Brabus Alloy Damage

This page covers the 2 failings of Brabus alloys, corrosion and bending.

 Why Do Brabus Alloys Corrode?

In general, alloy wheels aren’t the colour of the alloy they are made from. They are made, primed with phosphate and then sprayed the colour you expect.

Alloys wheels are made of an alloy mixture of aluminium. Aluminium oxidises very quickly. Unlike Iron’s rust, aluminium’s oxidation is the same colour as the base metal. Freshly stripped alloys will start creating an oxide layer almost immediately and in a very short time, the entire piece will be oxidised.

This isn’t a bad thing as the aluminium oxide is very strong and scratch resistant BUT if you don’t iron or zinc phosphate the wheels first, the aluminium oxide continues to grow.

Aluminium oxide is a light, crystal, almost fluffy layer. Not a good base for the powder coat. The phosphate stops the oxide growth and bonds it together making an excellent base for the powder finish. Without the phosphate pretreatment, the oxide layer grows very slowly and eventually you get the paint lifting off.This is a photo of a Brabus Monoblock wheel on a brand new smart just purchased from the dealer by Tony W.

This is the same problem you get with Brabus alloys, this is what causes the corrosion and lacquer lifting. Because Brabus alloys are a natural colour they can’t be pretreated as the pretreatment is grey (zinc phosphate) or blue to grey (iron phosphate) which would cover the natural colour. So, the Brabus alloys are just lacquered and a few years down the line, the lacquer starts coming off. The more the lacquer comes off, the more it corrodes.Here is a great photo of a rear Roadster Brabus alloy owned by Matthew JD.

This is a bad, but not unusual example of Brabus wheel corrosion. In a close up of the image from above, you can see the clear lacquer lifting around the bolt hole.

What Are The Options For Fixing The Corrosion?

You could have them acid dipped, refaced and relacquered but it wouldn’t be long until they corrode again.

The best option is to have them refurbished as a standard alloy wheel. Have them acid dipped, primed in phosphate to stop the aluminium oxide from growing and then have the wheel sprayed in a suitable colour.

Why Do Brabus Alloys Bend?

Brabus are known for their powerful cars. The easiest way to increase useable power is to reduce weight. Brabus decided to use lighter wheels as most of their cars have 20″+ alloys which would be quite heavy. The trade off to a lighter alloy is it’s not a strong as the alloy used in normal, heavier, car wheels. Here is Tony W’s Brabus alloy that was bent under normal road use.

Aluminium alloy is a mixture of aluminium and silicon (the metal, not silicone the rubber). The proportions of metal in the alloy determine both the strength and weight of the wheel. More aluminium in the alloy means a lighter wheel, but one which is more pliable and easier to bend in an impact. Less aluminium means a heavier wheel, one that does not bend easily, but may be more brittle and prone to cracking.

This is the knackered alloy from a set that OTV bought. The previous owner must have hit a landmine. A standard alloy wheel made of standard weight alloy would have shattered.

What Are The Options For Fixing A Bent Alloy?

Slight variations in the lip of the alloy can be pounded into a better shape using a rubber mallet. You can also use a short piece of wood to position your hits more precisely. I had to do this before every MOT when I owned my Roadster with Brabus alloys

If you don’t fancy taking a hammer to your alloys or they are a bit too bad to reshape, take them to a wheel refurbisher. They will heat, beat, roll and reshape the alloy to make it round again. Plus they will normally strip back any corrosion and refinish the wheel with paint. Expect to pay between £40 and £60 a wheel depending on repair.

It’s All In The Metal

Ronal use an alloy similar to 6061-T6 (70GPa elasticity). It has a much hight aluminium content which makes them lighter but less resistant to bending. Magnesium is also a light metal and that’s even softer than aluminium.

(Al) Aluminium ≈97%
(Mg) Magnesium 0.8–1.2%
(Si) Silicon 0.4–0.8%
(Cu) Copper 0.15–0.40%
(Cr) Chromium 0.04–0.35%
(Fe) Iron ≤0.7%
(Mn) Manganese ≤0.15%
(Zn) Zinc ≤0.25%
(Ti) Titanium ≤0.15%

Brabus (designer) and Ronal (manufacturer) refused to tell me what aluminium alloy they use for their Brabus wheels. I’m guessing they think I want to make copies. If I was, I’d not use the alloy they are using.

For a city car, there is no need for light wheels. There are big pot holes in the city. You can already buy copies of the Brabus alloys in A356.0 with a primed and painted finish.

However, the aluminium alloy that Brabus use contains more aluminium in the mix. This makes it lighter and softer. Another problem is that a higher % of aluminium also allows aluminium oxide corrosion to appear quicker.

Why Don’t Non Brabus Wheels Bend So Easily?

A356.0 is the normal aluminium alloy used when making alloy wheels.

(Al) Aluminium – 93%
(Mg) Magnesium – 0.2% to 0.45%
(Si) Silicon – 6.5% to 7.5%
(Cu) Copper – 0.25% max
(Fe) Iron – 0.6% max
(Mn) Manganese – 0.35% max
(Zn) Zinc – 0.1%
(Ti) Titanium – 0.25% max

The lower Aluminium and magnesium content and the higher silicon content makes it stiffer (80GPa elasticity).

That is also why steel wheels survive almost everything, they have a GPa elasticity score of 200.

Silicon Is Not Silicone

No, your alloy wheels do not contain the rubber sealant that waterproofs around the edge of your bath.

Modulus Of Elasticity – Young Modulus

It’s a rating in Gigapascals (GPa) that tells you the flexibility of a compound. The lower the number, the more flexible it is.

Average ratings:

Lead – 13GPa
Aluminium – 69GPa
Titanium – 110GPa
Brass – 120GPa
Iron – 200GPa
Cobalt – 209GPa
Iron – 210GPa
Steel – 215GPa
Molybdenum – 325GPa
Tungsten – 407GPa