kyb twin cham. using diffrent w oils

[freerider_australia]

what effects would using diffrent weight oil in outer and inner chambers

for example using a 2.5 w in top chamber and a 5w in bottom chamber

thanks

[RCannon]

I doubt there would be any difference. The outer oil does nothing except lubricate. The volume controlls the bottoming resistance, but not much else.

[racetech]

By running the heaver oil in the outer chamber creates more bottoming resistance.

[DaveJ]

By running the heaver oil in the outer chamber creates more bottoming resistance.

For as weird as this may seem, this is true.

The TCs have an end-of-stroke hydraulic oil lock in which a piston enters a cone that results in a hydraulic push of fluid as the two meet. The thicker the fluid, the longer the process, the greater the resistance.

Now by how much I have no idea.

Good point though.

[RCannon]

I did not think of that. Thank you.

So, the outer chamber is where the hydraulic oil lock takes place?

The forks on my 06 yz work so well I never bothered to check.

[thillsam]

The TCs have an end-of-stroke hydraulic oil lock in which a piston enters a cone that results in a hydraulic push of fluid as the two meet. The thicker the fluid, the longer the process, the greater the resistance.

This means that thicker oil in the outer chamber would change how the bottoming cones behave >> how "firmly" it would bottom once it got that far through the stroke.

I used to run Ultra-Light in the cartridge and 5 wt in the forks for this very reason on my CRF with Showa TC's...I had them softened up for trairiding but this prevented violent bottoming for occasional days at the track.

MORE oil(higher level in the outer chamber) would change how easily it got to that part of the stroke, because of the air volume change and subsequent additional airspring rate from having more oil in the outer chamber. Viscosity of the oil would have little if anything to do with this effect, other than the slightly more initial stiction induced by heavier weight oil.

[DaveJ]

This means that thicker oil in the outer chamber would change how the bottoming cones behave >> how "firmly" it would bottom once it got that far through the stroke.

I used to run Ultra-Light in the cartridge and 5 wt in the forks for this very reason on my CRF with Showa TC's...I had them softened up for trairiding but this prevented violent bottoming for occasional days at the track.

MORE oil(higher level in the outer chamber) would change how easily it got to that part of the stroke, because of the air volume change and subsequent additional airspring rate from having more oil in the outer chamber. Viscosity of the oil would have little if anything to do with this effect, other than the slightly more initial stiction induced by heavier weight oil.

Bingo.

You may have also noticed that some companies make pistons of various sizes which changes the gap between the piston and the cone, decreasing or increasing the fluid exchange, and therefore the rate of deceleration for the final inches (end of stroke).

By the way, I’ve been looking for who owns the patent on this end-of-stroke hydraulic lock thingy. If anyone knows, let me know.

And just for laughs, when I went looking for this, I found that the guy who invented and holds the patent on the inverted fork (yes, all inverted forks) lives in Los Altos (Bay Area, CA.).

We should go knock on his door.

[SC_Spode]

It's not Steve Simons, is it?

Whomever, we should give him a good smack on the head. ?

They should have been licensed for SX only.

[DaveJ]

It's not Steve Simons, is it?

Whomever, we should give him a good smack on the head. ?

They should have been licensed for SX only.

It is!!

What's the story behind that one?

[SC_Spode]

It is!!

What's the story behind that one?

Silly busy today but I'll fill you in on what little I know when I slow down.

[UpAllNight]

For as weird as this may seem, this is true.

The TCs have an end-of-stroke hydraulic oil lock in which a piston enters a cone that results in a hydraulic push of fluid as the two meet. The thicker the fluid, the longer the process, the greater the resistance.

Now by how much I have no idea.

Good point though.

Very true.... and different fluids do affect the way the forks bottom. I once switched from yamaha's S1 to Yamaha's 01 in the outter chamber only. I used the same volume of oil. The forks bottomed slightly more noticable with the 01 fluid (forks should reach bottom at least once every lap but not be noticable). I didnt think 01 and S1 would be much different but I guess they are.

