Oaky, I've got a 190/50 DHX 5.0 that doesn't get full travel. It's been pushed, not that I really saw much difference. The sag is okay and with the previous spring, sag was too much. Could I blame this on: -
a) the spring rate
b) the compression damping
c) the bottom out bumper
Even if I take the spring off, I'm only getting 45mm stroke at full squidge because of that bottom out bumper. I'm tempted to remove it or trim it down.
Anyone have any thoughts?
Sounds like there's **** all wrong with it TBH
the bottom out bumper is there for a reason - have you seen just how thin a fully compressed bottom out bumper can get?
What GW said - the last thing you want it a hard metal on metal bottoming out.
To me it looks like the bottom out bumper doesn't really get smaller than half its original height. When I say I'm not getting full travel, I mean I've paid for a 160mm travel bike and getting more like 140. When riding the bike I'm missing full stroke by 7 to 10mm even on the really big hits.
I know I don't want regular hard bottoming but I would like to use all the travel I've got.
The bottom out bumper is there to protect the shock (and you) from damage on really hard hits.
You could trim it down but it may fall apart if you remove too much material, I wouldn't remove it though.
It sounds like it (the bumper) just won't compress fully on anything other than huge compressions.
As long as the shock isn't bottoming with a clunk it sounds like it's ok.
How often are you bottoming it out? If you hucking or similar you may need the compression damping increasing a bit.
Oh and I would trust anyone that describes themselves as a suspension Guru 😉
OMG!!
cut it off then 7mm makes all the difference, especially if it hits hard enough to rattle your fillings loose - well that's what your mum/GF told me 😛 (sorry I was so drunk I can't remember the exact details 😉 )
In which case it could be a) or b) or
c) bent shock shaft (probably not)
d) the design of the shock that means it's hard to get full travel without excessive sag (my DHX air was particularly bad at this)
What bike is it on?
One with a seriously steep rising rate?
The bottom out bumber (rubber washer) is just as a precaution to help prevent heavy bottom out in case you have set up the shock incorrectly, iirc this is set to about 10% of travel.
It could also be that the pressure is too high in the bottom out / compression circuit and or the bottom out adjustment is wound too far in (under the blue knob), this should be set at 70 psi to start with and the blue piggyback dial wound all the way out. Increase the pressure to set the compression damping effect and wind in the the blue bottom out dial to set the required bottom out.
You can test if the shock is good by removing the spring, set the air in the bottom out to 35psi (temp. pressure for the test) and wind out the bottom out adjuster. Fit back to the bike and cyle the suspension by hand, measure the stroke length.
The setup in conjunction with the bottom out stop will have an effect on how good the shock feels.
A DHX coil should get full travel, it's almost certainly the bumper.
The DHX air 'ramps up' quite alot due to the air spring
LoCo, it NEVER gets full travel, even when I run a soft spring on it. I get full travel on the Van 36 forks (medium spring) with an occasional bottom out but not hard enough to feel. However, I've ditched the standard 500 in lb spring that came with it and I'm playing with a 700 that's too soft and an 800 that gives the right sag. I'm tempted to put the 500 back on just to see how much travel I'm not getting then. The push bottom out bumper is taller than the stanard for one but appears softer.
The bottom out adjuster is wopund all the way out. The air pressure is set at minimum and I've got no pro pedal would on. It's on a Turner 6 pack (HL) which is rising rate (very slightly) until a little way into the bumper where it then switches to falling rat (very slightly) for the rest of the stroke.
Konastoner, that was my thinking. If the bumper is there to protect the shock from bad set up and I've got the right spring, is it really needed?
Sorry ok,
33% sag
150psi in piggy back
Bottom out fully out
Propedal fully off
Rebound depends on spring and rebound stack tune.
The air pressure shouldn't be less than 100psi as they have a habit of getting air into the oil if it's too low.
Edit: you posted while I was typing, what did TF recommend when pushed?
Cheers for that LoCo. I've been running 80psi in the piggy back as it says 75 as a minimum and I added a little in case my pump was out (as I didn't want air to bleed past).
I'm setting up with 15mm of sag. Not 33% od the design stroke but it is 33% of the actually stroke I can get with the bottom out bumper in the way.
Sag on that should be 16.5mm for the 50mm stroke. Setup using the full travel of the shock.
Mail me with the year (2005?) and your rider weight if you want me to double check the spring rates for you.
Thanks. I've used both the TFT and the Mojo spring calculators. Mojo says 800 is the nearest and TFT says the 750 is nearest. You're right, it's a late 2005 model. Kitted up, I'm around 200/210 lbs depending on fit.
750 spring for 28% sag
700 spring for 33% sag
Is what I'm getting with 210 lbs rider weight.
Long shot but have you checked the movement on the sus with the shock removed?
Some bikes bottom out on the linkages, some with the tyre on the seatube, not all bikes are setup for the shock to be the limiting factor.
How do you know you're not getting 160mm of travel?
That aside why not fit a medium or soft bump stop. Oh and you're not going to compress the bump stop much by hand as they need to withstand very high loadings.
When I had the 700 lb spring on there, the bike sat far too deep into the strok while riding normally. Felt like I was falling off the back of it. The 800 rides a lot better. The feeling with the 700 was the reason I had the shock pushed.
The linkage is smooth and fine. Serviced not that long ago. The travel is limited by the shock rather than anything else, I've checked that. I know what travel I'm getting because I run a piece of dowel attached with P clips with a ziptie on it and points of interest (sag/max travel/linkage 90 degrees/bumper start). A bit low tech but it does the job.
Attached to what though. How does it measure the 'vertical' travel of the wheel?
attached to the shock eye bolts. I set it up without the spring. Compress the bike to the sag point and mark the dowel, then compress until the bumper just comes into play and mark the dowel, then compress until the linkage is at 90 degrees and mark the dowel and then heave down on the bike with all my might and mark. From these marks, compared to the eye to eye measure mean at each point, I can determine a scale factor for my dowel measuring device. Can't think of a better way of doing it.
(then refit the spring and go ride and see what was achieved via a zip tie pushed down the dowel with the top P clip as the shock compresses (just in case that bit wasn't clear))
So you're not actually measuring the rear travel.
Sounds more like you've convinced yourself you've got a problem that you don't have.
In what way have I not measured the rear travel? I'm measured it static and compared that to both the actual max travel achieved while riding and I can compare that to an extrapolation of the theoretical max travel.
Again, I think you're convincing yourself of a problem you don't have.
What bike is it on? As Tinsy says have you measured things at the back with the shock removed?
It's on a Turner 6 pack and it has been checked with the shock removed. The shock is the limiting factor in both compression and extension and the bushes are smooth and free so as to not be affecting suspension action.