Tire pressure gauge

[tuba_transport]

I have a Zefel which works ok but it lets a lot of air out of the tire with each use.

I bought a replacement of the same model and the results are totally different between the two. So I thought it was a dud.

I bought another brand. This time digital. It gets even more different readings.

Now I bought my fourth and it too gives different reading than the other three.

Also my Mountain Morph pump gauge gets its own readings along with my Ascent Floor Pump Gauge.

Does ANYONE make a reliable pressure gauge for presta valves which is accurate and well functioning?

And, YES, I have been geeking out with gear lately.

[DaveG]

I have a Zefel which works ok but it lets a lot of air out of the tire with each use.

I bought a replacement of the same model and the results are totally different between the two. So I thought it was a dud.

I bought another brand. This time digital. It gets even more different readings.

Now I bought my fourth and it too gives different reading than the other three.

Also my Mountain Morph pump gauge gets its own readings along with my Ascent Floor Pump Gauge.

Does ANYONE make a reliable pressure gauge for presta valves which is accurate and well functioning?

And, YES, I have been geeking out with gear lately.

I can't answer that but I feel your pain. My various gauges/pumps vary by ~20 psi; verges on useless. I've gone back to the "squeeze it and see how soft it is" approach.

[sourceofdenial]

Bosch makes a super nice one that is unfortunately only available in europe, but its super accurate. Its the official gauge of Belgium National Cyclocross team.

Otherwise, if you really want an accurate gauge, look through autoparts catalogs like Jegs, most have bleed valves and adapters for presta fittings, and you can get different ranges, accurate to 1/2 PSI sometimes. The most common are 0-60PSI in 1 PSI increments. Expect to pay 30-40 bucks though.

[BikerMiker]

Oh no, don't even get me thinking about this!

MY FLOOR PUMP GAUGE IS PERFECT! I SEE NUSSING! I SEE NUSSING!

mike

[sturner]

A gauge is a funny thing. The intention is measure something both precisely and consistently.

However, the problem you describe may not be with the gauge but with the valve on the tube. A presta valve looses a variable amount of air every time you attach or remove a pump or gauge fitting. Therefore, when you pump your tire to 40 psi, pull the pump off of the valve (slight air loss) and reattach the pump (potentially large air loss), you are loosing air but not the same amount every time. This may explain the variance in measurements using the same pump; but, this may not be the only source of error.

When comparing measurement from two or more different pumps, you have the presta valve issue described above but you also have differences in the volume of air that is necessary to "reach" the gauge in the pump. This volume of air varies from one pump to another and thus changes the sensed pressure at the gauge when comparing measurements from one pump to another.

Now, as far as bikes go, you are not necessarily concerned with precise measurement (i.e., how the gauge indication relates to the true pressure in the tire), but you are interested in a consistent measurement. If you can consistently measure the pressure in the tire, you can calibrate yourself to the pressure indication. So, you pump your tire to 40 psi for a couple of rides and you find that the ride is too harsh and you're breaking traction in the lose stuff. So next time you change the pressure to 37psi and the ride is dialed in. You know that the pumps indication of 37 psi is where you ride...you don't really care what the actual pressure is, you just want your ride dialed in. In order to get consistent measurement use the same pump every time and try to minimize air loss when removing the pump from and closing the valve.

Sorry for the nerdy dissertation.

[Dirt]

I use the cheapest Topeak Joe Blow pump. I bought one at REI 8 years ago and it finally died. It still worked fine, but I just couldn't handle Jabberwocky making fun of my baseless floor pump anymore. My self esteem is completely based upon his opinion of me. ;)

But seriously folks...

Short of the old Silca that I had for 20 years, the Joe Blow is the pump that released the least pressure when I removed the head from the stem. It lets loose a small PSST instead of a huge PSSSHHHWWWWWUUUHHH of air.... even when I'm inflating over 140psi. (Side note... I've gone back to running about 125psi in my vittorias even though they're rated to 160. I like the ride better and they actually feel faster. I'm not bouncing around so much.)

