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2005 Lotus Elise - Touring
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Super excited to have the LSS wheels scored off local Craigslist back from powder coat. They look fresh and can’t wait to get some tires on them!


1268805
 

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I was always under the impression powder coating the lss wheels compromised them due to the heat required during the process.
 

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I was always under the impression powder coating the lss wheels compromised them due to the heat required during the process.
The powder coat process used on aluminum is baked at a lower temperature and should not harm the aluminum temper.
 

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Awesome, I kind of want to powder coat mine anthracite...


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2005 Lotus Elise - Touring
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Discussion Starter #5
The powder coat process used on aluminum is baked at a lower temperature and should not harm the aluminum temper.
I told the shop I used was familiar with the process for forged wheels. They look a hell of a lot better than they used to!
Now to decide on tires...
 

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I had talked with a couple of local powdercoaters about having a set done for additional wheels and was told to find a powdercoater that used low temp powder rather than the high temp that most use. It looks like it would be ok at the lower temps and not affect the strength of the forged wheels.
 

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Super excited to have the LSS wheels scored off local Craigslist back from powder coat. They look fresh and can’t wait to get some tires on them!


View attachment 1268805
Wheels Looks good. Will freshen up the look. I ended up also having rotors and calipers powder coated when I did mine. Not sure how they will hold up to heat if I ever track. But it sure looks good. And keeps off the rust. Something to consider?
 

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Just to put numbers to something that often has a lot of opinions, here's what happens to tensile strength of forged 6061-T6 at various temperatures after various exposure times:

1268833


So if it is put in an oven at 350F for 5hrs, and tested in the oven at that temperature, it will be about 75% the strength it started at. I looked up the curves for 7075-T6 and 2014-T6 to see how much variation there is between allows since I don't know the alloy and temper of LSS wheels, but there was basically no variation. Now, if the alloy is T0 (annealed) already, then it won't weaken as much since it is already pretty weakened.

Another caveat is that we don't know the safety factor of any given wheel. If the safety factor is > 2, then a 25% reduction of strength is just fine. I do believe there have been some threads of LSS wheels failing after powder coating though [edit: Epic LSS Wheel Failure at Grattan Raceway]

Not saying to panic, but just to add caution since there are enough unknowns to swing it one way or another.
 

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2005 Lotus Elise - Touring
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Discussion Starter #11
Just to put numbers to something that often has a lot of opinions, here's what happens to room temperature tensile strength of forged 6061-T6 exposed to various temperatures for various times:

View attachment 1268833

So if it is put in an oven at 350F for 5hrs, it will emerge with about 75% the strength it started at. I looked up the curves for 7075-T6 and 2014-T6 to see how much variation there is between allows since I don't know the alloy and temper of LSS wheels, but there was basically no variation. Now, if the alloy is T0 (annealed) already, then it won't weaken as much since it is already pretty weakened.

Another caveat is that we don't know the safety factor of any given wheel. If the safety factor is > 2, then a 25% reduction of strength is just fine. I do believe there have been some threads of LSS wheels failing after powder coating though [edit: Epic LSS Wheel Failure at Grattan Raceway]

Not saying to panic, but just to add caution since there are enough unknowns to swing it one way or another.
Really appreciate this info, it's highly considered. Based on the chart, it looks like you may see around a 15-20% reduction in the fatigue strength at room temperature, especially considering most wheels aren't run at room temperature.... I see this influencing the choice of tires more than anything as I've been on the fence about buying some sticky Toyos or going with A/S Michelin and a more progressive non-sticky tire may be the better option to pull some load off the wheels in hard cornering.
 

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So how hot do they at speed on track, or after coming off track and parking on a hot day with brakes cooking inside of them?
 

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Really appreciate this info, it's highly considered. Based on the chart, it looks like you may see around a 15-20% reduction in the fatigue strength at room temperature, especially considering most wheels aren't run at room temperature.... I see this influencing the choice of tires more than anything as I've been on the fence about buying some sticky Toyos or going with A/S Michelin and a more progressive non-sticky tire may be the better option to pull some load off the wheels in hard cornering.
Actually, I think I grabbed the wrong chart, so I will edit that post to reword. This one may be more applicable. The above chart showed the strength when tested at the elevated temperature. This one below shows the strength after cooling back down to room temperature. If the oven is >400°F then it says basically the same story, BUT if the oven is less than 350°F then result is very optimistic. I apologize for misleading anyone.

1268876


@Spirit_R see the notes above since I think it will make more sense now. Also since there is a ton of air blowing over the spokes, they don't heat up nearly as much as in, say, a powder coating oven. My guess is that the hottest point inside the surface of a spoke is barely higher than air temp, and it is this core temperature that the above chart is referencing. Regarding when it is stopped with the brakes "cooking inside of them", that open environment just isn't going to transfer much heat, especially when iron rotors on a street car just don't get that hot in the grand scheme of things - even if you get them red hot in a braking zone, you aren't coming to a stop right away after that. You'll see F1 wheels start to smolder when they park, but they actually do a ton of design work to try to get heat into the wheel from the brakes to keep tire temperature up. Check out this article - What is F1 rim heating? - Racecar Engineering. - even in that one the calipers themselves max out at 230°C, so the spokes will be much, much lower than something in direct contact.

Since we don't know the exact alloy to begin with, this is all for just general guidance.
 
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