Big oops - rear shock studs

[Anonymous]

I recently acquired a 1980 GS1000GL. It came with a seat back and rack on the rear, and a big windshield on the front, which I opted to remove. I removed the parts no problem, but last night I tried to put the nuts back on the rear shock studs (at the top of the shocks, on the frame).

They are nylon-type locknuts. I was putting the original locknuts back in place. On one side, the nut was initially easy to thread, but got much harder. I figured this made sense, since it's a locknut and it seems fairly important that the nut doesn't come undone -- so why wouldn't they make it a tight fit, right? I got the nut completely on, and then realized I needed to install a washer or two, so I tried to back it off. It was about as hard as it was to put on... Then suddenly the end of the stud broke off with the nut. There was just a few millimetres of thread not broken off, and a couple millimetres of unthreaded stock before the shoulder in the stud.

I tried the other side, and as soon as it got hard to tighten, I tried to back it off. On that side the result was simply that the last five millimetres or so of the stud threads got stripped.

Thinking I had little to lose, I tried cutting additional threads on the first side. That side is now successfully threaded as M8x1.25, with 5-10 mm of thread going right up to the shoulder. I tried unsuccessfully to install a nut, but didn't realize until late last night that I was probably using the wrong nut. Will try again tonight/this weekend.

Anyway, I have two questions:

The first question, and in my mind the most important is, what did I do wrong? Is there something I need to know about nylon locknuts?

The second question is, what is the best way for me to recover from the situation? My thinking at the moment is that if I can thread the first side properly, I can install a nut and a big washer, maybe put a wire through it so it won't work loose... Since there's not a lot of side-loading on the stud, it seems like I really only need to get something on there to keep the shock from coming off the stud, right? Shouldn't take much.

On the second side, I reckon I can hack of the stripped bit, and I'll still have more than enough stud to do the same thing... I'm assuming the studs are as long as they are mainly so you can slide sissy bars, luggage racks, and such over them. If I don't intend to install those things (or if I figure I can get by without) then I don't really need such a long stud, right?

Now... What if it turns out that I don't have enough thread, or for some reason I can't get a nut on what's left? Is it possible to replace the studs? I assume some welding will be necessary -- who do I need to talk to about that kind of thing?

Thanks, guys.

Michael

 

[Jay B]

How are your studs attached to your bike? I just checked my 81 850 and they feel like they are spot welded to the fender and that the head of the stud is a big flat washer type head. If that is the case with yours you can do it one of 2 ways. Take the rear tire off and using some sort of cutting tool cut the studs loose and replace/spot weld new ones in or drill them out and replace them. If you cant get someone to spot-weld them then use a regular bolt with a large flat washer. REMEMBER which ever way you do it get bolts or studs with the same tensile strength. If you don't you could cause yourself some serious problems or even get hurt.

 

[Anonymous]

The studs on my bike also seem to be some kind of flat-head type stud welded in place. I was thinking, if I am unable to use what's left of the thread, that I could drill them out and have someone weld a new stud in place...

I also was thinking it might be possible to replace with a simple bolt-on arrangement. However, it seems to me that the welded arrangement derives much of its strength from the fact that force on the shock is distributed not just to the top of the mounting bracket, but also in a "pulling" action on the bottom of the bracket -- a bolt would distribute the force mainly as a push on the top of the bracket, which I think would eventually deform...

I guess one question would be, anyone know a source for replacement studs?

Michael

 

[Anonymous]

Re: Big oops - rear shock studs

The first question, and in my mind the most important is, what did I do wrong? Is there something I need to know about nylon locknuts?

Michael

If these are nylon locknuts like the nylon locknuts I work with, you did something wrong when you tried to reuse them. The way they work is the thread inside the nut is crushed as you thread it on the first time, and once you thread it off a lot of the threads have become debris. Usually you can thread them back on easier than that and they simply wont lock, but it sounds like some of the nylon jammed up. so uhh... don't reuse those locknuts, always buy new ones if they are nylon locknuts.

 

[Anonymous]

Nylon locknuts

Nylon locknuts

Sounds like that's what I did wrong -- I suspected afterward that the nylon locknuts should not have been re-used. I guess it's one of those lessons learned the hard way. Thanks!

Michael

 

[Motorcyclemodeller]

I don't think any shock studs are M8 they are usually M10 by 1.25. It is hard to find this pitch as most fastner companies have only M10 by 1.5. Sounds kind of screwy, you must have jammed nylocks with the wrong pitch on there. All suzuki M10's on the 3 GS's I have restored are M10 by 1.25.

