No bushing on my shock

havoc6538

I recently bought a 2007 Specializwd Stumpjumper with a Fox Triad shock. I has a go on it before buying and immediately noticed a little play in the lower shock mount. No problem, I think, as it's an easy job to replace a bushing. So I buy the bike.
Long story short, after having to drill out one of the lower shock mount bolts as at some point in the past its been over tightened and the Allen key socket rounded out I've got it apart to find there is no bushing! Never seen this before, but a quick Google confirms that sometimes, Specialized did this. Basically, instead of a standard set up, there's a hollow bolt that goes all the way through the shock link and the lower shock eyelet and is secured by an m10 screw in the other end. The bushing isn't missing, there never was one.

So, my problem is that my digital calipers show that the bolt has a diameter of 14.93mm and the internal diameter of the lower shock eye is 15.21mm. Hard to know which part is worn, but I can't believe anyone would sell a full susser without bushings. Did they intend that owners should replace the shock every time it wears out?!
Unfortunately, due to the age of the bike, no-one sells the replacement parts any more, but that's kinda my fault for buying vintage.
Everything I've read on the subject assumes standard eyelet sizing, spacers, bushings etc, none of which helps.
So what are my options here? Anyone had similar problems in the past or seen this before?

steve_sordy

In addition, the hole in the eye is unlikely to be round.

If you want to save it, rather than do what was done to you and sell it to an unsuspecting person, then you have a couple of options.

Ream the eye to a known size so that it is round and smooth. Then either:
Get a bolt made that will fit your new diameter and proceed from there.
Or: Have a bush made (it will be thin walled) and use a standard steel bolt if possible, if not get one made (from steel - you need the strength because it will be smaller diameter).

There are loads of people about that will be able to make a bush/bolt for you.

If you don't like the sound of any of that and still want to keep the bike, then establish the eye-to-eye measurement and the travel of the shock and go buy a used one on eBay (but not a Fox Triad).
I came across this which you may have seen already).
https://forum.bikeradar.com/discussion/13074058/replacement-for-fox-triad-shock-needed

thistle_

havoc6538 said:

but I can't believe anyone would sell a full susser without bushings. Did they intend that owners should replace the shock every time it wears out?!

The Giant Trance X bikes were the same - the top eyelet had a bushing but the lower one didn't. In theory due to the suspension design the bottom pivot didn't move so it didn't need one.
I didn't have any issues with the arrangement in the 10 years or so that I had the bike, but I went through 4 shocks in that time

havoc6538

Just seems like a spectacularly poor bit of design to me.

havoc6538

Thanks Steve. I've been thinking of something along those lines, but a bigger bolt won't fit through the bearings. I'll post some pics tonight of the set up.

havoc6538

steve_sordy said:

In addition, the hole in the eye is unlikely to be round.

Yeah, I know, although I did measure at multiple angles and got a consistent reading every time, at least down to the 2 decimal places on the display. It shouldn't be round, but it does appear to be so.

steve_sordy said:

Ream the eye to a known size so that it is round and smooth.

This is the bit I was thinking about. Because of the large bore of the eyelet, >15mm, there's not a huge amount of "meat" around it. If I was to have it reamed out to make sure it's perfectly round, IMO it would have to be fractions of a mm to avoid causing too much weakness. Again, I'll see if I can post some pics this evening so you can see what i mean.

We have engineers where I work, one of whom has already offered to make me parts if I need them (although I don't want to abuse this too much), so engineering a solution is possible.
With regards to just making a slightly larger shaft to fit the enlarged eyelet, this will then cause problems where the shaft passes through bearings in the shock link - the bearings would have to also be this new, non-standard size. Again, you'll see what I mean in the pics.

I have ideas for a custom part but it's hard to explain and I have doubts about the strength, long-term, at least. It would be easier to explain with a drawing, so again, I'll see if I can post something up later.

Cheers for your help so far.

steve_sordy

Your shock eye is 15.21mm which is 0.599" It might help if you can get some of the old Imperial sized reamers, you will certainly find a 5/8" (0.625"). But reamers used to come in all sorts of odd fractional sizes in 1/64" and 1/32". Someone will have some in their shed!

Ref the bolt: It only has to be oversize where it passes through the eye. If you make it the diameter needed for the bearings at each end, then it becomes an assembly problem. Instead of passing the bolt through the bearings, maybe push the bearings on over the bolt and into the frame at the same time.

I can't solve the problem for you, just trying to spark an idea for you.

havoc6538

Excuse the rotation of the pics. I've tried uploading rotated versions and non rotated but they appear in the same orientation whatever I do.
Anyway, this is the assembly as it sits in the frame:



and these are the components, minus the threaded part of the m10 retaining bolt which got drilled out:



The bearings push fit into the linkage from the inside, so no sliding them in place once things are in position.
Specialized thought of everything didn't they? 🤣

havoc6538

Forgot the pic of the eyelet:



Not much room for manoeuvre possibly, but hopefully a little.

steve_sordy

I would try reaming out that shock eye and then drifting in a thin-walled bush. If it is possible to do, the bush wall can be made thicker by making the bolt a fraction smaller diameter.

The shock eye will be some sort of aluminium alloy, the bolt was probably steel. It is important to avoid dissimilar metals reacting to each other and corroding. I know enough to know that is a potential problem, but I can't recall enough to know which metals go well with each other and which ones are bad. You will have to find that out for yourself.

mully79

Ok, so you have a 15mm holes in the linkage and the shock eye.
If you were to have a custom press fit 15mm brass bush made for the shock with a 12mm inside diameter and similar for each side of the linkage you could use a standard m10 shoulder bolt to pass through the lot and secure with an M10 nylok nut using washers to take up any sideways slack.