Scooberhawk

What happens if I have 5wt oil, because I want my suspension to be soft, but it is too soft, at the recommended level?

I think I'd need to add more oil to reduce the air gap. So couldn't I add more 5wt, or even 10wt or heavier, oil?

The other option I see is that the shim stacks are most responsible for what weight oil should be in the forks. So if the forks could definitely be too soft with 5wt oil, then I might as well use 10wt oil, and use the proper air gap, to achieve my preferred level of softness.


I am I thinking clearly on this matter? Are one or both of those possibilities plausible ways of thinking about setting up my suspension?

shayne

Generally oil height will have its greatest effect at the end of your stroke. Raising the oil height is often used to prevent bottoming out on big hits. If you are bottoming out, then you are on this right track in my opinion.

I would judge your oil weight on small bumps. If it is a bit rough you would need lighter oil and vice versa. Then you can adjust oil height once you have this sorted. Gold valves are really the best option if you can afford them, as everything else is a bit of a compromise.

Hawkrider

The 4-port Showa valves that are used in the SH tend to go into orifice control on big hits with the stock 10wt oil.

[Sidebar] About orifice flow: At some point, based on the size of the orifice and the viscosity of the fluid, an orifice will only be able to flow fluid at a specific maximum rate, based on the aforementioned factors. Pressure differences on either side of the orifice do not matter at this point.

So, the 4-port Showas have relatively small ports in them and large hits flow lots of oil. With the stock suspension and 10wt oil the valves cannot flow the desired amount and it feels like the forks lock up, or bottom out. They probably did not bottom out because we have these nifty little things in our forks called oil locks which significantly increase compression damping in the last 3/4" or so of fork travel.

Now, the stock compression stack is pretty stiff to try to compensate for the weak progressive springs Honda installs at the factory. So, if you go with heavier springs and lighter oil, on the compression side at least you'll be okay. You also move farther away from orifice damping when you choose a lighter viscosity oil. You could however be left with insufficient rebound damping in this case - depends on how heavy of spring you go with. The heavier springs will tend to extend the forks at a rate which exceeds the maximum damping force with the adjusters all the way in (hard).

So you are left with enough of one thing but not another if you are only to modify springs and oil. To get the best suspension you can of stock Superhawk parts you need to revalve.

Basic revalve guidelines:

1. Choose your oil (lighter is better in most cases)
2. Choose your springs (for your weight with gear)
3. Choose you valves (not so important if going with light oil)
4. Shim stack selection (varies from tuner to tuner and what the rider wants)
5. Adjust oil height so the rider does not bottom out on hard braking (stoppies)

Probably more than you wanted, but hey.....I love this stuff!

Scooberhawk

That's awesome. You want to write a chapter 2, I'm down!

I've got springs that would be slightly stiff on the street but slightly soft on the track (.85). I plan to have this be my main street bike for a couple/few years, and I ride pretty hard when in the right company. I've got gold compression valves. I'm on a bit of a budget (plus I'd love a Sargent, some quiet Yoshi's, and a jet kit, among other things), so I think I'm going to forgo the rebound valves for now.

Would that help you zero in on my needs?

The reason I don't want to throw in 10wt is because I'd have to empty it out if it's too stiff, where 5wt might be a little too soft, but I think I'd like that better than too hard, and then I could mix in some 10wt to compensate. From what I understand, different weight oils end up mixing to form a weight in between (as in, they are not like oil and water). So really, I'm being extra particular because of limited time and budget. I just want it as close as possible the first time around.

I appreciate both the responses I've gotten so far, of course.

-Matt

Hawkrider

Okay, so you have 5wt oil, .85 springs, compression GVs, and you weigh how much? Any idea what stack is being used on the GVs? If you have 5wt and running GVs I'd hope you have a different stack than what is recommended by RT. Their stacks are designed for 10wt Racetech oil which has a cSt of 32.9, which is a little lighter than stock Showa SS-8 (cSt of 36.47). The Gold valves with their standard stacks will not work as designed with anything else.

If you want plusher, I recommend going with a lighter stack, same oil, stock air gap (130mm I think).

FWIW, I run 1.05 Ohlins springs, 10wt oil (been a long time - don't remember brand), stock air gap, RT Comp GV with C36 stack, modified rebound needles. I'll be revalving this winter as well as sending the Fox out for service. I'm just short of 40k miles and am probably due for new seals, bushings, and oil anyway.

Scooberhawk

I'm at 150 with gear. I wouldn't mind being able to ride 2-up comfortably.

RT says c34 shim stack with #55 (1.3mm) hole drilled for street use. Also says 155mm oil level. I haven't decided on doing the rebound needle mod yet. That'll depend on the tools available that day.

I've been hesitant to place another order with RT because I'd want to get one of everything, but it sounds like it would be the smartest idea to use RT's oil as a baseline, and go from there if I have to. What would it be worth another few bucks to get, when I order the oil?

It makes me feel half like a jackass asking about something that will come down to rider feel in the end, but suspension is everything. And unfortunately, I, like others, don't have the time or money right now to experiment with lots of setups. Ugh.. it's so tempting to dip into my savings and get the shock valving kit and the fork rebound kit too.... man on a budget here... I shouldn't spend that money.

Should I get a Sag Master? It's 10 bucks...

Scooberhawk

Oh yeah, and I don't have spring instructions for cutting the spacers.

Hawkrider

Sagmaster? I use a metric tapemeasure and I think it was a stocking stuffer one year. Works for me.

Yeah, 155mm. That's it. Been a while. C34 sounds about right for the springs and your weight. Just need to get the oil right. PM me your email address and I'll send you a table of oil data. You don't need to get the RT stuff. If there is something close that's available in your local shop that'll work too.

You never made mention of your sag settings either. Chances are you may be close to what you want you just need to fiddle a little bit. Check out my site for instructions on setting sag. You'll need 3 people or 2 people and a wheel chock to get 'er done.

Ugh, spacers. Have you installed the springs yet? You're shooting for about 30mm rider sag with the adjuster in the middle. What are you at now?

Scooberhawk

The reason I can still ask questions on what else I need to be buying is because nothing is installed yet. My springs and gold valves and s/s lines and hh pads and front sprocket are all going to wait until the end of the month when I don't have 7 summer classes to worry about anymore.

So yeah, no sag settings yet. And I'm sure I'll be referencing your site again when it comes time to do the work.

shayne

You are right, suspension is everything. Dirt bikes has taught me this. You are far better off spending your money on this than engine parts in my opinion.

If you persist I am sure the end result will be worth it for you. That is why I decided to get a pro to do mine. He had done 16 VTR's before mine and new exactly what needed to be done, so I gave him my suspension to do, and I worked on other stuff! In my case I had never ridden the bike either so I didn't have experience with the VTR to make decisions as to what was needed.

It will be very satisfying for you to do it yourself though, and you will learn a lot along the way. Good luck with it.