Like changing tires on your car or group gaskets on your espresso machine, there are parts of your grinder that you're also going to want to change every once in a while to keep everything operating smoothly. Opinions vary on the exact frequency at which you ought to change your burrs, with some people advocating for changing them on a yearly basis, and others for changing them after grinding a certain number of shots. Others still, advocate for using a TDS meter but I don't think that's practical for reasons that are outside of the scope of this article. Personally, I don't like any of those approaches. Fifty shots of 17g will put more wear on a machine than fifty shots of 12g. Darker roasts are less dense than light roasts, meaning they don't make the machine work as hard. And if you're switching between more than one coffee, finding an exact threshold gets murkier still. Furthermore, if your burrs are rated for 4,000 pounds it's not like they'll work at 3,999 pounds and stop working well at 4,001--it's a more gradual process than that. In the end, all we're concerned about is the taste of our coffee, so why not use that as a metric instead?
Before we get to that though, have you tried cleaning your grinder first? The symptoms of a dirty grinder are very similar to the symptoms of worn burrs so it's always worth it to do a deep-clean before buying burrs. It takes a small amount of time but could potentially save you a lot of money and even more time overall.
At this point in time, there's not a lot of research out there about the mechanics of how burrs operate, and how those same functions change over time as parts age. Because of that, I can only point out those symptoms that I've noticed correlate to issues that were present in grinders that needed new burrs. In my experience, these are those factors:
Increased Shot Variability
If one shot is giving you two ounces in fifteen seconds but the very next shot is brewing in twenty five seconds and all other variables have been kept constant, then it can be said that you've got a large amount of shot variability. With as many variables in play as there are in all things espresso, some amount of variability can always be expected. Try to keep an eye on that range of variability though. In the weeks and months leading up to a burr change, you may notice that your range gets wider and wider.
As burrs age, the grinds that come out may feel warmer than the grinds coming out of a new, clean grinder. Whether or not warm grinds are an issue all it's own, or if it's actually a benefit depends on your point of view. I'm certainly a big fan of the Mythos Clima Pro, which does actually actively heat the burrs to make certain those grinds are toasty warm. Problem or not, if it's a change from the norm, then it's a sign that those burrs are on their way out.
Now this is a tricky one. There's a lot of different factors that could contribute towards grinds that are extra clumpy. A dirty grinder, a bent chafing spring, broken clump crusher, bad burrs; they're all suspects. It's best not to jump to conclusions about your burrs based solely on how clumpy your grinds are, because it could just as easily be something else. So unless you've got clumpy grinds AND some of these other symptoms, you're better off reaching out to our Service Department for help.
Slower Shot Times
Are you having to grind increasingly finer to achieve the same brew times? Then go ahead and get fresher coffee. Stale coffee has less Carbon Dioxide, which means you're going to get less of it off-gassing throughout the brew. That gas actually causes turbulence in the flow of water through the puck and slows the whole process considerably. If you're still having to grind finer after using a fresher coffee, then it could be time to change burrs.
Knowing all of this, if you'd still like the manufacturer recommendation of when to change your burrs, then I've listed a few of those specifications below:
|Machine||Burr Lifetime (lbs)|
|Baratza Forte Ap||1,000-1,500|
|Baratza Vario / Vario W||1,000-1,500|
|Bunn G Series||40,000|
|Compak F10 / F10 Conic||2,640|
|Fiorenzato F4 Nano||660|
|Mahlkonig EK43 / EK43S||13,000-15,000|
|Mahlkonig K30 / K30 Air||1,600|
|Mazzer Mini / Mini E||660|
|Mazzer Super Jolly||880|
|Nuova Simonelli G60||500-600|
|Nuova Simonelli Mythos / Mythos II||2,500-3,000|
The actual process for changing the burrs on your grinder will vary greatly from model to model. There are, however, a few tips I can share that you should keep in mind no matter what's sitting on your counter:
- Always lubricate the threads of your burr carriers! Not only will it keep things moving smoothly, you're less likely to have the threads seize down the line. This is especially important if your threads are brass or stainless steel, or of mixed alloys. Our recommendation for lubricant is to use a small amount of the food safe, highly effective Kluberpaste. Use too much, or use the wrong type and you'll pick up other contaminants and risk jamming the threads all over again.
- Don't force it! If something doesn't thread together with relatively little effort, then it's more than likely not lined up quite right or the threads aren't clean. To achieve the amount of adjustment resolution you would expect from a grind adjustment mechanism, those threads are often very fine. This means they are exceptionally easy to cross-thread or damage.
- Clean everything! In order for your burrs to be seated properly and for your carrier to thread well, you want everything to be immaculate. You can use a degreaser and a brass or nylon bristle brush to coax out those tough stains and buildups. You'd be surprised how even a few small grinds in the wrong place can cause a lot of issues.
As always, if in doubt, feel free to reach out. Our Service Department is here to help you to keep your machine working in peak condition.