Springer vs Girder Forks

[Buzz_Kanter]

Some people do not recognize the differenece between a set of Springer forks and a set of Girder forks.

To in very simple terms:

Springer forks, often used on older Harley motorcycles, have 2 sets of legs on either side. The rear set should not move, and the front set moves up and down with the road surface. The Springer forks pivot on the small rockers on the bottom and use a series of springs at the top for suspension.

Girder forks, often used on Indians and some aftermarket choppers, use one set of fork legs that move up and down with the road surface and use a set of parrallel arms and springs at the top by the steering head for suspension.

Anyone out there with a better description - please chime in.

[pogo seat]

Thanks for the info. I think this would be better if we added some phoos or drawings to show what you are explaining better.

Here is a girder fork, and...

here is a springer.

[rockstar]

Geeeeezzzz...

[Tom347]

This is U.S. terminology-in the U.K. and maybe other places as well any fork that isn't hydraulic or Earles types are girders.,e.g. Indian Chiefs,Scouts, and Harley springers are all girder forks.I suspect but don't know for sure that the different references may have started with the early days of the chopper craze,the same way that people started calling any foot clutch a "suicide clutch"whether it was spring loaded or not.Any(real)Old Timers know?

[Bigincher]

Since "girder" is actually a term for a structural design shape used in building construction, and since the legs of a girder front fork bear a striking similarity to that design, I would then have to surmise that the term derived from a generalization of the actual shape of the part, and really nothing more. Don't try to blame it on the 60's hippy-bikers, or we'll come after ya!

[Sarge]

Originally Posted by Tom347

This is U.S. terminology-in the U.K. and maybe other places as well any fork that isn't hydraulic or Earles types are girders.,e.g. Indian Chiefs,Scouts, and Harley springers are all girder forks.I suspect but don't know for sure that the different references may have started with the early days of the chopper craze,the same way that people started calling any foot clutch a "suicide clutch"whether it was spring loaded or not.Any(real)Old Timers know?

Who yoo callin' a REAL OLD TIMER, Sugarfoot? Heh. The first front ends were just "forks," because they had to support both sides of the front wheel simultaneously, and turn at the neck; like a bicycle. People soon got tired of having their teeth shaken out of their heads, on cobblestones and the like, and literally hundreds of different configurations of a few basic principles have been tried since someone tried to "suspend" the front wheel on some kind of springing, rebounding, steering mechanism.

As two-wheeled auto-motive science began to develop, it was realized that the less mass that was placed in motion (up and down) to cushion the ride, the more quickly it would respond to obstacles encountered, and recover, ready for the next one. The differences are obvious between a fork where the entire assembly of wheel, axle, brake and both fork legs are suspended, and the suspension occurs in pairs of parallel arms on each side of the steering axis at the neck, what we call a "girder," and, say, Indian's 1930s leaf-spring "springer," where the only moving parts are two trailing link first class levers at the height of the axle. The only other unsprung weight is the vertical connecting links up to the front end of the forward-facing leaf spring out over the "mudguard" (love that Brit terminology!) mounted under the steering head.

Harley took a different course, naturally, using leading links (I think they qualify as third class levers) pivoting from the rear (the rigid fork), with the load in front (the axle) and supported midway between by a light-weight moving fork, rebounded by a set of coil springs in front of the steering head. Harleys met an object head-on and transmitted the impact up the moving fork to the coil springs, whereas the rear ends of Indian's trailing links were deflected upwards, pulling down on the leaf spring (first class levers). The advantage was a bit like the difference between writing left-to-right across a page right-handed (letters flow out behind the stylus) and writing left-handed: the stylus is being pushed, pushed, pushed to form the letters.

The difference in ride is so negligible, in practice, that other factors, like size and "style," of the mechanism's attractiveness to the eye were the only considerations. Indian's long leaf spring jutted out over the front fender; Harley's springer was a compact unit all the way up to behind the horn and headlight.

The Brits, mostly, became enamored of what we call the "girder" fork, where the entire, necessarily heavy (-ier than the American configurations) wheel, brake fender/mudguard and box-like front fork assembly all rode up and down, bolted solidly to the front axle, and moved on a pair of parallel arms on each side of the steering head, with some sort of spring behind the headlight, usually, providing the rebounding. Stamped steel was used in some applications to reduce weight, and Vincent's "Girdraulic" used a long, thin variation on the shock absorber, mounted behind the fork's legs to accomplish the rebounding. Harley's 1947 2-stroke 125cc (7.5 ci) "Hummer" used stamped steel fork legs and five "rubber bands" behind the headlight to rebound. In the 1920s, Brough-Superior actually licensed Harley Davidson's springer, the JD-era version, with hidden, internal springs, for use on "Bruf-Sups." They recognized the elegance of a simple, eye-pleasing design.

I know, diagrams of all these would be useful, but they're all in my head, at this point. They've been published before. Nice point you made, Tom, BTW, about the Unknowing calling all foot clutches "suicide," unaware that as originally designed with an over-center coil spring, when they were "thrown out" (disengaged) they stayed there.

[2vls]

Here's a photo of the Indian Chief fork Sarge talks about. It has a leaf spring, a trailing link, and a girder-looking fixed fork leg.

This is one of a bunch of fine bikes on display Sunday in Anacortes, Wash. at the Washington Vintage Motorcyclists (AMCA Chapter) vintage bike show. I'll post more pictures in the next couple of days.

Walt
32V4191

[Chris Haynes]

[QUOTE=Sarge;Nice point you made, Tom, BTW, about the Unknowing calling all foot clutches "suicide," unaware that as originally designed with an over-center coil spring, when they were "thrown out" (disengaged) they stayed there.[/QUOTE]

The ones who really bug me are they guys who talk about Suicide Shifters. They don't have a clue what they are talking about.

[chiefj48]

Originally Posted by 2vls

Here's a photo of the Indian Chief fork Sarge talks about. It has a leaf spring, a trailing link, and a girder-looking fixed fork leg.

This is one of a bunch of fine bikes on display Sunday in Anacortes, Wash. at the Washington Vintage Motorcyclists (AMCA Chapter) vintage bike show. I'll post more pictures in the next couple of days.

Walt
32V4191

hey walt,

i think the front fork you have pictured is really called a leaf spring front end, as only the rockers move with the wheel. i always thought the '46-'48 indian front ends were the girders, as the whole fork leg moves with the wheel.

[Sarge]

Originally Posted by chiefj48

hey walt,

i think the front fork you have pictured is really called a leaf spring front end, as only the rockers move with the wheel. i always thought the '46-'48 indian front ends were the girders, as the whole fork leg moves with the wheel.

Yor both right, Chief! Walt said "girder-looking" (which it is: a rigid, triangulated assembly serves as the main, steering fork) and it is a springer, in this case a leaf spring springer, and it is also called a leaf spring front end after its distinguishing feature. And yes, the '46-'48 Chief forks were classic one-piece "girder" front ends, where everything hanging from the steering neck moved up-and-down.