Frame Hints

There are 2 categories of frames used in BMX, they are 20" & 24". Class frames accept 20" wheels, while Cruisers need 24" wheels.  

To find out what size frame you have most companies measure from the center of the head tube to the center of the seat tube. 
 

What type of geometry should I look for?
  

The higher the head tube angle the faster response in steering and the more forgiving it is if you get squirrelly. Shorter rear ends tend to stabilize easier after jumping or coasting and are much easier to manual.

Frame size will vary slightly with riders overall body size & build.

Crank Hints

The most common mistake made when buying cranks is to buy too big of cranks for your size!!!!

Too long of crank arms will make a rider swing their bike side to side, wag their tail, and or ride choppy at their hip line. If you're swinging your bike to the side & someone bumps you, where do you think you're going to go? DOWN! You don't win that way & you can get hurt.

Too short of crank arms and you don't get enough leg extension, therefore not enough power.

CRANK SIZING CHART

This chart is used by measuring where the leg bends in front to ½ way down on the foot. 3 piece cranks have the advantage of being able to find a larger variety of gear sizes to use, as well as being stronger, and easier to change gears. Be sure and find out if the cranks you purchase have sealed bearings or not. Sealed bearings run smoother and have LOTS less maintenance. European bottom bracket frame use 3 piece cranks, where the arms are often sold separately from the bottom bracket. The bottom bracket threads into the frame.

Use a bottom bracket press to install the cups on 3 piece cranks in American frames or you risk stretching the frame and damaging the cups and bearings!!!!!
 

3 piece cranks require 9/16" pedals, while one piece cranks require 1/2" pedals.

Brake Hints

V & A BRAKES are the most commonly used brakes for BMX racing. Frames must have canti mount posts to be able to use this type of brake. You will find 2 small posts located on the top tubes of the rear triangle of your frame if this type of brake will work for your frame. Mini V brakes are now available for the little guy's bikes.

Your brake cable will slide so much smoother by removing the inner wire & spraying it with a Teflon coating before hooking it up!

U BRAKES are most commonly used for street & trick frames. They have canti mount post requirements as well, but are located on the lower tubes of your rear triangle, so that your foot doesn't catch on the brake as you pull off great moves. They are also used on the front wheel for flat land & street tricks. They are often referred to as 990 brakes.

CENTER MOUNT BRAKES are most commonly used on older frames. Frames have a piece welded across the top tubes of the rear triangle behind the seat post tube that the brake hooks through.

When you fine tune your brakes check these things: the tire should be centered between the pads, the pads should be parallel to each other on each side of the rim, hitting the rim not the tire, & each pad should be the same distance from each arm if your spacers are right.

Fork Hints

Almost all of today newer frames accept threadless forks, stems, and headsets. If you don't know what you have you can simply look at it to find out if it has threads on the steer tube of the fork. One of the easiest ways to lighten your bike is with a lighter fork than comes stock. Use a spacer when you install your fork so that it is not cut too short for the next frame you buy. Be sure and check weight limits and warranty when you purchase a new fork. Aluminum, carbon fiber and magnesium forks are the lightest, but are not recommended for trails, street, and ramp riding. Use a good cromoly fork for heavy duty riding, as a fork is one of the easiest parts to break in those conditions. Use washers to fill the space between dropouts & hubs. Don't squeeze in your fork or frame dropouts - it creates stress & can cause cracks. Star fangled nuts should always be installed with the proper tool or your front end of your bike will continually loosen up. Star fangled nuts are a thin metal piece that fits inside your fork. Head locks & stem locks replace star fangled nuts, going clear through the fork headset, & stem and keep the front end of your bike running right.

Grips

Grips come in 1 or 2 ply rubber. Two ply grips are stronger & will take more abuse. You can also choose to use lock on grips which use locking collars to hold the grips in place. To take off grips without ruining them - spray a little WD40  under the grip by carefully lifting it up with a screwdriver, twist the grip, and repeat until you can slide the grip off. Most grips come in at least two lengths, don't use long grip if you have small hands!

 Wheel Hints

RIMS, SPOKES, NIPPLES, & HUBS, TOO!

WHEELS----- come in 20" & 24" sizes for BMX.  24" wheels are for cruisers.  20" wheels are for class. 

DO NOT USE ANY LARGER WHEEL & TIRE THAN NECESSARY TO SUPPORT YOUR WEIGHT.  As a racer pedals around a BMX track he may hit loose spots, mud,  & soft spots as he races in the real world.   The wider the tire, the wider trench a racers digs as he moves.  That will drain your energy at the finish line.  Wheels vary in width as well as diameter.  Sew ups, 19", 20x1 1/8, 20x1 3/8, 20x1.50, & 20x1.75 are available for class.   24" are available in the same widths as 20" except for sewups.  1 1/8" & 1 3/8" rims have a larger diameter than the others do.  The tires that fit 20x1-1/8 & 20 x 1-3/8 rims are interchangeable, but will not fit the other sizes because of the diameter difference.  The larger the diameter of the wheel the less energy it takes to move the wheel 100 feet. Sewup tires are narrow, but are a smaller diameter.  They are used by dinky dudes & dudettes who need the short diameter to reach the ground without ‘racking' themselves,  but also want to stay with a narrow width of tire.  The tires are tubeless and are glued to the rim nowadays; they used to be sewed on the rims, so that's how they got their name.   There are now 19" rims available instead of sew ups, the only tires for these are slicks.

