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Filling your RV Tires with Nitrogen

September 3, 2016
Filling your RV TIres with Nitrogen

Have you ever wondered if Nitrogen filled tires are worth it?  Race car drivers, commercial jets and the space shuttle thought it was a good idea, it must be right?  So the real question might be does the benefit outweigh the cost?  Claims are that it will provide a more constant air pressure in the tire, with less need to top the tires up thus leading to a more comfortable ride and better fuel economy.  But again, is it worth $20-30 per tire?

Lets look at some facts.  Air on earth at sea level contains about 80% Nitrogen naturally, with close to 20% Oxygen, and a very small fraction made up of other Noble gasses.  At sea level this means an unfilled tire has 1 ATM of earth air in it as soon as it gets mounted to the rim (with 80% Nitrogen in it).  To fill it the rest of the way with a compressor you are putting in 80% Nitrogen, so in my case (using ST tires), at 3.4ATM (50psi) I am still getting 80% Nitrogen in my tires.

Some common pressures:

  • air pressure at sea level = 1 ATM
  • air pressure of a typical car tire (32psi) = 2.1 ATM
  • air pressure of a typical ST trailer tire (50psi) = 3.4 ATM
  • air pressure of a typical class A truck tire (100psi) = 6.8 ATM

So is 100% Nitrogen worth it?  Well have you noticed one flaw so far.  You may not be getting 100% Nitrogen to begin with.  If the shop simply hooks up your tire to a Nitrogen tank and adds Nitrogen up to your required PSI, there is already air in the tire.  Remember, an empty tire fresh on the rim already has air in it (1 ATM at sea level), so to get a ST tire up to 3.4 ATM, you have to add an additional 2.4 ATM of pure Nitrogen to the 1 ATM of 80% Nitrogen.  This will actually leave you with about 95% Nitrogen, and about 5% Oxygen left over.  Now a proper shop should also be bleeding the tire and refilling it, but they cannot get to 0 ATM, as the tire will collapse, so in reality they can never achieve 100% Nitrogen unless the tire is in a vacuum.  Also bleeding means they waste Nitrogen that they are paying good money for.

As an RV’r I had always been taught to watch tire pressure like a hawk, Trailer tires are rumored to be poorly made and far more prone to blowouts.  So the rule had been, buy a good pressure gauge, check pressure before and during every trip and top up or invest in a TPMS system to watch pressure in real time.

So if you already get 80% Nitrogen for free vs close to 100% for $80-120 for a set of 4 tires is it worth that cost if you are checking tire pressure every trip anyway and your pressure is always at the optimal PSI giving you the best handling, performance and mpg?  I think I will risk just 80% Nitrogen.

From → RV Tech

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