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Discussion Starter · #1 ·
I feel like this is a known issue. I have definitely heard of both of these problems independently, and maybe together? Not sure.

The problem is that I cannot seem to locate anything by searching the forum (via google or the forum itself). And I'm 1500 miles from home so it would really behoove me to find out exactly what these symptoms mean before I go begging for tools and shock oil and stuff to perhaps get myself back up and running.

I suspect the answers are buried deep in the giant Mattoc thread, but words like 'rebound' and 'top out' are so common that I just can't figure out a search string that gives me any help.

So: Mattoc Pro 160, 2017 manufacture, I think? I have serviced it once. Never had any issues with it.

Today, I first noticed the clunk going off jumps. Even on a roller where you don't leave the ground, the fork will unload fully and forcefully with an audible 'clunk' or 'thump.' Then I noticed how the fork seemed absurdly fast- even for me, who never uses more than 1 or 2 clicks of rebound. Confirmed that shock feels the same with rebound knob fully open or fully closed. Compression knobs seem to work fine. Air is fine and the air side appears to be functioning normally (have drained and re-set).

I'm thinking something in the rebound stack has either come apart or maybe I've blown a piston o-ring. Something it letting everything work, except rebound.

I'm off to the hardware store to see if I can acquire the tools I need to pull the damper side...have allens, a shock pump, and a cassette tool. I think I just need sockets? If I have to pull the lowers off, I'm boned, because I'm never finding that stupid 8mm (I have one at home I made by grinding most of a socket away).

Pllleaaasseee help.
 

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Discussion Starter · #2 ·
Pulled the upper damper out. Looks like someone's been chewing on the pipe all the way at the bottom. One side is all mashed in and rough looking, like something's been beating on it. I can't pull the lower part right now since I don't have the 8mm to get the lower legs off.

What would cause this, and is it my problem? I'm assuming that pipe is supposed to seal to something at the bottom of the stanchion..
 

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Discussion Starter · #3 ·
update 2: dumped the shock oil out. A black plastic cylinder and a small ring with 4 slots fell into the drain pan. One end of the cylindrical piece looks like it's broken off from the rebound assembly.

What the ****, Manitou. As awful as my Rockshox forks have been, at least the DAMPER NEVER BROKE THE **** IN HALF.

edit: confirmed, found a flashlight and can see rebound piston laying sideways in fork.

I say again; THIS is the problem I have? The piston broke off from its guide? There shouldn't even be major forces in that direction...what kind of cheap crap is this made out of?

Frankly, I think I have grounds to be outraged, in case anyone is curious. A maintained fork, never bottomed, with proper fluid levels...just breaks apart inside. Okay.
 

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Well, that clearly implies your rebound damper has been hitting your compression assembly. Not exactly sure how that could happen.
 

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Discussion Starter · #5 ·
It doesn't help that there are no parts diagrams for the rebound damper. Every piece of documentation treats it as witchcraft and just shows an external view of the 'rebound assembly' i.e. a pipe.

I don't understand how this failure could happen. I understand how the compression damper is damaged; the rebound stuff became a pile of loose parts that were being shoved toward the compression damper. But...why did they become a pile of loose parts.
 

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Yeah, I can't say. I would try calling Manitou and see what they can do. Maybe they could ship you a new rebound assembly that you can have a shop install. Many trek dealers have manitou tool kits they use to service the Magnums that came on the Stache.
 

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Discussion Starter · #7 ·
I'm just riding at Trestle tomorrow and Wednesday. My hope was that this would simply be a part that was sticking, loose, or misplaced; something that I could simply clean, put back together, and refill, and my EXCELLENT pseudo-DH rig would be back in business. But this will require an entire damper. Probably that whole leg, because the oil was full of metal. Not just particles; shavings.

