Rockshox Reba SL - Valve Adaptor Required For Joe Blow Pump?

EViS

I would like to increase the pressure inside my Reba SL forks, however the valve adaptor on my Joe Blow pump is too bulky to fit the schrader valve (the fork body is in the way). Is there an adaptor of some sorts which can go between the pump and the fork's valve?

bails87

No. You can't use a track pump to inflate forks/shocks. You need a shock pump.

EViS

Oh! What is the reason for not being able to use a track pump?

And does anyone have any recommendations for a shock pump? Something which will get the job done in good time and doesn't have to be compact as I can't see myself taking it with me along the trails.

cooldad

Tyres = low pressure, high volume.
Shocks = high pressure, low volume.


Just get a basic one from Halfords or Ebay - around £15.

Jamieg285

Too answer the original question, one of these would probably do what you want

ebay - 90 degree valve extensions

cooldad

But that's a rubbish idea. Fork/shock volumes are very small, and you will never get anywhere near accurate readings with a track pump.
Shock pumps have a valve to release small amounts of pressure as well.

add595

As already said, you need a proper shock pump.

I tried increasing the pressure in my Marzocchi forks using a compressor and a valve extender, lost a good 20 psi just by removing the inflater from the valve!

I bought one of these and can thoroughly recommend it: http://cgi.ebay.co.uk/250871557021

cooldad

Good deal that, decent looking pump.

jon1993

have a look for a shock pump that doesnt let air in/out when screwing the cap on i have a bike hut one and it drops by 10psi every time you put it in, or take it out, it does my head in! so if theres a pump that stops this for the fine tuning of the forks get it haha.

bails87

jon1993 wrote:

have a look for a shock pump that doesnt let air in/out when screwing the cap on i have a bike hut one and it drops by 10psi every time you put it in, or take it out, it does my head in! so if theres a pump that stops this for the fine tuning of the forks get it haha.

Think about it.......

You pump up the forks to, say, 100psi. The air in the pump, in the hose and in the fork is all one 'chamber' of air all at 100psi.

You begin to unscrew the hose from the fork, the valve seals, so the forks are still at 100psi. The pump and hose are still 100psi.

You completely unscrew the valve, any air pressure above the atmospheric pressure (15psi) escapes from the pump and hose, but stays in the forks.

You start to screw the hose back onto the fork. The pump and hosee are now sealed, with the 15psi of air trapped inside them.

You screw the hose on further, the valve is opened, air rushes from the forks to the pump and hose, to equalise the pressue rather than having 15psi in one part of the 'chamber' and 100psi in the other part. You end up with something in between the two, say 90psi.

Then you look and go "oh maaaan, my shock pump's lost 10psi"

cooldad

jon1993 wrote:

have a look for a shock pump that doesnt let air in/out when screwing the cap on i have a bike hut one and it drops by 10psi every time you put it in, or take it out, it does my head in! so if theres a pump that stops this for the fine tuning of the forks get it haha.

They do that when you put them on because the air from the shock pressurises the pump.
The hiss you hear when you remove it is air from the tube, not the shock.
It's normal.

cooldad

I am a very slow typist.

bails87

cooldad wrote:

I am a very slow typist.

But a more concise one!

add595

If you want your forks to be exactly 100 psi, and you lose 10 when removing the valve...

pump them up to 110 :P

cooldad

add595 wrote:

If you want your forks to be exactly 100 psi, and you lose 10 when removing the valve...

pump them up to 110 :P

You don't lose anything when removing the pump.
See concise and long versions above.

bails87

cooldad wrote:

add595 wrote:

If you want your forks to be exactly 100 psi, and you lose 10 when removing the valve...

pump them up to 110 :P

You don't lose anything when removing the pump.
See concise and long versions above.

jon1993

well thats what i have to do and you can feel it in the fork also. Yeh i get what you mean but still annoying when trying to get it precise, adjustment is so fine on air forks.

cooldad

If you have removed the valve how do you know that the pressure has dropped?

bails87

jon1993 wrote:

well thats what i have to do and you can feel it in the fork also. Yeh i get what you mean but still annoying when trying to get it precise, adjustment is so fine on air forks.

The pressure showing on the dial before you start to unscrew the hose is the pressure that's in the forks.

If that's too soft then it's because of your weight and preference, not because the air is escaping....

EViS

bails87 wrote:

jon1993 wrote:

well thats what i have to do and you can feel it in the fork also. Yeh i get what you mean but still annoying when trying to get it precise, adjustment is so fine on air forks.

The pressure showing on the dial before you start to unscrew the hose is the pressure that's in the forks.

If that's too soft then it's because of your weight and preference, not because the air is escaping....

Unless there is a leak :P.

bails87

EViS wrote:

bails87 wrote:

jon1993 wrote:

well thats what i have to do and you can feel it in the fork also. Yeh i get what you mean but still annoying when trying to get it precise, adjustment is so fine on air forks.

The pressure showing on the dial before you start to unscrew the hose is the pressure that's in the forks.

If that's too soft then it's because of your weight and preference, not because the air is escaping....

Unless there is a leak :P.

Well, no, because then the dial would show a lower PSI....

EViS

bails87 wrote:

EViS wrote:

bails87 wrote:

jon1993 wrote:

well thats what i have to do and you can feel it in the fork also. Yeh i get what you mean but still annoying when trying to get it precise, adjustment is so fine on air forks.

The pressure showing on the dial before you start to unscrew the hose is the pressure that's in the forks.

If that's too soft then it's because of your weight and preference, not because the air is escaping....

Unless there is a leak :P.

Well, no, because then the dial would show a lower PSI....

That depends on how slow the air leak is and how quickly you disconnect the pump from the shocks after reaching the intended PSI :P.

bails87

Ok, so pump shows 100psi, leave it for an hour and 30psi has leaked, so showing 70psi. Then disconnect, the forks are at 70psi, as shown on the dial.

EViS

Haha, I'm just messing around mate .

bails87

EViS wrote:

Haha, I'm just messing around mate .

Don't worry, I thought as much!