TECH PAGE

FUN IN OKLAHOMA

MADDOG BICYCLEs

300 S. Ranchwood Blvd.

Yukon, Oklahoma

405-577-6999

BIKE-TECH

This page will be dedicated to helping parents & racers in their quest for the best information on bikes and gear...

HOW DO I KNOW WHAT SIZE BIKE I SHOULD RIDE?
Well, Here is a Little HELP...

BMX RIDER BIKE SIZING

Rider Height	Frame Size	Top Tube Length	Stem Length	Bar Rise	Bar Width	Crank Length	Gearing
4'0" & under	Micro-Mini	15"-15.5"	Mini	2"-2.5"	20"-21.5"	See Chart Below	See Chart Below
4'0"-4'6"	Mini	15.5"-16.5"	Mini Mini XL	2"-3.5"	21"-23"	See Chart Below	See Chart Below
4'4"-4'10"	Junior	16"-17.5"	Mini Mini XL	3"-4.5"	22"-24.5"	See Chart Below	See Chart Below
4'8"-5'4"	Expert	17"-18.5"	Pro	4.5"-6"	24"-26"	See Chart Below	See Chart Below
5'2"-5'8"	Expert XL	18"-19"	Pro	6"-7.5"	26"-27"	See Chart Below	See Chart Below
5'6" - 5'10"	Pro	18.5"-19.5"	Pro Pro XL	7"-8"	27"-28"	See Chart Below	See Chart Below
5'10"-6'1"	Pro XL	19"-21"	Pro Pro XL	7"-8"	17"-28"	See Chart Below	See Chart Below
6' & over	Pro XXL	20.5" & over	Pro XL Pro XXL	7"-8"	28"-?"	See Chart Below	See Chart Below

WHAT SIZE CRANKS DO I NEED?
Well, Look Below...

CRANK SIZING CHART

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

WHAT GEAR SHOULD I RUN?
Well, Let's See...
Most riders regardless of class seem to prefer a rotation of approximately 53"
To figure your rotation here is the formula.
Chainwheel divided by Freewheel times Tire diameter

GEAR CHARTS

20" X 1.75" GEAR CHART

Chainwheel	34	35	36	37	38	39	40	41	42	43	44	45	46	47	48
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	65.5	66.9
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	61.1	62.4
Freewheel 16	41.5	42.7	43.9	45.1	46.3	47.5	48.8	50.0	51.2	52.4	53.7	54.9	56.1	57.3	58.5
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	53.9	55.1
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	51.0	52.0

20" X 1.50" GEAR CHART

Chainwheel	34	35	36	37	38	39	40	41	42	43	44	45	46	47	48
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	64.6	66.0
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	60.2	61.6
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	56.5	57.7
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	53.1	54.3
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	50.3	51.3

20" X 1.3/8" GEAR CHART

Chainwheel	34	35	36	37	38	39	40	41	42	43	44	45	46	47	48
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	70.5	72.0
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	65.8	67.2
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	61.7	63.0
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	58.1	59.3
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	54.9	56.0

20" X 1.1/8" GEAR CHART

Chainwheel	34	35	36	37	38	39	40	41	42	43	44	45	46	47	48
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	67.1	68.6
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	62.7	64.0
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	58.7	60.0
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	55.3	56.5
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	52.2	53.3

24" X 1.75" GEAR CHART

Chainwheel	34	35	36	37	38	39	40	41	42	43	44	45	46	47	48
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	80.6	82.3
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	75.1	76.8
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	70.5	72.0
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	66.2	67.7
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	62.6	64.1

24" X 1.50" GEAR CHART

Chainwheel	34	35	36	37	38	39	40	41	42	43	44	45	46	47	48
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	77.3	78.9
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	72.0	73.6
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	67.6	69.0
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	63.5	64.8
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	60.0	61.4

24" X 1.3/8" GEAR CHART

Chainwheel	34	35	36	37	38	39	40	41	42	43	44	45	46	47	48
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	80.6	82.3
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	75.1	76.8
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	70.5	72.0
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	66.2	67.7
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	62.6	64.1

24" X 1.1/8" GEAR CHART

Chainwheel	34	35	36	37	38	39	40	41	42	43	44	45	46	47	48
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	76.0	77.6
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	70.8	72.4
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	66.5	67.9
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	62.4	63.8
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	59.0	60.4