JonTheFisherman wrote: To ab's point - I still have some suspicion that all this might be due to the black guider thing being pushed by the inner wall of the brew chamber and that event providing a more abrupt "swing" of the pressure valve. The previous linkage system has that black piece detachable and on most of the videos, the piece is not there.

On my F58, I don't have the new catch that keeps the linkage arm permanently secured to the pressure valve assembly. But in normal operation if I've properly seated the linkage arm to the pressure valve assembly, the black guide never contacts the inner wall of the brew chamber (causing it to push the pressure valve into proper alignment on top of the piston.)

That is what puzzles me; why your F58 requires that nudge from the black guide. If it always does that with the resulting mid-shot pressure drop, that would be a non-starter for me. Is this true? Does it ever work smoothly and/or with no pressure drop?

It may (repeat may) be due to the o-rings being stiff/new on the piston and the issue might decrease over time. But given it's a new machine I'd be asking for a replacement unit/part if I were in your situation. Yes please post a picture of the part you think is showing wear which may shed additional light on what is happening.

I don't think it's due to newness. I've had my flair for about six months and it's always been an issue for me.

Funny story about that locking mechanism. The second time I cleaned my flair I didn't put that lock back properly and a few shots later I had destroyed my chamber. That was about $150 repair. Can post pictures if anyone is interested but don't want to derail this conversation.

Got it. Reaching here but...

Does the linkage arm swing freely and have some side-to-side play where it is attached to the lever? (mine does) And does removing the lock from the linkage arm help? I could see where if the linkage arm connection to the lever was stiff that it could push horizontally on the pressure valve requiring the black guide to always re-center it into the group head when you pull a shot.

EDIT: At 39-40sec into the video as you start the pull, the linkage arm and pressure valve buckle forward toward the front of the F58. Hence the need for the black guide to later correct that. My F58 doesn't do that. When I start the pull the linkage arm and pressure valve move straight down into the group head.

Here is the mechanics of the linkage - I suppose it is more understandable from the drawing than from my explanation, with approximate forces at the position of maximum horizontal force. I actually didn't have information about the offset of joint P2 from the cylinder axis, so I used the value measured on Flair classic, I suppose there is no much difference. Positions of seals and joint P3 are taken from drawings in Flair manual; I hope they are correct there. When issue 0:57 happens (dashed lines), joint P3 moves leftwards and the ratio 1:15 decreases, so all horizontal forces increase additionally ... so the piston brakes itself more ... so higher vertical force needed from the lever to overcome the friction ... so horizontal force even higher ... etc

I think I have a solution or at the very least a significant improvement that happened on both of my shots today.

Before pulling a shot, grab the top of the plunger and ensure it's as horizontally level as you can make it.

So in essence:
1. Fill water chamber
2. Pull plunger all the way up
3. Fill a little more if you want
4. Grab and horizontally level plunger. Hold top of plunger for the first second or two of preinfusion.
5. Pull shot

First shot I did without step 3, second I did with step 3. Both had a small pressure drop but no where near as "violent" as the ones I normally deal with. Second shot had even less pressure drop.

Shot seems to be tastier as well but could be placebo. Leaning towards it's actually tastier since pressure is so much more consistent.

Checked various youtube Flair 58 videos - on most, issue is not visible or linkage isn't shown in that part of extraction. But visible here around 14:40, just less severe than in OP's video

Yep happens right at 14:42.

Another day another tastier shot for me with the method I posted. I can live with this until my Meticulous gets here in December.

OP, definitely try this method before returning it.

JonTheFisherman wrote:Flair actually agreed to take it back. I have mixed feelings about this because I really do like everything else about the machine and I'm sure there's at least 90% of users that are super happy with it.

You could return it an buy another in hopes it won't have this issue. But would understand the hesitancy.

JonTheFisherman wrote: Here is a picture of the worn part of the stem:

Mine has a similar wear pattern, which I'd expect given the design. There is also corresponding wear inside the linkage arm. More of a polishing than wear tho.

ab wrote: Another day another tastier shot for me with the method I posted. I can live with this until my Meticulous gets here in December.

Glad that's helping. But you are a braver man than I for wanting to try a completely new and unproven espresso machine. Solving the F58 issue may be child's play compared to getting the kinks worked out with the Meticulous.

It's funny how we can be so optimistic about new things, forgetting about all the issues with existing technology. Nothing is perfect. While I'm pretty happy with my machine there are definitely things about it that I wish were different.

But this klunk problem on a brand new machine would piss me off for sure. I'd ask Flair to send me a new one that they have verified doesn't do it straight out of the box. If they can't do that then I suppose I'd try to figure out what other machine would fit my needs. As far as I know there really isn't anything on the market quite like the Flair 58.