I'll be riding a shitty rental for a couple days. I can afford one of their nice demo bikes, but TBQH every Fox and RS fork I've ever felt paled in comparison to my Mattoc. I will gladly trade a $5-8k stock downhill or enduro bike to ride my shitty old Meta V4, because it's all Manitou, it has badass DH-worthy wheels and tires as well as brakes, and most importantly, it's MINE. Ugh.
 

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It doesn't help that there are no parts diagrams for the rebound damper. Every piece of documentation treats it as witchcraft and just shows an external view of the 'rebound assembly' i.e. a pipe.

I don't understand how this failure could happen. I understand how the compression damper is damaged; the rebound stuff became a pile of loose parts that were being shoved toward the compression damper. But...why did they become a pile of loose parts.
I'm not sure if you still need this but below is my Mattoc Pro 26 rebound assy disassembled when I changed the HBO Cone to 27.5. Each piece faces upward and goes on from left to right.

 

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update 2: dumped the shock oil out. A black plastic cylinder and a small ring with 4 slots fell into the drain pan. One end of the cylindrical piece looks like it's broken off from the rebound assembly.

What the ****, Manitou. As awful as my Rockshox forks have been, at least the DAMPER NEVER BROKE THE **** IN HALF.

edit: confirmed, found a flashlight and can see rebound piston laying sideways in fork.

I say again; THIS is the problem I have? The piston broke off from its guide? There shouldn't even be major forces in that direction...what kind of cheap crap is this made out of?

Frankly, I think I have grounds to be outraged, in case anyone is curious. A maintained fork, never bottomed, with proper fluid levels...just breaks apart inside. Okay.
The "black plastic cylinder" pipe is the anodised aluminium HBO cone. It slides inside the HBO cup on the compression assembly for the last 20mm of travel to provide bottom-out resistance.

Now for these to become misaligned and hit each other, either it has simply become unthreaded or there has to be damage to the rebound damper tube or shaft.
I haven't seen this in person, but twice I have seen photos where the damper has been overfilled and the resulting hydraulic forces at bottom-out have crushed the top of the damper cartridge tube downwards.

If this happens the HBO cup and cone eat each other on contact.

But it sounds more like it has come unthreaded. Which I haven't seen before. The HBO cone is the nut which holds the rebound piston and shims in place.

@aresab posted the picture that has the rebound parts all laid out correctly.

As far as materials. That's anodised aluminium. The only plastic in a Mattoc damper is the piston glide rings and seal backup rings.
 

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Looks like the HBO cones made intimate contact, something like: https://forums.mtbr.com/shocks-suspension/manitou-mattoc-899836-21.html#post13898701 ; or maybe it's just a matter of the piston not being torqued correctly (I think I saw something about that but can't find it right now).

I am actually thinking of disabling/removing the HBO, it seems more trouble than it's worth.
Actually, I think it is part of which gives the Mattoc that bottomless feel, but I do agree, the IRT with the HBO can almost be too much bottom out protection but I still have mine set full on to give that nice endless feel.

I'm not sure if you still need this but below is my Mattoc Pro 26 rebound assy disassembled when I changed the HBO Cone to 27.5. Each piece faces upward and goes on from left to right.

Aresab's post now makes me realize you can see the rebound assembly taken apart in the 26 to 27.5 wheel conversion video.


To the OP, I would still call Manitou and see what they can do. Unfortunately, craps happens. Often at the completely wrong time.
 

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Discussion Starter · #13 ·
I tried to get pics last night but they all came out blurry. Aresab has me covered- it's that whole top row that was in pieces at the bottom of the damper-side stanchion.

So the HBO (I had thought it was plastic with a steel insert) piece attaches how? Does it screw to the rod to hold the rebound piston and shims? If so, I believe that means the end of the shaft broke off inside the HBO. I don't see any threads on the HBO; just solid metal inside the one end, which looks like it snapped and then got slammed into something else a bunch.

My compression damper looks just like the link posted above- that guy clearly has the same problem as me, but I'm not sure if he knows it? I think his rebound assembly is apart/broken or in the process of coming apart.

