DHX 5.0 no compression damping? Suggestions please.

[kebarb]

After winter storage i had the following problems with my shock:

I have a 3" DHX 5.0 Shock on my Stab Supreme DH.

Springrate is 250lbs
Rider weight is 60kg, or 132lbs.
Stroke is 8"

The problem is that i can bottom the shock by just
holding the handlebar and jerking it backwards fast
and hard. (as if i am going into manual)

I started out 50psi in the boostvalve, raised to 150psi
and then 200psi no difference.

Bottom out is all the way out and propedal also. I want
a linear stroke and no propedal. Working the Bottomout
all the way in makes no difference, same problem.

Rebound damping works well.

Is there something rong with my shock? And what could
be wrong?

The only thing i could possibly have done wrong is to ride
with low boostvalve pressure, what problems might this
create?

thankful for help.

[dhkid]

have you gained weight over the winter? doing a manual wouldn't give the high shaft speed for the compression to be effective. it would come down tot spring rate. whats you sag on the bike?

[kebarb]

have you gained weight over the winter? doing a manual wouldn't give the high shaft speed for the compression to be effective. it would come down tot spring rate. whats you sag on the bike?

Actually i lost weight during winter but i went from 350 to 250 coil due to the lack of travel.

I used to have 17% sag with 350lbs coil, and i now have 30% sag with 250lbs coil. It matches up good in the TF tuned spring calc.

What i mean when i write "as if goging into manual" is that i am pulling the handlebar really hard and leaning backward to produce stress on the shock. Doing so i smacks right through, the stress is similar to a small drop say 40cm.

Turning the preload wont do any difference. I dont know if the shock acutually lacks compression in high speed.

Also i noticed that adding air in the boost valve reduces SAG, when i set it to 200psi i have about 20% SAG.

[dhkid]

screw in your boost valve a bit. it might just be that your bike design requires some bottom out resistance.
and of course you cant expect your bike to feel the same with 17% sag and 30% sag.

[kebarb]

screw in your boost valve a bit. it might just be that your bike design requires some bottom out resistance.
and of course you cant expect your bike to feel the same with 17% sag and 30% sag.

Same problem with the boostvalve all way in. I dont even notice any difference when adding air and turning the boostvalve.

[dhkid]

hmm.. maybe your shox has air in it... does the rebound adjustments still work? and is there a sucking sound towards the end of the stroke?

[Jensen]

you sir need a rebuild. mine had the same characteristics for about 6 or 7 rides, and the rebound worked fine leading me to believe it was breaking in or something? then my rebound started to go, and eventually neither work.

[dhkid]

^^ thats air in your shox for sure.

[kebarb]

thank you guys for all the answers.

Now i have a few more questions as you all seem to know.

What part is it that brakes or fails when riding with to low pressure in the boostvalve?

I did this with my swinger and the SPV failed, i just made a rebuild of the whole shock incl. SPV valve and then it was all good. Oil came into the SPV valve.

But what happens in the FOX shock?

Also i want to know what chemical the workshop uses for cleaning the shock when they dismantle it? I think they have some kind of solution in wich they leave the shock to dissolve all the dirt.

I will make an attempt on rebuilding this baby myself, guess it it is 7.5wt oil inside?

[kebarb]

hmm.. maybe your shox has air in it... does the rebound adjustments still work? and is there a sucking sound towards the end of the stroke?

No sucking sound, but the rebound works very well. If i dial it all the way in it is actually very very slow on the way back.

[dhkid]

if you want to take it apart your self, follow this thread (http://www.ridemonkey.com/forums/showthread.php?t=163201&highlight=dhx), has step by step instructions.... but do be careful, if you are not confident in doing it, send it to a fox service centre. and you do realise that this would void your fox warranty... not that it means much tho.


with 5ths if you run the pressure too low it would just blow the main seal... which is just an o ring on the main shaft.

i would presume a dhx would do the same.

oil went into the spv valve? i dont get that.. i think you mean the floating piston...

just use some alcohol to clean your shox. the contact cleaner that you get in spray cans it just alcohol....

the shox uses 10wt RSF (rear shox fluid). the stuff fox use is torco. but i have used silkolene and its great stuff. some ppl have used normall fork oil but its not recommended as its viscosity changes more drastically when compared to rsf at higher temperatures, resulting in loss of damping.

[dhkid]

No sucking sound, but the rebound works very well. If i dial it all the way in it is actually very very slow on the way back.

the reservoir of your shox is mounted on the top right? if so you could take it off the bike, take the spring off and hold it so that the reservoir is at the lowest point. if there is air in your shox there will be sucking sounds.

if there isn't then i dont know whats wrong with your shox.:poster_oops:

[kebarb]

if you want to take it apart your self, follow this thread (http://www.ridemonkey.com/forums/showthread.php?t=163201&highlight=dhx), has step by step instructions....

the shox uses 10wt RSF (rear shox fluid). the stuff fox use is torco. but i have used sikoline and its great stuff. some ppl have used normall fork oil but its not recommended as its viscosity changes more drastically when compared to rsf at higher temperatures, resulting in loss of damping.

My FOX service guy said to use 7.5wt, and now i also remember that different year/model har diefferent oil. Wich one has 7.5 and wich one has 10?

In my swinger i just put Motorex shock oil, 5wt and that works great.

[dhkid]

funny you say that, my friend who is a fox service guy uses 10wt. but also according to the guy senior to him the 05 dhx used 7.5wt then the new ones 10wt. but they just use 10wt for all dhx shoxs.

i use 7.5 wt in mine and there was not a drastic change rebound speed... it was just much smoother, cant feel the pp clicking now.

[SPINTECK]

I had the same problem, which I self inflicted by letting too much air out of the shock. I took it to the Fox tent at a national and the tech guy said you need to run at least 75PSI in that thing or you blow oil past some seal. The only fix was to have the fox guy rebuild it and put the proper amount of air in it. They did it for free at the national, but I tipped the guy $20- he saved me a huge head ache. Those guys are great.

[kebarb]

I had the same problem, which I self inflicted by letting too much air out of the shock. I took it to the Fox tent at a national and the tech guy said you need to run at least 75PSI in that thing or you blow oil past some seal. The only fix was to have the fox guy rebuild it and put the proper amount of air in it. They did it for free at the national, but I tipped the guy $20- he saved me a huge head ache. Those guys are great.

This sounds interesting, i really want to know what seal this is and where i should look for oil. Anyone knows about this?

[dhkid]

pretty much the two places where there is oil seals. on the main shaft and on the ipf. if there is no oil leaking out of the shox then the only other place it can go is the ipf.

[Dirtbike]

if there is no oil leaking out of the shox then the only other place it can go is the ipf.

Close.. oil tends to not go past the IFP, its the air that can be sucked past and into the damping oil

This sounds interesting, i really want to know what seal this is and where i should look for oil. Anyone knows about this?
You would not notice oil leaking out of your shock. When there is air in your oil, you get huge inconsistencies in damping performance. Usually you notice that your rebound is very fast, but then clunks, especially under a high speed shaft movement.