Air pressure guage

[fgrimes636]

Hi,

Odd question about air pressure gauges. I have been carrying a stick type for some time and all has been well. The other day I stopped at a tire shop to top off the tires before a long ride. The air hose had a built in gauge and was reading almost 8 lbs different than my stick gauge. Is there that much difference in air gauges? If so, can someone recommend a specific brand or type to be more accurate? I thought about a digital gauge, but I assume it can be just as off.

Thanks

Dave

06 RSTD Pearl White.

[Rick Haywood]

Hi,

Odd question about air pressure gauges. I have been carrying a stick type for some time and all has been well. The other day I stopped at a tire shop to top off the tires before a long ride. The air hose had a built in gauge and was reading almost 8 lbs different than my stick gauge. Is there that much difference in air gauges? If so, can someone recommend a specific brand or type to be more accurate? I thought about a digital gauge, but I assume it can be just as off.

Thanks

Dave

06 RSTD Pearl White.

 

I have 4 different gauges and everyone of them reads different by as much as 6 pounds. I go by the one that reads the 2nd highest pounds. Not sure if it is close or not but what is a guy to do. They range from cheap to $20 ones.

[mbrood]

Mechanical gauges have the problem of wear, so an older gauge can still be "reliable" but needs to be referenced to a calibrated source. If you KNOW it's 8 pounds off you can add this in your reading but it will still degrade slowly over time, and for the cost, it's economical to simply replace it. The digitals use a pressure sensor similar to the boost sensor on our bikes and the dial type use a pressure membrane (bellows?) that can degrade over time but much, much slower than the straight mechanical.

[Miles]

Some of the really new digital guages are pretty good, but I would not go for the $ 5.00 ones. If you want to go digital, go for a name brand one. As for the mechanical ones, I beleive that accu-gage probably still makes the best. In the old days, most motorcycle shops sold these. They were the dial guage that usually was a brass housing. The one I have been using for over 20 years also has the rubber boot on the outside of the brass housing, to protect it. I compare it to my Snap On hose/pressure gauge, for accuracy.

I do carry a relatively cheap digital one, just in case, as it is light weight and not a worry if I lose it.

 

http://www.autosportcatalog.com/tire-gauges/accugage-tire-gauge.cfm?mgsku=pp273&sc=57513&sc=57513&mr:trackingCode=78C6A2A7-8881-DE11-B7F3-0019B9C043EB&mr:referralID=NA&mr:adType=pla&mr:ad=16737320206&mr:keyword=&mr:match=&mr:filter=19459378246&origin=pla&gclid=CJvUn8iTm7QCFYp_QgodXX0AUQ

[djh3]

Mine is like this one. It reads dead on to my expensive race tire gauge. Both could be off I supose but my other digital I have reads within like .5lb. I forget hi or low now. The 2 stick gauges I have not even close one is like yours 8lb and I think the other is in the 5lb range. I dodnt even use them for the lawn mower tires. Usless.

[frankd]

Funny this topic came up. When we went on our trip last October, somehow I neglected to put my stick type air gauge back in the bike's pocket, and put it away in my tool cabinet, so I didn't have a gauge. When we were in Albuquerque, I went to the local Walmart and bought another gauge, but I goofed and bought the high pressure version. That meant the resolution wasn't that good, and besides, when I checked my tires, I thought that it was reading wrong because Albuquerque elevation is 5200' and it read just about where both tires were when we left home. I went back to Walmart and bought the correct gauge. It read the same as the high pressure version. My son-in-law got out his digital gauge and it read several pounds higher. Then he got out another digital and it read different yet.

 

The other day I decided to check the accuracy of my gauges. I made up a manifold with room for 2 gauges, and took a car tire valve stem and mated it to an air hose that I connected to a port on the manifold, and used the regulator on my air compressor to vary the air pressure. I reached in my spare parts drawers and found a brand new 60# gauge. The other 60# dial gauge I used was also relatively new. At 35 psig. both gauges read identical. Somewhere I've got a a 100# gauge that I calibrated on a dead weight tester, but that's one of those items that's hiding since we moved, so now I have to believe the 2 gauges that read identically. I started checking my tire gauges by connecting them to the tire valve. The 2 new stick types I bought read perfectly @ 35#. I've got a cheap digital that I thought read 1# low by comparing to my other gauges, and it read 1# low on my test setup. I've got about 5 stick types in my tool drawers and they all read within 1#. I've got a 'better' gauge type air gauge with a hose and a bleed valve, and it read about a quarter of a pound low when compared to the dial gauges. When my daughter and her husband come for Christmas next Friday, I'm going to have them bring their digital gauges. Then after we compare them here (700' ele.), I probably will send one of my new stick gauges back so they can compare them @ 5200' ele. Digital gauges are good, but the cheap ones aren't perfect.

