California Commercial Drivers Handbook:

Check out section #1 "Who needs a CDL?"
www.dmv.ca.gov/pubs/comlhdbk/comlhdbk.pdf LARGE 1485 K

Its says that Class C drivers only need a CDL if they are driving a vehicle that requires an endorsement. Specifically there are two that would be most common... hazmat carriers and hazmat waste haulers...

The air brake thing for CDL drivers is not an endorsement... but there is such a thing as "hydraulic brakes only" restriction. I took my CDL test in a vehicle that had air brakes.. no restiction. There is a whole list of restictions (ie-manual transmission only) but very few actual endorsements.... As far as I could tell by looking at the CVC and DMV literature today... restriction only applies to Class A or Class B vehicles and not to the very few Commercial Class C endorsed vehicles.

That's just my opinion on my reading. Probably your best bet would be to make contact directly with the DMV in Sacramento. Avoid calling the local DMV offices as you will probably get twelve different answers from twelve different people.

Hope that made sense. Here's the literature... Ab, I hope its not to long or maybe you could just send the rest to Sting.....

SoCalCapt

For the rest of it, click HERE... Ab.

HERE ARE THE ENDORSEMENTS:
CHAPTER 7. COMMERCIAL MOTOR VEHICLE SAFETY PROGRAM 15278. 

(a) A driver is required to obtain an endorsement issued by the department to operate any commercial motor vehicle that is any of the following:
   (1) A double trailer.
   (2) A passenger transportation vehicle, which includes, but is not limited to, a bus, farm labor vehicle, or general public paratransit vehicle when designed, used, or maintained to carry more than 10 persons including the driver.
   (3) A tank vehicle.
   (4) A vehicle carrying hazardous materials that is required to display placards or markings pursuant to Section 27903 or that is hauling hazardous waste, as defined in Sections 25115 and 25117 of the Health and Safety Code, unless the driver is exempt from the endorsement requirement as provided in subdivision 

(b). This paragraph does not apply to either of the following:
       (A) Any person operating an implement of husbandry who is not required to obtain a driver's license under this code.
       (B) Any person operating a vehicle transporting asphalt or coal tar pitch at a temperature that requires the display of a marking on the vehicle pursuant to Section 27903 and that is described and classified by the United States Department of Transportation as "elevated temperature liquid n.o.s. Division 9."

(c) This section does not apply to any person exempted pursuant to Section 25163 of the Health and Safety Code, to any person operating a vehicle in an emergency situation at the direction of a peace officer pursuant to Section 2800, or to a driver issued a restricted firefighter's license and driving a vehicle operated for the purpose of hauling compressed air tanks for breathing apparatus that do not exceed 2,500 pounds.