Why I Do Most Of The PM Myself......

........And try to keep my vehicles away from the dealer service dept as much as possible -

Picked up my new CX-5 GT last week, but today was the first time I checked tire pressure. Sure enough the tires were still set at the factory 48-50 cold psi's. I had noticed the ride seemed a bit jittery even though the CX-5's are known for their taut ride. Didn't help much either that the temps have been in the mid 90's here for the past few weeks. Brought my tires down to 36 cold psi's and it made all the difference in the world. Should have checked this sooner, my bad, it's not the first time this happened, at least I found it fairly soon.

And then today I got an email from my sales manager saying that I would soon be receiving a survey from Mazda, and that it would be the dealership's report card........Yeah, right, ok.......

But seriously, I can't complain, was very pleased the way the sales dept treated me.......no experiences with the service dept though as of yet - we'll see.

If this is your only issue, I wouldn't sweat it.

My dealer is who replaced my tires. They are ALL exactly 36psi cold or 40psi hot all the way around. Exactly. They must have some rare tire pressure gnome that puts the air in one molecule at a time or something.

ocinsomniac said:

........And try to keep my vehicles away from the dealer service dept as much as possible -

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I can tell you so many horrible stories of dealer screw-ups by their service department form my personal experience. They either tried to cover-up or lied to me after the screw-ups as they didn't know I have been working on cars by myself for many years. So I have the same mentality like you, unless it's really necessary, such as warranty issue, I'd stay away from dealer service department as much as possible. I do all the maintenance and repairs by myself on cars we have. I'll skip these free oil change offers by dealers as they sometimes will screw up the simple oil change such as overfill or using wrong type of oil. One time a tech even somehow poured in some oil into cooling system (I still don't know how and why) and the tech writer was trying to tell me "this is normal!" on our BMW 528i. The plastic water pump failed at 28K miles and I do believe that incident has something to do with it. My Mazda dealer uses an unknown brand of oil for "free" oil change so I told them "thank you very much"!

BTW, I put 38 psi instead of 36 on GT's 225/55-19 tires based on past experience as factory recommended tire pressure for the US market has always been too low IMHO. You can actually see different tire pressures recommendations under different load conditions in our CX-5's owner's manual for Mexico market. Our '98 Honda CR-V recommends 26 psi but I've been keeping 35 psi to prevent tire wearing on both sides of tread! I noticed many people on this forum are using 38 psi too.

Unobtanium said:

My dealer is who replaced my tires. They are ALL exactly 36psi cold or 40psi hot all the way around. Exactly. They must have some rare tire pressure gnome that puts the air in one molecule at a time or something.

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And they may even put in nitrogen instead of air for your tires like Costco does...

After 50,000 mostly interstate miles on my GT with tire pressure at 36 monitored closely the tire tread was worn more in the center than on the edges. 38 will give you better mileage but a bit rougher and likely less traction and from my experience will likely wear more unevenly from the center of the tire...

yrwei52 said:

BTW, I put 38 psi instead of 36 on GT's 225/55-19 tires based on past experience as factory recommended tire pressure for the US market has always been too low IMHO. You can actually see different tire pressures recommendations under different load conditions in our CX-5's owner's manual for Mexico market. Our '98 Honda CR-V recommends 26 psi but I've been keeping 35 psi to prevent tire wearing on both sides of tread! I noticed many people on this forum are using 38 psi too.

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Thanks for the info, yrwel52.....Gonna set my tires to 38 psi like you mentioned, and see how that goes. Never had a vehicle with 19" tires/wheels, but I'm with you, I believe recommended tire pressures are too low so I always set my mine 2-3 lbs higher on all my vehicles.

yrwei52 said:

And they may even put in nitrogen instead of air for your tires like Costco does...

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I usually opt for the blend. They have a 78% Nitrogen "blend" that's pretty cheap.

GAXIBM said:

After 50,000 mostly interstate miles on my GT with tire pressure at 36 monitored closely the tire tread was worn more in the center than on the edges. 38 will give you better mileage but a bit rougher and likely less traction and from my experience will likely wear more unevenly from the center of the tire...

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This may be true for mostly interstate driving but those of us who do lots of cornering, especially hard cornering, need to run higher than recommended pressure to achieve even tread wear. In any case, the CX-5 with it's relatively short wheelbase, tall center of gravity and high ground clearance makes for a far from ideal interstate cruiser. It only comes into it's element in the city, suburban parkways, curvy country roads (paved or not) and in the mountains.

Unobtanium said:

I usually opt for the blend. They have a 78% Nitrogen "blend" that's pretty cheap.

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Me too. But I've noticed the "blend", over time, starts to approach pure nitrogen. That's because the slow but natural loss of air through the tire is selective on the molecular level. In other words, hydrogen, helium and oxygen molecules are all smaller than nitrogen and therefore diffuse through the tire at a faster rate than the much larger nitrogen molecules.

For this reason I only "top off" with enough air to achieve the desired pressure (trying not to overshoot so I don't need to bleed off any of my nitrogen rich air). This really works and if you swap out to winter tires/wheels twice a year it works twice as well. Before I store the set for the off-season I add 2 psi and they are generally spot on 6 months later when I'm ready to install them. After a couple of years of this I notice they are losing less pressure over the off-season than originally and I only add 1 psi or less and this achieves proper pressure 6 months later. That's because nitrogen rich air diffuses more slowly.