Tire Pressure System

[Hottech]

Has anyone had any experience or recommendations for a tire pressure monitoring system? I googled Doran for $249 and Smartire was $199 but no longer available.

[MikeCam]

I've got one bike and one car equipped with factory TPM. Frankly, I don't see any advantage over manual checks.

[towerworker]

The wisest course of action is to go to your local HD dealer and pay $15 to $18 per tire and have them filled with good old nitrogen. Then you never have to check your tires again!! (at least that's what the local HD shop says)

[snowprick]

The wisest course of action is to go to your local HD dealer and pay $15 to $18 per tire and have them filled with good old nitrogen. Then you never have to check your tires again!! (at least that's what the local HD shop says)

No kidding? LOL

As and aircraft engineer, my understanding was that nitrogen filled tyres reduce the risk of tyre explosion when the wheel are subjected to severe heat soak or fire from the brake packs. Other that that I believe nitrogen tyres only empty your wallet. Sorry my 10 cents worth guys.

[boxermania]

Actually a little know fact is that since N2 makes 78% of the atmosphere and the force of gravity is 14.7 pounds that means if a tire is filled with N2 and it develops a leak it will never get below 14.7 pounds as the pressure inside the tire and outside will be balanced.

Some owners have used a blend of N2 and NO2, nitrous oxide to provide less rolling resistance and at the same time make the tires happy with a laugh or two.

[Hottech]

I noticed that I can buy an automotive tire sensor system much like the smart tire sensors that are no longer available. Do you think I could just use two of the four sensors that were made for the cage or even possibly put two sensers in each wheel.

[mjcraft]

Actually a little know fact is that since N2 makes 78% of the atmosphere and the force of gravity is 14.7 pounds that means if a tire is filled with N2 and it develops a leak it will never get below 14.7 pounds as the pressure inside the tire and outside will be balanced.

Some owners have used a blend of N2 and NO2, nitrous oxide to provide less rolling resistance and at the same time make the tires happy with a laugh or two.

Sorry, Boxermania, but this is just not true. Sure, the inside of a flat tire when measured against a vacuum might be ~14.7, but so would the outside. The difference between these two (inside the tire and outside) is the inflation pressure...and that's what is important. The inflation pressure is also what is measured by any manual tire gauge or any tire monitoring system.

The reason nitrogen is used for inflating tires is that N2 expands less than compressed air (w/ humidity) with increasing temperatures. Nitrogen use is really only important for racing applications where consistent tire performance is crucial. Also, I believe that N2 is still susceptible to leaking depending on tire composition so people using N2 should still check their tires, it may just hold the pressure slightly better than compressed air.

Also, the majority of rolling resistance comes from the internal damping of the tire (mostly at the sidewall) and while tire pressure does have an affect on this, it is small (provided the tire is inflated close to the proper pressure). Tire construction is the biggest factor here, regardless.

Sorry, don't mean to hijack this post, but just thought you all should know...

Michael

[snowprick]

Actually a little know fact is that since N2 makes 78% of the atmosphere and the force of gravity is 14.7 pounds that means if a tire is filled with N2 and it develops a leak it will never get below 14.7 pounds as the pressure inside the tire and outside will be balanced.

Some owners have used a blend of N2 and NO2, nitrous oxide to provide less rolling resistance and at the same time make the tires happy with a laugh or two.

Sorry, Boxermania, but this is just not true. Sure, the inside of a flat tire when measured against a vacuum might be ~14.7, but so would the outside. The difference between these two (inside the tire and outside) is the inflation pressure...and that's what is important. The inflation pressure is also what is measured by any manual tire gauge or any tire monitoring system.

The reason nitrogen is used for inflating tires is that N2 expands less than compressed air (w/ humidity) with increasing temperatures. Nitrogen use is really only important for racing applications where consistent tire performance is crucial. Also, I believe that N2 is still susceptible to leaking depending on tire composition so people using N2 should still check their tires, it may just hold the pressure slightly better than compressed air.

Also, the majority of rolling resistance comes from the internal damping of the tire (mostly at the sidewall) and while tire pressure does have an affect on this, it is small (provided the tire is inflated close to the proper pressure). Tire construction is the biggest factor here, regardless.

Sorry, don't mean to hijack this post, but just thought you all should know...

Michael

How strange! I always thought that standard atmospheric pressure was 14.7 pounds. 29.92Hg. 1013.2Mb. Like the man said there are 10 kinds of people that understand binary math, those that do and those that dont.

[Daryl_stamp]

One of the deals w/ checking tire pressure is also a visual inspection of the tire, wheel & stem.
Hi-tech is good, but old school is too.

N2 in the tires?
Perception is reality; let's not poo-poo the potential economic benefits to the mechanics trade by denying an opportunity for someone to aid in the separation of a fool from his (or her) money. I've got a Bostich N2 (well, about 80% N2) pressurization system in the garage I can hook locals up with; won't even charge ya.

[Sunbeemer]

The reason nitrogen is used for inflating tires is that N2 expands less than compressed air (w/ humidity) with increasing temperatures

For all gases!:
PV=nRT
P=pressure
V=volume
n=# moles of gas
R=Universal gas constant (you can pick your favorite units!)
T=temperature

Any gas will expand or contract according to the above relationship.

The only benefit from using 100% Nitrogen (vs. 79% in the atmosphere) is stopping oxidative decomposition to the tire's interior, which doesn't keep me from wearing the tread off too quickly! Mine are worn out before they decompose.

[mjcraft]

The reason nitrogen is used for inflating tires is that N2 expands less than compressed air (w/ humidity) with increasing temperatures

For all gases!:
PV=nRT
P=pressure
V=volume
n=# moles of gas
R=Universal gas constant (you can pick your favorite units!)
T=temperature

Any gas will expand or contract according to the above relationship.

The only benefit from using 100% Nitrogen (vs. 79% in the atmosphere) is stopping oxidative decomposition to the tire's interior, which doesn't keep me from wearing the tread off too quickly! Mine are worn out before they decompose.

Sunbeemer,

It's been a while since I've used the ideal gas law but I don't believe it can account for moisture content. You're point about the oxidation is definitely correct, but as mentioned in the following article, it may not make much of a difference unless the tire and rim are clean and dry to begin with, which is something I never considered.

http://www.popularmechanics.com/automot ... page=2&c=y

And there is some more info here:

http://auto.howstuffworks.com/question594.htm

And as you say, as long as we all can wear the tread off quickly enough, we shouldn't have much of a problem with tire decomposition!

-Michael

[bimrluvr]

I recently got the TPS from the SuperVisor guy...here's the link...I like it so far....been about 1 month. No wires...just screw on the caps and go. No noticeable difference in tire balance.

I find it an extremely convenient and comforting feature...and I commute 90 miles daily.

http://www.super-visor.com/tiresupervisor.htm

[Oilhead]

I have free access to a Nitrogen tire inflating machine at work and I can honestly tell you that I felt absolutely no difference whatsoever(contrary to claims by the manufacturer) and all my bikes lost air psi just as quickly as "pure" free air. I don't even bother with it anymore as even at free, it's not worth the trouble.