The post 86.5 cars have the ball joint turned over. Instead of being a trailing ball joint, ie the joint is mounted stud up, it's a upright joint. This places the weight of the car on the solid side of the cup, rather than the ring of material around the edge of the cup. This way the weight is pushing the joint together, rather than pulling it apart. It's pretty easy to see that it would be much harder to wear out the solid side of the cup, rather than the ring.
My information is from page 40-20, and 40-21, of volume 5 of the service mannual. It is also what I've figured out when I worked on my car.
I would be leary of welding anything in the set up. I have the feeling that most of the steel is some form of heat treated alloy, expecaly the bolts on the clamp. I would be worryed that even tack welding would screw up that critical angle between the head and the shaft of the bolt. Also, the tollorances are pretty tight, so you'd almost have to tack weld it with the bolts inside the clamp, and lower control arm. I would be even worryed about getting something on the lower arm screwed up. You'd probably be OK, but it would realy suck if it got screwed up.
04-06-2003, 04:28 AM
#10
Rennlist Member
You guys have too much time on your hands. Why recreate the wheel? Call Devek for the expensive proper Porsche way. Or call 928Intl for the inexpensive way of doing this. Both work.
