The new tires I bought were inflated with N2. The pressure was set at 35# in all four.The mfg.states pr. should be 29 front, 26 rear. Installer said higher pr. with N2 is used to match higher pr. that results when car is driven. Who’s correct?
Pressure is pressue; the installer is blowing hot air (nitrogen, carbondioxide, and water vapor)! I would use 29# on all tires for simplicity. Costco pulls this stunt on me when I go in for the free rotation. The Toyota dealer does the same. There might be some perverted logic that if they put in more air than is necessary, it will take the tires longer to get to the danger level, so fewer warranty clims!
If you plan racing or rallying with the car, 35# or more would be justifed.
The 35 pounds will not cause any harm to your car, it will just ride rougher.
Consider the manufacturer correct, as usual. And there’s no need to call the installer a moron even though he is one. Matching higher pressure, indeed!
You may lower the pressure yourself to the manufacturer’s recommendation or simply leave it as-is. It does no harm; the higher pressure simply gives you a ride not as soft as the manufacturer thinks everyone wants.
They do have a point. The pressures listed in your manual and on the door jamb are cold pressures. Which means pressures when checked after sitting for several hours(or overnight). If you have to drive there, the pressure should be higher to begin with. You can always check it cold the next morning and correct it as needed. It’s easier to do it that way with N2 if you want to keep it pure N2 and not mix in air. If pressure is too low cold, you would have to add air(since we don’t normally have N2 tanks around). Of course, I have no problem with air myself.
IMHO, the installer is right to put 35 psi in, but not for the reason stated, that was bogus. I have found that 34-36 psi seems to result in the best traction and longest tire life, and I have gotten over 100,000 miles on a set. BTW, air is 78% nitrogen.
First forget anything that has to do with nitrogen. Common cheap air is 80% nitrogen. For passenger cars nitrogen has no measurable advantages. For race cars it has a very very slight advantage. It is used strictly as a sales technique.
Next stick to the car’s manufacturer’s specs for inflation pressure. If the pressure really was 35 psi then that is evidence that the tyre dealer is not providing proper service and may not even know what the correct pressure is. It is also a good indication they don’t know or care about what the proper torque on the lug nuts should be.
Final note: The number on the sidewall is the maximum safe inflation for the tyre and does not relate to the proper inflation for your tyre, it only means that if your recommended inflation is higher than the max on the tyre that tyre is not safe on your car. Over inflation can cause unsafe handling. A few psi usually will not and it can help keep you from going under inflated which is dangerous.
I would lower the pressure to the manufacturer’s numbers (or up to three additional psi) using a known good gauge. Also consider that if you normally carry a full load of passengers or a lot of stuff in the trunk the recommendation is likely to be different, like 29 - 29. I will also repeat that those number are for the tyres cold, not after they have been running. It is easy to have the pressure increase 6 or more psi as they are driven.