# group head to puck gap (group head screen bolt imprint means too close ?)



## jpaul__ (Feb 19, 2016)

This is a general question too

but for me with a Bezzera bz02 I find that a LM 17g basket with only ~14g coffee gives a better shot

than a 14g Rancilio basket and similar amount of coffee, despite theoretically undercharging the LM basket

After a shot with the 14g basket it is clearly close to the grouphead since I have a bolt imprint.

The grouphead dispersion screen has behind it maybe 4 holes delivering the water from the boiler so

I can see that maybe a larger gap will ensure better water distribution across the head of the puck and

more uniform soaking as the pressure builds up.

what is your take ?


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## MediumRoastSteam (Jul 7, 2015)

Hi @jpaul_, I think the answer is "It's all relative". Some machines prefer a higher dose, some machines favour more headspace between the puck and the shower screen.

The bolt imprint could be just the solenoid valve (or equivalent - I am not familiar with this machine) sucking the puck up when the shot is finished.

Have you tried the 2p coin test? That consists of placing a 2p coin on top of the tamped coffee in the porta filter and locking it as normal. Then, unlock the PF and check the puck: If the coin is there still lose as you placed it, then the dose is too low; If there is a very slight, faint print, than that's just great; If the coin is buried into the coffee puck, then the dose is too high.

Not sure if the above is even relevant. For me, it's about getting the best taste in the cup and experimenting with different grind settings, doses, etc. If a lower dose works for you, great.

Sent from my iPad using Tapatalk


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## jpaul__ (Feb 19, 2016)

Interesting I did not know some machines have a solenoid in brew head above puck ... bezzera is just, as below,

... with a bolt imprint in top of puck (from 14g basket), I am talking

so I reckon volume of liquid above it is about 16ml (0.05^2*pi*0.002*1e6) fairly large vs shot size of 40ml


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