 

The pressure gauges in gas stations have never been very accurate. They lead a rough life. I'd believe your stick gauge more than the station gauge. Also, tire temperature makes a difference. You are supposed to set your tire pressure before you drive (or ride) on them. Car tires change about 1# per 10 degrees. On my E-350 van the rear tires use 80# or air, and they change a lot more when the temperature changes. I have no idea how much bike tires change. How much does tire pressure really change versus altitude? My son-in-law said that the uncorrected barometric pressure in Albuquerque is about 90% of that @ sea level. On Pike's Peak (14,000') I think he said it's about 70%. He also feels that because tires are somewhat flexible, they'd expand slightly at higher altitude and the actual measured tire pressure wouldn't be quite as high as you think it would be. Of course it's a lot colder up there, and that lowers the pressure.

 

Frank D.

[Miles]

Frank, the general rule of thumb is that HOT tires are usually 10 % higher in pressure than COLD tires. Yes, it is best to set your tire pressures when the tires are cold. That is not always convenient, and sometimes adjustments must be made. So if I set my RSMTD tires are 40 psi cold...then I should expect that when the tires are good and hot, they should read about 44 psi, given if the altitude has remained constant.

 

Yes, altitude does play a role in tire pressures, but not as large a role as some may think, or is assumed. The rule should be...set your tire pressures for the correct pressure...at the altitude where you live. If I live at sea level, then I set my tires to 40 psi. If I live in Leadville, Colorado, then I would set my tires to 40 psi. You see...40 psi is 40 psi, no matter where you set it. BUT...it is the change in altitude that can affect the pressure on the tire. Setting a tire at 40 psi at sea level, say in Miami, FL. at 6:00 am, and riding to Leadville, Colorado that same day (gulp) (that is a difficult ride), not only would the tire pressure change due to temperature conditions, but also due to altitude changes. What WAS 40 psi in Miami would not be 40 psi in Leadville.

 

On the road, I try to not dwell too much on the altitude changes on my tires. I do take that into consideration, but not dwell on it. I am more concerned about temperature changes of the tire. The best rule you can use...Set your tire pressures when the bike is cold, for wherever you are at, for the psi you are used to using, despite altitudes or ambient air temps. That means, if I set my tires to 40 psi in the morning in San Diego, and ride around all day, I can check them again the next morning in Leadville, CO. (a ride that is doable), and set them at 40 psi in that morning in Leadville, and my tires will be correct.

 

The real # 1 problem is not altitude or ambient air temps...the real # 1 problem is riders riding on under-inflated tires, because they assume that the motorcycle manufacturers are correct about what tire pressures they bike should run. In most cases, the motorcycle manufacturers are NOT correct, because they are using very outdated information when relevent to the new tires on the market. Example, when the Honda GL1800 Goldwing came out in 2001, Dunlop had not developed the E-3 radials yet. The original 1800 Wings were shod with either Dunlop D250 radials, or Bridgestone radials.

 

This...is what happens when I get up at 4:45 am, on a Saturday.

Edited December 15, 2012 by Miles

[fgrimes636]

Wow. Interesting reply's. I guess then that I will look for a moderately prices dial or digital gauge for the bike and rely on it more. I actually do make the trip from Denver to Leadville multiple times a year. My niece lives there.

When I lived in Phoenix, I bought a new set of Kenda Kruz tires for my then Suzuki Boulevard. The place I bought them from only sold and installed bike tires. And the owner was a racer/rider. I asked him about the tire pressure and he said forget the manufacture recommended pressure and go by what the tires said. I rode 40 # front and back and had not just a great ride, but better gas millage. Suzuki wanted 32 and 36 front/back.

But it did though me a bit when I used the car tire place gauge as described earlier. I hate riding under-inflated but am a bit paranoid to run over as we ride 2up almost all the time.

[GeorgeS]

Yes, be careful what you ask for on this site, sometimes you get more then you bargined for He He He !!

[mbrood]

I use a simple one that tosses in the tool bag nicely...

 

Harbor Freight 110 PSI Dial Tire Pressure Gauge SKU 90610

http://www.harborfreight.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/i/m/image_6694.jpg