Product: Works Performance Steel Tracker TRS Single Shock
Subject Motorcycle: 1991 BMW K100RS
First introduced in 1982, BMW’s K100 “Flying Brick” has been around a lot longer than most of us care to realize – over 25 years, long enough to qualify for “historic” tags in some states.
That means early K bikes are starting to get old, with more and more of them needing the kind of fettling and rehab work we generally reserve for the classic Harleys, BSAs, Hondas and Ducatis in our garages.
While early K bikes aren’t likely to incite the sort of passion as, say, a 1973 Norton Commando, they are solid, overly-engineered machines. More at home on the open road than the confines of the city, they make excellent commuting machines, which is exactly what I was looking for when I bought mine last year; something to carry me comfortably and reliably on my daily 60-mile roundtrip ride to work.
And while my Brick has delivered on all counts – great fuel economy, easy to maintain, reliable, and comfortable – the one area where it suffered was the rear suspension. Overly soft, it wallowed under compression, especially in tighter turns. Throw in an off-camber, decreasing radius with a bump in it, and it was almost scary.
With 64,000 miles on the clock, I knew the rear mono-shock on my K100RS was suspect, so I decided to check out my options. After looking at a stock replacement and even a rebuild, I settled on an aftermarket replacement from Works Performance Shocks.
Works Performance Steel Tracker TRS
The shock I ordered was a Works Performance Steel Tracker TRS. Featuring triple-rate springs (hence the “TRS” designation), the Steel Tracker TRS also features adjustable spring rates and comes with a remote fluid reservoir. Adjustable rate springs allow the rider to adjust spring performance for different load and road conditions, while a remote reservoir allows a larger supply of damping oil, helping the nitrogen-charged damping oil stay cool in high-load/high heat situations.
There are three springs on this unit; one above the stepped cup, and two below. The springs all work together to give a soft, initial response to inputs from the swingarm, but as loads increase the short springs quit compressing and the load transitions to the longer and stiffer main spring.
Once it’s set up it’s easy to change the spring rate by simply turning the unit’s indexing lever to the appropriate spot in the corresponding stepped cup at the top of the Steel Tracker shock. A wider gap between the lever and the stepped cup gives a softer setting by increasing the distance the shock compresses before the load is transitioned to the main spring; a smaller gap gives a firmer setting as the load is transitioned to the main spring sooner.
Once I made my decision, I called up Works Performance, where Ned Owens took my order. Ordering shocks from Works is a bit different than dealing with other companies, where typically you just pick a shock from a range of options, maybe choose your spring rate and then order away.
Works Performance asks for quite a bit more information before they’ll sell you a shock. In addition to the expected specifications of model and year of your machine, they’ll ask you about rider weight, rider weight with gear, how often you carry gear, passenger weight, percentage of time you carry a passenger, the type of riding you do and your skill level. All these factors are taken into account to determine the best combination of springs and damping rates for your shock, with literally thousands of possible combinations. Additionally, on K bikes and some others you can get lowered shocks to bring saddle height down, a useful option for shorter riders struggling with a K’s almost 32-inch seat height.
Since I do all my own work, there was no question but I’d install my new Works shock. Early K bikes featured BMW’s “monolever” system, a single-sided swingarm and monoshock, and later bikes (starting with the K1 in 1989 and then quickly adopted by the K100RS) featured BMW’s “paralever” system, which added a strut arm to the rear hub to negate the rise and fall induced by a driveshaft. While the specific shock is different depending on which system your bike runs, the installation process is the same.
Installing the Works Performance Steel Tracker TRS
Most home mechanics should be able to install the Steel Tracker TRS, as it’s a technically simple job requiring only one special tool, a torque wrench.
Before starting the job, get the bike up on its center stand and wedge a block of wood between the rear tire and the floor. This will keep the wheel at a constant height, and just barely unloads the suspension, making it easier to take the old shock off and put the new shock on.
To help ease removal and installation, go ahead and remove the entire seat/rear cowl assembly. While you can see and reach the upper shock mount with the assembly in place, it’s much easier to get at with it out of the way, and much, much easier to properly locate the Steel Tracker TRS’ remote reservoir on the frame.
Removing the seat assembly requires first removing the seat, which is a simple matter of opening it, removing the prop rod, the two seat pins, and then lifting the seat off. Once the seat’s off, there are six bolts holding the rear assembly in place; two Phillips-head screws at the forward (gas tank) end, two Allen bolts further back toward the middle of the assembly, and two locknuts inside the rear cowl in the tool storage compartment. Once these are removed slowly separate the assembly from the frame, pausing to locate the wiring to the rear tail light and turn signals. Once the wiring has been disconnected at the plug connectors just lift the assembly off and put it to the side.
