mis3

Not sure if I am the only idiot here.

I checked my tire pressures last night and they were all 4-5 PSI under. I recall the last time I checked it was near end-of-August. Also, I noticed the two front tires were more under-inflated than the rears.

Since all tires were under-inflated, I would think the root cause was temperature fluctuations in the last few weeks. On the same day, the difference in max and min temps can be 20C.

Rudeney

Yep, I try to remember to check mine monthly. I generally make it part of my routine when vacuuming and/or washing the cars.

craig001

I know some folks pooh-pooh this, but you could go to filling your tires with Nitrogen. I am considering this with my CLK. While I do not have any issues with air and since I have a compressor in my garage, topping off pressures is not a problem.


Nitrogen filled tires do seem keep more consistent pressures and have slower leak down rates. When I picked up my FEH the dealer had filled to tires with nitrogen. The only issue I had was on the drive home to Missouri from Mississippi last December. I had the TPMS light pop on when I got close to home where it was about 20F. It was in the 80's down south when I picked up the car. I ended up having to get my tires flushed and refilled (free from a Nitrofill delealer - top-offs are free as well) because the shop I took the vehicle for my state inspection noticed the low pressure and shot air into them. They totally over looked the special valve stem caps and NItrofill sticker in the windshield. Not a big deal since I was taking it to a Ford dealer for an ESP inspection so I found one who offered Nitrofill.


Here is an interesting factoid though - the Ford dealer charges $49.95 and the MB dealer where I got my state inspection on the CLK told me they charge $90 for the same service. Both use the Nitrofill system. I was told that you might need to reset the TPMS system though. Not a big deal IMHO.


Is nitrogen a gimmick? I don't know but it seems to work in my Escape and since the dealer did it before I picked up the car I do not really care. So, just a thought.

mis3

I read that a typical TPMS would report an alert when the difference in the recommended and actual readings is more than 25%. Not sure about the MB TPMS.

I am reluctant to go nitrogen because only a few tire stores here (Toronto) are equipped with nitrogen. I know the local Costco and Canadian Tires stores have nitrogen but they always have a lineup. On the other hand, regular air compressor is available in almost all gas stations.

I will certainly try nitrogen when I have a chance.

Rudeney

I usually buy tires from Costco and they use nitrogen, but I don't worry much about it when checking and refilling at home with my air compressor.

dave2001auto

Dry air has about 78% nitrogen. Nitrogen fill reduces oxygen oxidization and leakage of gas in the tires. Dry gas also limits the condensation of water when tires get cold, less pressure changes with temperature. Wet air can have about 4% water.

Costco has a semi-self service for nitrogen fills. If you are worried, you can bleed and refill with nitrogen or if you wait Costco will do it for you. I don't know the purity of Costco's nitrogen.

$90 is a lot $$for nitrogen fill or does that include the inspection?

omega48er

you get free nitrogen refill when you buy tires from Costco rite?

craig001

I agree that $90 is too much, but that was at the MB dealer. The Ford dealer that I take my Escape to charges $50. That is still a lot IMHO. Using a Nitrofill dealer gets you a year road hazard warranty from Nitrofill. I have noticed that I do not have to add air as much as when I filled the tires with plain air.

Rudeney

Yes, my Costco only uses nitrogen to fill tires and it is included when you buy tires there. They even use green valve caps to note that the tires are nitrogen filled. That can be a problem, though, as I have to always remind them I don't want the green caps replacing my nice metal valve caps. I noticed that my wife's Jeep came from the dealer with nitrogen filled tires, and they will top it off for no charge as long as we own the car. I would never pay for nitrogen.

mis3

Agreed on the green caps, pig ugly...

Gary C

I work in a Costco tire center part time. The nitrogen is checked daily. It is no lower than 94% and averages around 97%. We do put the green caps on. Now it is just a habit. But we do put regular caps on when requested. If I see nice chrome caps I put them in the car, as soon as I take them off. So if they forgot and put the green caps on, check your drink holder for your caps! Lol

dave2001auto

Thanks Gary for the info.
Topping off with air will not have much effect on the oxygen content. Maybe the water content.

My new Costco tires have a metal sleeve over the stem and a metal cap. It was about $3 extra for the 4 tires. I did not ask for them. Costco just did it and three of them look good. One is missing the sleeve.

Costco service is great except for the long wait. Good service attaches lots of customers.

Rudeney

Yep, I'm a Costco shopper, too. Every set of tires I've bought in the last 12 years has come from Costco. I like that they have a 2nd employee double-check the wheel bolt torque and they calibrate their torque wrenches regularly. That is in contrast to most tire shops that just go it it with the pneumatic impact wrench set to "damn tight".

dave2001auto

Costco has not charged me for the nitrogen addition even on tire purchased elsewhere. I have never asked them to flush (bleed out air and refill with nitrogen). I know that they will do that for free if the tires were purchased from Costco.

The Costco tires also comes with a road hazard warranty that is time and mileage limited. That's usually at least a $50 saving.