Midvalve starting points

[bclapham]

russ, i think that thread had the pistons off my 01 forks

john: i used a 1.5mm X 27mm X 11mm washer and a couple of 27.1's at the back of the stack to set the lift.

dbrace: those tracks sound a lot like the ones here in socal, many are hard pack SX style 2 and 3rd gear tracks. the only one i ride that isnt is glen helen, but its so rough there it takes a brave man to get the bike opened up in 4th there!

 

[JohnScott]

Bruce,

Are you removing the cupped washer or laying the 27mm dia shim against it? I'm guessing it looks like this:

cupped washer
collar
spring
27X1.5 washer
(2) 27X.1 shims
mv stack
mv
rebound stack

So I assume that during compression, the stack lifts and the 27X1.5 presses against the rim of the cupped washer. Am I right?

John

 

[russ17]

Bruce

I was looking at it yesterday it was a 2-piece piston it was under the midvalve thread

 

[bclapham]

john: yep thats exactly how it worked.:thumb:

russ: thanks, ill check it out!

 

[JohnScott]

Thanks Bruce! I'll have to give it a try the next time I have the forks apart.

John

 

[marcusgunby]

To lessen lift i look for a cheapo washer of the right i/d and a thickness of about 0.5mm then i can stack 2 to get 1mm or add a shim or 2 to reduce lift in 0.1mm increments.To use shims as spacers gets expensive.

 

[dbrace]

The std midvalve collar is 5.9mm long. To get .5mm lift i replaced the std collar with a shorter one that i had been using for sx. I then put some .25x11 shims under it untill i had the desired lift. The std midvalve setup also has a .15mm low speed bleed. By this i mean that the 3.1x27mm shims do not sit against the piston face. This is the std midvalve:
.1x16
.4x20
3.1x27
.1x24
.1x20
.1x16
3.3x14
.4x25
collar
2.25x11

 

[marcusgunby]

pretty crap shim stack IMO.The 20.4 is there to stop the shims overbending-may as well have fitted a checkplate;)

 

[steve125]

Carefull there Marcus! in a few weeks you may just become a bit fond of check plates :p :worship:  

 

[James]

The the lift on my Showas is .2 using Bruce's method. I don't think I need to tinker with that part yet. I might need to acquire the correct shims to stiffen the midvalve if my latest basevalve changes don't solve the problem. I guess I could also try reducing the lift another .05-.10mm. I think I have plenty of room to soften the basevalve if necessary.

I am still fascinated and puzzled by the size of the basevalve stack as compared to the midvalve stack considering the amount of fluid that flows through each. Just when I think I am grasping everything, I think of a new angle.

Fun stuff.

 

[dbrace]

I rode today with my new midvalve setting. The forks rode higher in the stroke which felt really good, especially when jumping into downhill braking bumps. I thought for sure that i would do one lap and be back into the pits to revalve the basevalve but the forks were not as hard as i thought they would be. I think it is because of that low speed bleed. I will try again without the .1x16 shim as i think this will make the forks stiffer allowing me to reduce the base valve valving.

 

[JTT]

James, remember the midvalve is "active" and sees lots of volume, but the base valve sees much greater pressures....that's why it needs to be much heavier.

As Marcus elluded earlier, the amount of change you can make at the BV is rather surprising, at least it was to me. Don't be afraid to go "radical" as you may be surprised with the results. I recently tried a new stack in my Showas...thinking I went WAY over the top and the bike may not even be ridable....well surprise! It was closer to the direction I was looking than anything I have done yet.