Just finished a post about rear shock air pressure and someone mentioned that bicycle pumps could cause permenant damage; could someone tell me how so. Last thing I want to do is ruin a set of shocks out of ignorance. Thanks

 

Well, now I'm interested too.

I tried pumping mine up last week with a bike pump to save a few bucks on the harley pump. It seemed to work ok.

 

There are 2 related problems.

The first is that you're dealing with a very small volume system. Therefore even a bicycle pump can overpressure the shocks fairly easily. The damage comes because the weak link in the system is the seals in the shocks. If you damage them, they aren't serviceable.

Second is that the Harley pump (or any suspension pump), is what's called a "zero-loss" pump. The flexible tube acts as a pressure chamber, and the fitting is specially designed to allow the Schrader valve to close, before it breaks the connection. This way the gauge reading is exactly what remains in the system when you disconnect the pump. A bicycle pump loses air when you disconnect the hose from the valve. The low volume of the suspension means this amount of loss will have a significant effect on the pressure remaining in the shocks.

Harris
Denver, CO

www.youtube.com/conedown

 

YUP! What he said. Get the Harley pump or one of the similar shock pumps on the market. The Harley pump is small with a small chamber and does not pump nearly the amount of air into the shocks that something with a larger pump chamber, like a bicycle pump, would. The zero loss feature is a must for adjusting the shocks.

 

There's nothing magical about using a bicycle pump that can cause damage. It depends on how much air you put into the shocks.

The small HD hand pump is very handy and you can carry it with you.

 

As long as you don't go over the required pressure you are ok...bicycle pumps displace more volume of air not more pressure.

 

I use a metal shock pump I grabbed from my son. He used it on his mountain bike. It is as described wrt #2 above. It also does not push a lot of volume and has a gauge on it. The pump also is serviceable. Never a problem.

 

Do to the cost of new shocks far out wieghts the cost of the pump I have the HD air pump. Its also good for checking tire pressures as the hose gets overand around things in the way when checking the rear tire. And no you can't pump air into the tires with it.....you don't have that long to live!!

 

If your careful with a bicycle tire pump you probably won't blow the seals. The volume of air in the shocks is not much so it might only take 1 stroke (I haven't tried). Then you will loose air when you remove the hose from the valve stem. Use a gauge to check the pressure and you will loose a little more.
A bicycle shock pump will work fine and is very similar to the Harley pump (in design and in price).

 

Even with the Harley pump i noticed one good pump goes a long ways, i'd have to go and look but it pumps about 10-15 lbs into my shocks with each full compression. After i saw it move so high i started only pumping a quarter or half to get it were i need it for solo or dual riders. I'm not ready to pay to upgrade my shocks yet!