00' CR250 tips?

[Jeff Howe]

Pete Payne,

What is it that holds the midvalve against the piston face? Is it the same spring that would hold the checkplate up?

How much force would it take to overcome that spring? Very little. The midvalve is nothing but a check plate at low velocities. It does nothing until you have a larger amount of fluid being forced over it. There is plenty of gap there to allow an almost unrestricted flow. Therefore, at lower displacements and velocity a distorted midvalve has little impact towards poor performance. Where the distortion really causes problems is on the rebound stroke. Instead of blocking off the flow the distorted shim will allow fluid to bleed past it resulting in a nearly uncontrollable rebound. At velocity or displacement levels where the midvalve would be doing it's job it WOULD be weaker, yes. But on the compression stroke this would be no worse than just having a standard checkplate installed. The most negative result of a blown(distorted) midvalve is poor rebound performance. So, in my opinion the result of this harshness has nothing to do with the midvalve. Harshness is probably in the valve stack, spring rate, oil level or any combination of these things.

So tell me, did you install Gold Valves and the necessary valving changes at the same time you removed the midvalve as per RT recommended instructions? Probably, since your an RT Dealer. So how would you know if it was the removal of the midvalve that gave your bike a better ride?

Maybe it was the Gold Valve? But, the 23mm Showa piston is almost an exact twin, in respect to flow rate, to a Type 1 Gold valve isn't it? Replacing that Showa piston with a Type 1 Gold Valve has ZERO advantage in terms of the piston itself. That would leave us with the valving. It IS possible that the RT recommended valving made your improvement. It is also possible that you could put a RT shim stack on the stock Showa piston and have it work equally well. Midvalve or not. Midvalve is mainly affected by larger swept volumes. Low velocity and low displacement levels are not a problem area with midvalves. Removing a midvalve is like taking away from your bottoming resistance. To gain that back you have to build your valving firmer. That could possibly make your ride harsh. Whoever came up with the midvalve idea did well in my opinion. I used to believe, like you, what we were taught. But, then I started to really think about it and changed my mind. Midvalves began to appear in like 95 I think. If they were the result of a poor performing fork do you suppose the OE suspension engineers would have figuured that out by now and took them out of production? I mean if they were really that bad of a thing they would be long gone by now. Think about that for one minute. If they were the sole cause or even a common denominator of 90% of all fork problems do you really think they would continue on with them? I doubt it.

 

[Pete Payne]

Shock Nut,
Yes I did install the RT valving and a Type 2 piston at the same time. But, I have also installed the Gold Valve Type 1&2 with the stock mid valve valving. The ride was harsh, Tryed to compensate with the base valve valving, it made a difference but still not good. I have also lightened up the mid valve valving and yes it did help. But I went back to the original RT recomended valving at the base valve and installed the RT check plate with no midvalve , and this works great. I have excellent botomming resistance and ride. What do you recommend?

 

[Shrimp on the barbie Jer]

Well I see this one is not going anywhere. I'll just say that the mid-valve is not the problem, or maybe the mid-valve valving is.. But it's not that it needs to be softer at least interms of "low-speed" mid-valving.. I'm tired and have a RoadRace test in the am so I'll move allong.. The mid-valves first apeared in 92CR forks.. Not that it matters..

Jer

 

[Jeff Howe]

I recommend you stick with whatever makes you smile Pete. I am glad to see there is a RT guy out there that is an advocate of the T2 piston. I feel it's the best one they have and overall a decent design. Last I heard though it was unavailable for the 50mm Showa shock. Did they make one for that app yet?

 

[JTT]

Originally posted by Shocknut:
Pete Payne,

What is it that holds the midvalve against the piston face? Is it the same spring that would hold the checkplate up?

How much force would it take to overcome that spring? Very little. The midvalve is nothing but a check plate at low velocities. It does nothing until you have a larger amount of fluid being forced over it.

Shocknut, I am trying to understand, but I am not very familiar with it. Let me understand...the valve stack is held against the piston by the spring. The spring takes little resistance to overcome. If this is true, then I can't see how the valve stack can effect much if the spring has allowed it to lift from the piston, meaning the oil is flowing freely past valving? Sounds like the midvalve would only effect "low velocity" flows, before it is lifted and rendered ineffective?

HELP! I am confused

 

[marcusgunby]

You are right in saying at low flow it has little affect but this is a mid valve that sees all fork movements low and high speed so under mid to high speeds the midvalve opens fully but only will allow a certain flow without restriction so as speed goes up resistance also does at this point the shims come into play and start to deflect.They will deflect so far depending on how fast the fork goes through the stroke.What you want is the base valve controlling low to mid speed and the mid valve to take the strain when the base valve is at its limit.Its asking alot of the base valve to controll all speeds.It can do it but not as effectively as when working with the midvalve.

 

[JTT]

Marcus, please forgive me for being dense, but what you are saying is that the midvalve shim stack has NO effect (ie; shims do not deflect and play a role in damping) while seated against piston (low speed situation, before higher forces, caused by piston speed, deflects spring, and lifts stack), but DOES deflect (and therefore effect damping) when suspended above piston?

 

[marcusgunby]

No not really, the shims will lift with almost no force just like a std plate would, as the spring is really soft.But then as speed increases the oil really start to try to go straight through the shims(which it cant )so it has to go around them as the gap between the shims and the piston is small it is forced to go through the gap.So as the oil goes through the small gap it starts to bend the edges of the shims.This is when the shim stack starts to do its job.At very low speeds the spring on the shims act like its just an closed or open bleed circuit.Hope this helps.Its alot easier if you can see/show the parts in front of you.

 

[Pete Payne]

Originally posted by Shrimp on the barbie Jer:
Well I see this one is not going anywhere. I'll just say that the mid-valve is not the problem, or maybe the mid-valve valving is.. But it's not that it needs to be softer at least interms of "low-speed" mid-valving.. I'm tired and have a RoadRace test in the am so I'll move allong.. The mid-valves first apeared in 92CR forks.. Not that it matters..

Jer

Jer,
I am not saying that the mid valve is all bad but there is more than one way to get to a good ride.When you have more time I would like to hear what you think more in depth. Remember that if there was only one way to do it , it would not be fun and if the manufacturers made it 100% awesome for everybody ( as if they could ) then the guys like you ,shocknut , race tech ,me and etc.would have to do somethung boring for a living.

 

[Pete Payne]

Originally posted by Shocknut:
I recommend you stick with whatever makes you smile Pete. I am glad to see there is a RT guy out there that is an advocate of the T2 piston. I feel it's the best one they have and overall a decent design. Last I heard though it was unavailable for the 50mm Showa shock. Did they make one for that app yet?

Shocknut,
No RT does not have a T2 50mm valve yet but I imagine that it will be available in the near future.As you know time and testing reveal what realy works. If it doesn't work in the real world it is no good.

 

[Jeff Howe]

I find that odd that they would not have that available for the 50mm yet. The 46 T2 has been out for what, 3 years now? Maybe more? If it works in the 46 it should work in the 50 I would think. Oh well......