# shock pump vs regular pump??



## Luckyr (Oct 21, 2012)

Noob question, I've tried searching but didn't see anything that really seemed to explain. What is the difference between a shock pump and a regular pump? I have a Trek Cobia with a RockShox Recon Silver TK 29 w/Solo Air spring and it looks like a regular schrader valve or am I missing something?


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## Zoke2 (Nov 16, 2007)

yes it is a schrader valve, but a tire pump is for high volume and a shock pump is for high pressure ... get a shock pump


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## gmcttr (Oct 7, 2006)

A shock pump makes a seal with the valve stem _before_ it actually opens the valve. This prevents air loss when you remove it. Due to the small volume of the air chamber in forks and shocks, the amount of air loss a normal tire pump would allow would be unacceptable. You may also have a difficult time reaching the pressures required using a tire pump.

Get a shock pump.


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## eatdrinkride (Jun 15, 2005)

In addition to the above mentioned points, a shock pump will also have a bleed off valve that you can use to very slowly bleed off small volumes of air to dial in the shock/fork pressure. Very important in small volume/high pressure applications. Can't be done with tire pump.

Get a shock pump


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## deke505 (Jul 29, 2012)

well the three posters here have summed it up pretty well. You will need a shock pump for a tire pump won't work.

oh yeah get a shock pump:thumbsup:


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## Luckyr (Oct 21, 2012)

This all makes sense. But how big of a priority is it for a noob with a finite budget? Is this a must have or next time somebody has one on clearance?


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## Le Duke (Mar 23, 2009)

Your bike should have come with one.

If not, go into the local shop. I'd be willing to bet they'd either give you one or sell you one for $5-10.

Yes, you need it.

And, the dental bill from doing a header into a rock because your fork compressed wayyyy too much on a descent, because you couldn't be bothered to shell out $10, might be a bit steep.


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## gmcttr (Oct 7, 2006)

Luckyr said:


> ...Is this a must have or next time somebody has one on clearance?


If your fork is close to the correct pressure (something like ~20% sag and doesn't bottom out), it can wait for a short time. A fork should hold it's pressure for a long time. Don't put it off too long or you won't have it when you do need it.

And just in case no one has mentioned it yet...get a shock pump.


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## ansky (Sep 22, 2012)

gmcttr said:


> A shock pump makes a seal with the valve stem _before_ it actually opens the valve. This prevents air loss when you remove it. Due to the small volume of the air chamber in forks and shocks, the amount of air loss a normal tire pump would allow would be unacceptable. You may also have a difficult time reaching the pressures required using a tire pump.
> 
> Get a shock pump.


My fork (g2 revelation) seems to let a bit of air out when I screw my pump on and off. Just a small hiss. Havent actually tried to check it but im not sure it would be accurate anyway if it is indeed releasing pressure.


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## ForrestJones (May 25, 2009)

That hiss is just the air in the pump's hose leaving. Its not from the fork, the schrader valve closes as soon as you unscrew the hose.


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## ansky (Sep 22, 2012)

Makes sense. Thanks.


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## gmcttr (Oct 7, 2006)

ansky said:


> ...Havent actually tried to check it but im not sure it would be accurate anyway if it is indeed releasing pressure.





ForrestJones said:


> That hiss is just the air in the pump's hose leaving. Its not from the fork, the schrader valve closes as soon as you unscrew the hose.


Correct...however, when you screw the hose on again, pressure is lost to refill the hose. This usually is around ~5psi and many people interpret this to mean the pressure was lost when they originally removed the pump and heard the hiss.

To test this, put 100 psi (or your normal amount) in the shock and remove the pump. Now screw the pump back on far enough to seal to the stem but not open the valve, pump it to 100 psi to fill the hose and then screw it on all the way and you should still read 100 psi. Clear as mud? If you screw it all the way on without pressurizing the hose, you will get a lower reading than what you put in before.


