Float fluid in air can passing through transfer/neg port on initial part of the travel. No such thing in a ShockPosted 4 years ago
Nitrogen leak yes as then you may get some cavitation in the shock part of the “Shock”
You dont say what type of Fox Shock it is, for instance a triad “Wheezes” when locked out and you hit a bump its the bit that shouldnt pass fluid through passing fluid through.
Takes it apart produces quick drawing, nope cant see one.
Now my early Triad does have a hole between the main air can and the one screwed on to increase the volume but its not a Negative chamber, any air going through the air piston into the “Negative chamber” would cause a lock downPosted 4 years ago
It’s also on the drawing in the top l/h you just posted the external pip at the wiper seal end of the air can, and on page 2 on the top drawing on the centre line.
Interesting you have a Fox breakdown picture too not sure these are available to the public are they? 😉Posted 4 years agorobinlaidlawMember
You can see where it is on the cross section view at the bottom of sheet 2 and from there figure out what it’ll do.Posted 4 years ago
I’m not an expert on shocks but it looks to me like it’ll defeat the seal on the air piston temporarily in the first part of the stroke, which will do two things, equalise the pressure on either side of the piston and since the seal isn’t holding pressure it’ll greatly reduce the seal friction from the largest diameter (and therefore draggiest) seal in the system as the shock starts to move.
But as I say I’m not an expert, I’ve never seen inside a shock before. I’m just an engineer reading a drawing 😉
robinlaidlaw – Member
it looks to me like it’ll defeat the seal on the air piston temporarily in the first part of the stroke, which will do two things, equalise the pressure on either side of the piston
Thanks good answer. But my thinking is sat on the bike 10% sag its way past the seal, so not sure then as to why it would be transferring anything once the initial stroke is madePosted 4 years agokhaniMember
The bleed port equalises the air pressure between the positive and negative air chambers, without it you need an air valve on the negative chamber to pressurise it like some rockshox air shocks used to have,, it’s the little bulge on the air can as said above..Posted 4 years ago
Edit, as Loco said, its either float fluid squelching through the port (ok) or air in the nitrogen charge (not ok) the nitrogen stops the oil from cavitating (foaming) when the damper is working..robinlaidlawMember
It won’t.Posted 4 years ago
Again, this is just me interpreting the drawing, so I could be wrong, but as far as I can see, it’ll only do anything in that very first part of the stroke so it’s purely there to ensure that the pressures on either side of the piston are balanced when the shock is full extended. As soon as the shock is further into the travel the seal will engage and pressurise the air above the piston in the normal way, providing your normal springing. Even when the seal is in line with the port, the difference in the diameters of the seals on the shaft at the left and the body at the right will still make the shock try to extend but as the seal on the body is a bit smaller than the one in the air can it’ll not be extended quite as firmly, which will help the shock to move initially. Immediately after the seal moves past the port you’ll still have some pressure both sides of the piston which will be helping to move the shock and then as it goes deeper into the travel the air above the piston will be compressed, and the air below will expand until it’s not doing anything to help, so the spring rate will ramp up.
So overall, it’s part of a system to tweak the initial break away friction and spring rate progression of the shock.
I’m sure LoCo will correct me if I’m not understanding that right.
As above, the noise might not be that, and I guess if you are getting it deeper into the travel it would suggest it’s nitrogen in the oil and it’s not good.
Only works at the very start of the travel/full stroke/fully extended, when you pump a shock up from flat you’ll usually hear it equalize at about 150 psi when off the bike.
Stops topout clunk and in theory may help with over coming initial stiction.
Have had a few people say the shock are noisey at very start of travel that can be caused by float fluid moving through the port, but with nitrogen in the oil the gas with often sit by the piston and make a sqweltch on the first bit too.Posted 4 years agomarko75Subscriber
Dear shock/forks experts….. looking at this maybe you can help me…. I have a RS recon solo air (silver) which I bought 2nd hand. There is some wheezing when the fork returns from being depressed (no Lithium jokes!) – does this just need a service and new seals?
cheersPosted 4 years ago
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