Stable Plaform

[S.]

oohhh... i get it now.... i was talking about sag.... i ment that it won't sag as much (ie compress as much?)....

but yeah... sag ain't adjusted by preloading the springs***according to the 5th element tuning guide***

Well that's bullshit, you might also adjust it by doing something else, but what else does preload do? It barely makes any difference to the overall spring rate (maybe 1% or something) before it starts inducing a movement threshold and stuffing up your rate. More preload = less sag.

 

[S.]

Yeah, my explaination is how it happens not why it happens. Low speed compressions is still low speed compression wether you use air or oil.

I didn't think they used the air for damping tho, which is what the oil does...

 

[shmity]

Air is a good spring, but not a good damper since it compresses, hence its not part of the damping system but part of the 'stable platform'.

 

[S.]

That's what I was thinking... but I don't own one so I'm not sure.

 

[shmity]

You dont really need one to understand that, look at air shocks, the air is the spring, then look at hydro brakes, they use oil because it doesn't compress.

 

[S.]

haha but look at some XC forks... air damping.

 

[nicklouse]

yep air is used to set the threshhold (sp) at which the shock starts moving. they really could have used a knob and used that to vary the threshhold but the shock would have been a lot bigger! using air allowed for a compact design and an easy way to set the threshhold point!

 

[nicklouse]

air can be used but the valving is smaller and needs to be more accurate hence more cost.

 

[MUNGUS]

on manitou swinger shocks, all of your sag should be adjusted by your preload, not your air pressure. if it is the other way around then your shock is set up wrong.

airpressure in ur shocks makes it harder for the spv valve to open up when compressed hence making the oil flow past the valve be harder or easier acording to airpressure. due to this, it is possible for the airpressure to have a bearing on ur sag because if you are running more airpressure then initially it is going to take more force to open the valve and oil to start flowing. this is the whole idea behind spv. so by having the shock set up correctly, you can still have a proper amount of sag which will be set by ur preload yet you will be able to achieve pedaling stability through ur air pressure. this stability effects how active ur shock will be to small and low speed compressions and due to this i don't like to run it on every track. if it is too stable the shock can start to become inactive over small bumps and that can affect ur bikes ability to keep the rear wheel planted on the ground which is what we all want. as well as the valve there is the low speed compression dial which does much the same thing. the other advantage of the air pressure is that the bottom out resistance of the shock can be adjusted. for racing i prefer mine almost all the way out but if freeriding you might like it quite a way in. theis resistance is very noticeable and can stop you fulling using the stroke of the shock if it is wound in too much when your not doing hucks. there is also the high speed compression dial which partners with the bottom out resistance dial to adjust how much and when the shock ramps up. and finaly there is the rebound which is the same as any other shock, no explanation needed.

this is how the spv shocks work as best of my knowledge and i hope it has helped clarify anything that you were unsure about.

 

[naz]

well put mungus, still think fox terralogic 'inertia' valving is easier to understand and would work well on dh if they tweaked it, the inertia valve is a brass clylinder on a spring and the damping elemen is in a tube goin through the middle wit a hole at the top, so when forks are unweighted the brass cyclinder is being pushed up by the spring bein locked out, and when u push down on the forks the inertia of the brass cyclinder wants it to move up thus still locked out elimininating any rider induced bob, but the minute a bump from the bottom of the forks comes thru, the brass cyclinder moves down openin the damping circuit.
hehe,
so any shock from underneath opens the damping and any from above(rider) keeps it locked out

 

[nicklouse]

simliar principle to a good old SU carb. (well similar not exactly but i think any petrol head will see the similarities).

 

[dillon]

Oh no the SU ! noooooooo........
My friend has been stuffing around with one and has finally admitted defeat to me and will go EFI on his Fiat 850 turbo.

(those bloody minis cause us trouble on the track Mate of a mate built some with Suzuki 1300 DOHC's.

 

[S.]

well put mungus, still think fox terralogic 'inertia' valving is easier to understand and would work well on dh if they tweaked it, the inertia valve is a brass clylinder on a spring and the damping elemen is in a tube goin through the middle wit a hole at the top, so when forks are unweighted the brass cyclinder is being pushed up by the spring bein locked out, and when u push down on the forks the inertia of the brass cyclinder wants it to move up thus still locked out elimininating any rider induced bob, but the minute a bump from the bottom of the forks comes thru, the brass cyclinder moves down openin the damping circuit.
hehe,
so any shock from underneath opens the damping and any from above(rider) keeps it locked out

The only problem with that is that it can and will lock out midair.... so that 40ft road gap is suddenly to a rigid landing

 

[Rik]

Gravity-affected damping is a bad thing IMO. I say it to customers and I beleive it, I want my bike to work no matter what the orientation of my suspension.

Fair enough for trail riding it isn't as huge an issue, but if I wanna ride upside down, i want my suspension to work :lol:

 

[naz]

it will lock out but the minute it touches the earth the damping will open up coz the inertia valve will kick in
it isnt gravity damping, its inertia, I. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.
so when a bump comes from below the the fork leg moves up wards the brass mass will remain in the same position but the internals will move upwards allowing the damping circuit to kick in once again hehe.

 

[naz]

hey i just made a flash animation to explain terralogic hope it helps
http://www.geocities.com/naz5210/inertia.html

 

[shmity]

now see, im a fan of mechanical as opposed to themro fluid solutions. I-drives cause me to jizz repeatedly in my pantyloons.

 

[MUNGUS]

yeah i still don't like the idea of that intertia thing. if i decide i want to force down on my forks to pump into something i want them to work, not to lock out.

even with ur flash thing, i'm struggling to get my head around how the downward force is different from a force from the bottom. as long as the fork compresses then isn't the compression rod going to ove as well which would mean the brass mass would move and therefore boycotting the whole idea??

i just can't see how it could work and work well.

i don't think spv or this inertia thing has a plce in forks at all, leave it to the rear shock. i want my forks fully active all the time. a bit of bob isn't going to do anything really

 

[naz]

its has notin to do wit compressin the fork, but the whole fork if it suddenly moves up the inertia of the brass mass does not move but teh fork moves around it, if u wanted to pump somethin just lift then pop the fork itll open the dampng

 

[S.]

now see, im a fan of mechanical as opposed to themro fluid solutions. I-drives cause me to jizz repeatedly in my pantyloons.

Same, cept I'm not much of an i-drive person.