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## Art.C (Oct 1, 2012)

The problem is that many beginners like myself have encountered that reconnecting the pump DID in fact prove that pressure was lost while disconnecting even after doing it repeatedly. No, I do not turn it gingerly when disconnecting resulting in unnecessary pressure loss. I am using some RockShox brand pump I bought with my bike and it is not cracked or damaged and there is no bulletin board message out noting it is defective. I have read in many threads that people have had experiences like mine and the response is always 'You're doing it wrong', 'It is broken', 'It is normal, don't worry about it', 'your shock valve is leaky', and "Shock pumps work poorly unless you buy one of the few good ones'. Using a pump with an anti-air loss feature proved that in my case it was just my pump and apparently every other pump I have used until then. It is sort of like the Avid Elixir brakes, they just perform at like 70% of what you would expect even when it is working 100%.

YMMV, IMO, IMHO, IME, etc.

I researched a replacement pump last week and resolved to order this one soon: Amazon.com: Topeak Pocket Shock DXG Bike Pump: Sports & Outdoors

It is a good choice because it has a solid reputation, is not overpriced, and has the all important feature of separating hose pressure from shock pressure prior to disconnecting.

Rock on fellow bikers.


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## eatdrinkride (Jun 15, 2005)

Luckyr said:


> This all makes sense. But how big of a priority is it for a noob with a finite budget? Is this a must have or next time somebody has one on clearance?


Not a MUST have as you can borrow one from a fellow rider or stop by the lbs and ask to borrow one...you might want to ask them to show you how to set up your fork and shock while you are there.

Once you are in the ballpark you can leave it alone if you are happy enough but you'll need your own when you decide you want play with your suspension daily and try to figure out what settings work best for you. It's a process that many folks just love to do and others are a 'set it and forget it' type person who never ever want to mess with it.

It's up to you.


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## zebrahum (Jun 29, 2005)

Art.C said:


> The problem is that many beginners like myself have encountered that reconnecting the pump DID in fact prove that pressure was lost while disconnecting even after doing it repeatedly. No, I do not turn it gingerly when disconnecting resulting in unnecessary pressure loss. I am using some RockShox brand pump I bought with my bike and it is not cracked or damaged and there is no bulletin board message out noting it is defective. I have read in many threads that people have had experiences like mine and the response is always 'You're doing it wrong', 'It is broken', 'It is normal, don't worry about it', 'your shock valve is leaky', and "Shock pumps work poorly unless you buy one of the few good ones'. Using a pump with an anti-air loss feature proved that in my case it was just my pump and apparently every other pump I have used until then. It is sort of like the Avid Elixir brakes, they just perform at like 70% of what you would expect even when it is working 100%.
> 
> YMMV, IMO, IMHO, IME, etc.
> 
> ...


I don't get it.You just described the exact thing that gmcttr went to great lengths to point out. Air doesn't typically get removed from the air chamber of the fork or shock when the hose is removed. Unless the pump is cheap or the fitting is defective, the air that escapes when you have fully pumped up your fork is from the hose.

Now when you reconnect the pump, of course you are going to loose air, the volume of the hose and pump needs to be filled with air and the only place for air to come from before you start pumping is from the fork's air cavity. Thus, the air pressure is reduced when you connect the hose to the fork/shock.

I think what we're all missing is that it doesn't matter if the air pressure goes down when you connect the pump or not. You should write down your air pressure settings and pump to those numbers each time you adjust your air pressure. If you are trying to dial in a different feel, pump the fork to a known pressure (write it down) try it out and adjust from there.

Let's say my fork is at 150 psi and it's feeling pretty stiff: I'm going to attach my shock pump, pump it to 150 psi and give it a quick test to make sure that it feels like I was expecting. Then I'm probably going to work in 5 psi increments to try and get the fork to feel softer; I'll attach the shock pump and adjust the pressure to 145 psi (I'll write it down somewhere so I know what my setting is) then I'll give it a try. If it's too hard still, I'll repeat the process if it's too soft, I'll pump it up to whatever pressure I think is best; the point being that it doesn't matter how much air is lost when the pump is connected it only matters that you know what pressure you're trying to reach.


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## eatdrinkride (Jun 15, 2005)

ART C. Like the others have stated when you reconnect the pump the hose and the pump chamber must fill with air from the shock, thus the pressure reading will be 5psi or so lower than what you pumped it up to before. You are not losing air from the shock.


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