Tire pressure

truck · 09-30-2017, 06:10 PM

I got a miniPRO about four weeks ago. I checked tire pressure and they were pretty even pound wise but real low, about 15psi. I blew them up to 45psi. The past few days the ride seemed different so today I checked the pressure. They were both at 33psi so I filled them to 45psi again.

I don't think ambient air temperature (it recently got cooler) had anything to do with the pressure drop because I store the mini indoors. I also don't think there is a leak because both tires dropped the same amount.

Is this just a break in thing like maybe the tires stretch and increase in volume thus lowering pressure?
Is anyone else experiencing this much pressure drop in this amount of time?

Don M · 10-01-2017, 11:34 AM

Every tire I've ever owned on any vehicle of any sort has always constantly lost tire pressure over time. Doesn't matter if they are tube type or tubeless, they all leak air at some rate - Some much more than others, but they all lose air. I add air to all my car tires at least once per month

The smaller the tire and the higher the pressure, the greater the loss which I think probably explains what you are seeing. My I2's with tube type tires and only 15 psi in them lose about a pound every month or so. I2 tires probably have three times the quantity of air of the MiniPro tires and only 1/3rd the pressure, so you're going to see a much faster loss. I predict if you were to check them once per week, you'll always see them going lower, week to week

To make matters much worse, cheap Chinese made tires (I have several small trailer tires made in China) lose air much faster than quality tires made in the USA or Japan

Don

SegNerd · 10-01-2017, 04:09 PM

I would agree. I had to pump up my MiniPro tires basically every week.

Pescador12 · 10-02-2017, 02:57 AM

I bet you lost most of the air while trying to check them. The high pressure with very low volume results in lots of pressure loss if someone even breathes on the valve stem.

I cannot check the pressure as I would loose too much pressure while attaching and removing the air gauge. I just use an air chuck that has its own pressure gauge to set the pressure to 47psi, then yank off the chuck as fast as possible. I guess it winds up at about 43-45psi. I do it about once a week.

truck · 10-02-2017, 09:43 AM

So, nothing new here it seems, I just need to get in the habit of checking and adjusting pressure every week.

cmonkey · 10-08-2017, 12:48 AM

Go to your local bike store, and pick up some liquid latex. Also search for threads on “slime”. Adding a liquid with tire sealing ability greatly reduces slow air loss.

truck · 10-08-2017, 08:31 AM

I wonder if nitrogen would be worth the effort?

airdale · 10-08-2017, 10:23 AM

Quote:

Originally Posted by truck

I wonder if nitrogen would be worth the effort?

NO!...It would just cost you more.....The reason for Nitrogen is it expands and contracts far less for overall tire improvement...aka better milage and less tire wear.

Try the green slim, I use it for my off road bike...

Don M · 10-08-2017, 12:07 PM

Nitrogen is dry (no humidity in it) so changes in ambient temperature doesn't cause as much change in tire pressure. Also, as the tire heats up, the increase in air pressure inside the tire is much more predictable - Important for NASCAR types who want to put 18.6 psi in a tire, knowing when the tire heats up it will reliably go to exactly 27.2 psi, which is exactly where they want it to be under race conditions. One or two tenths in tire pressure makes quite a difference in the handling of the car, so they need to be pretty precise

Nitrogen is also a larger molecule, so in theory it doesn't leak out as quickly. Worth the 'effort'? I suppose so, if you have a free source of nitrogen, but worth the cost if you have to buy it? I don't think so

Don

Pescador12 · 10-08-2017, 10:48 PM

I mostly put nitrogen in my tires. I then flavor it by adding a little oxygen, water, and secret spices.

If I was super concerned with the proper tire foot print in a wider range of temps, like Don's NASCAR teams, I would run straight nitrogen. But the mini pro is a gloriously low performance machine. So slow it won't spill your coffee.

Pure nitrogen fill is just sales hype for tires that never see a professional race.

Interestingly, if you measure each tire's foot print, multiply it by the PSI, you will have the weight of the vehicle. Air does carry you.

