Suntour rebound - loose knob

[Haibike_biker]

I have a brand new Cube Pro 800 Allroad with a Suntour Air fork. This has a red knob at the bottom of the fork, supposed to adjust the rebound. This knob sits loosely, if I leave it there I will loose it when cycling. When turning the knob, it is like unscrewing a screw inside the fork. The red knob has a long hex pin on it. I don't know how the rebound adjustment works, or whether it's supposed to feel a "turn" or "a click" when adjusting.

But isn't the knob supposed stick tight onto the bottom of the fork?

 

[PCeBiker]

I've also got Suntour air forks with the same red knob, and it doesn't unthread.

I've got 25 clicks from max-min rebound, then the rotation stops in both directions.

There's something definitely wrong with your adjustment knob.

Perhaps it's broken, or it was rotated with too much pressure when reducing the rebound and it unthreaded?

If it were me, I'd try to "tighten" it back up with a bit of force and see if it starts clicking/ratcheting when you reverse the rotation.

The ratcheting/clicking has a very light touch to it.

 

[stompandgo]

Let the air out of it before reassembling.

 

[PCeBiker]

Let the air out of it before reassembling.

Was my guess right?

Do you just tighten the knob back up?

 

[stompandgo]

It depends if the threads are still good. You just don't want to fight the air in the other fork chamber, if it exists.

Since the bike is brand new, I'd take it to the dealer.

 

[Haibike_biker]

It depends if the threads are still good. You just don't want to fight the air in the other fork chamber, if it exists.

Since the bike is brand new, I'd take it to the dealer.

You mean threads in the red knob? They are not screw in-out "threads" as far I can see, but "rings" with a rubber O-ring gasket.

 

[Haibike_biker]

Let the air out of it before reassembling.

How do I do that?

 

[stompandgo]

There should be a cap on the fork crown that when removed, has a Schrader valve inside. Depress the pin with a pick.

 

[PCeBiker]

The red knob has a long hex pin on it.

If this is the hex pin that you are talking about, then the other end of it is probably threaded, and has unthreaded from whatever it is supposed to screw into.

If it hasn't come complete out, then don't remove it.

How do I do that?

There is an air valve (Schrader valve same as an innertube) on the other end of that fork tube underneath a threaded cap.

There's about 200 psi of air in the fork and you'll need a shock pump to re-inflate the fork afterwards. (You forks will collapse when you let the air out.)

You don't wanna wreck anything, so if the dealer is riding distance away, then take @stompandgo 's advice and go see the dealer.
It's a brand new ebike.

Tell them that it was like that when you got it.

 

[Haibike_biker]

If this is the hex pin that you are talking about, then the other end of it is probably threaded, and has unthreaded from whatever it is supposed to screw into.

View attachment 211308


If it hasn't come complete out, then don't remove it.




There is an air valve (Schrader valve same as an innertube) on the other end of that fork tube underneath a threaded cap.

There's about 200 psi of air in the fork and you'll need a shock pump to re-inflate the fork afterwards. (You forks will collapse when you let the air out.)

You don't wanna wreck anything, so if the dealer is riding distance away, then take @stompandgo 's advice and go see the dealer.
It's a brand new ebike.

Tell them that it was like that when you got it.

View attachment 211309

Asked a bike mechanic today. He said it's normal, there is no "click" on this type. The red knob is loose but it's just a an adjustment tool, it can be stored elsewhere. And the rubber gasket is missing probably making it loose

 

[Chazmo]

Since the bike is brand new, I'd take it to the dealer.

Can you do this, @Haibike_biker ? You shouldn’t be dealing with the rebound adjuster coming off the fork tube like that. Yes, absolutely right that it should not be hanging unthreaded like that.

 

[Chazmo]

By the way, if you do bleed off the air, you’ll need a fork pump to put it back. It’s no big deal, but you won’t be able to get the right pressure with a standard bike tire pump.

 

[PCeBiker]

@Haibike_biker has a different model of Suntour fork than I have.

I've got the fancy downhill forks with 160mm of travel.

