I've seen some discussion in threads of the past regarding chrome vs. non-chrome wheels regarding the strength of the wheels. What's the difference? What's the science? Why does merely chrome-plating a wheel make it weaker? Does it somehow molecularly alter the wheel? Whazzzzzzzup??? -Mitch

I believe they have to acid bath or something like that to the surface to roughen it up for the chrome to stick.

This process I believe does make the wheel a very slight bit weaker.

Personally I like the look of chrome, but I hate the peeling/air sealing problems when the chrome does peel on the lip.

I prefer painted or polished rims myself.

Alon

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IMHO, I find it hard to believe that there is any significant difference in the strenght of a wheel if it is palated or not. The etching process is removing microns and I cannot imagine it having any discernable difference.

Chrome is very hard and resists scratching and corrosion better than paint. The polished wheels are clearcoated. If they chip, they will corrode under the clearcoat and will then need to be refinished to restore the look.

I would love to hear if there is a reason the chromed wheel would be significantly weaker. If it's an insignificant difference, the discussion is simply esoteric.

Steve
'85 SL500 Euro

My understanding is that the electroplating process is to blame. It can reduce the strength of the wheel by as much as 30% because it alters the molecular structure of the metal much like annealing or heat treating does.
Also...
1) Mercedes warns against chroming wheels.
2) TUV will not pass chromed wheels in Germany.

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The acid bath is only a small portion of what causes the weakening of a wheel in the chrome plating process.
The plating process does require a tremendous amount of heat and that causes a process called anealing in the metal. Anealing, which is commonly used in metal forming, makes metal softer and not as strong. In most cases the only wheels that have a significant change in strength are the wheels which are gravity cast. The gravity cast manufacturing is the least expensive method of making wheels but, also is the weakest process.
Thanks, Luke

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Okay guys, since I didn't believe it, I called a friend of mine who is a Metallurgical Engineer. Much metal plating is done cold (room temperature). I didn't know chrome is done hot, but he told me that chrome plating is done at higher temperatures for speed and ion saturation of the solution and so forth. Annealing is what causes the weakening, not the material removal from etching. I thank everyone for setting me straight.

Steve
'85 SL500 Euro

Just so I'm clear--your metallurgist friend confirmed that the chroming process does, in fact, weaken the wheels (at least to a certain extent)??? --Mitch

Yes Mitch, the process (theoretically) weakens the wheel. My friend told me that chrome plating is done commercially at higher temperatures, 200 to 300 degrees F to increase the chromium ion saturation of the solution which speeds up the process. The plater makes more money. What they do is put a positive electrode to the wheel and negative to the solution and this causes the chrome ions to bond to the wheel. The molecular change takes place by relaxing the metal through time and temperature. The longer the time and higher the temperature, the more annealing takes place. Heat treating and pressure casting aligns the grain structure (molecules) of the metal, increasing the strength. All metals have grain structure. The annealing process relaxes the stratification of the metal and allows a more random pattern of the grain.

At least, this is how I understand it. If necessary I could contact a big chrome plating company for more information as my friend does business with them.

Steve
'85 SL500 Euro

My car has 'alloy' wheels. Are these the best, and what is the better if not.

Thanks

David Weis
'95 280C

I have had both chrome look great ARE HARDER TO CLEAN and alloy scratchs easie.

Yes David, alloy wheels are the best. They have the best compromise between strength and weight.

Originally steel wheels were heavier but more durable than spoke wheels. Spoke wheels are actually lighter than alloy but they flex, require maintenance (truing) and are less durable than steel or alloy. The light wheels have a dramatic effect on ride and handling because they are "unsprung" weight. That means they are not supported by suspension. When you hit a bump the mass of the wheel must move and it causes a hard shutter. If they are light it is much less severe. Anything unsupported by the shocks should be as light as possible.

They used to call them "mags" or "mag wheels" because they were made of magnesium. It's super light and very strong but the cost and manufacturing problems have steered the industry to use a special aluminum compound (alloy). This is what is commonly used today.

Steve
'85 SL500 Euro
Original '85 AMG "Mag" wheels

The bigger (biggest) problem with chroming aluminum wheels stems from the fact that the base metal of the wheel becomes the anode and the chrome becomes the cathode in a cell. Beneath that beautiful chrome, the base metal is sacrificing itself. Finally, the deterioration is such that the plating peels. This usually happens in the bead area of the wheel and then the wheels leak air. I had this experience on a set of forged factory alloys on my "88 300TE. It ruins the wheels; not right away, but in five years, they're junk.

The wheels on my 86 300E were chromed in 1992 I want to say, by about 1996 the chrome started bulging out on the front wheels and now the chrome plating is just peeling off like crazy, I dont even wash my wheels anymore because of the risk of having more fall off. I am so tempted just to peel the rest off, paint the suckers and just wait till I can afford some painted 15 hole rims, at $165 each (used) it aint cheap.

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1986 300E. 115,000+ miles. 3.0L I-6 1st daily ride, around town only. (Gone)

We sell the 8-hole and 15-hole replica wheels new for $109.00 in 15" and $129.00 in 16".
Luke

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