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In the 1970's and 80's a study of professional cyclists was undertaken by Frenchman Claude Genzling to develop a rational frame sizing technique. Genzling interviewed hundreds of pro road cyclists gaining body measurements and respective cycle frame dimensions. This data was combined with photographic studies of the riders position on the bike. Working in close collaboration with five time Tour de France winner Bernard Hinault, Genzling developed basic relationships between body dimensions and cycle frame dimensions for "pro-style" road cycling.In the mid 1980's, I converted Genzling's graphical frame sizing technique into the simple analytical sequence given below. So, have some fun, get a buddy to help you and take the body measurements, calculate the ratios and plug-n-chug your way through the equations to arrive at seat tube centerline length, seat tube angle and top tube centerline length.With this done, if you wish to order a custom Strawberry frame, please fill out the custom frame order form and I'll get to work. An order acknowledgement will be sent out upon receipt of your order providing your custom frame serial number, description and delivery date. An invoice will be e-mailed to you upon completion of your frameset. Shipment will be effected immediately upon receipt of the balance due.HINAULT/GENZLING BICYCLE FRAME SIZING (trigonometric derivations by Strawberry) TOOLS REQUIRED A) carpenters square OBTAINING BODY MEASUREMENTS A) INSEAM "E": Place square between legs with the long edge against wall, raise as much as possible, then measure from top edge of square to floor (cyclist without shoes).B) THIGH "F": Sitting erect on stool press pelvis against wall and hold lower legs vertically - place square against kneecaps and measure from wall to square.C) LOWER LEG "J": Sitting erect on stool place long edge of square across knees just behind kneecaps - measure from floor to square.D) TRUNK "T": Sitting erect on stool press pelvis against wall - rest square horizontally on bulge of collarbone - measure from stool to square.E) ARM "B": In same position as for trunk measurement, grip dowel vertically - raise arm to horizontal and perpendicular to wall - measure from wall to close edge of dowel.F) FOREARM "A": Hold dowel perpendicularly to forearm - rest elbow on table with forearm perpendicular to table - measure from table to close edge of dowel.BODY MEASUREMENT RATIOS A) TRUNK TO INSEAM: T/E (average ratio = 0.76) If your T/E ratio is greater than the average, try increasing the top tube length L.B) ARM TO INSEAM: B/E (average ratio = 0.87) If your B/E ratio is smaller than average, try decreasing the top tube length L.C) FOREARM TO INSEAM: A/E (average ratio = 0.40) If your A/E is larger than average try increasing saddle/bar length S.D) THIGH TO LOWER LEG: F/J (man avg. ratio = 1.11, woman avg. ratio=1.14) If F/J is larger than average try setting saddle back further. If your F/J is smaller than average try increasing saddle height Hs.
CYCLE FRAME DIMENSION FORMULAS: A) SADDLE HEIGHT: Hs= 0.885E example: E=82cm., R=7cm. (Table 1), N=26cm. (Measure your saddle), Q= arc cos (20/0.885(82))=74 degrees E) TOP TUBE CENTERLINE LENGTH: L=1/tan t[(Hs-H)sinQ-D]+S-(R+G-M/2)+I example: E=82cm., Hs=0.885E, Hs=72.57cm., H=53.3cm., Q=74 , D=7cm. (from Table No. 1), t=73 (pick an angle), S=53 (from Table No. 1), R=7cm. (from Table No. 1), G=10cm. (pick a stem length), M=2.22cm. (diameter of English handlebar), I=14.7 (from formula "C") L=1/tan(73)[(72.57-53.3)sin(74)-7]+53-(7+10-2.22/2)+14.7=55.33cm.TABLE NO. 1
NOMENCLATURE H SEAT TUBE CENTERLINE LENGTH L TOP TUBE CENTERLINE LENGTH h CRANK HANGER CENTERLINE DISTANCE ABOVE GROUND t HEAD TUBE ANGLE I SEAT TUBE SETBACK Av FRONT WHEELBASE Ar REAR WHEELBASE M DIAMETER OF HANDLEBAR f FORK OFFSET G STEM LENGTH (CENTERLINE OF HANDLEBAR TO CENTERLINE OF BOLT) c TRAIL (CASTOR) Q SEAT TUBE ANGLE Hs SADDLE HEIGHT (CENTERLINE FROM CRANK HANGER TO SADDLE TOP) R SADDLE SETBACK FROM PLUMB LINE THROUGH CRANK HANGER N SADDLE LENGTH S SADDLE NOSE TO HANDLEBAR NEAR EDGE D HEIGHT DIFFERENCE BETWEEN SADDLE & BAR TOPS E INSEAM F THIGH (FEMUR) J LOWER LEG (TIBIA) T TRUNK B ARM A FOREARM Don't need a custom frame? Try our standard frames page. Photos: A. Newlands |