Verify your air gauges are accurate.

[billmac]

I add air with my gauge on the air compressor chuck and today thought I'd use the slime compressor I carry on the bike and I knew it ran high on the reading but I had big reading difference with the gauge I grabbed then tried another and another. I also add because of the feel on the bike but always used the same two gauges until this morning. thought after looking at old posts their may something new and more accurate out there. guess not but as much as they talk about checking air in our bike tires they would have a good gauge to sell us.

[dna9656]

I suggest using a air pressure regulator (diaphragm type) used on paint spray guns. It can be set from 0 PSI and up. Pressure regulators are by their design more accurate than pressure gauges (IMHO). We use diaphragm regulators for oxy-acetylene torches and regulating acetylene pressure is PRETTY IMPORTANT. Granted those regulators are larger and most likely built better...but I think the inline one I'm recommending here is accurate enough for this application.

A regulator used for spray guns is small enough to pack up in the fairing some place.

The rub is getting it between the air source and the shrader valve on the bike;. especially at some air source away from home! You can put an air chuck on the out put side and shrader valve on the input side to apply the UN regulated air.

This is really just an idea for a solution; maybe some one can figure this out for us all.

Currently I use the regulator on my 12 gallon Craftsman compressor. I turn it to the pressure required and apply the hose....when you hear the air stop flowing check the pressure with your gauge, if your gauge is good it should measure pretty close to what you set the regulator at. if there is no sound of air moving there is either more or equal pressure in the suspension than you dialed in. I do my tires the same way. It can take a little more time than shooting 125 PIS in and measuring the pressure/bleeding/adding air but it's way more easy on delicate seals that (maybe?) in the suspensions of our bikes.

[videoarizona]

Interesting Idea, Doug, using the regulator. Will look into that.

 

Well...with lots of miles under my belt on the road (fun travel), I've never met a gauge that was accurate to another. Just ordered that digital gauge. We'll see how that works.

 

Found my VR rear tire was scalloping...so I took it's air pressure to max on sidewall...the heck with 40 pounds!

[djh3]

I have several gauges. LOL some dial some digital, even some of the pencil ones. My 3 digital ones are wit in about a 1/2lb of each other. The dial type one is a race gauge and for me the most accurate as has been set by a tire manufacturer although quite some time ago. If I can get it on the subject I will compare the digital to it. Surprisingly I have a small compact dial gauge I had to buy one time out of town and then thing reads almost exactly what the race gauge does around 30-40lb.

[N3FOL]

Glad I came across this thread. I've never even thought my gauges whether they are accurate or grossly off. I have a good friend at work who works in our calibration department and see if he has something that can test my gauges and how accurate they are. At least this way I can compensate +/- psi... [emoji106]

[djh3]

The only pencil type gauge I own anymore is in the OEM tool kit. And I wouldnt trust it to put air in the mower tires. Those things are terribly unreliable. I have one like the blue covered one in the link minus the filler part. Was over $100 15yr or more ago. I sure dont want it bangin around in the saddle bags, and dont have the room typically either. From what I have experienced with the digital gauges I have purchased most have been within 1/2 lb of each. Like Dan said you just need to know it will read the same every time and where it reads for what you want. If its 5 high thats where it needs to be.

[frankd]

When I worked in the electronics department at Reynolds Aluminum, we had a dead weight tester available. A dead weight tester uses a vertical cylinder that you put precision weights on, and then pump up the pressure in the cylinder until the cylinder starts to lift the weights. Then you spin the weights to eliminate stiction from the cylinder seals, and you have a precision pressure source. I took several brand new 100# dial pressure gauges, and found one that indicated the applied pressure very accurately. Of course, I checked it at several pressures to verify that it was linear. Now I use this gauge to check the calibration of my tire pressure gauges. I cut a valve stem for a car tire off so that it would fit into a hose, and put a male half of an air chuck on the other end of the hose, so now I could connect the valve stem to my compressor with an air hose. I connected my calibrated air gauge to the valve stem with a 'T', so I could read the air pressure in the hose accurately. My compressor has a regulator with an air gauge, so I used this to adjust the pressure. I tested a digital tire gauge that I thought was a little off by how it compared to my other tire gauges, and it read 1# low from 20 psi. to 80 psi. I have a 2nd digital gauge that I carry on the bike, and it read what the calibrated gauge did. I have several pencil gauges, and they all read within 1#. So I marked the first digital gauge with a magic marker indicating that it read 1# low, and I compensate for this when I check tires. My compressor is over 30 years old, but the built in gauge is still very accurate, but I don't use the regulated air source very much (I use full tank pressure for my air tools and filling tires). I also tested my son-in-law's digital gauge, and it read good here in Illinois. When we were at their house in Albuquerque (5500 feet elevation) I seemed to remember that his didn't agree with one I thought was accurate. I sent an accurate pencil gauge home with him and he said it agreed with his digital gauge at home also. If you check gauge calibration and you use your gauge for car tires and motorcycle tires (35-50#) you probably want to check calibration at 40-45#. My E-350 van takes up to 80# in the rear tires, so that's why I checked my digital gauge and my higher pressure pencil gauges at 80#. There are two things that affect the accuracy of air gauges---zero and span. That's why you need to test them at 5-10 different pressures to show they are linear if you use them over a wide pressure range.

 

How important is it to be absolutely correct with air pressure? I don't know. NASCAR pit crews change pressure by .25# to adjust how the car feels, but our tires and use are way different. I'm sure that the tire manufacturers have some cushion in their maximum pressure ratings to account for air gauge accuracy. One thing I do know is the mechanical air gauges on small inexpensive air compressors are very in-accurate. They are subjected to a lot of vibration and pulses, plus they are very inexpensive gauges. The digital gauges on some small compressors seem to be a bit better. I do remember that our riding friends had a relatively new Ultra Classic and we'd been travelling for about a week. We walked out from dinner and I saw that his rear tire was down to the cords in the center. I asked him how much air he had in it, and he pulled out the gauge he uses for his tractor tires, and showed me that the tire was correctly inflated. I checked it with my pencil gauge (I knew it read 1# low) and he had his tire about 10# too high. We lowered the air pressure and rode back to our motel. When we got there, his wife was very pleased how much better the bike rode. He only had about 5,000 miles on the bike and the tire was shot.

[dna9656]

Years ago when I was a motor head I read in one of the magazines that the gauges with the little tube inside were the most accurate for the money. The tube (if memory serves hahahaha) is pressurized to N and the gauge mechanically compares the pressure in the tube against pressure measured I think.... So I always bought one like that.