BMX - Just attended my first bmx race

I have a few questions.

I was just spectating so don't get the idea that I was racing.

First, I noticed the tires they used were not nobby tires but more street looking tires. The dirt is red, like Mississippi, sure aint New Orleans mud. Do they use nobby tires at all anymore?

Second, most of the bikes were Redline, Avent, GT, and Haro. Several of the smaller 16" bikes were using disproportionate tires. Looked like tires bigger than what would come on the biles. Some of the 20 inch bikes had larger size tires, possibly 24". Does that seem right or is there some size between 16 and 20 and between 20 and 24??

Third, and finally, the back rims,, they don't have coaster brakes, it seems. What is thet called?

Sorry if not clear, I am primarily a signer, being deaf, not good with English.

Thanks

1. A lot of people use Intense Micro-Knobbies, and they do look a lot like street tires. I run regular knobbies though.

2. Those are probably the most popular kinds of race bikes. There is a 24" class called the cruisers.

3. Just about every bike that has been made in the past several years comes with caliper or hand brakes. They have replaced the use of coaster brakes.

Hope that helped.

ok yes thanks that helped.. but about the disproportionate sized tires.. the 16 inch with the bigger rims than what normally comes on them.. is that something new or do people themselves add this?

Most bikes come with rims that are 1.75" wide. You can fit a tire up to about 2.2" on that rim. A lot of people run fatter tires on the front such as a 2.125" for more turning traction and a skinnier tire like a 1.95" on the back for less rolling resistance.

You seem to be confused about the wheel/tire sizes and this is understandable as the same number is used to refer to 2 different sized wheels. All the bikes are referred to as 20 inch or 24 inch, the size you are referring to as 16 inch is likely 20. 16 inch wheels are the ones on little kids bikes.

There are basically two types of frames class and cruiser, these come in sizes for kids and one for teens/adults. The kids bikes come in a variety of sizes Mini/Junior/Expert, the size refers to the top tube length.
The normal wheel on a kids class bike is referred to as a 20 inch but it actually has an inflated diameter of around 21 inches (keep in mind that the tire choice impacts how tall the wheel/tire actually ends up being), this looks like a road wheel as it is usually only 1 1/8 inches wide. There is a non-standard 18 inch wheel used on Micro-Mini race bikes that really little guys would race, but these are not too common.
The kids cruiser bikes also have the very narrow rim and the wheel size is referred to as a 24 but they are closer to 23 inches. The kids race bike wheels are very light and usually have a weight limit in the 125 lb. range so when you start to approach that weight you move on to a different stronger wheel.

The adult/teen bikes also come in a variety of top tub lengths Pro/XL/XXL etc. and they use a smaller wider wheel than the kids bikes. It is referred to as a 20 inch but the inflated diameter is around 19 1/4. The cruisers use a bigger wheel that actually is close to a 24 inch inflated diameter.

Industry standard metric rim measurement makes way more sense in this case but is not commonly used.
You can find a chart on this site: http://www.bikeman.com/content/view/1636/115/

wow that was informative, andy. thanks! I did notice the micro and so forth when i was playing around on the haro and redline site. thanks yall.