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No Clue Crew
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Discussion Starter · #1 ·
I'll try to provide as much critical information as I can.

This is the stock fork on a 2019 Giant Trance 29-2, a Fox 34 Rhythm, 130 travel, Boost, 44 offset. It has one volume spacer installed, roughly 85 psi to run at 20% travel (I'm 190 in gear).

Pretty basic damper, so I run a little bit of compression damping on the dial (no detents on this fork, so roughly 20-25% of the dial) and 4 clicks of rebound damping.

Overall performance is OK, but I'm getting a really frustrating noise that I can't diagnose. My best description is a "thwack" sound, that's in tune with the fork movement (i.e., it moves in time with the fork moving through it's travel). It's not a metallic sound, almost sounds like plastic.

It sounds very much like a topout clunk, but I can't reproduce the sound in the normal way (pulling up into a manual, pedal wheelie off curb, etc.). Nor can I reproduce the sound by hitting the fork with my hand, twisting, picking up the front and dropping, or by just running into a curb.

The noise consistently appears at higher speeds and in tune with hitting square edges (of which, we have thousands here in Phoenix). So, I generally don't hear the noise while climbing.

The faster I'm going, the faster the thwacking sound. It does appear to get worse the hotter the fork gets. Small changes in compression or rebound do not make a difference as far as the sound is concerned.

I took it to my favorite LBS with mechanics I fully trust. They obviously couldn't reproduce the sound since it only appears at speed. The took the fork apart and didn't find anything amiss, damaged or obviously wrong.

Put it back together, I rode it down National Trail at South Mountain this morning. No change.

I understand that sound can migrate, but I can almost feel the thwacking in the bars and you can hear it's in time with the fork moving.

Sorry for the long read. Anyone have insight or heard anything like this? Thank you.
 

g=9.764m/s2
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Mine did something similar, would start making a chatter after close to an hour of riding, especially noticeable on rocky rooty downhills, then stop and the fork would feel stiff. Sent it to 馃 for warranty service and it has not reoccurred. Unfortunately no info was given about what they found.
 

Registered
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I find it very difficult to diagnose stuff like this over teh interwebz.

I would go headset first. I've had many, many people tell me 'it's not the headset, it's the fork' then we fix the headset and it goes away.

The dumb answer is to drop the lowers, cycle the air spring when empty and cycle the damper to see if anything shows itself...

mk
 

No Clue Crew
Joined
7,632 Posts
Discussion Starter · #5 ·
Yeah, I understand it's tough to diagnose online.

As stated in the initial post, it has been torn down and reassembled by a certified tech at my LBS. No change. I disassembled the headset and spacer stack, greased and reassembled. Tech did the same. Even swapped stem and bars. No change.

Fox has issued an RA, so it's headed back for diagnosis.
 

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I'm thinking I have the same issue. Evil Offering - 34 Elite 140mm. The noise was driving me mad and I could have sworn the sounds was from the headset. After multiple checks, swapping stems, bars, tying up cables, taking off mud guard, I'm thinking it has to the fork on flex. Its very hard to duplicate parking lot style (unless you bounce fork to the point of flex then it'll be consistent). Always at speed on chatter.

Has Fox gotten back to you on this?
 

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I had an older Marzocchi 66RC2X that had a clicking sound when cycled fast. Could not duplicate the sound on the bench only when ridden @ speed. I called Marzocchi tech and explained the issue and it was sent in (still under warranty) A couple weeks after delivery and no call back I gave them a call and spoke with the tech. He could not duplicate the problem and mentioned installing on his personal bike... I said WHAT! I asked don't you have a dyno or ??? Long story short they replaced the damper cartridge and the noise ceased. I thought I posed this same question to Fox and they said they had a testing dyno.
 

No Clue Crew
Joined
7,632 Posts
Discussion Starter · #9 ·
That bike is long gone, though I miss it.

Fork finally came back from initial service, which took weeks and I had to badger them to get it back. They diagnosed as a faulty CSU and replaced the crown assembly. Seemed like a bunk diagnosis, since creaky crowns are easy to replicate.

First ride was in Sedona, where it was fine while climbing and started the noise again a little bit down HiLine.

Sent back for a second service, weeks delay and they ended up sending a new 34 Elite Fit 4 to replace it. No diagnosis of what was wrong, but no further issues with the fork.
 
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