Skip to the middle to get to the things that you don't find everywhere else.
Yes, there are a zillion posts about this. None of them were actually complete, IMHO, so here we go.
For this example I will use:
• Donor: 2011 Ford Flex
• Recepient: 2016-2021 (4th Gen) Lexus RX350
Why? The used Ford wheels were 1/4 the cost of new Lexus wheels.
Bolt pattern: Should be obvious. Both cars use 5x114.3.
Bore / centerbore: Ford is 63.4mm, Lexus is 60.1mm. As the Lexus shaft is smaller than the Ford wheel hole size, I need hubcentric rings / centering rings that convert 63.4mm to 60.1mm.
Note that these rings are entirely intended to center the wheel during the mounting process, and do not bear any load once the wheels are torqued down. So they can be plastic or a lightweight metal such as aluminum, no problem.
Diameter: Both cars use 20" wheels. Important since too-small wheels will not clear the brake calipers, especially in the front. If you are unsure, the only way to check is to test-fit the wheels.
Width: Important since wider wheels may hit suspension components at the back side and/or fenders on the front side.
A test-fit is the best option. However, you can also use Tire Rack or other resources to determine the allowable width of a wheel on a car.
Here, both cars use 20x8 wheels, so no problem. The Lexus is also rated to accept 18x8.0 to 20x8.5 wheels, so anything in that range should also work.
Offset: The Ford wheels are 39mm. The Lexus stock wheels are 30mm, and the car can handle 27mm to 42mm.
Still, the Ford wheels will be 9mm further in. There is a slight risk of hitting the front or rear suspension components.
To confirm, I ran a hockey puck (25mm high) all around the back of both the front and rear wheels. There is at least 25mm of space there, meaning moving the wheels 9mm further in is no issue.
Note running wheels with an offset radically different than stock could lead to long-term suspension issues, even if the wheels "fit".
The above you find everywhere.
What you DON'T find everywhere:
Lug nuts: The donor wheels / car may take different lug nuts than your recipient car.
To ensure they fit properly, you need nuts that do the following:
• Seat: The nuts must have the proper seat type for the donor wheels.
The Lexus RX uses flat seat nuts, the Ford uses 60° conical nuts. So, in this case, nuts must be 60° conical, and I cannot use the Lexus OEM nuts on the Ford wheels.
Note: in marketing-speak, "cone" means "conical".
• Thread: The nuts must have the proper thread for the recipient car
The Ford uses 1/2"-20 threads, the Lexus uses M12-1.5 threads. The nuts must be M12-1.5.
• Length: The nuts must be long enough for adequate engagement on the wheel studs without bottoming out.
Regrettably, the only way to be absolutely sure is to measure the donor wheel when fitted to the recipient car.
Bottoming out is rarely an issue provided you aren't running extended-length wheel studs. But you must have a depth of engagement at least equal to the size of the wheel stud (i.e. M12 stud = 12mm minimum engagement).
[Note: some people say 1.5x. As far as I can tell, they're usually talking about open lug nuts on racing wheels, which is a totally different application. Such setups must pass racing safety rules, which are different than OEM specs.]
Note that cone nuts will fit into a matching cone recess in the wheel, giving you another 2-3mm of engagement. If necessary, you can count turns to determine the actual engagement.
If you can't test / must guess, you can compare McGard or Gorilla offerings for both the donor and recipient cars. Chances are that both cars use lug nuts that are between 1.45" and 1.5" long. If the lengths are about equal, chances are the new nuts will have plenty of engagement.
There is also the fact that car makers can't be sure what wheels will be fitted, wheel makers don't know what cars they'll be fitted to, and lug nut makers don't know either. So everyone plays nice to ensure that most wheel/car combos have more than sufficient engagement - meaning you're more than likely safe regardless of the wheel you stick on the car.
The Flex wheels allow 12mm of engagement plus another 2-3mm for the cone, for 14-15mm overall. That's close to the fitment of the OEM wheels and beats the minimum by a significant margin.
Do note that even 1 additional thread after 12 threads adds 8%, two add 16% and 3 is 25% over minimum. Those are non-negligible margins of safety, especially considering that the minimum engagement will include a significant safety factor.
• Hex drive: OEM nuts will probably be 13/16" or 3/4". If you want to use the OEM lug nut wrench, you want the new nuts to match. If you don't care, you can pick either, or go with a special drive type such as a spline drive or locking type.
• Style: You may have a choice between "cone" and "bulge cone".
Both types seem to offer equal functionality - except for the hex socket size - but some wheels might have smaller indents for lug nuts than others, in which thinner "cone" nuts may fit better. Otherwise the differences are purely cosmetic.
Here, old Lexus 13/16" "bulge cone" lug nuts from a 2005 RX330 fit with over 12mm of engagement, with no issues fitting into the Ford lug nut recesses. Given this, 13/16" McGard or Gorilla cone or bulge cone nuts would also obviously fit; 3/4" nuts would also probably fit.
Load rating: Not normally a problem, but if you're moving wheels from a lighter vehicle to a heavier one, it may be.
The Flex GVWR is 6150 lbs; the RX350 is only 5666 lbs. So the Ford wheels should be OK.
More specifically, the Flex wheels are rated for 2000-2200 lbs per wheel (depending on who you talk to), for 4000-4400 lbs per axle or 8000-8800 GVWR against:
• The Lexus GVWR of 5666 lbs;
• Assuming 60/40 front-back weight distribution (which is very conservative), that's 3400 lbs on the front Lexus axle; and
• Assuming 65/35 distribution, that's 1700 lbs per corner, maximum.
So the Flex wheels are fine.
Also know that GVWR is the absolute maximum for a fully loaded vehicle, and wheels have a significant margin of safety built in. Few people will ever load their cars to maximum, and the margin of safety will range from around 1.5x to over 2.0x.
Still, due to modern conveniences, many modern trucks and SUVs are considerably heavier than their older counterparts.
TPMS: All newer cars have tire pressure monitoring sensors (TPMS). The Ford sensors obviously do not work on a Lexus.
Of course, aftermarket wheels will also need new TPMS sensors. Just don't forget them.
Generally, sensor makers will try to make one model of TPMS that works in most wheels and with most cars. So - generally speaking - they're all physically compatible with all wheels.
In my case, I verified that ITM makes a Uni-Sensor Duo for both the Flex and the RX350. That means the sensor with the Lexus interface is physically identical to the sensor used in the Ford wheels, so they must fit.
Center caps: Purely cosmetic, so if you don't mind running Ford caps on a Lexus, no prob.
If you want replacements, you have to determine the center cap size of the donor wheels. Sometimes the internet knows, sometimes it doesn't. Sometimes you just have to measure them.
If you get all of the above, your donor wheels should be a good match to your recipient car.