2 stage mid valve, yay or nay?

[moto_psycho]

Hi all, I can't find any posts or anything in the racetech suspension Bible. What are the benefits of a 2 stage mid valve over a single stage? I'm guessing you get to stay up in the stroke on the low speed, but a bit more movement on high speed hits??

Edited October 1, 2019 by moto_psycho

[motrock93b]

You might want to check out Dave J’s (Smart Performance) midvalve modifications. They aren’t two stage, but offer digressive damping along the lines of the valid logic you’re pursuing. Friends have used his suspension and not one has anything but praise.

[turbo dan]

I like a single stage comp stack on the mid for MX.  Tuning the stack with a cross over seems redundant when the float has a much greater effect.  In my experience a two stage comp stack makes the low speed unnecessarily firm while still coming up short on damping for big hits.  If you pull the cross over and open up the float by that .1mm you have plusher low speed and the same high speed damping.  If you pull the cross over and close the float back up to where it was you have the same low speed and more high speed damping.

As far as keeping the fork up in the stroke I think between the spring rate and the base valve you should have it covered.

[numroe]

Hi all, I can't find any posts or anything in the racetech suspension Bible. What are the benefits of a 2 stage mid valve over a single stage? I'm guessing you get to stay up in the stroke on the low speed, but a bit more movement on high speed hits??

Interested in more opinions, but I say nay. A progressive stack goes against what I find works well in a mid. Eg.

Float tuned for enough low speed movement and desired speed/timing of when the medium speed damping ramps up.

Stack tuned for the desired medium speed linear damping.

Maximum valve open tuned for the amount of VHS damping.

But probably there are different bikes/riders/terrain or valve designs where a progressive mid shim stack is great.

[moto_psycho]

I think maybe to put it simpler, it would give the feeling of whatever your float is for low speed/ride height, then on bigger his it would give the equivalent of float+crossover size minus whatever damping is added by the crossover diameter.

I'm trying to create a nice compromise between enduro and Mx

[numroe]

1 hour ago, moto_psycho said:

I think maybe to put it simpler, it would give the feeling of whatever your float is for low speed/ride height, then on bigger his it would give the equivalent of float+crossover size minus whatever damping is added by the crossover diameter.

Yes and that's why I wouldn't like it.  Not enough travel when wanted at very low stroke speeds, then too much blow through when we hit big+sharp bumps. If blowing through a weak mid valve, then we either feel the base comp damping ramp up late (mid stroke harshness), or if the base comp damping is too soft, then even bigger issues.  

[GDI70]

Funny, i just did a setup that previously had a two-stage mv. The face shims were distorted significantly. It was a low-float, two stage mv config. The complaints registered were; too soft, and poor bottoming of the forks. The base was soft as well. This was in a '15 yz250. 

I use single-stage mids. With std components in the KYB SSS. 

[mlatour]

1 hour ago, GDI70 said:

Funny, i just did a setup that previously had a two-stage mv. The face shims were distorted significantly. It was a low-float, two stage mv config. The complaints registered were; too soft, and poor bottoming of the forks. The base was soft as well. This was in a '15 yz250. 

I use single-stage mids. With std components in the KYB SSS. 

 

Curious as to what were the before / after float measurements?

I'm trying to firm up some bottoming resistance a tiny bit but already have a relatively high oil volume.

Edited October 2, 2019 by mlatour

[turbo dan]

2 minutes ago, mlatour said:

 

Curious as to what were the before / after float measurements?

I'm trying to firm up some bottoming resistance a tiny bit but already have a relatively high oil volume.

Stack some shims above the clamp to limit max shim deflection. 

[MxGringo]

 
Curious as to what were the before / after float measurements?
I'm trying to firm up some bottoming resistance a tiny bit but already have a relatively high oil volume.

On my 2015 yz250 I run one less faceshim on mid comp with std float and rebound.
310 cc of oil and works spring seat to help with bottoming. Base is std except for a lighter bleed stack.
I'm pretty happy with this set up. Wish I tried different spring seats earlier in my experiments.

[GDI70]

20 hours ago, mlatour said:

 

Curious as to what were the before / after float measurements?

I'm trying to firm up some bottoming resistance a tiny bit but already have a relatively high oil volume.

The measured two-stage was .2. I shimmed for .25, and stiffened base valve also. The bleed stack was lighter than stock, but still there. The rider was on .46kg springs, and ran 325cc. The rider weighs 70kg

[mxaniac]

On 10/2/2019 at 8:30 AM, GDI70 said:

Funny, i just did a setup that previously had a two-stage mv. The face shims were distorted significantly. It was a low-float, two stage mv config. The complaints registered were; too soft, and poor bottoming of the forks. The base was soft as well. This was in a '15 yz250. 

I use single-stage mids. With std components in the KYB SSS. 

I'd be interesting in hearing your opinion on how much lift, or how tall of a clamp you can go before a stop, without face shim distortion.  Minimum number of face shims too, as this is where the discussion has lead on my AER stack thread.

[robw122]

On 10/1/2019 at 5:15 PM, moto_psycho said:

I think maybe to put it simpler, it would give the feeling of whatever your float is for low speed/ride height, then on bigger his it would give the equivalent of float+crossover size minus whatever damping is added by the crossover diameter.

I'm trying to create a nice compromise between enduro and Mx

http://www.ridejbi.com/jbi-pro-perch-2-0/

[GDI70]

19 hours ago, mxaniac said:

I'd be interesting in hearing your opinion on how much lift, or how tall of a clamp you can go before a stop, without face shim distortion.  Minimum number of face shims too, as this is where the discussion has lead on my AER stack thread.

The min amount of face shims i use is 2, but that is with a tight taper to a 12. It was older mod on showa/kyb. For the most part 3 min on two smokers, and 4 on four strokes.