Suspension technology has come a long way since many of our favorite bikes first rolled off the assembly line. And while the basics haven’t really changed — hydraulic front forks and rear shocks — the way those components function has progressed radically.
Beyond adjustable preload on the rear shocks, the bikes of 40 years ago didn’t give you much to work with. Front fork valving was almost universally the tried and true damping rod and piston, which while certainly functional left — and still leaves — much to be desired.
The main limitation is the system’s fixed compression orifices, which control the flow of damping oil under compression. Most are calibrated to give smooth damping under light shock loads, but this usually results in a harsh suspension when larger, more abrupt bumps, which make the fork move faster, are encountered. Any modifications on damping and load control are limited to changing springs, oil viscosity and orifice size, and while a seasoned veteran can affect some good compromises, they end up being just that, compromises, because there’s no way to fully control the flow of oil through the orifices.
Race Tech’s Gold Valve Cartridge Emulator converts a damping rod fork into a cartridge/damping rod hybrid, with compression fluid forced through the emulator, giving controlled flow thanks to the emulator’s load-sensitive, variable flow rate abilities. In a nutshell, the emulator valve responds to the speed of the fork allowing oil to flow as needed to relieve compression, smoothing out the ride. That’s what modern cartridge forks do, most using thin, bendable washers that “give” to the rushing fork oil when the forks hit a bump. Cartridge forks are stiffer when responding to small movements and softer when responding to large, more abrupt movements, the reverse of a damping rod fork.
For this project we enlisted ad man Rod Peterson’s 1974 BMW R60/6. While never considered poor handlers exactly, there’s no denying 1970s BMWs could use a little help in the suspension department, equipped as they are with fairly soft front forks that transition rapidly to stiff action on big bumps and rear shocks that perform only adequately when pressed hard.
In addition to the emulator valves and a pair of Race Tech HP fork springs, we also installed a pair of Race Tech’s excellent G3-S piggyback reservoir shocks. Installing the shocks is easy; remove three bolts and the nut on one stud and swap — other than dialing in final preload and rebound preferences, you’re done. One note of caution: On our bike we had to file the bottom of the left upper shock bracket for clearance.
Installing the emulator valves and new springs takes a bit more time and patience, but it’s easily within the range of most weekend warriors. Take your time, have a good service manual to help you understand how your suspension goes together and, most importantly, read all the literature that comes with the emulator valves, because the questions you’ll have will almost certainly be answered in the supplied paperwork.
It’s definately time well spent, as the change to our BMW’s ride and handling is nothing short of amazing. It’s smoother and more predictable, with better ride control in every way. The front end is firm, with excellent rebound control and minimal dive, while the rear feels planted in a way it never did with its old (and admittedly worn out) shocks.
We’re still dialing in our suspension, but if you log on to MotorcycleClassics.com and search “BMW Suspension” you’ll be able to find updates on our project and riding impressions on the improvements we’ve seen with our Race Tech upgrade. MC