CDan,
I checked the drawings for steel wheels as well and since it was also developed for the 80 Series, it is maxed out at around 1150kg. Unfortunately, just weighing more, does not mean it is stronger. Keep in mind that aluminum is about 1/3 the density of steel.
I checked a Hilux wheel today and found it has about the same spec. That might be good vehicle to use for ordering parts.
Keep in mind, the cracks occur from fatigue. Fatigue builds over time and there is a limit to the life of a wheel. If you buy a set with 250k miles on them, they will have much less life(strength) left.
>Warning, this next part gets a little long and technical, but if your good with google, you can get better detail and more. Also, these are not Toyota's actual specs and don't bother asking what they are.<
Something else which is important to understand is that material or process(forging, casting, stamping, etc.) are of no consequence in the strength/durability of a wheel. A wheel is designed to support a load. A good design is optimized for mass, cost, style and strength.
Forging is expensive and in an OE application is reserved for vehicles where mass is more important than cost. Lexus LFA and IS-F(thanks for the reminder, THEROK) are performance vehicles where every gram counts and cost is secondary. Camry, on the other hand, is a high-sales-volume vehicle and every $0.0001 counts. LFA/IS-F get forged wheels, Camry gets cast.
Back to the job of the wheel, supporting a load... if I am told that a vehicle has a max axle weight of 1000kg at fully loaded condition, I design a wheel to support 500kg for the "life" of the vehicle. "Life" is a carefully calculated amount of usage, but for the sake of an example lets say life is 60,000miles(this is wayyy low, but its a nice round number). I plug 500kg and some other vehicle characteristics into a couple formulas and I get back test loads for Cornering Fatigue, Radial Load Fatigue and an impact test. These are the 3 main tests used in the industry to qualify a wheel for production service on public roads. There are several groups, all with different standards, JWL(Japan), NHTSA(US), SAE(US and GLOBAL) and a few others. Everyone has a slightly different way of calculating life. For example, European standards are higher than SAE.
Cornering fatigue is important for loading in the front wheels during a turn. Cornering is very hard on a wheel.
Radial Load fatigue is important for rear wheels where the majority of the weight is in a loaded vehicle. The rear wheels do not turn, so the cornering forced are minimal.
The impact test is just that. Imagine hitting a curb or pothole at a decent speed, you wouldn't want the wheel to break.
Now that I have test loads for each test and a life requirement, I can design a wheel. A stylist gives me a design he likes and I slap him and tell him to try again. This repeats until we have a design that is worth simulating on a computer in specialized analysis software. In the old days, styling was much simpler and "easy" to predict with hand calculations. Now, styling is more complex and optimization is more efficient with the computer.
The computer breaks the wheel into a mess of very small pieces and calculates how the load is transferred from one tiny piece to the next, over and over and over again. The stress in the wheel is then analyzed by an engineer to determine if changes need to be made to the styling.
This is the key point: Each material has certain stress limits and each style/wheel design is optimized to reduce the mass and cost, keep the styling intent and(ideally) not last a single revolution past the design life from above. No matter what material i used, I want to make sure I meet all my targets. Typically this means the wheel is heavier than I want and costs a couple $ more because I had strength requirements to meet and a stylist to entertain.
An interesting rule of thumb from fatigue testing is that if you reduce your load by 20%, the life will be extended approx. 3 times the original. So if I design a wheel for 500kg and 60,000miles and then only ever load it to a maximum of 400kg, it will last 180,000 miles. Or the reverse, if I increase the load to 600kg, it will only last 20,000 miles. Even more interesting is that aluminium and steel show the same relationship in most cases. It is possible to get "infinite" life from steel at very low loads, but when was the last time you removed weight from your Land Cruiser and kept it off?
Oh, yeah, when your girl left you because you prefer to spend your time with your truck...
I can't wait to hear how many things are wrong above. I've got my nomex PJs on.
If people are interested, especially some of the senior members, I could start a separate thread to explain more detail, but I would still have to leave out Toyota specifics.
Scotty, I don't know how you got Lexus drawings. Whoever gave them to you was risking their job as well. I like my job and need the money, so I won't take that change no matter how many times I am asked.
Price is pretty hard to choke down.
