GLOSSARY OF BMX TERMS
AXLE: The shaft on which the wheel revolves.
BEAD: The outside edge of the tire, which is stiffened by a wire.
BERM: An embankment on a track built up on the outside of a turn to create a banked curve.
BMX: Abbreviation for bicycle motocross. BMX indicates a style of bike and kind of race or competition.
BOTTOM BRACKET: The mechanism at the bottom of the bicycle frame, which holds the spindle and crank.
BRAKE SHOE: A rubber pad that stops the bike by pressing on the tire’s rim, creating friction.
BRAKES: Any bicycle braking system which works by opening and closing two brake shoes on the tire’s rim in a clamping motion, like jaws.
BRAKE LEVER: A lever mounted on the handlebar used for activating the brake by pulling the cable.
CABLES: Steel wires braided into cables and sometimes covered with plastic coating. Cables are used to connect the brake levers to the brakes.
CALIPER BRAKES: A braking system that is centrally mounted to the frame. Two arms with spring mechanisms to provide the movement at the brake
pads to the rim.
CANTILEVER BRAKES: A dual post mounted brake where the brake spring is connected to the post.
CHAINSTAYS: The part of the bicycle frame that runs parallel to the chain. It connects the bottom bracket to the rear dropouts.
CHAINWHEEL: A one-piece front gear. The chain wheel is attached to the bottom bracket and crank.
CRANK: The L-shaped metal arm to which the pedals are attached.
DOWN TUBE: Part of the bicycle frame, which slants downward at an angle. It runs from the head tube to the bottom bracket.
DROPOUTS: Small, slotted openings, which hold the front and rear wheel axles. On many bikes the dropouts do not appear to be separate parts.
They are merely the opening at the ends of two other frame sections: the seat stays and the front fork.
ENDO: When the front wheel of a bike is stopped and rider falls over the front handlebars. (something you’d like to avoid!)
FORK: The double-pronged section of the frame, which holds the front wheel in place.
FREEWHEEL: A one-piece rear gear that allows the rider to back-pedal. Bearings are built in.
GEAR RATIO: A number, which indicates the relationship between the two gears and tells you how much work a particular combination of gears will
do. (Something you probably won’t ever figure out!)
GUSSET: A triangle of reinforcing steel located between the top and down tubes on your bike. A brake that reinforces frame-tubing junctions.
GYRO: A device that enable you to spin the handlebars a full 360 degrees without cable interference.
HEADTUBE: A short vertical tube at the very front or “head” of the bike. The front fork fits inside the head tube.
HOLE SHOT: Taking the lead position out of the starting gate and going into the first turn.
HUB: Cylinder, which holds the axle of each wheel.
LINEAR BRAKE: A particular type of brake that utilizes a side or linear pull system in which requires a v-type or linear lever. This system offers the
most braking force available. Generally used by racers.
MANUAL: The act of riding a wheelie without pedaling typically over the top section of various jumps.
MOTO: A single racing heat.
MOTO BOARD: An area where the moto sheets are posted before and during the race.
MOTOCROSS: Originally a cross-country motorcycle race, the term is now also used to describe BMX races held on dirt tracks.
RHYTHM SECTION: A series of jumps or rollers back to back on a track that pose as an obstacle.
ROLLER: An obstacle on a track that is rolled over as opposed to being jumped.
SADDLE: Another name for a bicycle seat.
SEATSTAYS: Section of the frame, which runs from the seat tube to the rear wheel dropouts.
SEW-UPS: A type of tire, which is actually sewn around the tube. Also called tubular tires. These are mostly used for youth racers.
SEATPOST: The tube, which holds the seat and goes into the frame.
STAGING: The area where the riders gather or are place in “chutes” for loading into the gate.
STEM: The part connected to the forks that hold the handlebars. Sometimes referred to as a gooseneck.
STEP-UP: A jump in which the landing is elevated about the launch.
SPROCKET: Same as a chain wheel or either the front or rear gear assembly.
TABLETOP: A jump on a track that is completely level or flat all the way across it from the lip to the landing.
TOPTUBE: The top horizontal tube on a bicycle frame, between your head tube and seat tube.
U-BRAKE: A U-shaped center pull brake that uses a ratcheting spring tension system. Generally more of a freestyle brake.
Gearing Charts & Rider Sizes
Rider Height Frame Size Top Tube Length Stem Length Bar Rise Bar Width
4'0" & Under Micro-Mini 15"-15.5" Mini 2"-2.5" 20"-21.5"
4'4"-4'10" Mini 15.5"-16.5" Mini-Mini XL 2"-3.5" 21"-23"
4'4"-4'10" Junior 16"-17.5" Mini-Mini XL 3"-4.5" 22"-24.5"
4'8"-5'4" Expert 17"-18.5" Pro 4.5"-6" 24"-26"
5'2"-5'10" Expert XL 18"-19" Pro 6"-7.5" 26"-27"
5'6"-5'10" Pro 18.5"-19.5" Pro-Pro XL 7"-8" 27"-28"
5'10"-6'1" Pro XXL 19"-21" Pro-Pro XL 7"-8" 27"-28"
6' & Over Pro XXL 20.5" & Over Pro XL-Pro XXL 7"-8" 28"+
Lets get cranky....
