Shock absorber mounting bolts - Lock-tite?

[Cutlass]

I usually use an anti-sieze compound on all nuts and bolts, but methinks that a lock-tite compound might be better on the front shock mounting bolts. Any other opinions?

 

[Keoke]

Me thinks a bit of that stuff should help keep em tight too Cutlass.--Keoke- /ubbthreads/images/graemlins/laugh.gif

 

[stinky60]

me three, but I wouldn't use it anywhere near aluminum. /ubbthreads/images/graemlins/driving.gif

 

[vette]

Cutless, About four years ago I rebuilt my shock mounts and installed new shocks. I placed a 3/8 inch plate inside the shock mounting surface to replace the captured nuts that had broken free. At that time I put locktight on the new bolts and wrenched them up tight. Now each year when I go over the car for a new summer of Healeying, I HESITATE to put a socket on the bolts to check their tightness because I don't want to break the locktight bond on the threads. So I just check them by visual inspection of the shock mating surface to see if they may have walked around a bit during the previous years running. Of course i also check for any movement in the suspension. But I don't retorque the bolts because they have locktight on them.
/ubbthreads/images/graemlins/cheers.gif

 

[nevets]

I'm no expert on the subject, but Lock-tite comes in a variety of flavours. You might want to check their website to find out about the specific properties of each, then decide which is best for your application.

 

[Dave Russell]

A "reprint" from an earlier post. This was on rear shocks but applies to front shocks also.
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I changed the bolts to grade 8 socket head bolts with "hardened" washers next to the soft aluminum shock bodies. External tooth star washers are used between the bolt heads & washers. I think a lot of the loosening comes from the bolts indenting into the soft aluminum shock bodies. Even a couple of thousandths of aluminum compression will reduce the bolt preload to zero. The hardenened washers reduce this indenting. There isn't much room for a large washer & you may need to reduce the outer diameter to fit in the available space. The socket head makes it easier to get a shortened Allen wrench on.

All of my shocks have steel sleeve inserts tightly pressed into oversize holes in the aluminum. The ID of the sleeves is a snug fit on the bolt shanks. The shocks came from Peter at World Wide with these inserts. I don't know if all shocks come with the sleeves or if it was done to salvage worn shock bodies. In any event, I think it helps the situation & would consider adding them.

The shock mounts are under designed & need all of the help they can get.

With these bolts torqued to 35 pounds, I haven't had any loosen in three years. I think it is even more important to do the same with the front shocks.
D
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I think Loctite is actually detrimental if it prevents periodic checking of bolt tension. It certainly is not going to reduce the aluminum indenting which is the main cause of loosening.
D

 

[Keoke]

[ QUOTE ]
I'm no expert on the subject, but Lock-tite comes in a variety of flavours. You might want to check their website to find out about the specific properties of each, then decide which is best for your application.

[/ QUOTE ]

--- /ubbthreads/images/graemlins/thumbsup.gif Yep, thats the secret use the right material for the application.---Keoke-

 

[Dave Russell]

[ QUOTE ]
So I just check them by visual inspection of the shock mating surface to see if they may have walked around a bit during the previous years running. Of course i also check for any movement in the suspension. But I don't retorque the bolts because they have locktight on them.
/ubbthreads/images/graemlins/cheers.gif

[/ QUOTE ] Pretty risky, I think. The shock body holes can wear, enlarge, BEFORE there is any detectable movement. There is hundreds of pounds of force on the shock bolts/mounts. Just checking for movement comes no where close to actual conditions. As explained above, loosening comes from deforming/compressing/indenting the aluminum mount ears, not from the bolts unscrewing.
D

 

[Cutlass]

This is interesting. If lockite is used at installation, then in theory, upon checking tightness, if there is any movement, the bolt would need to be removed, cleaned, and new locktite applied. I'm not sure about the hardened washers. Would it be better to have a bit softer flat washer, that might flex some before causing compression of the aluminum? I do like the idea of flat washers, though, to prevent galling by spring washers, and to distribute the bolt load over a larger area.

 

[Dave Russell]

Distributing the load over a larger area is precisely why hard washers work. If the washer flexed it would dish & concentrate the load over a smaller area & compress the aluminum more.

