07camry — First, I must correct a common error, namely the statement that nitrogen expands less with temperature than air (which is itself ~78% nitrogen). This is false for dry gases. Dry air and dry nitrogen both expand equally as a function of temperature — the gas law tells us so. The likeliest reason for this statement is that not all air compressors properly dry the air, and the presence of water vapor in the compressed air changes its behavior as a function of temperature. Nitrogen is likely supplied properly dried and thus doesn't suffer from the water-vapor problem (until one tops up the tires with compressed air!).

As far as the size of the molecules is concerned, I note that nitrogen is #7 in the periodic table, whereas oxygen is #8. I would thus expect the nitrogen molecule to be smaller rather than larger than the oxygen molecule (the opposite of what you say). Can you cite a reputable source regarding their relative molecular sizes?

Stan

 

Just put on a set of the new Nokian WR G2. I have had excellent experience in the past with the Nokian WRs on an Acura TL, and this is their newest incarnation. The TCH feels so much better compared to the original Bridgestones (lasted only 25k) it is hard to believe. Better ride, a firmer cornering, totally silent and dramatically improved wet and snow traction. The WR G2 is one of Nokian’s all weather tires, has a 60,000 tread life and is clearly one of the best all weather tires made for traction on ice, snow and wet. I can’t give any mpg information yet, but it is claimed to be a relatively LRR tire with silica and canola oil tread compound. So far I’m very pleased.

 

I think I've found the answer to the second of my questions in post #22 above. It's given in the paper "Are Nitrogen Molecules Really Larger Than Oxygen Molecules?" at:
http://getnitrogen.org/pdf/graham.pdf
For the process of "permeation" of the gas through the rubber of the tire, the nitrogen molecule's "kinetic diameter" is indeed larger than that of the oxygen molecule. Interestingly, as time progresses, the proportion of nitrogen in the tire would thus tend to rise. If one kept topping up the tire pressure with dry compressed air, one would eventually have achieved essentially the same as a pure nitrogen fillup in the first place! This process is, of course, just what one does when maintaining one's tire pressures — except that the compressed air used is probably not dry.

Stan

 

I have the Michelin tires on my Camry and my mom have the Bridgestones. Both cars have the tires rotated at 5000 miles. The Bridgestones are crap. They are loud and wore slap out at 32000 miles. My Camry has 40000 on it nd the tires are still fine. Michelins are hard to beat.

 

I have the Michelin Energy tires on my Camry. I hate them. I've squeezed out 39K miles in 2.5 years on them and they are desperately in need of replacement. I've had them rotated with every oil change and maintain the pressure at 40PSI on a weekly basis. I also do not drive the Camry aggressively. In fact, I describe myself as a little old lady when I drive it. I just don't think that 39K miles is all that great for a set of tires.

Perhaps I'm expecting too much as I've never owned a private passenger "family-type" vehicle. My 2002 Tacoma Limited has had the same set of tires on it for 4.5 years and I expect to get another year (total of about 80K miles) on those tires (BFG All-Terrain TA/KO). Perhaps I should lower my standards. I'm sure I will wind up getting the Michelin Energy tires again despite what I consider poor performance and an all-around ugly tire.

Anyhow, I love my Camry.

 

Where were you back when GM put only half the fluid in the shock absorbers to save millions of dollars. You buy a new GM car back then, maybe in the mid 60's. You not only had to buy new shock absorbers around 19,000 miles but also a new set of tires. For a few years it was the American car makers way of keeping the car prices low.

After many wrecks due to near slick tires caused by the fast wearing tires. The government stepped in requiring the American car manufactures to install longer lasting tires on the new cars. State inspections started and including a tire tread test for safety.

Tracy, the newer longer lasting tire replacement for your Energy tires is the Michelin Primacy MXV4. I'm going that route when the time comes to stick with the oem, LLR tire. The Primacy tire is slightly less on the LLR but in doing so has better traction and a longer tread life.

 

Michelin Energy .... shhhhhsh

 

I had the Primacy MXV4s put on my TCH when the original Bridgestones wore out at 27K miles about a month ago. They are a very nice- very quiet, great grip, excellent in snow. I had them pump them to 36psi, and no complaints about mileage. (Mileage is similar to my normal winter mileage)

They are also very cheap right now compared to the Energys. Sam's has them for about $135/tire, and also offer $80 off a set of 4 until the end of the year.

Beware- they are 'H' rated compared to the 'V' rating of the OEM tires. To me, I was willing to make the change.

 

This is second hand, as I do not have them. But on "another" hybrid forum, people have been saying very good things about the Goodyear Assurance Fuel Max. This is a new LRR tire, and Goodyear claims on their website that it is quiet due to newly developed tread compounds. The same compounds provide better mileage (tire comes with a mileage warranty) and the two posters that have them say FE is equal to, or better than, the energy, and they both love the tire.

You can find the writeup HERE = http://www.goodyeartires.com/goodyea...alcTab_ppg=1.5

I called Goodyear Customer Service and talked with them about it. They sound really excited about it, and you can sense that they think they have a winner here. Cheaper that Michelins too!

RFB

 

Just purchased Pirelli P4 tires for my hybrid. They have more than double the treadwear rating and were about half the cost of the OEM tires!

I'll let you know how the MPGs pan out...