Dialling in espresso in a coffee truck

Dialling in espresso
I have been running a coffee truck for two years now and we have a really hard time keeping our espresso consistent. We use a la marzocco linea classic and a mythos clima pro grinder. The espresso stays in the same range for a few shots and then suddenly a shot will be way too slow or way too fast. “Dialling in” in the morning almost feels useless as the results changes within 15 minutes. We use scales through every step as well. I’m wondering if anyone has any tips for us as we waste quite a bit of coffee and it can be very time consuming. Since we are in a mobile vehicle we think it may have to do with changing temperatures
Any suggestions will help!
Thank you

I recommend you to read this article where they go over the dialling in of the Barista express in details.

Everything in regards to keeping your coffee consistent is to weigh your beans, make sure the settings on your grinder is the same, and use the same beans, and the same pressure when tamping.

All of this should almost guarantee you get a fairly consistent coffee.

If your grinder settings change maybe it’s because of the fact that you are using a machine that is designed for casual use, as a professional one.
Meaning the grinder heats up and therefore will grind differently. One strange solution, to test this would be to try to keep the grinder in a cold storage area of your truck, and test it over a few hours, and see if it helps.

Good luck


I feel for you.

The initial shots on a Linea Classic AV are much cooler than when you make a lot of shots one after the other. When you have a lull in service your brew temp will also go down.

So if you have your PID set to say 94 you will likely be brewing around 80 - 90 ish as you dial in.

Before service if you run water through your groups with handles in as the manual recommends that will flush your filter, groups and heat your groups. Then wait for the boiler to recover. When the PID is back upto temp then run 3 shots of water on each group, then start to dial in. This will get you closer to normal operating temp. Don’t make any changes on your setup until around the 5th shot, don’t taste anything until you reach your target recipie then adjust.

When you have not made coffee for 5-10mins you’ll loose temp again so do 2 volumetric water flushes of the group to help bring the brew temp back up to normal. I usually then make a shot on the group and ditch it, then clean and make the shot I want to serve.

The above is due to the plumbing on the Linea Classic AV as the water passes outside then boiler and group through the flow restrictor / flow meter path you loose heat.

When you are making a lot of coffee on t he machine you’ll reach a stable temperature, much hotter than when you dial in.

Machines like the Linea Mini, PB, Strada AV won’t have the above issue due to their updated design.

Second thing. Mythos is designed to heat the dosing chamber and keep it around 40 - 50 degrees c. If you leave it on all the time it will help keep that stable temp and offer more consistency.

This issue happens to me a lot with the mythos when running training sessions where I dial in for tasting, I’m ready and happy then the shots run 6 - 8 seconds faster when I do the demo.

On the plus side the Linea Classic AV volumetrics can be very accurate if functioning properly which helps a lot with controlling consistent yield regardless of grind setting.

The mythos is also a great grinder overall and other competitors had similar issues with waste and shifting GB shot times. So the Mythos was at the time a big improvement when released. It’s clump crusher is good and burrs are good too.

You should experiment with flushing routines in order to reach more consistent brew temps, how many do you need based on your aims and environment temperature and also purging of the grinder as when coffee has sat in the mythos dosing chamber for a while it won’t extract in the same way as freshly ground doses. You should try variations of number of volumetric flushes followed by number or purged shots and see if that results in more stable setup.

Also get comfortable that you’ll probably need to dial in again throughout service.

Finally, Michael Cameron had written a lot about Mythos online so worth reading his suggestions there.

I believe if you use a different machine combined with a single dosing retail grinder such as Ditting Lab Sweet you would probably not have these issuesii. You could also try a Mahlkonig E65 GBW rather than a Mythos.

Ensure you have consistent dose, good distribution, level consistent tamp, consistent yield and don’t bang the group handle too as basics, as doing these badly will all affect the outcome a lot.

Good luck!

Hey! Thank you so much for such a thorough response. I will refinery give the flushing system a go!