List:
Upper shock nuts
Lower shock bolts
Upper triple pinch bolts
Lower engine mount bolts
Sprocket nuts

I would cut off the stud flush, find the exact centre, drill out the old stud. Have a machine shop make you a new stud, have it heat treated and hardened; then have it welded in the correct hole.

Hope this helps,

8) Andre 8)

 

[Paul]

I had the same thing happen to me a few years ago, the pin broke off when I tried to undo the top suspension nut.
I carefully centre drilled the boss that the suspension unit fits on, then drilled & tapped it (about M8 or 5/16") then screwed an allen pin in (using a "mudguard" washer to prevent the suspension unit coming off)

 

[Jethro]

My shock studs were so stripped from years of installing and removing a rack that I want to a welder to see about having new studs installed. The guy I spoke to said it was a bad idea to put this part of the frame through so many heat cycles (cutting off the old studs, welding the new ones). He also didn't think he would be able to get them straight anyway. luckly I had enough of the stud to run a die over, but I don't think you would have much luck getting these replaced successfully.

 

[Diamondj]

Michael - One alternative would be to see if you can get a couple of truck wheel studs to use as shock studs. I think the Chevy Suburban and a few other trucks use 10mm 1.50 pitch wheel studs. You can even get acorn nuts in 10mm 1.50 pitch these days. Check your local Canada tire or other auto parts store and see if these studs are similar to your shock studs. If they are, cut off the weld on the heads of your shock studs with a cold chisel or a dremel motor tool running a fiberglass reinforced cut off wheel. Gently hammer them out of the frame. With any luck the shock stud hole in the frame will be the same size or smaller and you can install the wheel studs. Of course you could also take the bike to a machine shop and ask them to do it for you. If it makes you feel any better, I think it was probably the previous owner (or who ever installed the seat back and rack) that did this to you. They probably lost the original acorn style nuts or figured the nylocks were an improvement and ran them down on to the shock stud without worrying with the pitch. And the 10mm fine versus coarse pitches are deceptive. You can actually get a few turns of one on the other before it get tight. Someone just didn't take the hint. After all steel is typically stronger than the nylon they use in the Nylock nuts - if it wasn't you would always strip any bolt you used them on! ;-) Good Luck and let us know how it works out!

Jim

 

[Anonymous]

Update

Update

Okay, did a bit of work on the bike this weekend. I believe the studs were originally threaded M10x1.25. There was enough stock left on the broken side to run a die down it, so I re-threaded it to M8x1.25, with enough thread to get a nylon locknut in place. On the stripped side, I filed down what was left of the old threads and re-threaded that side the same, then sawed it off to the same length as the other side (no sense having just one side long enough to take accessories).

This probably would have worked fine, but I thought it would be a nice touch to drill the nuts and fire in a small cotter pin, just so it wouldn't travel for sure. I broke the bit in the nut -- I'm getting tired of these experiences with busting hardened steel off in inconvenient places. However, I was able to twist the nut just enough to shatter what was left of the bit. Pulled out as many pieces as I could, and unthreaded the nut. Unfortunately, this damaged the threads on that side. I ran a die down it again to clean it up, but when I tried fitting a nut, it wouldn't take much load, and stripped.

There's enough there that I would feel comfortable limping the bike to a machine shop, which is better than where I was before. However, I have one more idea, pretty much what Paul suggested.

I'm thinking I can hack the threaded part of the stud off, so all I have left is the part where the shock sits. Then I can drill the center out using some kind of jig to keep things lined up properly. I can tap the inside to M8x1.25 and fit a bolt with a large washer. I think a bit of locking compound should be sufficient to ensure that the bolt won't travel. Seems like this setup won't significantly weaken the stud, since I wouldn't be leaving any "gaps" inside the stud -- provided the bolt is as strong as the original stud.

Does this sound like a good idea? Any suggestions how to drill the hole as straight as possible? How strong is the steel used in the stud? Does it make any difference if I replace with a regular bolt, or stainless, or what?

Thanks again!

Michael

 

[Paul]

The hardest part is ensuring that you drill the hole dead square & straight. All that the bolt will do is to stop the shock absorber from coming off. The load will still be taken by the stud, so don't drill too deep.

 

[Anonymous]

The hardest part is ensuring that you drill the hole dead square & straight. All that the bolt will do is to stop the shock absorber from coming off. The load will still be taken by the stud, so don't drill too deep.