Much like bolting an aluminum cylinder head down.

Loctite is only good to prevent unscrewing. If the bolts are tight to begin with, they won't unscrew. When the aluminum compresses & relieves the bolt tension is when it would unscrew. This is exactly when the bolts should be retightened.
D

 

[Cutlass]

Makes sense. Now my problem is finding enough partially threaded bolts to take care of both the shocks and bolting the front brake discs to the hubs. Only about nine survive from the disassembly. All the commercially available bolts I've found are fullly threaded.

 

[Dave Russell]

Some place like this should have whatever you need.
https://www.aircraftspruce.com/catalog/hapages/an6.php

Something like the AN6-10 should work. 3/8 - 24 thread, 7/16" grip length, 1 5/64" overall length. With a hard washer under the head it should be perfect for the front shocks & rears also with good nuts.

Note that there is a store in GA also.
D

 

[Cutlass]

Thanks. Forgot about Aircraft Spruce. They're right here near me. Rear shocks are mounted with 7/16 in bolts, which did survive the rebuild.

 

[Cutlass]

Bolts, bolts, bolts... The AN6 bolts are almost $3 each. I had all the bolts from the teardown zinc plated, including just the right size for the front shocks. Of course I'm concerned about strength of 40+ year bolts. But these bolts are threaded into mild steel tapped plates, most certainly not as strong as purpose made modern nuts. Also, the bolts are holding down rather soft aluminum. Since the force on the bolts is in tension, not shear, I'll bet that the last thing to give in that situation is the bolt, even a 40 year bolt. A grade 8 or AN bolt is probably overkill, and, in the case of the AN bolts, a waste of money. The two advantages of the old bolts are the correct head markings and the correct amount of grip length. Am I just deceiving myself?

 

[Dave Russell]

I think you are the one who brought up AN bolts. I just went along with it. I didn't use AN bolts myself. Thought that's what you wanted. Not a bad idea though. Didn't know you were going to make such a fuss over $24 worth of bolts.

I do know that a grade 8 bolt & the front captive nuts, can be safely torqued to 35 ft lbs. 35 foot lbs appears to be enough stretch on the front bolts that the shocks never lose contact with the mounts under bump loads. "Provided that the aluminum doesn't indent". If the shock body did lose contact with it's mount, the aluminum would be permanently pounded thinner & become loose on the mount.

To repeat,
The important things are that the bolt does not indent the soft shock body, hardened washers to spread out the load, & as any fastener, should be pre loaded-torqued-stretched, enough that it holds the shock tightly down under the tensile & twisting loads (suspension bump) applied to it. If the bolt indents the aluminum, the bolt preload-stretch will be lost. The stretch is only about .003" so it doesn't take much indent for the bolt to lose it's grip. Once that happens the shock can move around on it's mount. Heavier shock oil or stiffer valving makes the problem worse.

The rear shock bolts are not subjected to much tensile load, just shear load so they are not as critical. I still use hardened washers on them though. Socket head bolts make the rear shock tightening a lot easier.

The whole thing is probably over-kill. Folks have used the standard setup for years with only frequent tightening of the bolts. Just don't wait too long to tighten them! I have seen some pretty egg shaped shock body mount holes.
D

 

[Keoke]

" Am I just deceiving myself" Yep Cutlass, when the front shock bolts fail it is not the bolt but the underlying nut that strips out. IMOP the bolt size is too small. I went one size larger and retapped the nuts when I replaced the frame shock mounts. Again IMOP as for the British bolts I don't care what you do for them they are the cars worst enemy as far as rust is concerned---Fwiw-Keoke

 

[Cutlass]

I did replace one shock mounting plate with a 1/2 inch steel plate, but the other is stock. The tensile strength of even a 3/8 inch grade 2 bolt is pretty impressive, expecially when compared to the strength of the captured nut plate, and the aluminum 3/8 inch flange on the shock. One main concern is using a bolt that is not threaded where it might contact that aluminum. The old bolts are perfect. The AN bolts are also appropriately sized in this regard, but are more than are necessary. By many orders of magnitude.