Tire pressure for best mpg?

I just switched tires/wheels from the stock 15" Monterey/Michelin Energy's to 16" Avus with Michelin Energy's (stock tire size for a NB). What tire pressure should I be running for the best mpg? The roads that I travel don't have many seams, so I can live with higher pressure. The car is a 2003 Jetta Wagon, 95% of the miles is with me alone in the car, with a goodly % of the miles driven at speeds of 55 - 70 mph. I did make a high speed blast to Ohio and back last Sunday, I'll fill-up tomorrow to see how much of a mileage hit I took. I probably averaged 80+ mph for that trip - spent a good 5 minutes @ 4200 rpm in 5th, and the RX7 that I was letting play "rabbit" ran off and left me!

Thanks

The highest tire pressure that doesn't make your back complain and still falls under the sidewall maximum.

Mine are at 42/45 f/r: sidewall max is 51.

4200 RPM in 5th is how fast? 120 MPH?

Close, when I glanced down the needle was between 115 and 120..... Shhhhhhh....... I really wasn't paying much attention to the gauges, I was watching the road for any signs of the Ohio State Police. I still had more "go" pedal to push on, but I was following at a distance and didn't want to catch up. The rest of the time on the interstate was spent between 70 and 90.

As a side note, it was daylilght, on a 2 lane divided interstate, and no cars were passed during this time.

Valentine and Rocketchip - the only way to fly!

Thanks for the info guys (and gals). I filled up the tank today, (I cheated and threw in a bit less than 4 gallons a few days ago. With today's fill-up and the 3.92 gallons that I added on Wed, that came to 19.68 gallons (usa). I drove 831.2 miles during that time, so the mpg was 42.235. Not as bad as I thought for the speeds that I was traveling.

running with max tire pressure will likely cause suspension components to fail earlier than they might fail at a 'normal' tire pressure like 34. also it will make the car handle like crap and give you less grip than otherwise. it may increase braking distance in an emergency-stop. tradeoffs. no free lunch. is a couple of mpg of fuel economy worth all those other things? i say no, especially when it comes to the safety/handling concern.

i recommend 34 or 35 psi cold tire pressure. i may play an idiot here on tdiclub but some folks do actually consider me an expert on cars elsewhere!

On a 44 psi max side wall tire, I use 85%, or range of 38/36 psi. To my seat of the pants experience, over 38 psi the ride is a tad harsh. I currently have 62,000 miles on OEM GY LS-H's. At the last rotation (60k) I measured 4/32 consumption or 15,000 miles per 1/32 in. So if I run it to 2/32 in, the projected mileage will be 120,000 miles. I also do a 5 tire(cross) rotation, for the VW technical data as well as heads up reading on the TDI Club web site has indicated the right front passenger position wears faster over time. The 5 tire 10k interval cross rotation makes EVERY tire hit the front passenger position verses a max of two tires using the OEM rotation recommendation of front to rear, rear to front. Since I do not run max load, and want to offset the massive understeer our front engine front wheel drive cars inherently have, I run 2# less in the (36/34 psi) rears, fronts (38/36 psi fronts) The oem alignment, brakes and suspension parts are still compliant. (as evidenced by dead even wear across the tire tread) My fuel mileage range has been 44-62 mpg. So the structure is there to accomplish any goals set for fuel mileage. In addition, the SF/SJ CA roads are acknowledge to be some of the worst in the country. GY LSH's have not been considered the best OEM tires.

Hi, pilgrim,

Did I understand that you have made a big increase in tire diameter, and are still believing the car gauges?

If so, you may be luckier than you think about not getting a ticket. If you were driving faster than "normal", then you will get less mileage than normal, even with a better tire combination.

If you adjust the gauge readings so you are driving your "old speed" and properly allowing for odometer error, you should see a great improvement in fuel economy.

Ernie Rogers

Thanks for the info guys (and gals). I filled up the tank today, (I cheated and threw in a bit less than 4 gallons a few days ago. With today's fill-up and the 3.92 gallons that I added on Wed, that came to 19.68 gallons (usa). I drove 831.2 miles during that time, so the mpg was 42.235. Not as bad as I thought for the speeds that I was traveling.

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I have been using a portable GPS and it indicates for 195 65 15 a speedometer error of app 3/4 mph.

I run Michelin Energy MX IV 195/65 R15 H @40psi = great wear, better handling than at 32-34 VW recommended, and the turn squeal is gone.

I will continue to run them - Let me explain why:

I just had to replace my tires, and one rim (The '02 GLS 5 spoke alloy rims are amazing! read on) due to a piece of the highway being displaced by a large truck, and sitting on the macadam. I hit said chunk of road at about 50mph (cars on both sides, no hope to duck it, I will get an evo skid plate as soon as I can afford it) - needless to say even at 40 psi the tire compressed enough that the back of the rim dimpled and had a 4" offset crack toward the axle (big effin rock, huh?) There was no visible damage to the Right front tire, but I know the plies had to be shot after that hit, and I had to run about 1500 ft on a flat, with turns to get into a parking lot. Since I had about 29.5K (yup, just happened) on the tires, and they were about 1/2 worn I replaced them all. I've already given away the 3 good tires to another club member who lives nearby, I hear the pm's turning in your heads.
I wonder what the damage to the rim would have been if I had been running the 'soft' pressure (32-34) - another 3 motorists hit the same big friggin boulder - and let me tell you - steelies got flattened and crushed (don't know if they were running correct pressures, honda / toyota) but they must have hit the bead channel, so the sidewall should have helped a little. sorry for the digression.

I wouldnt be sure either what would have happened at almost any common PSI. The overwhelming % of tires are not made to be "bullet proof". So as a reason to run 40 psi.. I would say the subsequent roadside accidents were the luck of the draw. Sorry to hear about your roadside accident.