I was thinking of drilling right through. My reasoning is this -- if I drill only a little way into the stud, then when I tap it there's invariably going to be a little air pocket at the end of the hole where there is no thread, and which cannot adequately be strengthened with a bolt. I was thinking if I drilled right through, there are no "air pockets" which weaken the stud itself... The caveat, I suppose, is that the bolt must be at least as strong as the stud, but it should be no problem finding a suitable bolt, should it?

Thanks!

Michael

 

[Motorcyclemodeller]

Remember these studs are hardened, thats why everything keeps breaking. Reducing the stud diameter on a load bearing stud that holds one half of your suspension on is playing with fire. If it gives while you are riding your #@&%*&! Get it fixed properly, the choice is yours.

Andre

 

[Paul]

I know what you mean but if you only drill & tap the absolute minimum depth you are still retaining the maximum strength of the stud. If you "flat bottom" drill the hole, and use a "plug" tap to finish threading the hole you will minimise the dead area at the bottom of the hole.
If you drill straight through you are turning the stud into a tube, and the bolt won't add a lot to the strength unless the stud starts to flex. Remember that the bolt is a clearance fit in the threaded hole - if it wasn't you wouldn't be able to screw it in!
Use a stainless bolt and you will have no trouble undoing it in future.
I've done this on my own bike & had no trouble, and I've seen the exact same things done on other bikes.

 

[Anonymous]

Get it fixed properly, the choice is yours.

I wouldn't mind spending a bit of money to get it fixed properly, because I definitely understand the importance of those studs. But I guess the question is... How does one get this fixed properly? Is it possible to get a replacement part, and have that installed by a machine shop?

Michael

 

[KrazyKarl02]

what I did

what I did

I broke off a shock stud in a similar situation. What I did was cut the remaining stud out, go to the hardware store and find a big bolt that matched it. Drilled out the old stud, put the bolt in, and mig welded it up. Most of us do not have mig welders, but this worked, I then ground the head of the bolt off and welded that side too, the end result is you can not tell the difference!

 

[Anonymous]

I know what you mean but if you only drill & tap the absolute minimum depth you are still retaining the maximum strength of the stud. If you "flat bottom" drill the hole, and use a "plug" tap to finish threading the hole you will minimise the dead area at the bottom of the hole.

Two terms I'm not familiar with here -- "flat bottom" drilling, and "plug tap". I assume the latter refers to a tap which can be used to finish the thread right to the bottom of a flat hole -- can I find such a tap at most hardware stores? How do I "flat bottom" drill the hole? Special drill bit?

Also, how deep did you drill into the stud?

Thanks!

Michael

 

[Paul]

Two terms I'm not familiar with here -- "flat bottom" drilling, and "plug tap". I assume the latter refers to a tap which can be used to finish the thread right to the bottom of a flat hole -- can I find such a tap at most hardware stores? How do I "flat bottom" drill the hole? Special drill bit?

Also, how deep did you drill into the stud?

Thanks!

Michael

Flat bottom drilling - a normal drill has a point at the end, which leaves a pointed hole, a flat bottomed drill has been ground so that the end fo the drill is flat so it leaves a hole with a flat bottom. Normally you would drill with a standard drill, then follow through with a flat bottomed drill to produce the flat bottom oin the hole.

Plug tap - taps usually come in sets of 3, referred to as 1st, 2nd & 3rd or taper, 2nd & plug. The 1st (or taper) has a long tapered form so that it will tend to self-centre itself in the hole, the 2nd has less taper, while the plug has no taper so you can get maximum thread in hole.

I threaded about 12/15mm into stud, I think the depth of thread was dictated by what bolts I had to hand at the time!

The stud was hard to drill though.

 

[Anonymous]

I drilled the studs this weekend. First I cut off the old threaded parts, and filed the end so it was clean. Then I used a regular drill bit to start the holes, then used an end mill to finish off the bottom. I couldn't find the "plug tap" that Paul referred to -- found a tap which said it was "plug-style", but sounds like what Paul described as the "#2" tap, just less taper than a normal tap. Anyway, I bought two of them, and one I ground off at the end to make a tap without taper. I drilled about 14 mm into the stud, tapped first with one tap then the other, then installed a bolt and washer to secure the shock. The bolts bottomed out just as they took purchase on the washer, which is perfect I think. I put a bit of thread-lock on the bolts so they won't shake loose, although I was able to get them nice and tight, so I doubt it would have been a problem.

The finished mod looks great, and leaves most of the original stud in place. Thanks for all your help!

Michael