After months and months and countless tear downs, talking with Suspension Gurus, and borderline OCD front end tweaking, I am finally happy with the handling of my Cartridge Emulator equipped front forks. Here is the "final" addendum and tuning notes to my previous Emulator post
http://forums.sohc4.net/index.php?topic=76521.0 including a side-by-side compare of Reacetech vs. MikesXS Emulators.
Hopefully, this will save you guys some of the grease time and clear up some of the suspension mystery when custom tuning your own suspensions. . .
For those of you with short attention spans or reading aversions, here are the cold hard numbers of my final setup:
Racetech Cartridge Emulators (Blue 40lbs/inch springs) 3 turns
Racetech Springs 1.00kg
15W Bel Ray Oil
180mm of Oil
1 Rebound hole welded shut
Rider Weight: 190lbs
Spacer length 66mm with 1 washer provided
20mm of preload
32mm of static sag
The basic problem of my front suspension post Emulators was an unwieldy front end rebound. Here is the eventual tuning solution that I’ve been working out these last months along with resources to general motorcycle front fork tuning.
If you don’t know the difference between compression damping and rebound damping, or preload vs. spring rate, check out the Suspension Tuning Guide at Sportrider.com and pour over the associated links first to better familiarize yourself with general suspension tuning.
http://www.sportrider.com/suspension_settings/suspension/146_1004_sport_rider_suspension_guide/index.htmlOn Emulators, brands, and tuning. . .
I originally tried the MikesXS emulators thinking, heck, I’ll save some bucks. Well, call it my perfectionist tendencies or never ending search for piece of mind, but I finally broke down and bought a pair of Racetech Emulators. In comparison, these units are very similar, albeit identical. There are at least two key differences which led me to use the Racetech brand vs. the cheaper MikesXS brand.
1. Racetech has 2 valve plate bleed holes, compared to 1 on the MikesXS version. An extra hole means the Racetech unit will navigate low speed compression damping far ie small bumps, road chatter, better than the MikesXS unit.
2. Racetech gives you 3 sets of springs with different spring rates depending on your set up.
Let’s be honest, the MikesXS Cartridge Emulators are knockoffs of the original design Racetech developed and tested over who knows how many prototypes. What was the R&D process of MikesXS besides blatantly ripping off the design? I’m guessing not much. I also couldn’t tell you what spring rate they are using in the valve spring or spring shim. Racetech, however, DOES provide you with spring rates and 3 choices. So, considering I am a guy who usually plays it safe, and got tired of taking my front end apart constantly, the Racetechs were the obvious choice. This is not to say someone won’t find the MikesXS units an improvement over the archaic damper rod style front end these bikes came with. But if you are a perfection psycho like me, again, the Racetechs are the better option.
Springs. . .
In my original build I went with cutting the Progressive springs I already had. Don’t do this as the progressive springs render it fairly impossible for the accurate tuneability of your forks with Emulaotrs installed. At the very least, find a set of original single rate stock springs and cut those. Although, this too is a poor option. The best option to get the best performance out of your front end with emulators, which is why you are doing all this in the first place right? is to get a pair of single rate springs made for Emulators.
The reason you can’t use normal length CB springs is because the emulators are about 20mm or so tall. And because the emulators are installed below the springs, you are adding 20mm of preload to the springs. Not a good thing. So that leaves two options, cutting original springs or getting shorter springs. Cutting springs makes them stiffer. So unless you want to figure out how much you can cut the springs in relation to spring rate in relation to your body weight, just buy shorter springs with known spring rate. I called Racetech for mine, who calculated both bike weight and rider weight (I weight 190lbs) before sending me out a pair of 1kg springs.
I believe spring rate and preload were the main contributers in my original problem of too much rebound or not enough rebound damping, however you want to state it. In aiming for 30-35mm of static sag, I had to preload the stock cut springs (shortened around 20mm) far more, than the stiffer RT 1kg springs. So with the RT springs, I am at what is considered the normal amount of preload for street application, around 20mm with a very firm spring. The end result is SWEET!
So, again, either way you need shorter springs with Emulators. If you choose to cut stock springs, figure out the spring rate you are shooting for, and cut accordingly. Or just save yourself the hassle and buy new springs.
Rebound damping tuning. . .
After speaking with a few race tuners and suspension techs, and working under the assumption that my bikes rebound evils were due to an under-sprung condition, I decided to play it safe and re-drill 1 rebound hole (I had previously welded both on each damping rod). Welding both holes closed is still probably fine, especially considering how bad your damping rod seal, inner fork tube wear, and rebound check valve wear is. However, with new fork tubes, new damping rod seal, and 15w oil, my suspension rebound is about right where it needs to be with 1 hole welded closed. It has been asked, but if you weld both holes closed, where does the oil go?
Check out diagram 1 here:
http://www.sportrider.com/tech/146_9502_tech/photo_01.htmlOn the compression stroke, oil is pumped up thru the rebound check valve built in to the fork tubes. Then, on the rebound stroke, the check valve’s job is to close the rebound chamber so that the pressurized oil has no where to escape but the rebound holes. Problem is, and as I found in my tests, the damper rod OD is not exactly a tight fit within the ID of the check valve. Meaning, some check valve oil blow-by is inevitable. This, to answer the question, is where the oil naturally goes if there are rebound holes present or not. So again, depending on the sealing of your rebound check valve, you may be fine welding both holes and using 15w or welding 1 and using 20w. It kind of depends on your set up. For the moment, I have settled on 15w with fairly good rebound results. Though I might try 20 or 25 just for testing.
Oil height. . .
Oil height, or oil level, or air chamber are all the same measurements. Basically, you want to use as much suspension travel as is allowed before either spring binding or bottoming out occurs. Fork oil does basically 2 things: 1. It provides the necessary damping characteristics of your suspension and 2. It saves your fork internals from bottoming out by providing a kind of cushioning effect. Because your fork is air tight (unless it’s leaking!) the oil level, or more importantly, the amount of air above the fork oil will compress when you hit a bump. Too much oil/not enough air space, and your suspension will not allow full travel. Not enough oil/too much air space, and your fork internals will have nothing to stop them from mechanically bottoming out when you hit a harsh bump.
You want to measure fork oil level with the forks completely compressed and with springs and emulators removed. After much testing, I found that the forks work the best in the ballpark of 175-190mm oil level. This is confirmed by RaceTech’s guide,
http://old.racetech.com/evalving/menu/searchdirtvs.asp which given my weight, recommends 180mm of oil.
That is about it. After all the work, months of tuning and head scratching, my final thoughts on the matter are: unless you want to spend the time tinkering, tuning, and repeatedly tearing apart your front end, spend the money and get the kit from Racetech. That is not to say the MikeXS route won’t work. And there are other springs makers that can make you springs. But at the end of the day, I like to ride. If I wanted to work on my bike all the time I would have gotten a Triumph or Harley!
I am super stoked on my final suspension set up. Well, with my front forks anyways. Sigh. With a set of Ikons on the way and swing arm sent out to Hondaman, my rear suspension awaits. . .
Other reading etc.
http://www.racetech.com/page.aspx?id=30&menuid=93#19http://www.vmaxoutlaw.com/tech/cartridge_emulators.htmhttp://www.feelthetrack.com/downloads/Suspension41.pdf