Accuracy of pumps

[Polar]

Not many talks about how accurate a pumps or gauge is and according to Cycplus their pumps are within +-1 psi which I don't believe is correct since I get 3 psi different readings on a Cycplus AS2 pro pump and Topeak D2 gauge.
Which one is most accurate?

 

[Paulquattro]

Unless you have the gauges tested and calibrated you wont know exactly .

 

[steve_sordy]

I agree with @Paulquattro , but if I had to put money on it, I'd go with the Topeak D2.

However, the important thing is not how accurate the gauge is but how consistent it is. The D2 is very consistent in my 20-years experience. I spend quite a bit of time getting the tyre pressures that work well for me. Once I have them, I record them and use my D2 to check and set before every ride. If I'm going somewhere markedly different or with trail conditions different, then I may alter the tyre pressures by a psi or two. Because I always use the D2, I don't have to worry about its accuracy.

I use the same gauge to measure and set tyre pressures on my car as well. The gauges found at petrol stations and companies that fit your tyres appear to vary enormously, so I always overfill and then correct with the D2.

 

[Polar]

Unless you have the gauges tested and calibrated you wont know exactly .

How can both be tested and calibrated?

 

[irie]

However, the important thing is not how accurate the gauge is but how consistent it is.

Agree. We always use the same pump (Topeak JoeBlow Mountain Floor pump) with the indicated pressures that we know work best for us in the conditions we ride in (UK South Downs) with the tyres we have (Maxxis High Roller 3 DD front, DH rear) on our bikes (blinged 2022 Trek Rail 5's). Indicated front 23psi, rear 25psi but don't know neither do we care what the 'true' pressures might be.

 

[RustyIron]

How can both be tested and calibrated?

It doesn't matter. It's an exercise in futility. The gauges most of us use are imported trash, and there's nothing you can do to change that.

Over the years, I've accumulated a variety of gauges, both analog and digital. Digital gauges can vary with battery charge. Analog gauges are made of parts stamped from junk material. Both are susceptible to accumulated contamination from microscopic droplets of sealant. I've found that most start giving grossly erroneous results after six months or a year.

A while back I decided to "calibrate" my gauges. I found a couple that were in agreement at the pressure that I run my tires. I assumed that those were more likely to be correct. I set the other gauges to show the same reading as the "correct" gauges. On some, the "zero" was off, but that doesn't really matter for what I was doing.

Despite putting in a lot of effort on calibration, consistency didn't improve. Over time, the readings on the gauges changed again. Needless to say, I was disappointed.

My current setup is to set the pressure using the gauge on my Joeblow Mountain pump. The pressures I like are 26/23 on THAT pump. Maybe the actual pressures are different, but it doesn't matter as long as I can fill my tires to the way I like them. This pump is just over two years old, and the pressures still seem consistent. If the gauge starts getting weird, I'll eventually be able to feel it on the trail.

 

[Polar]

Agree. We always use the same pump (Topeak JoeBlow Mountain Floor pump) with the indicated pressures that we know work best for us in the conditions we ride in (UK South Downs) with the tyres we have (Maxxis High Roller 3 DD front, DH rear) on our bikes (blinged 2022 Trek Rail 5's). Indicated front 23psi, rear 25psi but don't know neither do we care what the 'true' pressures might be.

It doesn't matter. It's an exercise in futility. The gauges most of us use are imported trash, and there's nothing you can do to change that.

Over the years, I've accumulated a variety of gauges, both analog and digital. Digital gauges can vary with battery charge. Analog gauges are made of parts stamped from junk material. Both are susceptible to accumulated contamination from microscopic droplets of sealant. I've found that most start giving grossly erroneous results after six months or a year.

A while back I decided to "calibrate" my gauges. I found a couple that were in agreement at the pressure that I run my tires. I assumed that those were more likely to be correct. I set the other gauges to show the same reading as the "correct" gauges. On some, the "zero" was off, but that doesn't really matter for what I was doing.

Despite putting in a lot of effort on calibration, consistency didn't improve. Over time, the readings on the gauges changed again. Needless to say, I was disappointed.

My current setup is to set the pressure using the gauge on my Joeblow Mountain pump. The pressures I like are 26/23 on THAT pump. Maybe the actual pressures are different, but it doesn't matter as long as I can fill my tires to the way I like them. This pump is just over two years old, and the pressures still seem consistent. If the gauge starts getting weird, I'll eventually be able to feel it on the trail.

It's like other products not all can be trash, some better than worst but as far as I have understood it's best to use the same gauge every time to get the most precise measurements.

Anyway I'm satisfied with the D2 and now just jumped on the Cycplus hype but kept my $10 pump in reserve so I got a open return.

 

[irie]

It's like other products not all can be trash, some better than worst but as far as I have understood it's best to use the same gauge every time to get the most precise measurements.

