I installed cartridge emulators from Race Tech today. They promise to give me the balanced response in my front suspension that I have always dreamed of. The emulators sense the amount of force the forks are subjected to and adjust the amount of damping accordingly. This way you can have a firm ride on smooth pavement but have the forks ''give'' when you hit an abrupt bump like a hard edged pot-hole. Old school forks have pre-determined fixed rate damping that neccessitates a lot of comprimise. Therefore they can feel kind of mushy at low speeds and mild bumps but be very harsh when large hard-edged bumps are encountered. OK, enough of the sell job (no financial interest). Here's the basic installation procedure.
First, because you want the emulators to take over the damping duties, the original damping holes in the damping rod are enlarged plus new ones are drilled. This will virtually negate the effect of these orifices on damping. For my size of emulators, the original 5mm (3/16'') holes were drilled to 8mm (5/16) and an additional two 8mm holes were added.
Don't forget to de-burr the holes and then wash all filings away so that you don't end up scratching the crap out of your fork tubes.
Here's the original "progressive'' spring (top) and the new custom made spring from Cannon Racecraft in GA. The new spring has a constant rate of 1kg./mm. According to Race Tech, progressive springs have it backwards. They are mushy under light loads and harsh under heavy loads. All of the progressiveness you need is provided by the air volume inside the fork which is naturally progressive.
Here's a photo of the actual emulator (at last) in between the damping rod with top-out spring and the main spring.
This is how it will be installed in the fork tube.
This was my idea to determine the amount of fork oil I will need to get the same oil level that I originally had. I dropped the emulator into 100ml of water and measured the displacement at about 10ml. Therefore, I will start off by adding 10ml. less oil than specified in the manual to arrive at the same overall level as before. The oil level can be altered slightly to adjust the amount of ''progressiveness'' desired. (you can just make out the water level in the photo and the emulator in the cup)
What about rebound damping? The emulators do not effect the original rebound damping which will be at a fixed rate. The rate can be adjusted with oil viscosity without affecting the variable compression damping unlike the original fixed set-up.
The main spring pre-load, which affects static sag, is adjusted by changing the spacer length. Here I have sawn off 16mm from the original spacer to get the pre-load I need. If you need to increase
pre-load, you can use aluminum conduit or pvc pipe of the appropriate length and diameter.
One thing that I have not yet mentioned, the damping rate of the emulators is highly tunable. two valve springs were supplied, one very stiff ''racing'' spring and another more compliant spring for normal street riding. The pre-load on the spring is also adjustable by varying the number of turns on the adjusting screw. Once installed, adjustments are easily made by pulling out your main spring and then fishing out the emulator with a telescoping magnet (or wire hook).
I will post a review of the perfomance of the emulators as soon as weather permits. If they are as good as all the rave reviews I have read, then I would think that these are the most bang-for-your-buck upgrade you can do to your vintage bike. I mean what good is increased horsepower if you have to hold back because of your antiquated suspension?
Here's a link to Race Tech if you want to know even more.
Emulators-How They Work