login
Floor pump tire pressure accuracy
-
No new posts
 2014-09-18 1:05 PM |
 128  |  Subject: Floor pump tire pressure accuracyHow accurate are the gagues that come on bicycle floor pumps? I have a Serfas TCPG pump which works great pumping but maybe not. Yesterday I pumped up my tires to 110 lbs and today while getting out some stuff from a race I found my Topeak D2 digital gague. I don't regularly use this but I wanted to make sure I could still operate it properly and it said they were 140lbs. I was kind of shocked that they were that high and I don't know which one to believe. Has anyone had problems with either floor pump gagues or digital gagues being that far out of whack? Keba |
| 2014-09-18 1:35 PM in reply to: KebaNYC |
Regular 606  Portland, Oregon | Subject: RE: Floor pump tire pressure accuracy I think you need a 3rd opinion. Bring them both to a bike store and go crazy! |
| 2014-09-18 1:40 PM in reply to: KebaNYC |
1502 Katy, Texas | Subject: RE: Floor pump tire pressure accuracy Originally posted by KebaNYC How accurate are the gagues that come on bicycle floor pumps? I have a Serfas TCPG pump which works great pumping but maybe not. Yesterday I pumped up my tires to 110 lbs and today while getting out some stuff from a race I found my Topeak D2 digital gague. I don't regularly use this but I wanted to make sure I could still operate it properly and it said they were 140lbs. I was kind of shocked that they were that high and I don't know which one to believe. Has anyone had problems with either floor pump gagues or digital gagues being that far out of whack? Keba That's a bit concerning. I just always trust my floor pump. Here's the thing though; I've pumped up my tires to 105 psi, then disconnected it, then put it right back on (with VERY minimal air release) only to show like 80 psi. It's almost as if the gauge doesn't work until you actually start pumping, because I give it a very small pump and it pops up past 100 again. |
| 2014-09-18 4:07 PM in reply to: 0 |
| Subject: RE: Floor pump tire pressure accuracy Originally posted by 3mar That's a bit concerning. I just always trust my floor pump. Here's the thing though; I've pumped up my tires to 105 psi, then disconnected it, then put it right back on (with VERY minimal air release) only to show like 80 psi. It's almost as if the gauge doesn't work until you actually start pumping, because I give it a very small pump and it pops up past 100 again. You have to realize how a pump works. When you pump up your tires to 105 psi, and disconnect the pump head, there is 105 psi in the tire/tube and the hose connecting the pump head to the gauge. When you remove the pump head, you usually hear that quick "hissing" sound. That is the sound of the air pressure that is in the hose of the pump releasing, not the sound of air coming out of your tube. Thus now you have zero pressure in the hose, and your gauge reads zero to reflect that. When you reconnect the pump head, in order for the gauge to work, the hose connecting the gauge to the tube valve needs to be pressurized again. Remember...it has zero pressure in the hose to start. When the pump head goes on the valve, it usually engages the tip of the valve, and thus releases some pressure from the tube into the hose. That's why you see the gauge flick up from 0 psi to 80 psi. The reason it doesn't say 105 psi is because you lost around 25 psi filling up the hose with air pressure that came out of the tube. A few pumps, and now the tube and the hose is back to 105 psi, thus when you remove the pump head, you still have 105 psi in the tube. Edited by Jason N 2014-09-18 4:08 PM |
| 2014-09-18 4:11 PM in reply to: Jason N |
