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Monday, July 2, 2012

Motorcycle suspension: Girder or springer? Definitions

I have an admission to make. I don't know the difference between a motorcycle "girder" front suspension and a "springer." In writing this blog about Royal Enfield motorcycles I've tossed in the word "Girder" when I meant any kind of motorcycle front suspension more vintage in appearance than the telescopic fork legs on my 1999 Bullet.

But now I have been gently called out on this error by none other than Maj. Bunty Golightly. Commenting on my recent description of a customized Royal Enfield, he wrote:

"Blasco you chump, those are springer forks not girders — strewth even my idiot butler Ballsack knows the difference; you're supposed to be a knowledgeable journo — shape up old fellow!"

The good Major probably would have me busted back to an assistant apprenticeship at the Redditch works. But I am too lazy for that. Let us instead turn to Wikipedia's entry on the Motorcycle Fork.

(First it's necessary to learn that "girder" and "springer" forks typically attach to the top front of the frame by a pair of "triple trees," one above the other. These are also called "triple clamps" and I suppose each "triple" has one connection to the frame and one connection to a fork leg on each side of the wheel: 1+1+1=3.)

Wikipedia illustration of a girder front suspension.
"A girder fork is distinguishable from a springer fork by the wheel being fixed firmly to the (usually a long diamond shape) upright. The pivot points are short links mounted to the top and bottom triple clamps. The spring is (usually) mounted to the girder and compressed against the upper triple clamp."

Meanwhile:

Wikipedia illustration of a springer front suspension.
"A springer fork is distinguishable from a girder fork by its two parallel sets of legs. The rear is firmly fixed to the bottom triple clamp (usually brazed or welded). A short leading link holds the wheel and the forward leg which actuates the springs (usually mounted on the triple clamp)."

Got that? Easy way (for me) to see the difference is that the springer has a short "leading link" visible at the connection to the wheel, and this no doubt gives it that handling advantage over the girder design. A girder design does all its cushioning at the top; the springer splits the cushioning movement between top and at the wheel.

I apologize to readers for tossing about terms I didn't understand. As a schoolboy, I enhanced many a final exam essay on the Middle Ages by throwing in the words "Flying Buttress." Just attach a Flying Buttress, my thinking went, and a church becomes a cathedral and struggling mankind is safely conducted to the next phrase I remembered from the textbook: the Cotton Gin.

I admit I have never understood what a Flying Buttress accomplishes. I suspect it is a kind of permanent kickstand to keep a church from falling over.

Never mind what I thought a Cotton Gin was.

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