 RIMS----- single, double, or triple wall

Single wall rims have 1 layer of metal that the nipples go thru. They are usually the least expensive, because they are not designed to take much abuse. Double wall rims have 2 layers of metal.  They second layer of metal acts as a shock absorber for landings. They are recommended for racing. Riple wall rims are the heavy duty rims that are designed to take more abuse than any others are & have extra reinforcement. They are used mostly for street, trails, & ramp riding. Rims come in a variety of spoke holes for BMX the most common are 36 holes.  42 hole are used mostly for street & trails, 28 & 32 hole rims are used for littler racers who do not weigh as much as the big guys.  

SPOKES------ straight gauge, titanium, or double butted Straight gauge spokes are the same thickness throughout the spoke, and are considered stronger than most other types.  They are the most commonly used. Double butted spokes are thinner in the center of the spoke, and thicker at each end for strength.  They are lighter than straight gauge spokes, but not as strong. Titanium spokes are the light weight & strong spokes, but also the most costly.
  

NIPPLES------ alloy or brass Alloy nipples are light weight nipples and are available in a variety of colors.

Brass nipples are stronger and slightly heavier than alloy nipples.  They are available in silver only.
  

HUBS--- sealed or loose ball, high or low flange, cassette or threaded, & don't forget flip flop vs. single sided

Sealed bearing hubs have a HUGH advantage of not needing to be taken apart and cleaned and greased on a regular basis like loose ball hubs.  They turn smoother, and are way, WAY, way more durable than loose ball hubs.  Sealed bearing hubs are definitely a much better value, and a good investment. The flange of the hub is the part of the hub has the holes for the spokes to go through.  High flange hubs are heavier than low flange hubs, but are argued to be used to build stronger wheels.  (That's never really been proven.) 

Cassette hubs have the internal mechanisms of freewheels built into them and are usually considered easier to switch from one size than another.  There are a few cassette hubs with sealed bearings, so there is more maintenance for cassette hubs in general than threaded style.

Threaded hubs come in 2 styles, flip flop & single sided.  Flip flop hubs allow you to use one size freewheel on one side of the hub and another size freewheel on the opposite side.  This lets you switch sizes of freewheels without taking one off & putting on another between motos. All you have to do is flip your wheel over. Single sided hubs accept 16, 17, &18 tooth freewheels only.  Flip flop hubs accept any size freewheel.   Don't limit your options when purchasing hubs! 

 TIRE HINTS

The tread of the tire you use is determined by the conditions of the track. The smoother, shorter treaded tires work best on hard, dry tracks while tracks with more loose, soft, or wet spots require a deeper, heavier treaded tire. 20x1-1/8" and 20x1-3/8" tires will fit on rims of either size, 20x1.50, 20x1.75, and up will fit on rims of either size. If you use 2 different sizes of tires (example: 20x1.75 & 20x 2.125) use the wider tire in the front for more control & less resistance. It is NOT necessary for all riders to use a wider tire on the front!!!!!! The wider the tire the heavier it is, and the wider trench you dig as you pedal. Don't use any wider tire than you have to support your size. You will be digging a wider trench with a wider tire and use more energy if you do. Certain tire tread is considered directional. Most of these tires are marked to show you which way they should rotate through the dirt. A good rule of thumb is the front tire should rotate where it plows a trench (<), while the rear tire shovels it backwards. Check your air pressure regularly!!! It saves wear & tear on tires, tubes & rims. It also will change your roll out and gear ratio. Be sure your brakes are not rubbing on your tire!!!!!

 Gears, Chain rings & Sprocket Hints

CHAIN RINGS are lighter than full sprockets, but are not nearly as sturdy.  They require a spider that is either built into the crank arm, or an additional part.

SPROCKETS are strong. They are a combination of a chain ring and a spider together. CNC machined chain rings & sprockets are round and true, helping to eliminate loose & tight spots in chains, while other are stamped out of a sheet of aluminum creating a tiny bit of ovalization.

YOUR ROLLOUT HELPS YOU TO UNDERSTAND HOW MUCH YOU ARE SPINNING.  THE LOWER THE NUMBER THE MORE YOU SPIN TO WIN.  THE HIGHER THE NUMBER THE MORE YOU ARE PUSHING THE BIKE.

WHY DO I NEED TO SPIN TO WIN & WHAT IS IT??  Spinning sets the acceleration of your bike after you have been stopped, like when you're in a gate, in the air, or coasting thru a berm or obstacle.  It improves your second pedal & gives you faster acceleration at critical times.  

Handlebars

How Wide? Hands should grip bars at a natural drop from the shoulders. If your bars are too wide or too narrow you loose control and crash...OUCH!!  Use a little WD40 under your grip to take them off, mark them with a magic marker, then use a pipe cutter or hack saw to shorten them. Don't forget to file the rough ends or you will put holes in your grips. How Tall? Stand flatfooted on the ground beside your bar, with your hand on your grip. Younger racers bars should be about hip bone high. Older racers bars will be at the bikini line.  Try to pop a wheelie; the odds are that if the bike goes clear over & you are walking - not riding, your bars are too tall. We DO want you to be able to get the front wheel off the ground if you are experienced, just not where it throws you clear off backwards.  What Angle? From a side view the angle of your bars & the angle of your fork should be the same if your frame fits you properly. If your frame is too short you can use a longer stem, & push your handle bars a little forward. If your frame is too long, you can use a short stem & bring your bars closer to you. Try not to angle your bars too much either way, or you won't have enough control.  Handlebars with a taller rise have crossbars to help strengthen them, some are welded and some are clamped on.