Generic information that I’ve found is that you want wheels that are rated to handle half of the weight of the heaviest axle of the car (sticker inside door jamb). For my S60, the max load is for the front axle at 2645 lbs. Cut this in half and you have 1322 lbs per wheel. I’ve also found something in the Volvo online specs about the minimum load capacity for tires is code 94 which corresponds to 1477 lbs, or about 125 lbs more capacity than half of the heaviest axle, which seems a little backwards to me that the tires are “stronger” than the wheels – though air pressure probably introduces other differences here. The original P-Zero tires (235/40R19) have a loading capacity rated at 96, which is 1565 lbs each.
Then there are significant differences in wheel construction: gravity cast wheels (which are cheapest and potentially weakest), low pressure casting (more expensive and potentially stronger than gravity cast and also seems to be OEM spec for many cars), “rotary/flow forged” wheels (typically more expensive than cast, appear to have potential be to stronger than cast), and fully forged wheels (most expensive and strongest – mostly for track applications).
So, after countless hours of poking around and reading information and specs, I’ve found a variety of wheels that are flow/rotary forged (potentially stronger than cast), but have a load capacity of only 1350 lbs which just meets the “half of the axle” standard, but is also less than the load rating of the stock tire at 1565 lbs. I suspect these wheels are a bit lighter than the stock wheels as well, but this spec seems less important to my needs. It also seems odd to me to have a tire capable of supporting more weight than the wheel is rated for, but I’m just a noob at this. Maybe flow/rotary formed wheels have more resistance to impact/shock than cast wheels and might stay round longer, but I suppose generalization like this are had to come by because of the many variations in design… It is enough to make your brain hurt for sure!
In the end, I just ordered a set of 18″ BBS wheels (low pressure cast) also check this guide for pressure ford fiesta psi that are rated for 1650 lbs each. This gives the same construction technique as my OEM wheels (so I’m not stepping backwards in terms of construction technique/quality), exceeds the minimum “half of the axle” load capacity by a comfortable margin of 325 lbs, and is rated higher than the load index of the stock tires by 125 lbs. An interesting element is that since BBS wheels are manufactured in Germany, they are subject to EU regulations concerning post-production quality specs and required testing protocols. It seems that there is no uniform standard for wheel production here in the US, which is not very much of a surprise at all. Europe seems to be ahead of the US in many areas that are actually important for consumers (pesticide use, food ingredients, cosmetic ingredients, safety standards, etc). Here in the US, we’ve recently stripped the Consumer Protection Agency of the teeth that they need to actually do anything useful for consumers. Go figure…
Tesla model 3 tire pressure guide here Tesla Model 3 Tire Pressure [Correct PSI] – Nerdy Car
Thus, it does seem to come down to brand trust which is a daunting exercise in a field with countless players that the average noob like me has never heard of before. I’m hoping my new 18″ wheels with 245/45R18 tires give me a somewhat softer ride and more insulation against bending rims than my original stock 19″ wheels with 235/40R19 tires. The best part of this wheel/tire combination is the overall diameter is less than 1% different from the overall OEM wheel diameter. Since this difference in size is less than the difference of new/worn rubber on stock tires, it doesn’t look like any reprogramming of the speedometer or stability control systems is necessary.