Wheels take the worst of it

It is not dust in any ordinary sense. Braking generates enormous heat, and what comes off the pads and discs is metallic particles leaving at speed and at temperature.

Those particles land on the wheel and, because they are hot, they partially embed into the surface rather than sitting on it. Then they oxidise. That is why a wheel goes from dusty to genuinely stained, and why a hose and a sponge stop working after a few months.

The same particles land on the lower quarter panels and sills, which is where that orange bleeding on light-coloured cars comes from. Iron decontamination is what removes it, and no wash will.

It is also why we keep wheel equipment completely separate from paintwork. A mitt used on a wheel and then a door is carrying embedded metal across your clear coat.

Most wheel cleaning is faces only, because that is all you can reach with the wheel on the car. It looks fine from three metres and it is half the job.

Taking the wheels off gets the barrels, which is the inside surface where the majority of brake dust actually accumulates, and the arches behind them, which almost never get touched. On a car that has done a few years without it, the difference in what comes out is genuinely unpleasant to look at.

It also means the wheel can be properly decontaminated and coated on both faces, which is the only way a wheel coating does its job. Coating the front while the barrel is still contaminated is protecting the part that was easy anyway.

Wheels off adds time, so it is not right for every job. On a maintenance wash it is unnecessary. As a one-off reset, or as part of a full detail, it is the thing people notice most afterwards.

The sequence is the same as paint, for the same reasons. Decontaminate, clean thoroughly, dry, then coat a surface that is genuinely clean rather than one that looks clean.

A coated wheel does not stop collecting brake dust. What changes is that the dust sits on the coating instead of embedding into the wheel finish, so it rinses off with far less effort and does not stain. The practical effect is that a wheel you used to scrub now largely cleans with a pressure rinse.

That matters beyond appearance. Less scrubbing means less contact, and less contact on a wheel means fewer scratches in the finish over time. It is the same argument as coating paint.

Coating is best done with the wheels off, on a fully decontaminated wheel, and ideally when the wheels are already off for other reasons.

This is the part that gets skipped, and it is the difference between a wheel coating that lasts and one that quietly stops working.

A wheel face sits directly outside a brake disc that reaches temperatures no body panel ever approaches. A coating formulated for paintwork is not designed for that, and applied to a wheel face it degrades far faster than its rating on paint would suggest.

So wheel faces get a product rated for the heat they actually see, not whatever is left in the bottle from the bodywork. It is a different product for a different job, and any detailer coating your wheels with the same bottle they used on the doors is either using something genuinely heat-rated or has not thought about it.

Ask which product is going on the wheels. It is a reasonable question and the answer tells you a lot.

Painted and clear-coated wheels, which is most factory alloys, behave much like paint. They can be decontaminated, machine polished where the finish is marked, and coated.

Powder coated is tougher and generally more forgiving, though a heavily textured finish traps dust in a way a smooth one does not and benefits most from coating.

Polished or machined faces need care. The bare metal is lacquered, and once that lacquer is compromised the metal underneath oxidises. Aggressive wheel cleaners will attack it, and a strong acidic cleaner can permanently stain a machined face in one application.

Matte and satin finishes must never be polished, because you will burnish shiny patches into them that cannot be undone. They get cleaned and coated with matte-safe product only.

Tell us what you have when you book, or send a photo. Using the wrong chemistry on a machined or matte wheel is one of the few genuinely irreversible mistakes in this trade.

Wheels first, always, before you touch the paint. Their own bucket, their own brushes, their own mitt that never goes near a panel.

Do them while the wheels are cool. Cleaner sprayed onto a hot wheel after a drive dries almost instantly, which both stops it working and risks staining the finish.

Use a pH-neutral wheel cleaner on coated or delicate wheels. The strong acidic products sold for neglected wheels will strip a coating and can damage machined and polished faces permanently.

A soft barrel brush is worth owning. Even on coated wheels the barrels collect the most, and they are the surface that stays out of sight until you take the wheel off.

The full aftercare guide covers the rest of the wash.