How refreshing the wonderful world of motorcycles can be. Even to a jaded old hack like me who's been everywhere and done everything and got a wardrobe stuffed with tee-shirts to prove it, I never get tired of marvelling at the sheer creative energy new generations of bikers bring to customising their bikes. Only in the custom bike world will you find the very latest technology getting combined with examples of classic design principles that keep pushing that creative envelope a little bit further. And what better example of a design classic is the Harley-Davidson springer fork.

The springer fork owes it's origins to the earliest days of motorcycle design and you'll find examples on Harleys dating back to almost the beginning of the last century. At the time, designers in Europe and the USA were faced with the problem of developing a suspension system capable of coping with the rough, and sometimes frankly non-existent roads of the day. It had to be simple and rugged, and many designs were introduced by the various factories before they all eventually became replaced with the growing technology of hydraulic telescopic forks. Whilst our own manufacturers favoured girder forks for a long time, our cousins across the pond invested much time and energy in more complex designs featuring numerous methods of springing. Indian, for instance, developed a front suspension system around half a leaf spring sticking forwards above the front mudguard. It worked well, and didn't look too bad, but the ultimate prize for combining practicality with design elegance had to go to Harley-Davidson. The classic Harley springer fork appeared as standard issue on many thousands of Flatheads and Knuckles and, fitted to the 45 cubic inch WLA, played it's part in liberating Europe from the Nazi hordes in World War 2.

Andy Mitchells seventies style 650 Triumph chop. Andy interrupted the planning stage of the bikes winter rebuild to let us get these shots of the classic post Easy Rider look. Custom springers, hand made by someone unknown, kick the front end out by roughly 10"

Up close you can see how the rockers carry the wheel spindle up front, and pivot on the rear legs at the back. The centre pivot on the rockers pushes the (twisted) front legs upward to transfer wheel movement to the springs. Note the hand carved caliper mount with its bearing on the wheel spindle, and the brake torque arm which pivots at both ends. Andy has mounted the front guard to the front legs, but has still had to allow a good distance above the tyre to allow for suspension movement

Up top, the front legs compress the main springs against their mountings. The upper springs control rebound. Winding down the top pike nuts will adjust rebound settings

When some of those ex WW2 servicemen returned home to the States and began to form bike clubs, they adopted the classic Harley with its springers and fatbobs as their transport of choice. The bikes were cheap and readily available, and when club members began building the first chops by lopping off Harleys standard hulking great mudguards and dual seats the custom Harley fatbob as we know and love it was born. Check out "The Wild One"; Lee Marvin's Flathead "bob job" easily out classes Marlon Brando's stock Triumph in the cool stakes, even if it was probably much slower and more of a handful to ride.

As bike customising evolved the springer fork was never forgotten by the customising fraternity even long after Harley had adopted Hydraulic forks, and by the late sixties aftermarket springers were being made in variety of lengths and styles to fit all kinds of bikes. The design still holds a place in many bikers hearts, a fact recently ackowleged by Harley-Davidson who completed the circle of history with the FXSTS; a modern "Evo" powered vee twin with a springer front end.

The springer fork lends itself particularly well to customising and can be built in a variety of styles. Custom builders of the sixties and seventies took the basic design and developed extravagant gothic touches like twisted front legs and enormous sculpted lower rockers. Unfortunatley many of them overlooked the structural loads bourne by the rear legs, and lots of custom springers have shown signs of bending below the bottom yoke. If checking out an old pair look for signs of cracking chrome here and be prepared to undertake some structural remedial work. Stock Harley springers have substantial oval section rear legs and are much sturdier. Despite their ubiquity on long front-ended chops, springer forks work best at stock lengths and rake angles. Kicking the front end out too far means the whole front end assembly will flex up and down over bumps instead of compressing the springs. Another reason for choosing a design with beefy rear legs. I well remember holding a steady 80mph alongside my mate Boz on the motorway, and watching in alarm whilst his 12" over springers flexed up and down like they were made of elastic. Meanwhile he was busy laughing at my springers, which were apparently doing the same thing. The next set of springers we built had much stronger 1 1/2" 3mm tubing rear legs.

And here's the problem area on this type of springer fork. Constant load below the bottom yoke had produced a tell-tale flaking of chrome as the rear legs began to bend. Aware of the dangers of a potential catastrophic fracture, Andy had substantial gussets welded in to beef up the problem area

Component parts of a set of Harley style springers we snapped under construction at B & I Engineering in Huddersfield. Rear leg assembly on the left, front legs on the right. Tony at B & I has many years of building and riding bikes with springer front ends, and has evolved through several designs to arrive at something remarkably close to Harley's original. Major components are cast specially for B & I and give the forks an authentic fifties look

B & I's caliper mounting loosley assembled with an FJ1200 caliper. The wheel bearing will be fitted before final assembly. The rear torque arm mount has still to be welded in, but Tony is holding an example of the type of rose joint linkage he always uses. Not the cheapest solution, but by far the best

Another frequently overlooked area on custom springers is the front brake mounting. If you're using a hydraulic disc brake (you are using a hydraulic disc brake aren't you?), the caliper should mount to a plate which can swivel about the wheel spindle. The best way is to incorporate a wheel bearing in the caliper mount. The caliper mount then needs a torque arm mounted to the rear (not the front) fork leg. This torque arm should be parallel to the rocker centres (and parallel to the ground) and needs to be able to swivel at both ends. The best way is to mount it on rose joints (aka spherical rod-ends) so the torque arm can float. Ignore these design principles and the front brake will lock up the front suspension when you slam the anchors on. Don't expect MOT testers to understand this engineering; I once had to argue the toss for a pass slip from a dickhead tester who insisted he could "feel movement" in my front brake torque arm, and was unable to grasp the principle of a rose joint. It's also tricky mounting the front mudguard to anything but the rear legs, which means it will have to be high enough off the wheel to clear the tyre on full suspension bounce.

Part assembled, the B & I springers on the front of Tony's own fifties style bobber Harley. The rear legs waist in at the top to clear the fatbob tanks on full lock. Note the "dog-bone" risers, not my favourite handlebar mountings as they can swivel under severe provocation and bring your chin into contact with the top of the springs. Ouch. Peg them at the construction stage to avoid this problem later

And here's Tony's solution to the threat of rear legs bending under load. These rear legs are hand made from solid oval section and have been tapered, leaving the widest and strongest section of the taper to support the bottom yoke. Not content with that, Tony has also added extra sleeving to spread the load further. Now you can see why well made springers are expensive; countless hours of work goes into producing parts like this

Rocker bushes will wear in service and will eventually need replacing. Unless you're using genuine Harley springers this may call for a bit of specialist engineering. Some people have added grease nipples to the rocker pivots; I found oilite bushes gave acceptable wear rates. And of course you may well want to chrome your springers. This can be an expensive job and you might want to consult your chromer first; the bottom yoke will sometimes be a hollow fabrication which will retain liquids from the process and continually leak rusty streaks ever after.

But for all that, little compares to the aesthetics of a well designed and carefully prepared set of springers on a tidy chop. A perfect blend of art and engineering. My thanks to Andy Mitchell, and Tony at B & I Engineering for allowing me to bother them with my camera. B & I offer a range of classic Harley replica parts including forks and frames, as well as full custom engineering services; call them on (01484) 511534 and say I sent you.

Dr.Rod