Not that it matters much, but I have since stuck with S1 for the outter chamber as well as the inner chamber. keeps things simple (and expensive).

[SC_Spode]

Okay, hit a lull (thankfully).

I'm familiar with Steve Simons starting back in the 70's. I had a set of his forks (the yellow RSU ones with the "Simons" sticker on the side) on my 79 YZ250. They, along with the Fox Forx, were considered about the best thing you could do for your front suspension back then.

Mine had the lovely pneumatic seals and were a real pain to change.

Below are some pics of the two forks.

A side note: Simons also produced a kit called the Anti-Cavitator. It had a float that capped a chamber to isolate the oil from the spring to prevent frothing and provide more consistent damping. I had a set in my 83 YZ250 forks.

In 1982, Brad Lackey won the 500 World Championship on his works Suzuki equipped with the then stunning Simons UDX-60 forks. This was the debut of the now ubiquitous USD forks.

Rumor has it that Suzuki was so insulted by Brad insisting on using non-Suzuki forks on his bike that he was dropped form the team right after winning the World Championship.

The forks became available to the public later and were heralded as works equipment for the masses. They provided a rigidity and steering precision not previously available in RSU forks.

However, 25 years later we're still trying to get the bugs worked out of them! ?

They didn't catch on with the Big 4 until 89-90 but KTM had a White Power version in production as early as '84.

I don't remember when, but eventually Simons faded from the MX scene.

Last I heard, Steve Simons was partnered with Paul Turner in a business making MTB suspension named RockShox and getting filthy rich. Since I don't know boo about mountain biking, I'll have to plead ignorant.

This concludes this History Channel Special Feature.

?

[thillsam]

Last I heard, Steve Simons was partnered with Paul Turner in a business making MTB suspension named RockShox and getting filthy rich. Since I don't know boo about mountain biking, I'll have to plead ignorant.

This concludes this History Channel Special Feature.

?

Fascinating report!!!! For those of us still in diapers a the time, it's very hard to find information like this about the past to learn from.

I wonder why the first RockShox were of a conventional design if Simmons was involved in their design?

Also, was there anythign specialu about the damping mechanism inside the inverted forks on Lackey's bike?

When is the next History Channel Special Feature?

[DaveJ]

I think I just had an 80's flashback.

Well...I had no idea you would be coming back with so much detail...and photos no less.

??

Here's another one - all of the Fox guys live down the road from me, of which I didn't even know until I started reading over their patents.

Their shop, when I was growing up, was 5 minutes from my house, (Campbell, CA.). Now it's about 1/2 hour away in Watsonville. I could be running into these guys at the local market and not even know it.

Such a small world.

[SC_Spode]

I wonder why the first RockShox were of a conventional design if Simmons was involved in their design?

If I had to guess, it would be that he learned that the USD design had issues that made the RSU a more desirable configuration for trails.

Also, was there anythign specialu about the damping mechanism inside the inverted forks on Lackey's bike?

I've never been inside a set but they pop up for sale from time to time.

When is the next History Channel Special Feature?

Hopefully not for a while. This episode made me realize just how old I am. Not sure if I can handle another dose of reality real soon.

Dave - I would think Steve's patents have expired on the original USD. Besides, I'm sure the manufacturers found a way around them, even while they were current, to avoid licensing fees.

If you happen to bump into them in the produce section, how about asking them if they've got a set of cherry Forx they could send your Spode buddy for an old project bike he's got and needs to finish?

Tell them it's tax deductible. ?

And I'm glad it's a small world... it works better with my small mind!

?

[KTM-Lew]

it works better with my small mind! ?

A smart ass would call you a pin-head... ?

[SC_Spode]

A smart ass would call you a pin-head... ?

If the shoe fits! ?

BTW, "Your suffering will be legendary, even in Hell".