Caster block mounting holes stripped-best repair procedure
#16
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Location: San Francisco, CA Porsche: '92 968 Blk/Cashmere
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Originally Posted by jonnybgood
Serge, did the threadcerts work? I was installing 968 caster blocks this weekend and could not get one bolt to click on the torque wrench. Before I realized what was happening I stripped it. Seems like Porshche should have put some captive nuts in there.
#17
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Inside there are three circles or rings, the outer ones have a nut spot welded in place. The three rings were then spot welded to the frame by Porsche. Mine had been helicoiled once and it didn't hold so I was out of options, but in most cases that should work.
#18
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I fixed my problem tonight. Fortunately the bolt holes in the frame rail were not stripped. They are in fine condition with a good 12mm of clean thread on the captive nuts. I over torqued the bolts and the one I thought stripped was actually stretching and it snapped when I went to remove it. It was easy to get out and I had some replacement bolts ready so all is well.
For any future reference to this thread the correct torque is 34 ft lbs. The bolts are M10x65 1.5 pitch and 8.8 stregnth.
Iceshark, that is weird about the different size holes. Mine went on fine.
Chris, The used caster blocks are rescued from the garbage and I will be glad to give them to you. I can't make it for the belt party this weekend. I am going skiing with my daughter. Perhaps I can get them to Dimitry or somebody who is heading your way.
For any future reference to this thread the correct torque is 34 ft lbs. The bolts are M10x65 1.5 pitch and 8.8 stregnth.
Iceshark, that is weird about the different size holes. Mine went on fine.
Chris, The used caster blocks are rescued from the garbage and I will be glad to give them to you. I can't make it for the belt party this weekend. I am going skiing with my daughter. Perhaps I can get them to Dimitry or somebody who is heading your way.
#20
Nordschleife Master
Originally Posted by jonnybgood
Iceshark, that is weird about the different size holes. Mine went on fine.
So when you order the blocks have the vendor run an 18mm bolt through the bushings before they send them to you. Zims made things right and paid for my machine shop charges but I had to run around town which threw a monkey wrench into the plan. Of course some problems always pop up when working on these cars.
#21
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Jon,
Glad to see it all worked out without any added grief. The manual says 34 lb for these bolts, I guess 55 will snap them. That's good to info know, I have to do a swap here very soon.
Glad to see it all worked out without any added grief. The manual says 34 lb for these bolts, I guess 55 will snap them. That's good to info know, I have to do a swap here very soon.
#22
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Originally Posted by jonnybgood
I
Chris, The used caster blocks are rescued from the garbage and I will be glad to give them to you. I can't make it for the belt party this weekend. I am going skiing with my daughter. Perhaps I can get them to Dimitry or somebody who is heading your way.
Chris, The used caster blocks are rescued from the garbage and I will be glad to give them to you. I can't make it for the belt party this weekend. I am going skiing with my daughter. Perhaps I can get them to Dimitry or somebody who is heading your way.
#23
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Originally Posted by KuHL 951
Jon,
Glad to see it all worked out without any added grief. The manual says 34 lb for these bolts, I guess 55 will snap them. That's good to info know, I have to do a swap here very soon.
Glad to see it all worked out without any added grief. The manual says 34 lb for these bolts, I guess 55 will snap them. That's good to info know, I have to do a swap here very soon.
I don't think this one event at 20lbs over was the only overtorquing of these bolts. I compared the thread on the other good bolt and 12 to 15mm from the end the thread pitch was stretched and did not match a new bolt. You might want check your bolts when you install them to see if they are stretched.
#24
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I had the same issue with over torque'ing one of these 2 bolts, but when I looked @ it closer it appeared that the actual bolt was stretched out (hour glass shape). So I went to ACE and got the same M10x65 1.5 pitch and 10 (instead of 8.8) grade bolt as well as 10x1.5(pitch) tap. After I ran a tap through the frame hole and used the new bolt I was able to torque it down to 34lb. Weekend saved.
#27
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Torque wrench?
No wonder you broke it! These bolts are best tightened by feel. This feel is quite the result of lots of experience, however. They simply do not need to be cranked super tight to do their job. I use a standard 6" 3/8 ratchet handle. This does not allow me to get too much leverage and risk trashing one.
This would fall under the same heading as Porsche (and many other makers) reverting to torque angle specs instead of tension. Torque tension specs cannot be achieved with a fastener that is stretching or pulling out threads. If you have no sense of impending doom, the next thing you know...PING!
No wonder you broke it! These bolts are best tightened by feel. This feel is quite the result of lots of experience, however. They simply do not need to be cranked super tight to do their job. I use a standard 6" 3/8 ratchet handle. This does not allow me to get too much leverage and risk trashing one.
This would fall under the same heading as Porsche (and many other makers) reverting to torque angle specs instead of tension. Torque tension specs cannot be achieved with a fastener that is stretching or pulling out threads. If you have no sense of impending doom, the next thing you know...PING!
#29
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Originally Posted by Serge944
For future references, you should also be able to access the bolts from the top and put a nut on them in case you strip the mount.
I like torque wrenches. I have a good feel for a bolt and I knew I was in trouble as it was happening, just thought it was stripping not stretching. I still don't think this one episode would be enough to break the bolt.
#30
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Mike S, Do you have the pics you mention in this post? I'm about to do the same thing. My idea is to use a plasma cutter to remove the "rectangle" outside the caster block area and remove OE "nuts" and weld in grade 8 M10x1.5 nuts then wire-feed the piece back in.
Last edited by pharmacy; 05-24-2018 at 09:13 PM. Reason: add name