As for the accuracy of the gauge... I don't really care if what I'm getting in the tires is actually 125psi. It would be okay with me if it was 130 or 120. What is important to me is that it is relatively consistant. In general, I feel that it is. With my mountain bike tires, I can feel if the pressure is a little low or high. The Joe Blow has consistantly given the same feel at a given pressure.

Since I haven't ridden the mountain bike more than once or twice this year, I can't really say if the new Joe Blow measures the same as the old Joe Blow. I'll let you know when I figure that out.

Hope that helps.

Pete

[walsh]

A gauge is a funny thing. The intention is measure something both precisely and consistently. Sorry for the nerdy dissertation.

If we must be nerdy, then I'm going to have to call you out. In statistics, precision is used to describe a measurement that can be consistently repeated (i.e. measuring the same thing ten times results in ten similar readings.) Accuracy refers to how closely a measurement reflects the actual value being measured, on an absolute scale.

It looks like Sean is dealing with some low-accuracy measurement tools. Though it's frustrating, I agree with you that if he's using the same pump each ride, precision is the real concern.

People who own torque wrenches and spoke tensiometers, however, better be concerned about precision AND accuracy.

[sturner]

If we must be nerdy, then I'm going to have to call you out. In statistics, precision is used to describe a measurement that can be consistently repeated (i.e. measuring the same thing ten times results in ten similar readings.) Accuracy refers to how closely a measurement reflects the actual value being measured, on an absolute scale.

It looks like Sean is dealing with some low-accuracy measurement tools. Though it's frustrating, I agree with you that if he's using the same pump each ride, precision is the real concern.

People who own torque wrenches and spoke tensiometers, however, better be concerned about precision AND accuracy.

I guess terminology varies by your area of expertise. I would actually call the two terms validity and reliability but I thought measurement theory might be esoteric.

[walsh]

...but I thought measurement theory might be esoteric.

:D:D

(ten characters)

[philvw]

It lets loose a small PSST instead of a huge PSSSHHHWWWWWUUUHHH of air....

I was under the impression that some pumps (maybe the good ones) have an air chamber under the guage that needs to fill with air pressure and equilize with the tire. So if the pump is 'empty', and you attach the pump, presta valves are held closed with air pressure,which is still not equalized with the chamber. Then you pump (the chamber) to the tire pressure, where the presta valve opens when equal w/tire, and then pump up the chamber/tire to the desired pressure. Then you pop off the connection, whereas the presta valve (instantly) slams closed (which it is designed to do) leaving the tire at the advertised pressure, and the PSSSHHHWWWWWUUUHHH !! is the air running BACKWARDS out of the pump chamber out the hose. I've never worried about the PSSSHHHWWWWWUUUHHH of air from the pump.

[Squirrel Girl]

If we must be nerdy, then Oh, please, please, PLEASE may I correct the typos in this thread!?!?!?!?!?! They're driving me NUTS!

[philvw]

PLEASE may I correct

By all means, feel free. Make sure to highlight in red when you do.

[silly_yak]

Get some of these...

http://www.accu-pressure.com/cgi-bin/Store/index.cgi?cart_id=5491557.94045&pid=3

Gregg

[walsh]

Oh, please, please, PLEASE may I correct the typos in this thread!?!?!?!?!?! They're driving me NUTS!

Knock yourself out. In my little world, "grammar" is an elderly female relative.

Sorry to offend your sensibilities. The internet must be a cruel place for you.

[Squirrel Girl]

Knock yourself out. In my little world, "grammar" is an elderly female relative.

Sorry to offend your sensibilities. The internet must be a cruel place for you.I hadn't noticed any typos that *you* made. And yes, sometimes the internet can be a miserable place.

It's not my fault. My mother did this to me. I handed her a copy of my dissertation, and the first thing she said was, "Did you realize you misspelled 'acknowledgements'?" That was in the day before Microsoft underlined your misspelled words (not to mention self-corrected them).

[Squirrel Girl]

As for the accuracy of the gauge... I don't really care if what I'm getting in the tires is actually 125psi. "Squeeze my tire??????"

[Squirrel Girl]

Sorry to offend your sensibilities. The internet must be a cruel place for you."Disk breaks"? I think I'm going to die today.