Can’t for the life of me work out where this is coming from.

Most of the time, no issue, but if I hit a fair old dip, like a bomb hole, and compress enough, I get a loud knock like frame hitting something kind of knock. Not sure if it’s on full compress or uncompress. Doesn’t always happen, but needs a good firm compress on the rear to do it.

Sounds like the rear. Fork isn’t bottoming out, no where near. Rear shock isn’t either according to the rubber ring.

Checked lower link rubber stop and that’s present.

Just can’t see what’s doing it or what could hit the frame in that way. Pretty sure it’s not the chain slapping against frame. Different sound anyway as it does occasionally, but it’s under tension with the clutch mech and even on rare occasions it hits the frame it hits the rubber chainstay protector.

It’s only recently started doing it. Have serviced rear shock (Monarch Debonair) and bushes plus replace mount kit with TF heavy duty kit. No play in that. No play in BB. Mech seems fine.

Only vague thought is the bottom of the upper link potentially hitting the frame on uncompress but I can’t see how as shock fully extended there’s still a gap between it and the frame.

Baffled.

Air out and compress to see what knocks?

I’ll try that again, but had the air out to service the shock and didn’t notice. I’m not sure if it’s actually on the rebound and maybe when it tops out rather than under compression, but it does it infrequently so I don’t catch when it does it.

Volume reducer in shock loose?

So, it was doing it again at the weekend, especially at Cwmcarn on descents on Cafall which have a fair bit of pump type trail. Still can’t quite work out when the knock occurs, however I just noticed this discussion on Monarch knocking…

http://singletrackworld.com/forum/topic/knocking-rs-monarch

Could be that?

As for volume reducer, I don’t believe I have one, or I didn’t notice on doing the air can service. I’m not sure what it would look like. Just a plastic/foam ring?

Really noticeable with a loud knock, but depends on the trail. Previous day was a big Black Mountains loop (not trail centre, xc) and nothing really during that even on the rocky bridleway descents and odd occasion popping off stuff. It’s the compression when pumping through things, bomb holes, etc that does it.

As soon as I saw the thread title I thought Monarch knock, I’ve had two that have done it. It’s a kind of hollow wooden clunk part way into the travel. Should go away temporarily if you do an air can service