Modern sportsbikes have a penchant for instability due to the aggressive rake and trail numbers needed for quick handling, combined with front tires that are designed to give the sport rider more contact patch when leaned over at the expense of a smaller contact patch when upright. These factors combine to provide us with motorcycles that will change direction in a heartbeat, but may act a little nervous in a straight line.
As technology and design have improved in the last 15 years, manufacturers have come up with stronger frames, swing arms and forks to allow motorcycles to handle more extreme rake angles and cornering loads, without shaking themselves apart in a straight line, which permits them to hit the ever moving target of improved handling with lighter response. Again, the trade off is motorcycles that border on instability under had acceleration.
Along comes the technology band aid – the steering damper. Steering dampers introduce friction between the frame and the front wheel, to dampen unwanted oscillations of the steering stem, forks and wheel. Early steering dampers were integrated into the top steering stem nut allowing the rider to essentially crank down on the steering head bearings, adding, mechanical friction to produce the desired resistance to motion to quell these unwanted oscillations in the weak frames of the day. Steering dampers in their present sealed hydraulic form appeared in the late '80s, simply mounting somewhere between the frame on one end and the steering set (triple clamp and forks) on the other. The devices were simple oil filled units that had a variable orifice plate that lined up with a fixed orifice that was adjusted by twisting the exposed rod not attached to the fork. These early hydraulic units were crude and didn't provide much thermal expansion capacity to accommodate the expanding oil as they warmed up and as such were prone to leaking and short service lives. Newer, more improved steering dampers, used a small closed foam insert to both absorb shock and permit thermal expansion as the oil warmed up, as well as a tapered needle and seat to provide a wider range of adjustment than the earlier orifice plate style of steering damper, offering 18 or so options of resistance, rather than the five or six options of the orifice plate type. This side mounting location offered the strongest mechanical advantage, but was very prone to extensive damage in a crash, and has recently fallen out of favor with the preferred mounting area, now found above or below the triple clamps.
Current versions of this hydraulic type steering damper have an oil separating piston much like in a shock absorber that maintains oil pressure with a spring or low nitrogen charge, permitting the oil in the damper to expand and contract from heat or shock, yet avoid body leaks or flow cavitation. The modern steering damper has become so commonplace and accepted, that almost all current sportsbikes have one to help the motorcycle maintain street stability while permitting chassis dimensions previously enjoyed only on Grand Prix race machines.
Some currect OEM dampers offered on today's new motorcycles are electronically modulated to increase damping at high speeds for safety, yet reduce resistance at low speeds to maintain manoeuvrability. However, on the race track, the stock unit with a quality adjustable aftermarket unit to give you the best combination of performance and safety.