Are you sure about that?

 

[Jackware]

It's like other products not all can be trash, some better than worst but as far as I have understood it's best to use the same gauge every time to get the most CONSISTENT measurements.

FIFY

 

[Polar]

Are you sure about that?

I'm never sure about anything

 

[Paulquattro]

How can both be tested and calibrated?

There are company's around that will do this in the UK but not sure about your home turf where they are
Google would be a good start

PS . It probably wont be cheap .

Search Results: Gauge Page 1 | Calibration House

Whatever you are looking for, you should be able to find it on our site using our search feature. If not, contact us, we are always happy to help.

www.calibrationhouse.com

Pressure Calibration | Vacuum Equipment Calibration | Gauge Calibration

We offer Pressure and Vacuum Equipment Calibration. Accredited calibration of all types of pressure devices including pressure gauges, vacuum gauges, manometers, barometers and more.

www.calibrate.co.uk

 

[Type1]

The actual number isn't necessarily that important, its more the consistency of the figure. It gives you a datum point to start from and tune from there.

 

[Stihldog]

My bike cave shop compressor is hardwired to a barometric weather sensor and a vacuum container for automatic and accurate calibration with nanometer sensitivity ..…Whoa! Sry bout that, just woke up. No coffee yet.

My regular method of psi testing on my tires is the pinch test using the index finger and thumb. I do this before each ride, or sometimes during a ride if I feel something weird. If I’m switching between road and trail I will use a gage.…but mostly for trail. 22-26 psi. I’ll drop the psi lower (12-16 psi) for snow conditions.

CushCore helps, and the fact that I hate loosing psi. A soap and water spray formula helps me find the source and I do everything in my power to solve that.

I’ve only had two punctures and two burps on the eMTB. I now carry a C02 cartridge and adapter only because I’m close enough to home.

 

[Overkillit]

My bike cave shop compressor is hardwired to a barometric weather sensor and a vacuum container for automatic and accurate calibration with nanometer sensitivity ..…Whoa! Sry bout that, just woke up. No coffee yet.

My regular method of psi testing on my tires is the pinch test using the index finger and thumb. I do this before each ride, or sometimes during a ride if I feel something weird. If I’m switching between road and trail I will use a gage.…but mostly for trail. 22-26 psi. I’ll drop the psi lower (12-16 psi) for snow conditions.

CushCore helps, and the fact that I hate loosing psi. A soap and water spray formula helps me find the source and I do everything in my power to solve that.

I’ve only had two punctures and two burps on the eMTB. I now carry a C02 cartridge and adapter only because I’m close enough to home.

I've been waiting for someone to say something along the lines of the feel test. I typically push down on the tire from the top with my palm as a feel test. Not recommending this to the OP since accuracy sounds like a priority but it gets me close enough.

 

[Polar]

My bike cave shop compressor is hardwired to a barometric weather sensor and a vacuum container for automatic and accurate calibration with nanometer sensitivity ..…Whoa! Sry bout that, just woke up. No coffee yet.

My regular method of psi testing on my tires is the pinch test using the index finger and thumb. I do this before each ride, or sometimes during a ride if I feel something weird. If I’m switching between road and trail I will use a gage.…but mostly for trail. 22-26 psi. I’ll drop the psi lower (12-16 psi) for snow conditions.

CushCore helps, and the fact that I hate loosing psi. A soap and water spray formula helps me find the source and I do everything in my power to solve that.

I’ve only had two punctures and two burps on the eMTB. I now carry a C02 cartridge and adapter only because I’m close enough to home.

CO2 cartridge is outdated and bad for the environment.
Anyway what l have learned today is to always use the same gauge therefore I will from today only carry AS2 pro and leave D2 at home.

Coffee won't do it you need a Napoli style ristretto.

 

[Stihldog]

CO2 cartridge is outdated and bad for the environment.

True…but it’s lighter than my hand pump.

I've been waiting for someone to say something along the lines of the feel test.

I must be in a rush to get outta the cave. We must be sensitive souls to have metacarpal accuracy (+\- 4 psi).

 

[Arminius]

Nobody here that is using the RGDM? Maybe this a local thing worth to share. To be most accurate for setting up the tires it does not help to have pressure to the psi in your tires as your RTRW (ready to ride weight) and TRTFF (temperature related tire flex factor) can never been taken accurately into account. To eliminate this some guys apply the RGDM: Rim-Ground-Distance Measurement! For finding a starting point for measurements you first pump your tires to recommended psi. It is very helpfull to have a smartphone at hand for taking video of the 6 o’clock wheel position while getting on/off your bike. From there simply increase or decrease value to find your sweet spot. Doesn’t take long, gives excellent result and saves you some stretching exercises before you go.

