Ouch! Team dynamics spoke failure!

[2Cool]

So many forum posts on Google about this subject that it seems like breaking/cracking after powder coating happens often enough to be a real concern.

From what I have seen, the powder coat curing temp is over 400 degrees F. Apparently some coaters will increase that temperature to hasten the process. That may be a contributing factor to these failures.

The alloy in question makes a difference. I also see that when temperatures are continually over 100C (212F, water boiling point) that weakening has to be taken into account - http://www.aluminiumdesign.net/why-aluminium/properties-of-aluminium/

Basically I would pay for a good paint job rather than a powder coating for any of my own wheels, just out of paranoia.

 

[RAAMaudio]

Powder coating can also add a bit of weight to the wheels, I do not know how much but I do not want added weight in anything I do unless it serves an important performance purpose. I am a bit anal about weight as many here know but is a lifelong approach that has served me very well like close to 20 years ago when I built the lightest full suspension cross country mountain race bicycle in the world at 20.4 lbs and it was very strong and around 4lbs lighter than any other mountain bike.

The powder coating on the magnesium fork legs took off several oz just on those two parts. It was fun maintaining them afterwards as the bike was fully polished and also being built for a booth in InterBike, biggest bike show in the world to promote a line of titanium parts I was working on. I had to polish the fork legs everyday as they would tarnish that fast.

Adding weight and making wheels weaker in the name of style seems quite the wrong way to go when dealing with such critical parts on a car.

I wish wheels could be bought in the hardened finish the forged Alcoa wheels on my dually came with, 3 years old, parks outside in all seasons, salted roads, 118 degrees, never waxed, 35,000 miles, shine like new!

I had CCW make me a custom set of 18x11.5 and 13" wheels for the C6 wide body Vette convertible I put together from Z06 body parts, fully polished inside and out including sides of the spokes. They were 6061 billet, CNC, TUV rated, a sprinkling of rain made for a lot of time polishing them back to look right again, never again!

OK, rambling on here long enough, factory painted, polished or powder coated, wheels would be best to use on any car, then there is spray paint for wheels and the removable stuff you can spray on which is rather heavy I imagine is the way to go. Atermarket poder coating not so unless one can determine the process is done to exacting standards to not weaken the wheel which I would imaging is not going to be easy to verify even if a shop says they do it that way.

 

[meFiSTo]

I also see that when temperatures are continually over 100C (212F, water boiling point) that weakening has to be taken into account - http://www.aluminiumdesign.net/why-aluminium/properties-of-aluminium/

That's interesting. Don't wheels get hella hotter than that when running on a hot day at the track? The brake hardware (caliper, rotors, pads, etc.) sure does and wheels are in quite close proximity to all that. Thinking in particular about the rotors.

Some interesting notes in a KNS Brake sponsored article I found regarding rotors/pads.

One comment on rotor temps: "...Core Temperatures of rotors used on track days are generally in the 450?C to 600?C (1110?F) range and peak surface temperatures up to 800?C (1470?F) for 5 seconds or more."

In any event, wheels can be pretty hot in "racing" situations, although that does not appear to apply specifically to the example cracking problem that started this thread.

 

[2Cool]

That's interesting. Don't wheels get hella hotter than that when running on a hot day at the track? The brake hardware (caliper, rotors, pads, etc.) sure does and wheels are in quite close proximity to all that. Thinking in particular about the rotors. Some interesting notes in a KNS Brake sponsored article I found regarding rotors/pads.

One comment on rotor temps: "...Core Temperatures of rotors used on track days are generally in the 450?C to 600?C (1110?F) range and peak surface temperatures up to 800?C (1470?F) for 5 seconds or more."

In any event, wheels can be pretty hot in "racing" situations, although that does not appear to apply specifically to the example cracking problem that started this thread.

I agree, rotors get much hotter than 100C in normal use, much less racing. The hats likely don't get quite as hot, but still warm as heck. Most likely the comment in that article was directed at relatively pure aluminum, instead of the alloys used for automotive applications.

 

[M-Sport fan]

like close to 20 years ago when I built the lightest full suspension cross country mountain race bicycle in the world at 20.4 lbs and it was very strong and around 4lbs lighter than any other mountain bike.

The powder coating on the magnesium fork legs took off several oz just on those two parts. It was fun maintaining them afterwards as the bike was fully polished and also being built for a booth in InterBike, biggest bike show in the world to promote a line of titanium parts I was working on. I had to polish the fork legs everyday as they would tarnish that fast.

I love the almost no maintenance, raw titanium (3-2.5 alloy tubing) finish of my Merlin Road (Campy Record gruppo/Mavic wheel equipped) road bike, as it just will not; corrode, pit, be scratched, chipped, or anything else.
I cannot even imagine trying to maintain raw magnesium, not that anyone would ever use that material for a bike frame.

The UCI (Union Cycliste Internationale) has set minimum weight limits for complete road and track bicycles (NOT sure about mountain bikes used in international competition, but I would think they exist?), and they do actually weigh them at ANY & ALL races sanctioned by them, or run under their auspices.

I had CCW make me a custom set of 18x11.5 and 13" wheels for the C6 wide body Vette convertible I put together from Z06 body parts, fully polished inside and out including sides of the spokes. They were 6061 billet, CNC, TUV rated, a sprinkling of rain made for a lot of time polishing them back to look right again, never again!

WHY if I ever owned a set or two of CCWs, they would be painted by them (CCW), extra grams be d****d!