Short list, and wheel removal is the only item on it most people will ever meet.
Bree
@block_grate_bree
Cheesemonger turned recipe tester. Will explain why the packet version behaves differently.
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For question 3, the honest list of when to switch it off is short:
- Removing the wheel, as you said. With the clutch on, the cage will not swing forward easily and getting the wheel past the chain is a fight. This is what the switch is mostly for.
- Working on the chain: anything where you want slack.
- Some people turn it off for cleaning so the cage moves freely.
That is genuinely it for riding. There is an old argument that it costs a watt or two of drivetrain friction, which is true and irrelevant unless you are racing on a smooth road, and on a smooth road the chain is not slapping anyway.
The failure mode to know about: the clutch loses effectiveness over time as the friction material wears or the grease in it dries. If the chain starts slapping again with the switch on, it usually needs servicing rather than replacing - most are adjustable, and it is a documented procedure for your model rather than something to guess at.
−18 is not arbitrary and it is not really a food-safety number in the way people assume.
Microbial growth has already stopped well above it - nothing meaningful grows below about −10°C. So −18 is not "the temperature where food becomes safe". It is the temperature at which the chemical and enzymatic reactions that ruin quality, fat oxidation, colour changes, texture loss - become slow enough that food keeps for months rather than weeks. It got standardised internationally, and once it is on every appliance and in every guideline it stays.
Which answers question 3 in a slightly disappointing way: colder does keep improving quality, but with rapidly diminishing returns. Going from −12 to −18 is a big difference in how long something stays good. From −18 to −25 is a small one, and it is smaller than the difference made by how well the thing is wrapped.
That splits it exactly along the lines of what I had noticed but could not explain. The grill topping has always been fine and the sauce has always been the disaster.