Just built up a 2nd hand Mojo frame and put in a reverb, on compressing it there’s noticeable resistance caused by the air in the frame, I can hear it escaping round the headset bearings.

The headset in it doesn’t fit snugly and I’m about to change it and I suspect any gaps will be closed or at least much reduced.

There are two bottle bosses in that unusable place under the downtube but I don’t particularly want to leave them open to the elements.

Anyone else had this issue and solved it?

I don’t have a Reverb, so I don’t know, but when it compresses does it bleed air to atmosphere? I would have thought it was a sealed unit but even if it’s not, I can’t see that the small amount of air displaced is going to be noticeable in the whole volume of the frame tubes.

That shouldn’t happen the reverb is a sealed unit. nothing is displaced in the frame when the seatpost is dropped. strange one that

As he said – the reverb is sealed. Are you sure it’s coming from the headset and not a sound from fork/shock compressing?

take out one of the bottle boss bolts and see if the headset noise stops.

Same happens with my Yeti ASR-5 / Reverb combination. It’s not a problem. Once I’d cycled the Reverb a few times it seems to stop (for me at least).

The Reverb isn’t completely sealed. The’re an empty area around the air spring shaft that’s open to the bottom of the post. I guess it’s 20-30ml which is displaced when the post is compressed.

My KS isn’t sealed, and yep you can hear the air coming out past the headset when you drop it. It’s never been a problem, though. (the frame’s got a hole in the BB shell which you’d think would let the air out easily, but it seems like it’s enough air moved quickly for other exits to get some flow as well).

Definitely not my imagination, when you drop the post the air takes is still escaping under pressure once the post is down, new headset just arrived in the mail, I’ll install it and see if its an issue.

my mates does that on his nomad

clubber – Member
As he said – the reverb is sealed. Are you sure it’s coming from the headset and not a sound from fork/shock compressing?

I dont think it is sealed, my reverb did this until I took the heli tabe off the drain hole of the BB on my covert. I had issues with the reverb getting graunchy with mud and crud getting in through the bottom and messing up the bushings.

Are these Carbon frames?
Im guessing they are, so they won’t have the little “blow holes” like they do in steel or ally frames near the tube ends. Meaning the frame is “sealed” once all the components are fitted.
You could either drill a holes in the BB area or a more elegant solution would be to fit a hollow bolt in place of one of the bottle boss bolts.

My Blur frame use to do this with a normal post.

When you pushed the seat post down you could here the air leaving via the head tube.

Was a bit weird but didn’t cause any issues

Yep, headset fitted, completely sealed now, a hollow bolt in the boss would work but as its down in the muck under the downtube it will suck crap in on the upstroke.

Strokey beard thinking time.

Same here on a five frame and reverb.Weird init…

get one of these in a suitable colour.

Zip tie around the head of a hollow bolt and bingo – bladder for the escaping air to come out of the frame into and then it will let the same air back in when you next raise the post. No contamination!