Once the assembly’s out of the way, remove the nut on the lower shock mount. This takes a 17mm (or 11/16 inch) socket. Assuming your block of wood is still in place under the rear tire, you should be able to wriggle the shock off the lower mount. Now remove the bolt holding the shock in place at the frame. Again, it’s a 17mm, but this time a nut and bolt instead of a nut and stud as on the lower mount. Once the nut’s removed, hold the shock and pull the bolt free, collecting the two washers that will likely fall out. Slide the old unit out of place and that’s it, you’ve removed the shock.
Installing the Works unit is straightforward, but there are a few things to check. First, lay the old and new units side by side and measure the distance between the mounting eyes; they should be the same or within a ¼ inch difference; you’ll check the Works unit again once it’s installed. Second, thoroughly clean the lower shock mount threads.
The Works unit comes with split sleeves that fit inside the upper and lower mounting eyes. Put two sleeves in place in the upper mount (they’ll only install with the larger diameter washer edge to the outside) and slip the upper end of the Works Steel Tracker into its slot in the frame. Push the upper locating bolt into place, making sure the thick washer is under the bolt head. Install the wavy spring washer on the protruding bolt on the other side and thread the nut down hand tight. Make sure the remote reservoir isn’t getting caught up anywhere and let it hang free.
You should still have a split sleeve for the lower mount. Slip one half of the sleeve over the lower mount, with the larger diameter washer edge against the final drive unit. Gently guide the lower end of the Works Steel Tracker over the stud and the sleeve and install the other half of the sleeve, this time with the larger diameter washer edge to the outside. As there’s no spring washer used on the lower mount, I applied a thin coat of medium-strength (blue) thread locker on the clean, exposed threads. You can opt to use thread locker on the upper mount, as well, but it’s not as critical. Finally, install the nut. You’re almost done.
Installing the Remote Reservoir
This is where you’ll be glad you removed the seat assembly, as you need to position the remote reservoir under the right rear frame wheel. The Works unit comes with a pair of rubber mounting blocks and a pair of stainless steel band clamps to hold it in place. Unscrew the clamps so the ends are free, and then slip them around the right rear frame rail a few inches behind the threaded mount for the seat assembly. Thread the clamps together again and slip the remote reservoir in place, the clamps holding it like a sling. Take the pair of rubber mounts and position them between the reservoir and the frame. The mounts are molded to fit the frame and reservoir; the smaller side goes to the frame. At this point it’s handy to have someone hold the reservoir while you tighten up the clamps, but if you work patiently it’s easy enough to do alone.
As the clamps get close to being tight, check the free-length in the stainless steel hose that runs from the shock to the reservoir. On my bike, I positioned the reservoir almost exactly between the threaded seat mount and the weld for the rear frame loop, leaving a nice relaxed S-curve in the hose that reminded me of an old Studebaker logo. Primarily, make sure the hose isn’t pulled tight and that the reservoir doesn’t hit anything. Tighten the clamps a bit more, make sure you’re comfortable with the reservoir location and then cinch the clamps down the rest of the way.
I’ve always been taught to tighten suspension bolts with the suspension loaded, the theory being you can introduce a bind if you tighten them with the suspension unloaded. With everything in place, push the bike off the center stand and have a friend hold it while you torque the upper and lower mounts to 25-30ft/lb. If you don’t have a torque wrench, experience will tell you if it’s tight enough. At this point, go ahead and reinstall the seat assembly.
With the bike off the center stand, climb on board and compress the suspension a few times. Next, have a friend measure the distance between the lower shock mount and a point directly above it, such as the main frame or the frame for the hard bags, if so equipped. Record that number then pull the bike back on the center stand. Now measure that same distance again. If you’re installing a standard-length shock, the difference should be between 1-1/4 inch and 1-5/8 inch (3/4 inch to 1 inch with short shocks). If the difference is less than the minimum, loosen the spring preload by turning the large nut on the lower end of the shock unit to the left. This extends the shock. If the difference is more than the minimum, tighten the spring load by turning the large nut to the right. This compresses the shock unit. Measure again following the same method outlined above until the proper difference is achieved.
The big moment comes when you finally head out on the road to experience what your hard-earned money bought you and whether installing the new shock was time well spent. While I anticipated at least a noticeable improvement in compression and rebound control, I didn’t expect the revolutionary difference in handling I experienced from upgrading to the Works Steel Tracker TRS.
Situations that previously unsettled the bike and made aggressive riding pointless, especially any kind of suspension compression while turning, became an excuse to have some fun and push the bike a bit. At over 600 pounds my K100RS is a porker, so I’d just assumed it would never handle with the sharpness I expect out of smaller, lighter machines even like old Commandos. Yet while it’s never going to have the handling characteristics of a modern sport bike, the improvement in wheel control offered by the Steel Tracker’s superior rebound and damping capacity gives the rider a vastly more controlled and therefore safer riding experiencing that’s miles ahead of the stock unit. Simply said, the performance is spectacular, making the Works Steel Tracker a highly recommended upgrade for owners of older K bikes. – Richard Backus
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