Fox 36 ebike knock

AusE

Member
Dec 3, 2019
71
20
Australia
Thought I had a loose headset but seems more like coming from air shaft side of fork, its only done 400k. Thoughts?
 

brash

Well-known member
Jul 19, 2019
105
130
Aus
Internal or external battery? Firstly check to see if your battery is loose in the holder/cradle. This is a common thing that people believe is CSU noise. Even take the battery out and try to replicate.

Next port of call, take note of Air spring pressure, slowly release air from Air Spring and undo air spring/spacer top cap with 32mm (off top of my head) chamferless socket/tool.

Inspect the air spring, sometimes the volume spacers can unclip and rattle in the air spring but this is very rare in my instance especially with the fox "clip" design. We see this common with the cheaper Rockshox forks though.

A CSU creak is a very distinguished "cracking" or creaking noise. Fox are well aware of the issue and will replace under warranty but from my experience the Ebike rated forks have had a good track record with CSU's, the normal 36's can't say the same.
 

#lazy

E*POWAH BOSS
Oct 1, 2019
1,334
1,448
Surrey
My mrz forks creak like an old mans knees ! Doing the loctite trick tonight , if still bad can warranty them !
 

mxh

Active member
Aug 27, 2018
105
45
Australia
I had the CSU creak on my Fox 36 Ebike forks - I also thought it was a loose headset to start with as does sound a bit like a rattle when going over rough ground. If it is the CSU you should be able to force the noise to happen when stationary - I took the bike back to the shop, demonstrated the creak and the shop got them changed under warranty with no issues.
 

AusE

Member
Dec 3, 2019
71
20
Australia
Thanks for the replys but definitely not a creak but a knock cant really hear it when riding. I read somewhere about oil draining from the bushings and causing bushing slop so I turned the bike upside down manipulated the fork a few times put back up and knock gone, surely there cant be that much play in new forks.
 

brash

Well-known member
Jul 19, 2019
105
130
Aus
The old saying goes, Rockshox give you minimum oil, Fox give you none at all.

The amount of times I've dropped the lowers on a new bike and it been bone dry in there is too many to count.

Bushing tolerances have also a lot to be desired. Having them sized and replaced is always a good bet come first service. MTB suspension centre in Sydney are good for this service.
 

AusE

Member
Dec 3, 2019
71
20
Australia
Cheers guys definitely not a csu creak, I'm pretty sure its bushing play when the oil drains to the bottom as it only seems to be there after bike has sat for a while. Time to crack them open for a look.
 

redrhino

Member
Mar 24, 2020
45
23
california
I just got a YT Decoy 29 Pro and am noticing what sounds like the same issue with bushing play. You can hear it knocking and I can put my hand down around the legs at the seal where the uppers and lowers meet and feel movement. Bummer. I checked two other bikes with normal 2020 Fox 36 forks and they have no play like this.
 

Uberpunk

New Member
Dec 19, 2020
1
0
manchester
Hi, I have exactly the same bike ( Decoy Pro29 and exactly the problem with my Fox 36 Elite forks. They knock and you can feel it in the fork leg when you hold around the seal and rock the bike.

Wondering did you get this sorted ?
 

AusE

Member
Dec 3, 2019
71
20
Australia
Hi, I have exactly the same bike ( Decoy Pro29 and exactly the problem with my Fox 36 Elite forks. They knock and you can feel it in the fork leg when you hold around the seal and rock the bike.

Wondering did you get this sorted ?
Yes mine got covered under warranty with new bushings, to check if its bushing play turn the bike upside down and pump the forks a few times this will push the oil between the stanchions and bushing. Turn back up the right way and check for play it should be gone until oil runs back down into lowers. Hope this helps
 

redrhino

Member
Mar 24, 2020
45
23
california
YT directed me to the Fox warranty form on their website. They had me return it and fixed it under warranty. It took about 2 weeks here in the US when I did it.
 

E-Bandit

Member
Sep 1, 2020
30
6
Australia
I have the same issue, after washing the bike I could feel the knock looked at everything and seems to be the fork, turned upside down and pumped the forks then picked bike back up and knock is gone.... is this normal or should I take back to 99bikes? Bike is 10months old.
 

redrhino

Member
Mar 24, 2020
45
23
california
I have the same issue, after washing the bike I could feel the knock looked at everything and seems to be the fork, turned upside down and pumped the forks then picked bike back up and knock is gone.... is this normal or should I take back to 99bikes? Bike is 10months old.
When you turn it upside down oil moves around the bushings and takes up the space that causes the play. It will likely come back after a ride.
 

E-Bandit

Member
Sep 1, 2020
30
6
Australia
Ok I’ll keep an eye on it,
Think that fox warranty is only for USA , I’m in Australia, does anyone know how to contact fox locally here?
 

Mteam

E*POWAH Elite
Aug 3, 2020
1,780
1,718
gone
A friend of mine had this with his fox 36 ebike forks, we happened to just turn them upside down and cycle them a couple of times , and the knock went away, and hasnt come back since, that was about 300 miles ago.


My 36 ebike forks havent had the knock .
 

E-Bandit

Member
Sep 1, 2020
30
6
Australia
A friend of mine had this with his fox 36 ebike forks, we happened to just turn them upside down and cycle them a couple of times , and the knock went away, and hasnt come back since, that was about 300 miles ago.


My 36 ebike forks havent had the knock .
Completed one ride and when I got home the knock is back... time to take it to the shop
 

E-Bandit

Member
Sep 1, 2020
30
6
Australia
Got my fork back yesterday and all covered under warranty, replaced the bushings , replaced lower bath oils , seals, foam rings and air side service. See if it doesn’t come back.
 

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