| 1502 Katy, Texas | Subject: RE: Floor pump tire pressure accuracy Originally posted by Jason N Originally posted by 3mar That's a bit concerning. I just always trust my floor pump. Here's the thing though; I've pumped up my tires to 105 psi, then disconnected it, then put it right back on (with VERY minimal air release) only to show like 80 psi. It's almost as if the gauge doesn't work until you actually start pumping, because I give it a very small pump and it pops up past 100 again. You have to realize how a pump works. When you pump up your tires to 105 psi, and disconnect the pump head, there is 105 psi in the tire/tube and the hose connecting the pump head to the gauge. When you remove the pump head, you usually hear that quick "hissing" sound. That is the sound of the air pressure that is in the hose of the pump releasing, not the sound of air coming out of your tube. Thus now you have zero pressure in the hose, and your gauge reads zero to reflect that. When you reconnect the pump head, in order for the gauge to work, the hose connecting the gauge to the tube valve needs to be pressurized again. Remember...it has zero pressure in the hose to start. When the pump head goes on the valve, it usually engages the tip of the valve, and thus releases some pressure from the tube into the hose. That's why you see the gauge flick up from 0 psi to 80 psi. The reason it doesn't say 105 psi is because you lost around 25 psi filling up the hose with air pressure that came out of the tube. A few pumps, and now the tube and the hose is back to 105 psi, thus when you remove the pump head, you still have 105 psi in the tube. That makes sense. I'm kind of embarrassed I didn't figure that one out. |
| 2014-09-18 4:49 PM in reply to: Jason N |
Member 622 Franklin, TN | Subject: RE: Floor pump tire pressure accuracy I've wondered the same thing. Thanks for the explanation. |
| 2014-09-19 8:32 AM in reply to: KebaNYC |
| 631 | Subject: RE: Floor pump tire pressure accuracy As far as the OP, I would think the 110 is more accurate than 140. To pump up to 140 it would need to be a pretty good pump and you would need to work those last pumps. |
| 2014-09-19 2:45 PM in reply to: Sidney Porter |
| 128 | Subject: RE: Floor pump tire pressure accuracy Originally posted by Sidney Porter As far as the OP, I would think the 110 is more accurate than 140. To pump up to 140 it would need to be a pretty good pump and you would need to work those last pumps. I just borrowed two more floor pumps from my neighbors to test the accuracy. My floor pump mentioned above seems to be the culprit. Using the other two pumps to pump my tire up to 110 results in the digital gauge showing 110 and 114 respectively. I have always expected the gauges on high quality pumps to be accurate but in this case it is way off. |
| 2014-09-19 4:12 PM in reply to: KebaNYC |
Extreme Veteran 717 Chicago, USA | Subject: RE: Floor pump tire pressure accuracy Most high quality floor pumps when brand new are likely accurate (when used correctly) to approx +/- 5%. After use and some time and some drops/knocks, the error might increase some. There is a floor pump out there that is accurate to +/- 1%, but it ain't cheap. But with some experience, you'll be able to easily tell the difference between 105 psi and 140 psi. If you're strong, 105 psi is quite hard to your thumb pressure, but there is still a little bit of 'give' when you press hard on the side of the tire. 140 psi, on the other hand, makes for a rock hard tire. And also a slow tire on any surface short of a velodrome ... Greg @ dsw |
| 2014-10-02 11:38 AM in reply to: KebaNYC |
| 128 | Subject: RE: Floor pump tire pressure accuracy Just a follow up to the original issue: I did e-mail Serfas who said it was likely that the digital gauge was not accurate but sent out a new gauge anyway. Today I swapped the pressure gauge module with the new one and it is reading pressure accurately again. Thumbs up for Serfas customer service but I'm still a little shocked that my pressure reading was off by 30+ lbs. Keba |
| 2014-10-02 12:01 PM in reply to: KebaNYC |
Pro 15655 | Subject: RE: Floor pump tire pressure accuracy This pump has been excellent......and accurate. |
| 2014-10-02 12:27 PM in reply to: KebaNYC |
Pro 4578 Vancouver, BC | Subject: RE: Floor pump tire pressure accuracy |
|
|
|
| |||
| |||
| |||
| |||
|
| ||||
|
| |||
|
View profile
Add to friends
Go to training log
Go to race log
Send a message
View album
CONNECT WITH FACEBOOK