09-30-2017, 06:10 PM	#1
truck Member Join Date: Aug 2017 Location: Breinigsville PA Posts: 138	Tire pressure I got a miniPRO about four weeks ago. I checked tire pressure and they were pretty even pound wise but real low, about 15psi. I blew them up to 45psi. The past few days the ride seemed different so today I checked the pressure. They were both at 33psi so I filled them to 45psi again. I don't think ambient air temperature (it recently got cooler) had anything to do with the pressure drop because I store the mini indoors. I also don't think there is a leak because both tires dropped the same amount. Is this just a break in thing like maybe the tires stretch and increase in volume thus lowering pressure? Is anyone else experiencing this much pressure drop in this amount of time?

10-08-2017, 12:48 AM	#6
cmonkey Member Join Date: Nov 2004 Location: Orange, CA, USA. Posts: 1,064	Air loss Go to your local bike store, and pick up some liquid latex. Also search for threads on “slime”. Adding a liquid with tire sealing ability greatly reduces slow air loss. __________________ Charriot of Fur - Onward!

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10-01-2017, 11:34 AM	#2
Don M Member Join Date: Jun 2016 Location: Ocean Springs MS Posts: 242	Every tire I've ever owned on any vehicle of any sort has always constantly lost tire pressure over time. Doesn't matter if they are tube type or tubeless, they all leak air at some rate - Some much more than others, but they all lose air. I add air to all my car tires at least once per month The smaller the tire and the higher the pressure, the greater the loss which I think probably explains what you are seeing. My I2's with tube type tires and only 15 psi in them lose about a pound every month or so. I2 tires probably have three times the quantity of air of the MiniPro tires and only 1/3rd the pressure, so you're going to see a much faster loss. I predict if you were to check them once per week, you'll always see them going lower, week to week To make matters much worse, cheap Chinese made tires (I have several small trailer tires made in China) lose air much faster than quality tires made in the USA or Japan Don

10-01-2017, 04:09 PM	#3
SegNerd Member Join Date: Dec 2008 Location: Portland Posts: 672	I would agree. I had to pump up my MiniPro tires basically every week.

10-02-2017, 02:57 AM	#4
Pescador12 Member Join Date: Dec 2016 Location: USA Posts: 168	I bet you lost most of the air while trying to check them. The high pressure with very low volume results in lots of pressure loss if someone even breathes on the valve stem. I cannot check the pressure as I would loose too much pressure while attaching and removing the air gauge. I just use an air chuck that has its own pressure gauge to set the pressure to 47psi, then yank off the chuck as fast as possible. I guess it winds up at about 43-45psi. I do it about once a week.

10-02-2017, 09:43 AM	#5
truck Member Join Date: Aug 2017 Location: Breinigsville PA Posts: 138	So, nothing new here it seems, I just need to get in the habit of checking and adjusting pressure every week.

10-08-2017, 08:31 AM	#7
truck Member Join Date: Aug 2017 Location: Breinigsville PA Posts: 138	I wonder if nitrogen would be worth the effort?

10-08-2017, 12:07 PM	#9
Don M Member Join Date: Jun 2016 Location: Ocean Springs MS Posts: 242	Nitrogen is dry (no humidity in it) so changes in ambient temperature doesn't cause as much change in tire pressure. Also, as the tire heats up, the increase in air pressure inside the tire is much more predictable - Important for NASCAR types who want to put 18.6 psi in a tire, knowing when the tire heats up it will reliably go to exactly 27.2 psi, which is exactly where they want it to be under race conditions. One or two tenths in tire pressure makes quite a difference in the handling of the car, so they need to be pretty precise Nitrogen is also a larger molecule, so in theory it doesn't leak out as quickly. Worth the 'effort'? I suppose so, if you have a free source of nitrogen, but worth the cost if you have to buy it? I don't think so Don

10-08-2017, 10:48 PM	#10
Pescador12 Member Join Date: Dec 2016 Location: USA Posts: 168	I mostly put nitrogen in my tires. I then flavor it by adding a little oxygen, water, and secret spices. If I was super concerned with the proper tire foot print in a wider range of temps, like Don's NASCAR teams, I would run straight nitrogen. But the mini pro is a gloriously low performance machine. So slow it won't spill your coffee. Pure nitrogen fill is just sales hype for tires that never see a professional race. Interestingly, if you measure each tire's foot print, multiply it by the PSI, you will have the weight of the vehicle. Air does carry you.

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