fork preparation
 

I've got Racetech springs and gold compression valves that I am getting ready to put in. I am curious about what other parts or seals I should get before taking stuff apart.

I also want to know if I need to pull the fork tubes from the lowers. It looks from the different write-ups I've read that it is not necessary. I assume that means I do not need the inner or outer fork bushings, or fork or dust seals. What about the copper washer for the damping rod bolt?

So I'm thinking that I just need to get fork oil. I've read through 20 or 30 suspension posts and can't find any consensus on which weight to use. The Racetech site says 10wt, but others say Racetech means to use that if you are not using the Gold valve kit. It seems more than one person has had success using 5wt. Which is the way to go here? If it matters, I weigh 145 or 150 and have .85 springs.

Also about fork oil.. does anyone know how thick Racetech's is compared to what you are using? It doesn't seem like a bad idea to use Mobil Synthetic ATF, but in any case, I just want to have the best shot at getting it right the first time; and it would be nice to not have to order anything from RT.

You won't have to seperate the lowers from the upper tubes unless you want to replace the seals while you have everything apart.

As for the oil, I went with 10w becuase that's what the Race Tech site recommended... have heard people using 5w, 7.5wt, 10w..... seems like you could experiment if you wanted.... but the 10w seemed to work just fine for me.

I weigh 175.... and have the .85 springs and Gold compression valves.

Interesting... thanks for the response. My bike only has 1500 or so miles on it, so I will not be replacing any seals if I don't have to.

SlowHawk is correct. 10wt is the way to go, and you will not need to tear the forks all the way down. If you watch the movie from RT, they show you how to get the seals off without destroying them.

Get a good fork oil. Don't skimp here. The cheaper oils will change their viscosity more with temperature. Racetech uses Motorex oils (US2 for 10wt) and this oil has a cSt (viscosity - higher number is thicker oil) of 32.9 and a viscosity index (VI) of 200. The higher number the better on VI. This is what tells you how much viscosity changes based on temperature. By comparison, Belray 10wt has a cSt of 33.00 and a VI of 123. This is some crappy oil! I do my own suspension work and use Silkolene RSF Pro exclusively. This stuff is THE BEST fork oil you will find out there. The 5wt oil I use has a cSt of 26.7 and VI of 372, but this will be too light for the Gold Valves. The closest you will be able to get is their 7.5wt which is 37.0/322. This will be good for you though since it's slightly thicker oil than the Racetech stuff and will allow slightly more rebound damping adjustment. I suggest finding a local Silkolene dealer or ordering online.

Hawkrider,

Thanks for the input. Based on other responses of yours, I can tell you are well-informed. I know of a dealer or two around here, at least, that has Silkolene. I like the idea of going that route, but now I'm curious...

Most folks seem to go either 10wt or lighter... If I am going slightly heavier, does that mean my shim stack should be modified to compensate for the thicker oil?

Also, I could guess why thicker oil would allow for added rebound adjustability, but I'd probably be wrong. I would think it would change the range of its effectiveness. Feel like expanding on that thought??

No, you should be fine with the "heavier" weight oil. Remember, it's only about 4cSt heavier, which really is nothing. The RSF Pro is labeled as a 7.5 wt, but then you can't really go with those numbers. That's why I go with actual viscosity numbers. You'll have slightly more high and low speed compression and a tad more rebound. Stick with the stack that best suits you, your springs, and your riding style. The more of those 17mm shims, the stiffer it'll be. I don't remember the stock stack, but I seem to recall a bunch of 0.010mm shims. You can acually use these to fine tune the stack if you don't find anything you like, i.e. substituting (1) 0.010 shim for (1) 0.015 shim to give you *slightly* less damping, and where you put that shim makes a difference too! There's an endless possibility. :)

Yes, with no changes to the rebound stack, a thicker oil will increase the damping and a thinner one will reduce it. Your rebound stack is about 3 times more stiff than the comp stack, as a thumbrule. Remember, there are also check valves in there. These are either springs or wave washers with a check shim on the back side of the valve (where the shim stack isn't). Increasing the stiffness or number of springs on that check valve will directly affect your LOW speed compression on the other circuit. The shim stack itself mainly affect HS damping. If this is unclear let me know and I'll elaborate.

When revalving, you have to follow a systematic approach. First, select the correct spring. Then select the oil you will use. Next, select the shims and number of check springs appropriate for you and the bike. Lastly, you adjust oil height high enough to prevent foaming/cavitition AND prevent bottoming on extreme braking, but low enough to minimize the "air spring" effect. The secret is in the shims. :)

In fairness to Bel-Ray, they do make an HVI (high viscosity index) fork oil with similar properties to the Silkolene RSF Pro. If you look at the basic Silkolene (not Pro RSF) and the basic Bel-Ray, you will see that they have similar properties. High viscosity index oils have additives which increase viscosity index at the expense of longevity. The basic oils will last longer without changing properties, but, like you said, they have crappy viscosity index. They are more for set-it-and-forget-it applications than performance applications where the oil will be changed on a regular basis.
Here's a link to an interesting chart with specs for many different brands and weights of suspension fluid. Scroll down towards the bottom of the page for the chart.
http://www.peterverdonedesigns.com/lowspeed.htm

Hehe, I've had that table since its inception. I didn't generate it, but I've had good rapport with Peter for some time now. Yes, I realize BelRay makes some good stuff, but I've never seen it anywhere, and nobody that does a lot of suspension work uses it.