Reba problem

Chunkers1980

I've got RS Reba SL 2008 100mm version.

They only travel 45mm atm

-/+ air pressure removed from each and at different times. Travel max remains 45mm

I think the poploc does not work either as it makes no difference even if you adjust the internal floodgate and manually change the external with your hand.

Something is up interally right, could anything have fallen off and be stopping full travel as it just bottoms out at no more than 45mm and does not seem to travel enough on the stanction which with no -ive air measures 45mm of travel, 70ish mm above that to the top with the whole lot measuring 110mm.

What can be wrong, as it seems serious...

nicklouse

dual air?

looked in the FAQs?

the answer is there.

stumpyjon

And another one bites the dust

Sorry, classic symptoms (well described too) of seal failure in the damper leg, quite common on REBAs, not fatal and fairly easy to fix. More detail here.

Last time it happened to mine I didn't even replace the seals, just cleaned and refilled the damping circuit with oil. Been alright for the last six months. I've got into the habit of storing them with the lockout on, not sure whether that has made any difference though.

Chunkers1980

Cheers Stumpyjon and Nick

Looked at TF tuned. cost approx £120 with posting
LBS RS dealer service aprox £80
DIY approx £50 - simply not worth it.

So - sent them back to Merlin £6 postage and got this back - YAY!

We have received your forks back from Rockshox, on this occasion they have inspected and serviced under warranty and we will return to you today.

I have enclosed a sheet of their Service intervals to ensure your forks are covered under warranty agreement going forward.

Now that's a result considering they only cost £224 new.

nickfrog

I was about to post something along those lines as I only get 80mm of travel out of 100mm BUT my poploc works perfectly. Yes I am sure I have a 100mm.

However, after emptying both neg and pos springs, I inflate the positive no problem, but if I inflate the negative to the same level, then remove the pump, then immediately replug it, it's already down by half so I am not sure if the neg is keeping air or not, as the fork seem to behave the same way.

Funnily enough, i have had the same problem on my 99 SID : it's impossible to ever know how much air is in the negative spring.

Is my problem the same problem as above?

Are Fox any better ?

Is air a stupid idea for a spring despite the weight benefit ?

bails87

Is air a stupid idea for a spring despite the weight benefit ?

No

However, after emptying both neg and pos springs, I inflate the positive no problem, but if I inflate the negative to the same level, then remove the pump, then immediately replug it, it's already down by half so I am not sure if the neg is keeping air or not, as the fork seem to behave the same way.

Think about it....
When the dial on the pump reads 100psi, that includes any air in the pump and the connector hose, as well as the negative chamber. (The negative chamber is very small btw)
When you start to unscrew the hose from the valve, the valve shuts before the seal breaks, so you have the chamber with 100psi in, and the pump and hose with 100psi in. When the hose is fully disconnected, the pressure in the hose and pump escapes, but you still have 100psi in the negative chamber.

When you reattach the pump, some of the air that was at 100psi in the chamber 'escapes' into the pump and hose. So you have whatever amount of air is needed to give 100psi in the chamber, now filling the chamber, the pump and the hose.

Which means the pressure drops, as the air is occupying a larger volume.

Chunkers1980

Yes but he makes it out to be losing half its pressure... That is not the release amount of air that'll escape. I only allow about 5psi for that. Don't forget though, at the top end (160psi) you put any more than that in you are pushing the seals to their limit.

supersonic

It is much more than 5psi when I reconnect.

The seals can take upto 280psi.

nickfrog

bails87. What you say makes total sense so thanks a lot for that. It's only taken me 11 years to understand something so obvious!!!
I am now confident neg pressure is correct and I am gonna leave the fork alone, no matter how much travel I have and I'll look at it again in 2015 I think.

richg1979

the neg air chamber can loose up to 50% of its pressure by attaching a shock pump as the chamber is so small . ie you can loose up to 100psi by reattaching a shock pump twice

i alwasy empty boths chambers then blow up + chamber until you get correct sag then blow up the - chamber to what ever you put in the + chamber minus 10psi, anymore in the negative chamber and its starts sucking travel.

bike-a-swan

that's interesting- I tend to whack both chambers up to the same pressure, at the point I previously had the +, then check the sag and tweak as necessary. I'll then fine adjust with the -, but always seem to come back to the - a good 10psi over the +. Must be personal taste I suppose.

stumpyjon

I personally prefer a bit more in the negative chamber to make them plusher over the small hits, but then my REBAs are on my hardtail which I'm more likely to be riding XC on.

The Northern Monkey

can't wait to set up the rev's.. sounds like its gonna be fun..... noooottttt!

stumpyjon

It's easy, pump up chamber one, pump up chamber two, forget to note down pressures, go ride and never worry about them again despite the fact that they're really badly set up. It's what the rest of us do

Chunkers1980

supersonic wrote:

It is much more than 5psi when I reconnect.

The seals can take upto 280psi.

Must have misunderstood something here.

We're not talking air loss from month to month. I was saying the difference between when you pump them up and then re-check immediatly. Air in the pump tube and the hiss of lost air.

Yes I suppose seals will take more. But if you run it at 160psi and compress the chamber to 50% of its size then the seals wil be on 320psi. Anything above the 160 will just add to this.

supersonic

I still lose 50psi!

Max rating appears to be 220psi.

Chunkers1980

You must have a big hose..... oh and chamber with a lot of hiss. Best say away from you.

bails87

Chunkers1980 wrote:

You must have a big hose..

Get yer coat SS, you've pulled!

nickfrog
Set up the fork, note the pressure, detach the hose and then reattach. Note the air loss.
Pump it back up to your desired pressure, detach the hose and leave/use for a week or 2.

Then reconnect the pump and see if the airloss from this reconnect matches the first. If it does, or it's at least close, then you don't have a problem.

richg1979

bike-a-swan wrote:

that's interesting- I tend to whack both chambers up to the same pressure, at the point I previously had the +, then check the sag and tweak as necessary. I'll then fine adjust with the -, but always seem to come back to the - a good 10psi over the +. Must be personal taste I suppose.

it is personal taste but more neg pressure results in a lot of travel loss, even 10psi more neg pressure will drop my revs and rebas travel down 20-25% and your original sag setting has gone out the window, but does give a very smooth ride but will bottom more easyly.

Chunkers1980

Just got them back from Merlin, am stoked.

Noticed they've now fitted an External floodgate (rather than the allen key internal) that I sent them off with.

Any reasons for this anyone know of? Just a more modern and reliable system? The only one they had to hand in the workshop?

Any ideas? It's much better in my book.

Is it now not an SL but effectivly a Race as that's the only difference?