oslermarine

Seems like this is a heavily debated topic across forums. The satin gt4 wheels are super prone to chipping. Anyone thought about powdercoating them? Or does it mess up the integrity of the wheel? Thanks!

Fowwiee

I think the folks at the 991 GT3 forum said that the heating process will mess up the integrity.

oslermarine

Got a link to that thread? Yea sounds like touch up paint is the way to go if needed.

neanicu

They chip like mad! Of course I'm going to paint them,powder coat them...whatever. Any good wheel place will do a better job than Porsche to be honest. That paint is so soft,I could probably chip it with my nail.
I don't see why painting or powder coating will affect anything if they're properly balanced.

Alan C.

A reputable Powder coater will be able to Powder coat your wheels without issue. What you want to avoid is precipitation hardening, artificial aging, of the aluminum.

Forgeline powder coats their wheels and I haven't heard of a pro team or an individual experiencing a failure due to the powder coating process.

ExMB

But can you say that about wheels which have been heated during the paint drying process and then reheated during the powder coating later versus the heating of the powder coating right away? Please provide verifiable data to support your position.

Alan C.

6061 T6 can withstand 60 hours at 350F and not drop below 35 ksi minimum standard of the aluminum industry. If you go to 390F it will take about 30 hours to get to the 35 ksi minimum point.

Take your wheels to a reputable shop and ask what temperature they use for curing their powder coated products. Keep in mind the curing temperature and the actual temperature of the part, a wheel, will be different.

I've had wheels powder coated by Forgeline and later changed my mind on color. Forgeline stripped and re-coated them for me. Those wheels were used for three years of Club Racing and DEs and I never had a problem.

oslermarine

Looks like the GT4 wheels are cast aluminum not forged don't know if that changes anything

DrPhil Gandini

Just before the flame war starts flares up here, while not forged, the GT4 wheels are flow formed, which is a different process than the traditional casting process the term "cast wheels" might suggest. They are not crappy, they are reasonably light.
But I agree, the paint finish gets messed up really easily. The rears on mine after 6500 miles look like poop.

neanicu

There shouldn't be a " war " Doc. But I'll paint the damn things. There's nothing out of the ordinary about these wheels IMO...

sonorous

I am not a powder-coating or wheel expert but as an engineer I like to understand the technical details. This is what I collected:

From this thread https://rennlist.com/forums/gt4/8971...ls-forged.html we have concluded almost 100% that the wheels are not forged but cast. Flow forming is a post process to casting that forms the outer part of the rim with heat and pressure from rollers. So to be clear, flow formed wheels are cast. I don't think that we know for sure the GT4 wheels are flow formed but it is a reasonable assumption considering the cast construction, manufacturer, size and relatively low weight.

From BBS: http://www.bbs-usa.com/expertise/processes/
The alloy used to cast the GT4 wheels is marked on the wheel: GK-AlSi7Mg. This is a 3000 series aluminum alloy which can be work hardened (i.e. flow forming) but not heat treated. Its service temperature is listed as 450 C.

Forged wheels are typically made with 6000 series aluminum which can be heat treated to higher strength and lower ductility. The typical aging profile would be something like 177 C for 8 hours.

Typical powder coating seems to require a dwell of 200C (392 F) for 10 minutes (maybe longer). This is greater than the aging temperature used for these 6000 alloys. Is it an actual problem? There seems to be a lot of debate on the subject but it does not matter here because the GT4 wheels are almost certainly cast.

Therefore, since the GT4 wheels are cast, there should be no concern in powder coating them.

DrPhil Gandini

I wish there was a LIKE button on Rennlist, like there is over at Planet 9! Thanks so much for a very informative post, sonorous.
BTW, I wasn't trying to argue that flow formed wheels are not cast, but I understand there are various methods for casting (eg gravity, low pressure, etc.) and that wheels like HRE's FF wheels are not your bog standard "cast wheels."

oslermarine

Nice so this means the GT4 wheels can be powder coated without affecting structural integrity! Is it hard to paint match satin black with powdercoating?

Jimmy-D

sonorous - Great info.. I recommend beatint the heck out of these and when you finally can not tolerate the chips than powder coated. I will do a Bronze of some sort when the time comes

gmgracing

Great input, to add to that I have a couple things. During my largely miss-guided teen years I worked as a powdercoater for an 8 month spell. We did wheels to steel beams. When it got busy, everything was shoved into the oven at once with the temperature set considerably higher than 392F (and often the timer was set for longer than 10minutes).

My point is, don't expect your powdercoater to play by the book. Don't expect the same results from the industrial-sized place compared to your specialty shop (someone like Renewed Finishes for example).