I did not overfill the damper. Set the level per Manitou's spec with one of those fancy height gauges with the plate and the sucky tube.

Any chance Manitou will warranty this outside of a year? With needing whole damper and likely right stanchion, it seems totaled. I would even just take a pro-rate and I'd be happy to send them this one for analysis if they want. Gonna be chuffed if they just take a '**** happens, you're outta warranty' stance...
 

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The all black part of the HBO cone threads onto the compression rod. Does the compression rod still have threads as in the photo? If so , start from the top left and put one piece back on at a time. Once you get the the HBO cone, put blue locktite on the threads (so this does not happen again :) ) then use a torque wrench (Torq Spec per Manitou for cone 3-3.5 NM 26-31 inch lbs - 28 recommended). Too tight and rebound damping will be all messed... trust me.
 

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With needing whole damper and likely right stanchion, it seems totaled.
Worst case is a new rebound damper and new HBO cup. You don't need to replace the stanchion as nothing slides inside the stanchion, the rebound damper has it's own tube.

Do you have threads on the end of the rebound shaft still? I've never seen one broken before.
 

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Discussion Starter · #16 ·
All or nearly all of the rebound shaft threads were in the HBO. I removed the threaded metal bit; it didn't turn out freely, but it wasn't seized. Actually it kinda squeaked like screws into plastic often do...just sayin'. I can see that part is alu now; now obviously I'm thinking 'this hollow threaded rod probably should've been made stouter,' which could be either better steel or just more of it.

Still, though, what was the root cause? Making parts stronger doesn't hurt, but it's probably preferable to just fix the thing that forced it to break. Did the HBO bang up the bottom of the compression damper before the rebound shaft broke? I'm thinking no. Is there simply not enough support on the rebound piston? I.e. a thin piston with a single o-ring is going to be most prone to the rocking that must have happened...right? Seems like that piston had to encounter some very uneven pressure in order to torque the rebound rod and apply those perpendicular forces needed to shear it.

So was the problem simply too much fluid pressure in the rebound circuit?

...okay, then what cause THAT?

LOL. I got no idea what happened. I'm watching some gopro right now and seeing if I can actually find an event (i.e. jump) where I broke my thingamajig or whatever.
 

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All or nearly all of the rebound shaft threads were in the HBO. I removed the threaded metal bit; it didn't turn out freely, but it wasn't seized. Actually it kinda squeaked like screws into plastic often do...just sayin'. I can see that part is alu now; now obviously I'm thinking 'this hollow threaded rod probably should've been made stouter,' which could be either better steel or just more of it.

Still, though, what was the root cause? Making parts stronger doesn't hurt, but it's probably preferable to just fix the thing that forced it to break. Did the HBO bang up the bottom of the compression damper before the rebound shaft broke? I'm thinking no. Is there simply not enough support on the rebound piston? I.e. a thin piston with a single o-ring is going to be most prone to the rocking that must have happened...right? Seems like that piston had to encounter some very uneven pressure in order to torque the rebound rod and apply those perpendicular forces needed to shear it.

So was the problem simply too much fluid pressure in the rebound circuit?

...okay, then what cause THAT?

LOL. I got no idea what happened. I'm watching some gopro right now and seeing if I can actually find an event (i.e. jump) where I broke my thingamajig or whatever.
Upload some high res photos and we'll see what we can see.

I've never seen threads broken on rebound before. It's not a common problem that needs parts redesigned. More a one-off mystery to solve.
 

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Upload some high res photos and we'll see what we can see.

I've never seen threads broken on rebound before. It's not a common problem that needs parts redesigned. More a one-off mystery to solve.
I second this. I haven't heard of this happening to a Mattoc over it's 5 years of existence. Something weird is going on here.

Something was assembled wrong after a service or something. The design is not the issue as this is at best, a extremely rare instance
 
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