Even though many budget bikes have engines with fuel injection and four-valve cylinder heads, their suspension—particularly the front fork—remains mired in the past, relying on inexpensive damper rods to help control wheel movement instead of the sophisticated cartridge damping found on pricier models. Ricor’s Intiminator fork valves bring cartridge performance to damper-rod bikes.
Some suspension basics first.
When the front wheel hits a bump, the fork compresses to let the wheel go over the bump. The spring in the fork first resists this compression, then extends the fork after the bump. But without some way to control the speed at which compression and extension (also called rebound) take place, the wheel would bounce, oscillating until the energy of hitting the bump was dissipated. In order to control wheel movement, that energy has to be damped.
In a damper rod fork, that’s accomplished by forcing oil through an orifice inside the fork. But this method doesn’t work well at slow compression speeds, when the oil is moving so slowly as to provide no real damping, or at very high compression speeds, when it’s moving so fast it doesn’t move through the orifice at all, a condition called hydraulic lock, which effectively stops the fork from compressing.
The Intiminator sidesteps the limitation of damper-rod forks by taking the damper rod out of the suspension equation. This is done by using 5wt fork oil, which is so thin that it passes through the damper orifices without producing any noticeable damping effect, almost no matter what the wheel speed.
The Intiminator itself is an improvement over the fixed orifices in the damper rod. It uses a flexible shim stack (in the larger-diameter base) like those in sophisticated cartridge forks, and an inertial valve (the brass-colored part under the nut on top) that opens up a bypass for faster oil flow at high compression speeds.
At low speeds over the kinds of bumps you encounter on the street, the shims alone provide damping, controlling the flow of oil and bending to allow more through if needed.
At higher speeds the spring-loaded inertial valve takes over. It sits on a light spring, and remains closed until the wheel begins to move upward sharply; it then slides down and opens a port through the middle of the Intiminator that lets the fork oil flow freely, allowing the wheel to get up and over the bump as quickly as possible.
Under braking, which causes the front end of the bike to pitch as weight transfers onto the front wheel, the inertial valve remains closed, and the shim stack’s damping effect moderates dive. In this way the Intinimator reacts differently to wheel movement (hitting a bump) and chassis movement (hitting the brakes).
Installing the Intiminators in my 650 V-Strom, which came with damper-rod forks, was relatively easy. I removed the forks, drained the oil, dropped the Intiminators down the fork tube onto the damper rods, replaced the springs, and poured in the right amount of 5wt fork oil.
The Intiminators add a half-inch of spring preload; Ricor suggested trimming the spacers that sit on top of the V-Strom’s fork springs to bring preload back to zero, which I did.
Only a few miles into the initial road test, I was sold. The Intiminators smoothed out my favorite backroad, reducing what used to be tooth-jarring pavement breaks to minor wrinkles hardly worth noticing, and taming front-end dive under braking. Especially noticeable was the effect in bumpy corners; the front wheel stayed planted instead of trying to leap into the weeds on the outside of the turn. Off-pavement compliance was improved, too, although my dirt skills are not such that I pushed very hard.
The Intiminators have been working their magic for several thousand miles now, and the fork compliance remains as good as it was the day I installed them. —Jerry Smith