His adjustment knob is just a "stored tool" on his forks. (Like how my grinder wrench stores in the handle, or how a Schrader valve adapter stores on the Presta valve.)

Mine is directly connected to the air chambers inside the fork.

@Haibike_biker Can you post a better picture of your adjustment knob?
Mine is aluminum alloy.
Is yours plastic?



I wish I could remove my adjustment knob.
It's a delicate knob at the lowest point of the fork so it hits the floor when the wheel is removed, and it could hit a rock or stick when riding.

There's no metal shroud molded into the bottom of the fork tube to protect the knob, because it would weigh at least as much as a nickel and that extra mass could make the difference between winning and losing your downhill race.

 

[PCeBiker]

Asked a bike mechanic today. He said it's normal, there is no "click" on this type. The red knob is loose but it's just a an adjustment tool, it can be stored elsewhere. And the rubber gasket is missing probably making it loose

@stompandgo
Is that bike mechanic full of or is it me?

If I can remove my "fork tool" I'm gunna store it elsewhere before I break it.
I don’t "use" it anyway.
I just leave it on extra smushy.

 

[stompandgo]

I'd have to see the bike, but it wouldn't be the first time a mechanic was full of it.

 

[Haibike_biker]

@Haibike_biker has a different model of Suntour fork than I have.

I've got the fancy downhill forks with 160mm of travel.


View attachment 211337




His adjustment knob is just a "stored tool" on his forks. (Like how my grinder wrench stores in the handle, or how a Schrader valve adapter stores on the Presta valve.)

Mine is directly connected to the air chambers inside the fork.

@Haibike_biker Can you post a better picture of your adjustment knob?
Mine is aluminum alloy.
Is yours plastic?



I wish I could remove my adjustment knob.
It's a delicate knob at the lowest point of the fork so it hits the floor when the wheel is removed, and it could hit a rock or stick when riding.

There's no metal shroud molded into the bottom of the fork tube to protect the knob, because it would weigh at least as much as a nickel and that extra mass could make the difference between winning and losing your downhill race.

Exactly, the dealer told me the same. It's just a tool. It's not broken, now I tried adjusting +_÷ rebound and it surely works. Guess water into the whole is not a big issue but I'll order a new know with gasket it'll probably stick better. Dealer confirmed this fork doesn't give "click" when turning. Fork return max slowly when know is tightened as far as possible. When loosening a few rounds fork return much faster. This fork probably not "premium"..This spec is from the ad site..cannot confirm if its the actual fork

 

[PCeBiker]

That's just an Allen key without a bent shaft.

Doesn't matter if you lose it.
Just use a regular metric Allen key.

 

[PCeBiker]

,.. This fork probably not "premium"..

I wasn't looking for a "premium" fork, I just wanted as much fork travel as possible (160mm) and I had to go with "premium" downhill forks to get that much travel.

I Really Like my forks though.
Even if I do disrespect them by never cleaning them, I don't even wipe off the stanchions.

I never wiped a stanchion on any of my motorcycles, so I ain't gunna start now.

 

[Haibike_biker]

That's just an Allen key without a bent shaft.

Doesn't matter if you lose it.
Just use a regular metric Allen key.

Yeah should the entry on the fork bottom be closed due to moist and dust?

Thx

 

[PCeBiker]

Yeah should the entry on the fork bottom be closed due to moist and dust?

Thx

Suntour forks are supposed to be pretty good at dealing with real world conditions.

Everything all up in there is almost certainly sealed to keep everything out.
(Even the tool apparently. )

But if it were me, I'd try to put an O-ring on that "tool".

It looks like it's got a groove in the base for an O-ring?

Maybe yours is missing?


Might as well try to store the tool in its designated spot.
Even just a wrap of tape around the base to make it fit more snuggly and stop falling out.

If it were me, and I had no need to remove it, I'd put a tiny drop of crazy glue or loctite on the tip of the Allen key, and glue it in place.

Just a tiny drop. You don't wanna seize the whole mechanism and stop it from rotating.