 

[Stihldog]

Nobody here that is using the RGDM? Maybe this a local thing worth to share. To be most accurate for setting up the tires it does not help to have pressure to the psi in your tires as your RTRW (ready to ride weight) and TRTFF (temperature related tire flex factor) can never been taken accurately into account. To eliminate this some guys apply the RGDM: Rim-Ground-Distance Measurement! For finding a starting point for measurements you first pump your tires to recommended psi. It is very helpfull to have a smartphone at hand for taking video of the 6 o’clock wheel position while getting on/off your bike. From there simply increase or decrease value to find your sweet spot. Doesn’t take long, gives excellent result and saves you some stretching exercises before you go.

That’s a lot of Mathing …but as long as it’s perfect that’s close enough.

Good tips

 

[RebornRider]

I have a few inexpensive gauges for bike and car tires, and one expensive gauge that I bought from an industrial supply company. I had the fancy gauge calibrated recently by a company that uses a deadweight tester. The cal report states that the largest error is 1/2 psi over the 10-60 psi range. Roughly once a year I compare my cheap gauges with my 'gold standard' and use the measurement difference to correct the cheap gauge reading.

All that said, I agree with the comment above about repeatability being an acceptable substitute for accuracy. You will learn what reading *on your gauge* is best for you. Stick with that number, even if it is not the truth.

FWIW, my Topeak D2 matches my calibrated industrial gauge to the nearest full psi (D2 has 1 psi resolution, calibrated gauge is analog)

 

[KnollyBro]

I start with the pitch test. If that feels close, I try the squish test with my elbow on the wheel, on hard ground but always end up using an analogue gauge. I have noticed that when using Cushcore that the pressures can be off when pumping up the tire (the pump gauge reads high) and it some times seems more difficult to pump up the tire (so much that I could not use a small hand pump). I have also wondered if sealant can affect the workings/accuracy of a tire pressure gauge over time as every time you use a gauge the must be a little bit of sealant going into the gauge. Then again, pressure is pressure and it should be equal in a closed system.

 

[Amber Valley Guy]

I think you guys are being (to say the least) are being a bit over expecting . Any pressure gauge whether or not of analogue or digital display works on mechanical principles regardless of if the display is digital or analogue, they aren't quartz watches with a known frequency of vibration (or tuning fork as in some older watches).
They work on bellows or a closed tube (Bourdon) which is measurable. The smaller the actual 'working mechanical parts' the less accurate they become. Those old large pressure dials you'd see in a stream engine or power plant are way more accurate than a tiny guage in any digital pump. Don't be fooled by digital displays if the underlying mechanism is a teeny weeny mechanical mechanism of dubious quality. Stick to one pump and it gauge and move on.

 

[RebornRider]

I thought digital gauges were based on piezo elements or strain gauges, not bourdon tubes. I guess I'll take one of mine apart. Inspection beats speculation!

 

[RebornRider]

Here's the guts of my Jaco compared to the gauge from the industrial supply company (McMaster).

 

[Amber Valley Guy]

Which do you trust to be accurate?

 

[RebornRider]

Which do you trust to be accurate?

The Span, which I just had calibrated by a calibration service that used a deadweight tester. I trust the calibration service, who provided a letter of accuracy.

The Jaco isn't too far off, but my Topeak is closer to matching the Span at 20 and 30 psi.

Edit, FWIW. The Span lives a pampered life resting on its back in a padded drawer. It comes out roughly once a year so I can compare its readings with my digital gauges. It is not used for routine measurements.

 

[Amber Valley Guy]

Why would the larger Span be more accurate in you opinion?

 

[RebornRider]

Why would the larger Span be more accurate in you opinion?

Because I had it professionally calibrated 2 months ago. Did you read my post?

Edit: Per the letter of accuracy, as-found, the Span was about 2 psi off. This means, prior to being calibrated, the large Span was less accurate than the little Topeak D2.

 

[Amber Valley Guy]

Did you read mine?

 

[Stihldog]

I have found that the operation of the valve core, size of the valve, clearance to CushCore, initial psi, type of psi gauge, and condition of air valves can have an effect.

I’ve seen some valves look like a cauliflower of sealant. Other types of sealants can clog up the passages or they can act like air-flaps. Incorrect readings are then possible.…or at least need a moment before the psi equalizes.

99% of the time I use the shop compressor and the Park Tool gauge …after I do the “squeeze test “. A floor pump is good enough. A hand pump on the trail takes too much time …but hey, it works. I’ve got one digital gauge but the battery (2032) is sometimes dead.

 

[Amber Valley Guy]

Because I had it professionally calibrated 2 months ago. Did you read my post?

Edit: Per the letter of accuracy, as-found, the Span was about 2 psi off. This means, prior to being calibrated, the large Span was less accurate than the little Topeak D2.

So was the Topeak calibrated at the same time, and can it even be re- calibrated? And what happened to the Jaco?