High Perfomance Sidecars

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Chasing the Big Dogs 

 

I learned one thing attending the 2003 High Performance Sidecar (HPS) Gathering at Maggie Valley.  Iím not one of the big dogs.  I have never rode so hard and only to end up as the slow guy.  My main goal was just to show up at the restaurants before every one else was getting their bills. 

The upcoming 2004 gathering will probably move me down even further in the pecking order.  Doug Miller has a new Hayabusa / RDS rig.  Jay Hall an FJR1300 / RDS, and Larry Miller a K1200RS / RX5.  Bill Ballou and Roger Symington both have new Center Hub Steering (CHS) front ends, designed and built by Bill, on their Honda Blackbird rigs.  Obviously my K1100RS / EML was not going to cut the mustard with this group.  Upgrades are required.

HPS or Not

What makes a rig an HPS as opposed to a normal rig?  Most HPSers would agree that automotive tires are required.  Car tires put a lot more rubber in contact with the road than a motorcycle tire, increasing the traction available for turning, accelerating, and stopping.  Also replacing the motorcycle wheels with 14 or 15 inch car wheel reduces the gearing, returning some of the acceleration lost due to the weight of the sidecar at the cost of some top end speed.

Standard motorcycle telescopic forks are not designed for sidecar use.  They have too much trail to steer easily with the extra weight and wider tires of a HPS.  They were never designed to handle the sideforces that a sidecar rig can generate.  Both leading link and CHS front ends are better suited for sidecar use.  These front ends can be specifically set up for sidecar use.  A leading link has the disadvantage that the wheel turns up on edge a little when turning, reducing the tire contact patch.  A CHS front end keeps the wheel flatter on the ground, keeping all the rubber on the road.  Many sidecar riders resist making these changes.  These modifications turn the motorcycle in to a dedicated sidecar tug.  It can no longer be easily turned back into a single-track motorcycle.

Another item found on many HPS is a sway bar.  A sidecar sway bar is a torsion spring connecting the bike rear wheel and the sidecar wheel.  Its purpose is to reduce the amount of lean when cornering.  In a right hand corner (right hand mounted sidecar), a rig will lean to the left.  The bike suspension is compressed and the sidecar suspension is extended.  The compression of the rear motorcycle suspension twists the sway bar, which in turn preloads the sidecar suspension, reducing the amount it extends.

Others include sidecar wheel steering as a requirement for an HPS.  This reduces the amount of scrubbing the sidecar wheel does in corners, allowing the sidecar wheel to have more lead, with out making the steering effort overwhelming.  The additional lead better stabilizes the rig in left-hand corners.  (This article assumes a right hand mounted car, for left-hand mounted cars everything reverses.)

Perhaps itís just a state of mind.  Like a bumper sticker I saw years ago in the parking lot at an SCCA race ďEvery Car is a Sports Car Some of the Time.Ē  Maybe there is no recipe for an HPS other than the riders willingness to push the state of the art a little and modify or design a rig so that it handles a little better than the average.

My rig already had a leading link front end and automotive tires on all three wheels.  So I have many choices for my upgrade path, convert to a CHS front end, adding sidecar wheel steering, or adding a sway bar.  As anyone with much experience rigging sidecars has learned, rarely if ever can you go to the local motorcycle shop and purchase what you need.  A few parts can be ordered form specialty shops, but if its something different, you have to make it.  Nobody I know of makes sway bar kits for sidecars, there are just too many possible combinations of bikes and cars to cover.

Likewise there are no retrofit kits to add CHS or sidecar wheel steering to my rig.  So whatever path I take, the parts will have to be custom designed and made.

After many discussions and emails, I decided that the most bang for the buck, performance wise, would came from adding a sway bar to the rig.  Plus, this was the option that fit my budget and was within my skill level to fabricate.