Rocket group gasket 8.5 mm – the thicker version for a portafilter that turns too far
The portafilter slides into the group, turns a little, and then comes that solid click after which nothing drips any more. That is the job of a narrow rubber ring between the group and the portafilter, which holds the full pressure with every extraction.
Under heat and pressure, rubber loses its elasticity over time, hardens and shrinks. This item is the 8.5 mm thick version; we stock the second thickness alongside it, because that is exactly where the two differ when fitted.
When it is due
The first sign is the portafilter handle: it turns further than it used to before it sits tight. If it travels well past the centre, the gasket has shrunk.
On top of that come coffee leaking out at the side of the group, a portafilter that can only be released with force, and a gasket that is hard and cracked rather than elastic when removed. If you film the extraction, you can also see it at the rim of the portafilter: water escapes there that should actually pass through the coffee.
At a glance
| Type |
Brew head gasket, also called group gasket |
| Thickness |
8.5 mm |
| Location |
In the brew group, between the group and the portafilter |
| Fits |
Rocket portafilter machines. Exactly which series is not documented for us – we check it using the serial number. |
| Version |
We stock the second thickness as a separate item |
| Installation |
Fitting by a qualified professional recommended |
| Brand |
Rocket Espresso |
Our documentation does not give a part number for this gasket. We do not enter one we cannot verify – if you have one from a service document, send it to us and we will check it.
Important for installation
The gasket sits in the group, and in operation the group is hot and under pressure. Before replacing it, the machine must be switched off, unplugged and cooled down; only then is anything loosened at all.
We deliberately do not give step-by-step instructions here. If you are unsure, bring the machine to us or have the replacement done by a qualified professional – it is a small job, but one on a component that holds the full brewing pressure.
Who it is for
For anyone with a Rocket whose portafilter turns noticeably further than it used to, or where coffee runs past the side of the group. One of the cheapest parts of the machine, with the biggest effect on a clean extraction.
What goes with it
The second thickness is the 8 mm group gasket. Which of the two fits is decided by the position of the portafilter handle, not by the model.
The same group also holds the brew group flange gasket and the fine filter for the group. Both are cheap and belong on the table every time the group is opened.
For cleaning, we stock machine and grinder cleaning products. You will find more in the Rocket accessories and spare parts and service parts categories.
From our workshop
When we replace a gasket, we always put the fine filter next to it. A new gasket on a clogged filter is only half the job, and the filter costs less than a second visit to the workshop.
And we check the position of the portafilter handle right after fitting: if, once locked in, it sits roughly at right angles to the machine, the right thickness has been chosen. If it travels far past the centre, the other thickness is the better choice. That is our routine in Bern and Zurich, not a manufacturer specification.
To go with it, in Bern and Zurich we most like to drink Nutty Delight, Cozy Chocolate and, when it should have no acidity at all, Very Nutty. You will find the whole range in our coffee beans.
Returns excluded
Service parts are excluded from exchange and return. They are procured specifically for each order and cannot be resold once they have been fitted or test-fitted on a machine. So before ordering, check the model, year of manufacture and serial number of your machine – or send us a quick message and we will clarify the fit together. Your rights in the event of defective goods remain unaffected.
Frequently asked questions
When do I need 8.5 instead of 8 mm?
When the portafilter still turns far past the centre even with a new 8 mm gasket. The extra half millimetre of material takes back exactly that travel.
How can I tell that the gasket is due?
The portafilter turns further than it used to, coffee leaks out at the side of the group, or the old gasket is hard and cracked when removed.
What is the part number of the gasket?
Our documentation does not give a number for it, and we will not make one up here. Send us the number from your service document and we will check it.
Does the thicker gasket fit every Rocket?
Exactly which series the two thicknesses cover is not documented for us, and we do not guess here. Send us the model and serial number and we will check it before you order.
Can I see the part before buying?
Our showrooms in Bern (Gerberngasse 44) and Zurich (Hagenholzstrasse 50b) show a wide selection, but not our entire range – the display changes. Drop us a quick line at [email protected] before your visit, and we will check whether the product you have in mind is currently there.
Unsure about the fit? Write to us at [email protected]. We deliver across Switzerland and to Liechtenstein in 2-4 working days.
