Jim’s Tech Talk
By Jim Langley
This week’s technical topic is in response to a reader named Paul’s question. He read our review of the Silca Pista floor pump, which has a bleed valve built into the chuck… (a pressure release button). He asked,
“Just to clarify, in regards to the Presta bleed valve on the Pista’s pump head, if I was to say, pump my tires to 120 psi, could I used the bleed valve to lower the pressure to 100 psi without having to remove the chuck? Or does the bleed valve only remove the extra air from within the hose so you can remove the chuck easily? As I have a habit of over Inflating – so being able to reduce the psi in the tires without removing the chuck would be a huge win for me.”
Different Strokes (as in pump strokes) For Different Folks
That’s a great question, Paul because modern road bikes run the gamut from full-on race-ready rockets requiring higher pressures to spirited steeds that serve double-duty seamlessly pounding the pavement and grinding the gravel on tires run at much lower pressures.
Getting the pressure right is key for top riding performance and flat resistance. And, especially when you run low pressures, such as for venturing off road, a few psi can make the difference between excellent control and traction versus bottoming out and possibly bending a rim – or with tubeless tires, rolling them so far that air escapes (called “burping”).
Bleed and Air-release Features
Now, back to Paul’s question. The Silca Pista’s bleed valve (the small black button in the photo) is only for releasing the pressure inside the pump head so that it’s easier to remove the pump head from the valve (under pressure its grip is quite strong). It does not let you fine-tune the pressure inside the tire.
In order for a pump bleed mechanism (also called an air release valve), to let air out of the tire, it must hold the valve open so that air can escape. Most road bicycles have Presta valves. The tip of Presta valves must be held down in order to allow air to release.
Some pump heads do this and some, such as the Pista pump do not. Another favorite pump of mine, the Pedro’s Super Prestige does keep Presta valves open so its bleed valve works the way Paul wants. It’s the small silver button under the lever in the second photo. Pressing the button lets you easily drop as much or as little air as you like. The needle on the gauge lets you watch and stop at the exact pressure desired.
To learn more about both these pumps, see our reviews here:
Do Your Due Diligence When Pump Shopping
If you’re hunting for a new floor pump and you want this bleed feature to work the way Paul does and not just to make the head easier to remove, you may need to call the company’s customer service to make sure – or visit a bike shop to inspect the pump in person.
I recommend this because looking at many pumps online that have bleed/air release buttons from Lezyne, Topeak, Specialized, etc. I couldn’t find any that clearly state their purpose in the online description, specs or videos.
A Gauge That Lets You Release Air
In searching for pumps, I also found an accessory for dialing in tire pressure. I haven’t tried it. Topeak’s Smartgauge D2 has a feature for releasing air that looks promising. Using a separate gauge in conjunction with a floor pump with a built-in gauge would be helpful for double checking tire pressures, too.
A final tip for those who enjoy mixing road and dirt on rides: If you carry a mini-pump with an accurate gauge you can head out with say, 55 psi in your fat tubeless tires for the tarmac and when you hit the dirt, use your gauge to drop the pressure to maybe 24 psi for max traction, control and comfort. Without a gauge, you’ll have to wing it.
For this, I especially like my Silca Tattico Bluetooth mini, which I reviewed recently. It works in conjunction with an iPhone app, giving you the largest, brightest gauge you will ever see. I know it sounds a little overcomplicated, but the performance, accuracy, convenience and wow factor have won me over. If you try one I think you’ll be impressed, too.
Ride total: 9,101
Jim Langley is RBR’s Technical Editor. He has been a pro mechanic and cycling writer for more than 40 years. He’s the author of Your Home Bicycle Workshop in the RBR eBookstore. Check out his “cycling aficionado” website at http://www.jimlangley.net, his Q&A blog and updates at Twitter. Jim’s streak of consecutive cycling days has reached more than 8,000. Click to read Jim’s full bio.