My tire rim is always dirty?

No.

You must have a leak in the front axle.

Go to a mechanic to get it checked.

Dirty Rims

Most chemicals call for washing off excessive dirt and mud before applying the chemical in a spray. Read the instructions carefully and try an inconspicuous area if possible such as the back of the wheel. These are usually very caustic and allowing the chemical to sit too long can damage the finish. These chemicals should only be used on cool wheels. If the vehicle has just been driven, the brakes will be hot, and liquid chemical will turn to steam. This steam can be harmful, especially if it contains asbestos from the brake pads. Use an old toothbrush or nylon brush for scrubbing dishes to get into all of the corners and ridges. Rinse well and use a clean cotton rag to polish the mag or rim.

Most likely the it is brake dust. You might want to have your brakes checked out by a mechanic since your are only having a problem with one. To confirm this theory after driving check your rims for heat. Chances are is that the dirty rim will be hotter than the others. You should do this so because if you have a problem it will become progressively worst.

You can get brake shields and they do help, but if its only one wheel and its after a few days you should get it looked at. One of the pads could be dragging. Could be from a bad caliper piston. You also didnt say if its the front. Front will get the most dust, but still both sides are pretty much equal in the amount, and it wouldnt be after a few days. Better to get it looked at before something happens that worse than dusty wheels.

What your seeing is brake dust. If you are only seeing it on one wheel on that axle then you have a good indicator of a brake problem such as a sticking or stuck caliper which would cause the brake on that side to be "on" even when you are not applying the brakes. This in turn will cause the brake to overheat, creating all the brake dust you see.

I would recommend taking it in to have the calipers checked.

1.How long can you drive on a flat tire before damaging the rim? Never ever drive on a flat tire (one that is noticably flat) it is just not a safe thing to do. 2.What is the correct tire air pressure? correct air pressure if i remember right depends on the tire/car 3.How often should your car’s oil be changed? What kind of oil should you specify? Do you need a new oil filter also? Dependig on how old your car is the oil will need to be changed ever 3,000-5,000 miles (newer engines can go a bit longer and be fine) or every 3 months which ever comes first. The mechanic will know what kind of oil to use on your car, brand doesn't really matter much but the type depends on your car. when the mechanic checks your oil he will also check the air filter to see if it needs replacing, usually he will ask before hand if this is alright (mine always does) and if he has permission to change it if needed. 4.How much per year will your insurance cost when you get your license? How much will it go up if you get in a $5000 accident that is determined to be your fault? Insurance is very variable. it depends on the insurance company its self, how old you are, what kind of car you drive, how much you drive, and where you live are the major ones. You need to speek to an insurace adjuster to figure these things out and to get an estimated rate. you can also seach for insurance companies online and get a free quote from them. it will give you an idea of what your payments will be but may not be exact. 5.What are the recommended maintenance services for a car and when should you get them, and how much would they cost approximately? Again depends on your car and how old it is. i would say as long as you keep your oil changed and all the fluids in your car where they are supposed to be and you don't have any problems with then it doesn't really matter. But as soon as you notice something wrong get it checked out right away! that is the most important thing. it could be something small but you ignore it and it becomes bigger. 6.What do collision, comprehensive, uninsured motorist, and liability insurance cover? What are the insurance deductibles? (this might be personalized im not sure) Collision insurance is if you are in a collision(accident) uninsured motorist is if the person who hits you doesn't have insurance and it is their fault your insurance company will pay to have your car fixed. Liabity is if you are in an accident and its your fault your insurance company will pay for to fix the other car but not yours. Insurace deductubles are what you have to meet before your insurance company will pay 7. What should you do if there is smoke coming out of your hood? If there is smoke comming out of your hood turn the car off, get out and get away from the car as fast as your feet will carry you and call 911.

its brake dust...it should be on both your front wheels but not uncommon to see it on just one...as long as your car doesnt pull hard to the left or right when u hit the brakes u dont have a problem just keep cleaning them...they make some thin discs that u can put behind your wheel that help reduce that dust that u can buy from autozone pretty cheap

I'll bet it's a German car. German law requires a higher percentage of graphite in the brake pads. The graphite is shaved off into powder when you step on the brakes. That powder makes your rims black.

Get some brake dust shields installed:

http://www.car-stuff.com/brakedustshields.htm

sounds like you have brake dust on that rim. usually it forms on the 2 front rims, there is a cleaner that you can put on the rims that keeps it from sticking, then just hose it off

That is brake dust, and you can buy sheilds for the front wheels that attach behind the rim