Riders Inseam 20" 21" 22" 23" 24" 25" 26"
Crank Length 140mm 145mm 150mm 155mm 160mm 162mm 166mm
Riders Inseam 27" 28" 29" 30" 31" 32" 34"
Crank Length 171mm 175mm 177mm 180mm 182mm 185mm 190mm
20" X 1.75" GEAR CHART
Chain wheels 34 35 36 37 38 39 40 41 42 43 44 45 46
Freewheel 14 47.4 48.7 50.2 51.6 53.0 54.4 55.7 57.1 58.5 59.9 61.9 62.7 64.1
Freewheel 15 44.3 45.4 46.0 48.1 49.4 50.7 52.0 53.3 54.6 55.9 57.2 58.5 59.8
Freewheel 16 41.5 42.7 43.6 45.1 46.3 47.5 48.8 50.0 51.2 52.4 53.7 54.9 56.1
Freewheel 17 39.0 40.2 41.3 42.5 43.6 44.7 45.9 47.0 48.2 49.4 50.5 51.7 52.8
Freewheel 18 36.8 37.8 39.0 40.1 41.2 42.3 43.3 44.4 45.5 46.6 47.7 48.8 49.9
20" X 1.50" GEAR CHART
Chain wheels 34 35 36 37 38 39 40 41 42 43 44 45 46
Freewheel 14 46.8 48.1 49.5 50.9 52.3 53.6 55.0 56.4 57.5 59.1 60.5 61.8 63.2
Freewheel 15 43.6 44.9 46.2 47.4 48.8 50.1 51.3 52.8 53.9 55.2 56.5 57.7 59.1
Freewheel 16 40.9 42.1 43.3 44.5 45.7 46.9 48.1 49.3 50.5 51.7 52.9 54.1 55.3
Freewheel 17 38.5 39.6 40.8 41.9 43.1 44.1 45.2 46.4 47.5 48.7 49.8 51.0 52.2
Freewheel 18 36.4 37.4 38.5 39.6 40.6 41.7 42.8 43.9 44.9 46.0 47.0 48.1 49.2
20" x 1 3/8" GEAR CHART
Chain wheels 34 35 36 37 38 39 40 41 42 43 44 45 46
Freewheel 14 51.0 52.5 54.0 55.5 57.0 58.5 60.0 61.5 63.0 64.5 66.0 67.5 69.0
Freewheel 15 47.6 49.0 50.4 51.6 53.2 54.6 56.0 57.4 58.8 60.2 61.6 63.0 64.4
Freewheel 16 44.6 45.9 47.3 48.6 49.9 51.2 52.5 53.9 55.2 56.5 57.8 59.1 60.4
Freewheel 17 42.0 43.2 44.5 45.7 47.0 48.2 49.4 50.7 51.9 53.2 54.4 55.6 56.9
Freewheel 18 39.7 40.7 42.0 43.2 44.4 45.5 46.7 47.9 49.0 50.2 51.4 52.5 53.7
20" X 1 1/8" GEAR CHART
Chain wheels 34 35 36 37 38 39 40 41 42 43 44 45 46
Freewheel 14 48.6 50.0 51.4 52.8 54.3 55.7 57.1 58.6 60.0 61.4 62.8 64.3 65.7
Freewheel 15 45.3 46.7 48.0 49.3 50.7 52.0 53.3 54.7 56.0 57.3 58.7 60.0 61.3
Freewheel 16 42.5 43.8 45.0 46.2 47.5 48.7 50.0 51.2 52.5 53.7 55.0 56.2 57.5
Freewheel 17 40.0 41.2 42.3 43.5 44.7 45.9 47.0 48.2 49.4 50.6 51.8 52.9 54.1
Freewheel 18 37.7 38.8 40.0 41.1 42.2 43.3 44.4 45.6 46.7 47.8 48.9 50.0 51.1
24" X 1.75" GEAR CHART
Chain wheels 34 35 36 37 38 39 40 41 42 43 44 45 46
Freewheel 14 58.3 60.0 61.7 63.3 65.0 66.9 68.6 70.3 72.0 73.7 75.3 77.0 78.9
Freewheel 15 54.4 56.0 57.6 59.3 60.7 62.4 64.1 65.5 67.2 68.9 70.3 72.0 73.7
Freewheel 16 51.0 52.5 54.0 55.5 57.0 58.5 60.0 61.4 63.1 64.5 66.0 67.4 69.1
Freewheel 17 48.0 49.4 50.0 52.2 53.6 55.1 56.5 57.9 59.3 60.7 62.1 63.6 65.0
Freewheel 18 45.3 46.5 48.0 49.4 50.7 52.0 53.3 54.7 56.0 57.3 58.5 60.0 61.4
24" X 1.50" GEAR CHART
Chain wheels 34 35 36 37 38 39 40 41 42 43 44 45 46
Freewheel 14 55.9 57.5 59.1 60.7 62.3 64.2 65.8 67.4 69.0 70.6 72.2 73.8 75.7
Freewheel 15 52.1 53.7 55.2 56.7 58.2 59.8 61.3 62.8 64.4 65.9 67.4 69.0 70.6
Freewheel 16 48.4 50.3 51.8 53.2 54.6 56.0 57.5 58.9 60.3 61.8 63.2 64.6 66.2
Freewheel 17 46.0 47.3 48.7 50.0 51.4 52.8 54.1 55.5 56.8 58.8 59.5 60.8 62.3
Freewheel 18 43.4 44.7 46.0 47.2 48.5 49.8 51.1 52.4 53.7 54.9 56.2 57.5 58.9
24" X 1 3/8" GEAR CHART
Chain wheels 34 35 36 37 38 39 40 41 42 43 44 45 46
Freewheel 14 58.3 60.0 61.7 63.3 65.0 66.9 68.6 70.3 72.0 73.7 75.3 77.0 78.9
Freewheel 15 54.4 56.0 57.6 59.3 60.7 62.4 64.1 65.5 67.2 68.9 71.3 72.0 73.7
Freewheel 16 51.1 52.5 54.0 55.5 57.0 58.5 60.0 61.4 63.1 64.5 66.0 67.4 69.1
Freewheel 17 48.0 49.4 50.8 52.2 53.6 55.1 56.5 57.9 59.3 60.7 62.1 63.3 65.0
