Determining Fork Length


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Cycle Exchange
PO Box 275 – Hwy 51 South – Minocqua, WI 54548
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One item of widespread confusion between the custom buyer andbuilder is an uncertainty as to exactly how long his extended fork will be. Itmay be close to what he needs, but a difference in two will be. It may be closeto what he needs, but a difference in two inches or so either way can make amajor change in the looks and performance of an otherwise carefully designedscoot.

Trying to decide what length of fork, size of wheel, and theamount of rake can be a pain in the neck, so we have compiled some figures foryou that should make it a little easier. With the rear wheel and tire you’regoing to use installed on the frame, remove the fork and block the bottom ofyour frame until you have the height you want. Then get out your tape measureand play with some numbers until you come up with the combination you like. Wehave included a chart below to show what lengths our springers are (size =length in inches). To determine what length of fork tube to use for a stocktubular fork, measure the stock fork with weight on it before removing. Forexample, if your stock fork is 20 inches from the bottom cup the center of theaxle, and if after playing around with tire sizes, height, and so forth, youdetermine that you need 29 inches between the cup and the axle, you would ordera 9 inches over stock set of tubes for your bike.

FORK OVER STOCK SPRINGER (inches)

FRAME CUP TO AXLE (inches)

3 23
6 26
9 29
12 32
15 35
18 38

 

TIRE SIZE AXLE HEIGHT (inches) TIRE DIAMETER (inches)
300×16 11 22
250×18 11 5/8 23 1/4
275×18 11 3/4 23 1/2
300×18 12 24
275×19 12 1/4 24 1/2
300×19 12 1/2 25
325×19 13 26
275×21 12 3/4 25 1/2
300×21 13 26
500×16 12 7/8 25 3/5
500×18 13 26
400×18 13 1/4 26 1/2
400×19 13 3/4 27 1/2

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