We recently tested 11 big-brand shock pumps in an effort to discover which is best when it comes to adding the right amount of air to your suspension. During our testing, we learned things from industry experts and realized other things from our time checking pressures.
With that, here are five things we learned about shock pumps.
1. There’s not much originality in a pump
So a source tells us that there are basically two manufacturers in Asia producing all the shock pumps for everyone else. Knowing that, the similarities between different brands start to become far clearer – and a different handle here, or gauge there isn’t enough to overcome the clear likenesses.
Some brands don’t even try to hide it. For example, the latest digital shock pumps from Fox and direct competitor RockShox are identical – except for the logo of course.
Others, such as those from Birzman and Topeak, are different in design (but not manufacturer), and so there are still plenty of familiar characteristics.
This isn't to say the most expensive shock pump is the same as the cheapest, but it does mean if one brand looks identical to another – it probably is.
2. The air release is from the pump, not the fork
Some pumps offer a two-stage valve, but is it needed?
Some pumps claim to have special valve heads that isolate attachment and the valve pin engagement; others don’t say much about the fact.
The reality is that just about all shock pumps have a head designed to not release air from the shock’s air chamber when unscrewing the chuck. Yes some are better than others, but they are all pretty close.
You will inevitably hear air escape – this is coming from the chamber and hose of the pump that’s at the same pressure as the air inside your shock. Try it yourself: connect your pump and very slowly release the chuck from the valve, and you’ll hear a sudden air release at a certain point. You won’t get a slow hiss, which would happen if the pin were still engaged.
Therefore, assuming your pump is not faulty, you do not need to ‘overinflate’ the shock to counter for air loss. That said, your shock will lose pressure when attaching your pump, as the pump’s chamber and hose need to fill to pressure.
3. Accuracy and low cost – pick one
Gauge accuracy comes at a cost, and shock pumps are traditionally focused on lower prices and portability. Josh Poertner of Silca told BikeRadar: "People want a portable shock pump, and manufacturers assume that riders only want to buy/own one.
"With small gauges you have two major issues," Poertner added. "First, the internal mechanisms just cannot be as precise. It's like a Swiss watch in there, but made in China for less than a dollar! Also, you have readability issues – with the small gauge faces between the needle width and the line width on the face you can have +/-10psi error purely from printing."
Our inline benchmark gauge was the way we knew what was accurate, and what was not
For our own testing, Brady Kappius of Kappius Components made us a custom inline pressure verified gauge. He offered us the special deal of making this custom model for the usual price of his +/-1% ‘linearity, hysteresis, repeatability’ verified tyre pressure gauges – US$159. However, for double the price he offered one with +/- .5% accuracy, or for approximately five times the price, one with +/- 0.05% accuracy. Clearly, the price of accuracy is not linear.
Poertner agreed, analogising the relationship between accuracy, precision, and cost to throwing darts: accuracy being how close you are to the bullseye (for a gauge, how close is 100psi to 100psi?) while precision is how repeatable your darts are.
"If you're always hitting the 20 but you can tightly cluster your darts you're inaccurate, but precise. Similarly, if you hit left of bullseye, bullseye and right of bullseye, your average accuracy would be good, but your precision would be bad," he said. "For pressure gauges, accuracy is a combination of design and manufacturing of the internals, followed by a careful calibration to make sure that 100 = 100."
But Poertner pointed out that there are numerous moving parts that must also be very carefully constructed to produce precision – and that fixing these issues requires design and manufacturing processes with nonlinear cost/benefit relationships.
With that, see our next point.
4. Gauge accuracy doesn’t matter so much, but repeatability (precision) certainly does
So gauge accuracy comes at a significant cost, but the good news is that repeatability is more important for you. With this, if you use the same shock pump every time, then it doesn’t matter if 100 on your gauge is 100 by lab standards, but rather what it does say for your suspension. Of course, the risk is that repeatability is also costly and it’s tough to know if your pump is precise in this regard.
Now the toughest situation is that over time your pump is likely to degrade in its accuracy and repeatability – and that leads to further challenges.
Gauge accuracy can save setup time, but the correct suspension sag is all that matters in the end
However, always remember that it’s the sag that you’re setting your suspension to, and the gauge is merely a tool to help aid this – either way, the desired outcome can still be achieved without a gauge.
5. Durability is a factor
Shock pumps get abused. If they’re not stuffed into a dirty backpack, they’re linked to a shock and injected with air seal oil. Sadly, that old pump is likely letting you down in the accuracy stakes.
In our testing, we found the older, much-used pumps to be the most inaccurate – sometimes off by as much as 15 percent. Poertner has found similar results, seeing some pumps off by as much as 40psi at 250psi.
So what’s the answer? Well, if you can, buy one pump you don’t mind stuffing into your hydration pack, and then keep one in the workshop for your careful tuning.
All gauges, including digital ones are susceptible to accuracy drift
Poertner provides the following advice: "Remember, all gauges, including digital, are subject to damage from shock, vibration and moisture, so keep your reference protected, clean, dry, and so on. All pressure gauges are [also] sensitive to fatigue, even the digital ones which use the deflection of a small membrane to determine pressure. After a few hundred cycles you'll begin to lose accuracy in all of them due to the fatigue of the deformable components. We recommend replacing every three to five years for most users and our pro team users replace annually."
So there you go.