RM125(02) showa midvalve mods, need spacer??

bclapham

LIFETIME SPONSOR
Nov 5, 2001
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i am trying to make the forks on my rm a bit stiffer, they are way soft and i weigh 220lbs!. i thought a good way was bring in the midvalve a bit more into play. Currently, the midvalve is very weak, 4 X 0.1mm shims and no clamp shim!

20.1(2)
17.1(2)

with a lift of 0.2mm.

the problem i have is that there is no room to add more shims! the 6mm (id) X 8mm (od) spacer that seats inside the piston only protrudes 0.6mm from the surface of the piston, so it appears i need another one of these spacer/collars.

any ideas on where to get them?

has anybody messed with the midvalve on these forks?

i know 0.5mm is a good number for midvalve lift, but should i stick with 0.2mm on these forks?

thanks in advance

BC
 

Jeremy Wilkey

Owner, MX-Tech
Jan 28, 2000
1,453
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BC,
Smaller lifts are always better as the rate of valve area growth will not suffer any quick rate changes as speed increases.. (Read inconsistent ) on a 23mm cart., .5 is huge.... In a 32mm cart. that would be closer to good..

Most of the time tuners run more lift to soften the impact of the midvalve, the best idea is to bring it in sooner with less over all influence. (Read high speed damping coefficient contribution.)

I make posts in varying incrmaents to allow easy set-up.. The simple way to adjust subtle flaot values is by inserting 6mm ID 8mm OD .1mm or .2mm shims under the post..

Hope that gives you a few more ideas to grapple with..


BR,
Jer
 

jimt_yz400

LIFETIME SPONSOR
Dec 25, 2000
314
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How about no lift at all and then valving llighter in the mid valve. You may also need to lighten up the BV some since you will have more HSC dampening coefficient, (quoted from JM above).
Would you also need to go ligher on the spings then since the fork would hold the bike up more (no lift/bleed)?
 

georgieboy

Member
Jan 2, 2001
416
0
I read in yr other topic about that you are happy with these forks now.
Will you tell us yr secrets? Just a little
 

Jeremy Wilkey

Owner, MX-Tech
Jan 28, 2000
1,453
0
BC,
I got to thinking about it, you know the final shim on the stack is a 9mm which serves as the pivot even though it does not float on the stack right?

I was not sure you got that by reading your first post.. If you did sorry for the bad assumption.. This style midvalve is what lead me to my best discovery in years, its been quite a RandD nighmare, but its been a fruitful journey..

BR,
Jer
 

bclapham

LIFETIME SPONSOR
Nov 5, 2001
4,340
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jeremy. glad to have you back on the board- i heard you had joined a cult and spent your days sitting in a dark room chanting 'shimmmms', 'shimmms':)

the rm midvalve has been a bit of a journey for me- i was locked into the idea about using more midvalve etc, etc. i went with some taller posts and went with a more tapered stack with about 6-7 shims if i remember and a more classical 10 or 11mm clamp 8mm id shim thats floated. No matter what i did with the passive, the forks were always harsh. in the end, i went back to essentially the stock midvlave and got the forks working real nice with just passive mods. its interesting that the back plate on the rm midvalve measures at ~11.5mm, so if you think of that as the "clamp" shim i suppose you would think of the stack as being stiff, but, since there are only 4 big shims, i think they kind of "cone" rather than bend accross a clamp.

now the yz midvalve, there is a constant source of frustration!
 

Jeremy Wilkey

Owner, MX-Tech
Jan 28, 2000
1,453
0
BC,
You know I never work on many RM's, so my memory is cloudy. Well unfortunaly thats an issue. Some time if you have a chance reduce the pivot dimater.. That was a big problem for the RM.. A 10 or 11 pivot is huge and if you stack some metal in there its going to be harsh..

If you can get your dimater down you can run way less float and still use only a few shims.. You get the best of everything..


BR,
JEr

The monistary of Super Moto has been my dellwing as of late, but I've had a break in the schedule and all the worker bees here MXT are doing part of my day job so I can come play on the boards.. ;)
 
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