There is a carpet at Home Depot that will work. It looks like a bunch of fibers pressed together. It is sold by the linear foot. In case you don't know that term, it means 1 foot by what ever the width of the of the product you are buying. Like if you buy a piece that is 3x8, you only pay for 3 feet. This carpet will fuzz preaty bad so make sure to keep your car clean!
You didn't mention what scale r/c you are racing, so let me offer an alternative to carpet.
For mini-z (1/24) and micro (1/18th) scale cars you can use foam pieces that fit together like puzzle pieces. A some point there was at least 1 company that made track pieces for small scale r/c cars. They sell this type of material at home improvement stores. I've also seen similar foam pieces sold in toys stores or possibly educational stores as play mats for children. You might do an internet search for mini-z tracks and find some ideas. Here is a link for track that will work for xmod and mini-z (http://www.atomicmods.com/ProductInfo.aspx?productid=10775)
If you are going to be racing outside on concrete/asphalt there really isn't a need for carpet. Just clean the area of loose rocks, dust and debris. Get a portable chemical sprayer from your hardware store apply a mixture of cheap soda and water to the racing surface. I am not sure of the proper ratio of soda/water, but you should be able to find info on this sight or the internet. Even with foam tires, you will be surprised at the amount of grip that can be achieved with a bit of careful prep.
If you are looking for carpet, ozite is the best. However, there probably is some cheap carpet with short fibers that may work okay.
1/10th indoors, the cement has been sealed so traction is non existent..... even with purple foams and a 4300 motor it looks more like a drift competition
i went to the home depot today..... they sell ''home office carpet'' which looks like it would work great.... there wasnt anyone around to check price on but i am going to hit up my local carpet shop this week one day and see if they have any drops
the CRC seems a bit extreme for my application.....unless i can find a carpet sponsor lol..!
One thing that hasn't been mentioned is getting old carpet from an existing track when they replace their carpet. Tracks periodically replace their carpet as it wears out, usually due to rips or tears. However, the carpet should still have life left in it if you can find some. Try contacting any local carpet tracks in your region and see if they will give you their old carpet.
If you are going to run on sealed concrete you will have to put down some traction compound/coke mixture if you hope to have good traction with foams. You would also need to run a very soft setup and tires. Foam wouldn't be the way I'd go in that situation. Purple foams aren't the softest foams, so I'd try pink to see if that helped. You might also want to try some soft rubber slick tires to see if that works. I realize that you probably don't have hundreds of dollars to invest in tires, but you must have some money if you are willing to get carpet.
I say finding a way to put some traction on the concrete combined with rubber tires or foarm might be a better investment. Unless the area you are racing at doesn't have any other use you will want to factor in setup/tear-down of the carpet track. Not sure what you are going to do for barriers, but you may want to at least have outside barriers. You will also have to store it when not in use. A local "track" I race at sets up the carpet in a gym of a local lodge and it works great. Luckily they have on site storage for when the carpet isn't in use.
If you ask the guy at Home Depot for indoor/outdoor carpet. It is the cheapest carpet sold by the linear foot. There is some carpet that looks the same but is more expensive and would work also. It comes in gray, blue and maybe green or tan. I don't know about using soda inside. Outside when it is sunny it is OK, but if it is cold or damp it won't work. Also, you need to be able to clean it off once in a while or it will get glazed over. Is this just for you and some bud's?
I bought some old ozite from a local track that had replaced theres... the 'indoor/outdoor' carpet will work, but is probaby not good for anthing really serious and/or 10th scale... for 18th... some indoor/outdoor will likely be fine.
I would NOT put sugar water on my basement floor... can you say "ANTS"?