I have a 2006 CTS Cadillac, which is rear-wheel drive. I have custom 20 inch rims on them, but recently broke 1 of the four hitting a pot-whole.
Nobody has been able to find the brand of rim that I have “Forge Tec”, I want to just replace that rim. I have been on the spare donut for a month now.
Discount tire tells me I have to replace all four, because my suspension can suffer, if the exact rims are not on all the way around. Is this true?
Can I just buy 1 rim that is not made by the same manufactor as the other three, but the same size?
Or do I have to buy a whole set?
pot hole, unless you hit an actual sauce pot 
at least 2 of the same rim, each end, but ideally all 4. Here’s your chance to go back to 19s or 18s so you have enough rubber that a hole will not bust one.
Thanks for your response. What would happen if I replaced just one? Just trying to understand why if the 1 replacement is the same wheel size as the others, why would I need to replace all four?
I search for “Forge Tec wheels” and found the company has not renewed the web site. Perhaps they are a causualty of the economy. You may have some luck and find the same wheel on ebay. It seems forge tec wheels were popular items for Cadillac and Harley Davidson bikes, but I couldn’t pull up a catolog of products they used to sell.
If you don’t mind a slightly different look, you CAN put on a single of a different brand…BUT,
With after market wheels you must measure more that the rim diameter.
Bead width must match, and also the hub setback.
Only matching all three perameters will a differnt style rim “match”.
In a pinch, put the two absolutely matching rims in front and the two slightly different on the back.
When you hit the pot you say it was whole. Is it now in pieces or did you just squash it ?
Who put the wheels on? The dealer?
If the dealer installed the wheels the vehicle sale file should contain the information on where the wheels were purchased.
"I have been on the spare donut for a month now. " Not a good idea. On many cars you can damage sine drive line parts, using the donut that long and that can be expensive. In addition that tyre may no longer be safe. As I recall the only OEM donut I have had had an 80 mile life.
There is also a safety issue, especially if you are in a snow or ice area. Handling can be compromised.
I really recommend getting rid of those 20" wheels. Looks are a personal thing, so if you like the looks fine, but while they provide nice road feel, they don't offer good protection from damage from pot holes. Your story is rather common with those fancy wheels. BTW while the professional race drives buy wheels that are lighter and stronger than the old steel wheel, they may pay more per wheel than you paid for your car. The consumer market alloy wheels are generally weaker than steel wheels.Get the doughnut off of there. They’re only designed to get you to safety, not to drive around on.
If you replace that rim with one of the same rim width, offset, and tire size, (of course the bolt hole and center hole have to be correct) the car will never know you have an odd rim. Only the neighbors will.
What you must match is how tall (diameter) the tire is. On AWD (All Wheel Drive) vehicles, all the tires must be nearly exactly the same height (diameter). You could put on a tall skinny tire, on a smaller rim, as a temporary spare, as long as it was as tall as the other tires.
There are places which handle used wheels (1, or 2, or 3, or 4). They have such names as: Hub-Cap City, Hub-Cap Annies, Hub-Cap something, or Wheel City, etc. You might find a wheel there.
I have mc2 wheels also on my cts.You can find some styles on ebay.I bent one of mine but I cant find my style for sale.If you buy new rims do you want to get rid of the mc2 s?
Go to EBay. I just did. There were 14 different Forge Tec 20 inch rims for sale.