Freewheel 18 45.3 46.5 48.0 49.4 50.7 52.0 53.3 54.7 56.0 57.3 58.5 60.0 61.4
24" X 1 1/8" GEAR CHART
Chain wheels 34 35 36 37 38 39 40 41 42 43 44 45 46
Freewheel 14 54.9 56.5 58.1 59.7 61.3 63.1 64.7 66.3 67.9 69.4 71.0 72.6 74.4
Freewheel 15 51.3 52.8 54.3 55.8 57.3 58.8 60.3 61.8 63.3 64.9 66.3 67.9 69.4
Freewheel 16 48.1 49.5 50.9 52.3 53.7 55.1 56.6 57.9 59.5 60.8 62.2 63.9 65.1
Freewheel 17 45.2 46.6 47.9 49.3 50.6 51.9 53.2 54.6 55.9 57.2 58.6 59.9 61.3
Freewheel 18 42.7 43.9 45.2 46.6 47.7 49.1 50.3 51.5 52.8 54.0 55.3 56.6 57.9
Make your own Bike Rack (Click on photos to enlarge)
Fits in the back of your truck to carry three bikes in style.
Time needed = about 1 hour. Total Cost = Under $20.
Materials Needed:
30 feet 1" schedule 40 PVC pipe
18 connecting T’s
6 90-degree connectors (elbows)
PVC pipe cement
For a 4-bike rack, see the parts list and cutting instructions at the end of this article!
Cut PVC pipe to the following lengths:
6 – 18 ½”
6 – 16 ½” *
6 – 8 ½”
6 – 9 ½”
8 – 1 ¾”
*the 16-1/2 lengths fit a Ford F150 truck bed. You may need to vary this length for your particular truck. You can
assemble it without gluing and then make adjustments.
Here's what all the pieces look like cut to length.
Assemble the frame as pictured at right. This is a view looking straight towards the wheel-slots. The horizontal pipe in
the middle (seen behind the main assembly) receives the support struts. See the photos below.
Assemble the entire structure without gluing. This lets you adjust fit and set a correct angle for the elbows and Ts.
Here we're assembling the main support frame. The two close pipes at the left of the photo form a slot, into which a
bike wheel will slide. When complete, this part will be turned over so the Ts face down into the support struts.
Here the support struts are seen coming up into the support bar. Lying against the ground are the wheel-slots that will
receive the bike tire. (In use, the structure will be turned over. The part that's sticking up here will be on the bottom of
the truck bed.)
Glue joints one at a time, then let dry. In this photo, the support strut is ready to receive a T-connector.
Here the rack is complete, and has been turned over into its position of use.
Drill a hole in the underside of the top connectors for bungee hooks (3 total). The bungee will hold the bike into the
frame. Size the hole to fit hook style (plastic hooks work best.) An alternative is to wrap the bungee around the upper
pipe and hook it back on itself.
Notes:
Glue connectors touching each other for standard mountain bike tires. Leave about ¼” space for 3” tires.
Use bungee cords to tie rack down to truck bed.
Hook bungee to seatpost or pedal to hold bike in place.
This design should clear an 8” rear brake rotor.
This design can be altered to make a 4-bike rack! Here's your parts list:
40 feet 1" PVC pipe
26 T-connectors
6 90-degree elbows
PVC cement
The cut pieces will be:
8 - 18.5 inch
9 - 9 3/8 inch (in place of 16.5)
8 - 8.5 inch
9 - 9.5 inch
12 - 1 3/4 inch
Follow the design above, but substitute the 9+3/8 pieces for the 16.5-inch lengths.
Thanks to Damon of Salt Lake City, who sent us the photos and instructions for this bike rack!







Technical BMX Terms, Gear Charts and how to build a bike rack!
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