Upper shock mount sheared, ideas please.

[Blue2]

My flat tracker has a high level exhaust that attaches at the right rear upper shocker mount. Vibration and the fact that the exhaust wants to sit further out means the stress has sheared the bolt.

I plan to drill out the old threaded rod that the nut that holds the shocker on screws on to. The use a longer shouldered bolt through the thicker bush so that a fist nut can hold the shocker in place then on the extended thread use two nuts with washers to hold the exhaust, this will allow the exhaust to sit further out, where it wants to be.

Question. Is the threaded rod actually screwed into the bush? or is it part of the bush? or is it welded in?

I'll try and load some pictures.

 

[hotrdd]

Sorry I'm not I understand the question. I believe the shock mount and threaded section are all one piece. I would first change the exhaust mount to alleviate the stresses you are talking about. Then weld on a new piece of threaded rod. There should be very little stress on this bolt.

 

[XSLeo]

Yes, the shock mount stud is one piece. I think it's hardened to, not sure, it may be hard to drill and tap. Do this just to hold the shock.
Then as hotrdd suggests add another bracket from the frame just above or beside the shock mount to support the mufflers, this way no strain on the shock mount stud.
Leo

 

[weekendrider]

This has come up a couple of times. iirc the others didn't have exhausts mounted there and still had a broken mount.
What was suggested was to contact someone doing a hardtail and asking them to cut the shock mount out/off so they could reweld to theirs.

 

[Blue2]

Hi all,
I managed to fix this by;
1. Filing the remaining threaded stud flat.
2. Sharpening my centre punch and putting a punch mark as central as I could.
3. Drilling down the centre of the stud with a new 5mm pilot bit .
4. Then reamimg the hole with a 7mm bit and then a 9.5 mm bit.
5. Finally inserting a M10 bolt to hold the shocker in place.
I nearly used a 10mm drill bit for the M10 bolt, but using a micrometer found that M10 bolts are about 9.70mm and the 9.5mm bit gave a nice fit. If you use a 10mm drill bit you drill out a fair bit of the actual boss / bush that the shocker fits over. I'll post a picture later.
Ok. The middle picture is the stub filed flat and centre punched. The picture on the right is the pilot hole at about 5mm, might have been 3mm looking at it. The photo on the left is the final 9.5mm hole. The metal is fairly soft, not hardened at all. I tiny error at the start means the last drill hole is very slighlty off centre. A cure would have been to tack weld a guide tube to centralise the drill but I had no way to do that.
Now, if you insert a 110mm or 120mm shouldered bolt from the tyre side you can use the bolt and a washer + nut to mount the shock as per normal with pleanty of extra thread for a second locking nut if wanted. This still leaves plenty of thread to mount an extra stabilising nut for the high level exhaust. You will need to extend the thread down the shoulder of the bolt to get the thread where the shock mounting nut needs to be as the longer bolts have too much shoulder.

 

[Detale]

Are you using a hardened bolt though(grade 5)? Id be concerned that a regular hardware grade wouldn't hold up and may shear again.

 

[Blue2]

Are you using a hardened bolt though(grade 5)? Id be concerned that a regular hardware grade wouldn't hold up and may shear again.

Hi,
just getting used to this forum and posting.
the torque on those nuts is only 22 ft lbs in old money. So I'm using a standard cap screw. My torque wrench starts at 60 ft lbs so this is new teritory for me..... !

I'm guessing over tightening was the real cause of the shear.
I'm using a second braket to mount the exhaust.

The metal that the original stud was made of that I drilled out was pretty soft.

 

[visimpact]

I have lots of scrap pieces if u want to re weld on a stock post. I have at least 3 rear stock back pieces in my metal scrap pile.

 

[gggGary]

Good job and nice write up. I think in general bolts are "tough" and not "hard" they are usually rather easy to drill making nice long curls of metal.