Beware Kinesis Wheels! Look at this!

Much different aluminum alloy Bruce

 

So all HRE's that have failed at the track were not real HRE's? What a coincidence! I didn't even refer to any specific instances. How you can know exactly those which I'm talking about is amazing.

 

That and the amount of metal used. When you design anything, loads are calculated and a safety factor added. If I know the metal is going to be at 500F, I can look up the strength at that temp. If I assume normal wheel tire temps and know I want the wheel as light as possible, I'd spec a heat treated and probably work hardened alloy because they have the best strength to weight ratio…but you have to know the temperature window they will see. For a piston, you would not select a heat treated or work hardened alloy.

Aluminum heat treatment and annealing happen at much lower temps than steel and 400F will definitely put you in the trouble range. Also, aluminum heat treatment is very different from steel in that when you quench steel it is full hard, then you temper it (warm it back up for a time/temp) to pull some of the hardness out and it becomes weaker, but more ductile. Aluminum is precipitation hardened which means it’s not hard after quenching, a post heat treatment called aging is required and there is very definitely an optimum amount of aging that should be done. When you exceed the optimum point, the material strength begins to drop, but unlike steel that becomes weak and ductile, aluminum becomes weak and brittle which is the worst possible material condition since it tends to fail without warning and fail catastrophically.

 

Hey, please don't HRE hate here. Halle Berry and HRE wheels is what I dream about at night. Both are beautiful, and I prolly won't rough either up. Just TLC all the time.
Bee Jay

 

The aluminum that is used for casting MOST wheels is A356. This alloy is typically heat treated to a condition just below T6 and aged to final hardness. If you are going to powdercoat this alloy you should use the powdercoat temp to assist or artifically age the part to final hardness. This can be a little tricky because you cast, heat treat, machine then finish (paint or powdercoat). The aging process takes about 24 hours on its own if I am remembering correctly. If you heat a part that has already been heat treated and aged to a high enough heat for enough time you start to anneal that part. It is my opinion that if you are refinishing you should not powdercoat and when removing existing coatings use the least agressive method possible to remove that coating, and never hot strip. Hot strip is very quick, however it is very hot and will reduce temper by 50% or greater. Forged aluminum wheels are usually made from 6061 also heat treated to T6 (or just below and aged). The same bad stuff happens to this material when it gets hot.
Tire temps, radiant brake heat and transfered brake heat are not high enough for enough time to anneal a wheel, at least not yet. I say that because wheels are engineered to withstand a certain level of stress based on vehicle weight and possible stress loading, lateral g-loads for example. The problem is that tires have gotten much better. The numbers used with a large margin of error, or safety margin, in the past don't work anymore. You can't predict where tire technology is going to go or how quickly, so you can't design for that future technology until it is a problem unless you want to make wheels heaver than the market will accept. Eventually wheels may see enough heat in use that something needs to be done to combat that.
Wheels develop stress cracks. I have seen wheel failures on everything from original equipment wheels on high end cars to the most expensive, highest quality aftermarket wheels to wheels on dedicated race cars (those guys spend a crap load of money on engineering).
I think somebody mentioned that the current owner of the broken wheel is not the original owner, so the previous history is unknown as well.

 

You see this?
More bad posts about Kenesis
http://www.ferrarichat.com/forum/showthread.php?t=174696

 

That thread has nothing to do with Kinesis.

 

+1...lol

 

Most wheel manufacturers powder coat their center sections these days. I have a set of custom Forgeline wheels I got 2 years ago for my track car and all of their race wheels are powder coated forged centers. They supply wheels to numerous racing teams. My original one piece magnesium wheels I painted myself because I was more worried about being able to observe any developing cracks.

Bob S.

 

Bruuuce!!! I just read the whole thread.... ...... I am glad you and your 348 challenge are still with us... !! That sucks huge !!!

I am very glad you sensed the danger in time.... I guess its time to install those 355 challenge wheels now.... !!!