Should the reducer in a DHX rotate?

RealizE

Likes Bikes
Greetings,

I've just pulled the DHX4 Coil out of my SX Trail and noticed that the reducer in the top eye (ie, the one closest to the main body) does not rotate. When I tighten the through bolt that attaches the shock to the frame, it binds the shock and it does not rotate around the bolt.

The Fox manual shows a gear puller being used to extract the reducer from the shock so that makes me think it is supposed to be fixed (in contrast, the one on my Rp3 spins freely).

Can anyone confirm whether the reducer should rotate inside the eye? If not, I'll need to machine up some kind of crush tube to stop the shock mount tabs closing in on the shaft and binding it.

Cheers,
Scott.
 

miko

Likes Bikes and Dirt
I have no DHX experience, but I know my old Van rotates. Generally the bushings have a coating on them so that they do rotate around the reducer. If you tighten the shock bolt and it binds, then somethings wrong.

Try new bushings. I ended up having to polish the reducer shaft on mine by using very fine grit sand paper and the reducer in a power drill. Be careful with that one though!
 

udi

swiss cheese
Understanding how the assembly operates will probably be a good start to understanding if your setup has a problem or not.

In a conventional setup, which I'm fairly sure the front shock mount of the SX trail is, this is how it works.

- Shock eyelet has a pressed in DU bushing
- Bushing does not rotate in shock
- Bushing has a reducer shaft pressed through it
- The reducer does rotate in the bushing, however it shouldn't by hand
- The reducer is clamped tight by the frame (or link, or whatever) from both sides.
- The spacers either side are essentially just locators, so that the shock eyelet (and du bushing) can't slide left to right on the reducer. They shouldn't be a tight fit between the frame and shock eyelet itself.

If the reducer rotates in the DU bushing by hand, then the bushing is on its way out. A DU bushing is a thin steel bushing with a red coating low-friction coating on the inside. I mention that because some specialized frames will use alternative setups on the rear shock mount (ie. the one that meets link/swingarm, not mainframe) which the above info won't apply to.
 

b_S

Likes Bikes and Dirt
Bushes and reducers are so cheap that you should replace them as a precautionary measure anyway.
 

udi

swiss cheese
Reducers aren't cheap, and they shouldn't wear or need replacing (ever) if things are looked after correctly.
 

S.

ex offender
Reducers aren't cheap, and they shouldn't wear or need replacing (ever) if things are looked after correctly.
Alloy ones (which most bikes use) are at least as soft as the DU bushes a lot of the time - they do flog out over time.
 

RealizE

Likes Bikes
Thanks for the informative posts!

When the shock compresses, I can see the shock rotating around the bolt, but I can't tell whether it is the outside faces of the reducer slipping against the mounts or whether it's the reducer rotating inside the bushing as it should.

I tried gripping the reducer in a vice and then rotating the shock around the reducer, but it didnt budge. Should it be that tight?

Edit: I should point out that the suspension movement is nice and smooth. The only reason I began looking at it was because I had it apart after replacing the linkage bearings.
 
Last edited:

S.

ex offender
Thanks for the informative posts!

When the shock compresses, I can see the shock rotating around the bolt, but I can't tell whether it is the outside faces of the reducer slipping against the mounts or whether it's the reducer rotating inside the bushing as it should.

I tried gripping the reducer in a vice and then rotating the shock around the reducer, but it didnt budge. Should it be that tight?
Personally I don't reckon they need to be that tight, but they usually do end up like that in my experience. Seems to work fine in the bike though (usually). If you want less friction, take them out and sand them down (on a lathe preferably) super smooth, so you get a polished finish, and grease the bushing before installation. Ideally the reducers should be a tight non-interference fit - you should be able to press them in either with a lot of force by hand, or easily with a vice. Tighter than that is just unnecessary.
 

udi

swiss cheese
Alloy ones (which most bikes use) are at least as soft as the DU bushes a lot of the time - they do flog out over time.
No specialized bike that I know of uses that garbage, hence my post. It's always three piece (stainless shaft / alloy spacers) unless it's a completely custom setup (like the demo), which is usually a step ahead yet again.
 
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