My son wants to know if there are 16 wheelers

Yes, but it's not a common arrangement.

I have seen a couple of 8 wheel semi tractors with a single drive axle and a lift axle with single wheels pulling a normal tandem axle trailer. In Europe is is more common to have a tractor set up that way but they usually pull 3 axle trailers making them 20 wheelers.

Here's some European examples of an 8 wheel tractor.
http://www.fleetex.co.uk/tractor_6x2.asp

Another 16 wheel setup is a Double trailer combination with wide base singles on the convertor dolly and duals everywhere else (Fedex has a fair number of doubles set up this way)

 

I drive a 16 wheel straight truck.

 

I have a 14 wheeler tractor trailer

 

It can vary with how many axles you have and/or if you are running any super singles.

 

and of course if you really want to confuse him, tell him about the steering wheel, fifth wheel and fly wheel.

 

What about taking the inside tire off of the slave axle(you know the axle in front of the drives), are company wants to start doing that so they can save weight and get better fuel mph's

 

Here's my 16 wheeler.

 

How about a 16 wheel trailer?

 

Sure, everytime I pull doubles with a single axle tractor and have a dolly with super singles, it is a 15 wheeler.

And everytime I pull a set of triples with a twin screw tractor and a regular dolly, that is a 30 wheeler.