Rockshox does not rebound

[Martin PJ]

I have a problem with a Rock Shox 120 mm on a 26 er. This shock has been serviced three times, most recently three months ago. The age of the shock is around 8 years, it looks in good condition. It was ridden by myself for three years, then the past five years been on various bikes that are not ridden much. In that time it was couriered twice to Cape Town and a service done there by the agents.

 

The problem is that one to two months after the service is complete, the shock does not rebound after it warms up a bit. By warming up I mean riding for 20 minutes or so. If you ride down any hill, the shock will slowly sink to the bottom and does not rebound at all. If you stop and take all the pressure off the shock, then it does rebound.

 

At the moment my wife is riding the bike and is pretty soft on the bike. I have attached a pic of the shock in its normal riding state. The shock will sit like this the entire ride with about 2 cm of travel showing.

 

I am ready to try one last mechanical intervention before I toss the shock into the bin. Are there any suggestions?

[Capricorn]

which model fork is that? 

[igg]

Single or dual air? If single, pull the bolt on the bottom of the left leg and press the valve in there. If the fork springs back to it's original position it means the air chambers aren't working correctly.

 

You've possibly got air moving past the piston from the positive to the negative chamber, thus "equalising" at the bottom of the travel instead of the normal position. There's a venturi valve notched on the inside of the stanchion where the piston would normally sit at rest (toward the top of the travel); this allows air to equalise between the 2 chambers in normal operation.

 

Possible causes: scratches on the inside of the stanchion, worn gaskets/washers, excess grease buildup.

Edited April 2, 2016 by cairbre

[BaGearA]

Easiest (not cheapest) wil be to put in a single-air damper asembly then it wil run on only 1 air chamber , like most forks of today, it wil also give the fork a new feel

 

This wil probably cost quite a bit (not ridiculous ) but expect about R900

 

But Then the fork should go strong for another 4-6 years 

[Martin PJ]

The only markings on the shock are SL, I think it is Tora SL 120 mm, model is 2006 or 2007. The shock is single air.

 

To service the shock is R500 to R600, so the R900 conversion sounds like a good option.

[igg]

Both Rockshox solo and dual air have 2 chambers (positive/negative spring). The designs are not interchangeable.

 

Solo air has 1 fill valve and a valve on the inside of the stanchion. This lets air travel past the piston to equalise pressure at the top of the travel.

 

Dual air has 2 fill valves and the negative/positive chambers can be set to individual pressures.

[BaGearA]

Both Rockshox solo and dual air have 2 chambers (positive/negative spring). The designs are not interchangeable.

 

Solo air has 1 fill valve and a valve on the inside of the stanchion. This lets air travel past the piston to equalise pressure at the top of the travel.

 

Dual air has 2 fill valves and the negative/positive chambers can be set to individual pressures.

I know That (and probably should have said aswell) but i was just pointing out that the single air assembly could solve the problems he has been having.

[Martin PJ]

I know That (and probably should have said aswell) but i was just pointing out that the single air assembly could solve the problems he has been having.

 

I understand then that it is already one air chamber as there is only one point to pump the shock up to required pressure.

Edited April 2, 2016 by martinpe

[igg]

I know That (and probably should have said aswell) but i was just pointing out that the single air assembly could solve the problems he has been having.

Fair enough.

 

I'd first try releasing the pressure in the negative chamber and seeing if it springs back to it's normal position, as it sounds like an air leak to me.

 

Either way, a service will be required on top of whatever is done to fix. I'd start by replacing all the rubber washers, as it's a lot cheaper than a replacement air spring. That said, if the air spring shaft is scratched and the source of an air leak, replacement is the only way to go.

 

Then there's the possibility that it's actually the damper rod that's getting stuck, which negates all of the above .

[droo]

That's the old solo air spring, and what I'm guessing is happening is that the fork dives into its travel under a very light load.

 

If so, you've got a problem with the valve on the piston head which is a pretty common problem with this design, and unfortunately very difficult to fix short of sourcing a replacement air spring.

 

I'd suggest having a chat to Calvin or Enzo at CCS, they should be able to help you. If you don't come right, PM me and I'll see what I can do.

 

Edit: What model is it? I'll need the exact description to know which version of the spring is in there.

Edited April 4, 2016 by droo

[droo]

I know That (and probably should have said aswell) but i was just pointing out that the single air assembly could solve the problems he has been having.

 

As Cairbre said, the two systems are not interchangeable. To fit the new solo air spring you'd need to replace the CSU as well.

 

It might be possible to fit a dual air spring, but the configuration needed will depend on what model of fork it is.

[Martin PJ]

The model is Tora SL.

 

That's the old solo air spring, and what I'm guessing is happening is that the fork dives into its travel under a very light load.

 

If so, you've got a problem with the valve on the piston head which is a pretty common problem with this design, and unfortunately very difficult to fix short of sourcing a replacement air spring.

 

I'd suggest having a chat to Calvin or Enzo at CCS, they should be able to help you. If you don't come right, PM me and I'll see what I can do.

 

Edit: What model is it? I'll need the exact description to know which version of the spring is in there.

 

The shock is Tora SL. I checked again. What other details do you need?

[droo]

The issue is almost certainly a broken or missing wave spring on the air piston. Get your LBS to give the agents a shout and speak to the guys in the workshop - if the service was done 3 months ago they should repair at no charge.

[Martin PJ]

Some feedback on the shock problem. Took it to my LBS mechanic as a last resort, told him if he cannot see anything obviously wrong, then bin it. He found there was an o-ring seal missing. This was after the shock had been serviced three times by various parties.

[FCH]

always the smallest component causing the most issues!