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06 KYB's
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Posted by: bedell99---------------------

I was looking over yamaha's 06 info on the dirtrider.com site and was looking over the pic of the new 06 fork. Notice it is more like a showa TC with the spring on the bottom. I also was wondering what exactly is speed sensitive damping compared to position damping. I though7 all pistons are setup for speed. the faster you try to push oil thru piston the more damping effect you have. Have I been wrong all these years.

http://dirtrider.com/tests/motocros...0506_yamaha_06/

Erik

Posted by: WhiPit---------------------

Intersting, for sure. It does look a lot like the Showa set-up, but the pic only shows a small part of the fork. "Speed Sensitive"?.....Can't wait to check it out.

Personally, I think the Ti shock spring is retarded (forgive me for not being politically correct with that comment). What's the suspension shop to do when they have to tell a customer, "Well sir....since you weigh 225 pounds, we recommend "such-and-such" rate for your '06 YZF. Sorry you have to toss that nice Ti spring and put on a steel one to get the correct rate......or, if you'd like, we'll sell you a Ti spring in the correct rate - for $400.00". OUCH!

The 50th Anniversary bikes look nice, but an extra $200.00?? Did One Industries have a bunch of left over Hurricane kits, or what?

Posted by: bedell99---------------------

Whipit if your a flywait or heavy weight you have to ditch that nice new titanium spring, but look at the bright side, think how much they can get for it on the internet from early model year YZ owners.It can probably be enough for there new springs.

I also can see a greater benefit with moving the springs to the bottom and getting rid of all the plastic parts. It increases the amount of oil in the fork. The 05's had very limted(only 250cc) of oil in the fork. I also wonder if they preloaded the ICS, similar to what the aftermarket tuners where doing.

Erik

Posted by: marcusgunby---------------------

Its a interesting idea-i wish i knew/understood more on how they achieve it.

Posted by: KTM-Lew---------------------

I suspect as usual the magazines have screwed this up. The forks are likely "position-sensitive" INSTEAD of speed sensitive. All cartridge forks are SPEED sensitive that is what the shims provide.

I spoke with Juha Saliman's(sp?) mechanic at the last GNCC and he indicated the 52mm WP they were using are a twin-chamber but different than any other out their. It has aluminum lower tubes! He said they felt like "something was broken" when you first took off as they had absolutely NO stiction and moved thru the first 6" of travel like they had no comp damping. He didn't come out and say they were position-sensitive but that was what I gathered.

It's been quite awhile since NEW technology has been introduced. The Showa's have been around for along time. Great to see things moving along!

Posted by: bedell99---------------------

Hey KTM lew yamah even say they are based on speed, which I always though forks where based on. As for 52mm using aluminum for the lower fork tubes. I wonder what the tube thickness is?? 52mm is huge.

Erik

Posted by: KTM-Lew---------------------

All modern forks are SPEED sensitive to start with. The air-spring is "position sensitive" but not the actually valving. The old Marzocchi Magnums were the last attempt at combining the two theories from what I recall? They had holes/slots in the cartridge and shims on the pistons.

On the 52mm WP he said they were the lightest forks he had ever seen. I wonder if they have ANY steel in them? Maybe titanium springs too? I asked when they would be available and he said he doubted they ever would be for a production bike. The 52mm dia makes them strong enough to not have to be very thick.

Let me re-phrase that. He was as open as he could be without really telling me anything? Does that make sense?

Posted by: KTM-Lew---------------------

Quote:

MXA
Yamaha did away with the Kayaba AOS (air-oil-separate) fork and came up with a new S³ (Speed-Sensitive System) designed 48mm fork. The damping force is controlled by piston speed rather than the position of the fork. The different feel of this type of suspension might seem too soft, initially, but the all-new fork is said to feature better bump-absorbtion and improved comfort.

Yea......this is about screwed-up! They have ALWAYS been speed-sensitive. Guess we will see if they make a correction?

Posted by: steve125---------------------

What Yamaha is trying to say is by getting rid of the 05's big plastic oil lock chamber in the lower leg. That is position sensitive. They now use an upper bleed through under the main spring and spring guide, simular to Showa, that is speed sensitive.

Posted by: marcusgunby---------------------

Steve the spring guide on a rm showas(ie older design) is just a big plastic ring-it wont seal at all-the cr type showa has the proper piston type setup, but i wasnt aware of a bleed setup in it?

Posted by: bedell99---------------------

Is that what they mean by the bleed. I know on my showas what is holding the top of the spring has a bushing on it with some bleed holes. I never knew it actually sealed anything. i though the holes where just so there was an air spring for the bottom of the travel.

Erik

Posted by: steve125---------------------

The new 06 fork is much more simular to a Showa than the 05. Simular, but not the same. Sorry if it read that way.

Yamaha is using this bleed area to create speed sensitive damping. Simular to the RB washer and cartridge check valves from the bladder forks.

Posted by: KTM-Lew---------------------

Speed-sensitive to air flow?

Posted by: steve125---------------------

’05 generates secondary damping from cylinder piston penetrating the plastic TCV located below the spring.

The interaction of piston in plastic cylinder (kind of mild oil lock) makes the secondary damping dependant on the position of the fork.

For example….deep in the stroke damping is high.

’06 secondary damping comes from restricting the flow of oil past the main spring and spring guide, therefore the damping is based on the speed that the fork is compressed; the speed the oil is forced up thru this restriction.

For example….deep in the stroke equal same damping because damping force only increases with speed of fork compressed.

Posted by: WhiPit---------------------

bedell,
I don't think you have to be a flyweight or a heavyweight in order to need a different than stock spring rate. For example, if Yamaha's target rider is 170 pounds, 10 pounds either direction of that is going to need a spring change. That hardly qualifies for flyweight/heavyweight.

You are correct about older model YZ owners. They should be able to pick up these springs for a song off e-bay.

Posted by: Satch0922---------------------

Quote:

Originally Posted by steve125

’05 generates secondary damping from cylinder piston penetrating the plastic TCV located below the spring.

The interaction of piston in plastic cylinder (kind of mild oil lock) makes the secondary damping dependant on the position of the fork.

For example….deep in the stroke damping is high.

’06 secondary damping comes from restricting the flow of oil past the main spring and spring guide, therefore the damping is based on the speed that the fork is compressed; the speed the oil is forced up thru this restriction.

For example….deep in the stroke equal same damping because damping force only increases with speed of fork compressed.

interesting...

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06 KYB's

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