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Old 02-21-2008, 01:10 PM   #1
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Tire pressure = MPG gains?

Hi all..newby here.

I've just spent a couple hours scanning these forums..(in spite of having work to do )and it would appear that raising your tire PSI is one of the most recommended and easiest things to do to increase mileage. I recently put new BFG Tractions T/A s on my car and I believe they were set at 32 PSI cold. I'll check this tonight and I believe the side wall says max 44 PSI. Would 40 PSI cold be the way to go?

BTW car is 02 Acura TL-S, new air filter, new tires, starts and runs perfect. Oil and filter changed every 5K kilometres I drive it easy too but want to increase mileage as gas is $$$$$$pensive.

2002 Acura TL-S, stock
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Old 02-21-2008, 02:16 PM   #2
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It might be worth reading your owners manual, as alot of them that I have read recomend 4-6 psi above what is recomended on the door jam if you are doing much highway driving, this does two things, it gives better gas milage, and it reduces the tempeture of the tires.
Alot of us, like my self, run at max side wall presure and for me that is 44psi for my summer tires and 51psi for my snow tires, some people are of the opinion that your tires will not grip well enough, and at least for my self, livng on a winding road, and having some sharp corners that I take on my way to work, I have never had a problem while going the speed limit or even 5mph over, unless it is sheer ice, I can defently tell a differnce in how well my car rolls, it takes less effert to get it moving, is easier to steer, and I feel like I have more controle all around.
With that said I recomend that you find out for your self, of course you should remember that you are respoonsible for your own actions, so make sure that you pay attention and don't put anyone in danger, but find a reasonably empty road or street, and find out how fast you can stop befor your tires chirp, then pump them up a bit and find out if it's enough differnt that you feel uncomfertable, if you don't feel safe then drop the presure down again!

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Old 02-21-2008, 02:20 PM   #3
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You can go up to the highest rating on the sidewall, without any problems. Nobody can tell you what you should run, over that, after all it could create liabilities. I have tires which are rated 32 max and I have been running them at 55 for about a year and a half. I can't quantify how much of an increase they give, but I can say the car will roll, in neutral for what seems like 2x as far.

I'd also suggest you give a grill block a try. This time of year, you can block everything, but if you want to be a little cautious, give yourself a 2x4 inch opening and it will be more than adequate.

Of the items I've tried, the tire pressures and grill block have given me the most noticeable improvement. The incremental increase starts to get smaller from their, but it is their.
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Old 02-21-2008, 03:13 PM   #4
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Originally Posted by Gary Palmer View Post
I have tires which are rated 32 max and I have been running them at 55 for about a year and a half.
I think my Taurus tires are rated a little higher, but I am running 55psi also. I haven't see any gains really as of yet that I can quantify. But I'd like some warmer weather to get a better feel.
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Old 02-21-2008, 06:28 PM   #5
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Those concerned about traction issues probably haven't autocrossed. As one who has participated in autocross for over 15 years now, I can say that I have NEVER experienced a loss of grip due to overinflation of non-competition street tires. More often, grip is sacrificed due to underinflation. (Purpose built race tires, DOT approved or not, are a different story however.)

Just as a practical note, I've raced on plenty of tires at 10-15 psi over their maximum rated pressure and never experienced a failure from it. If ever there was a more punishing test of overinflation, I've yet to find it in any practical use.

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Old 02-22-2008, 12:11 PM   #6
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on snow/ice, traction decreases somewhat with really high pressure. 35 vs 55psi on my cressida is a noticeable difference but they're also about at most 3/16 tread and they received very low snow traction ratings in the first place. on dry pavement... pump em up!. you won't lose tracton till you get stupid high like what even people here would call dangerous. with tires, like other things in the world, the ratings include a LOT of cushion space for 'just in case', mfr defects, and idiots like us that pump them up much higher.
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Old 02-22-2008, 04:13 PM   #7
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TL-Super ,
Welcome to the place.

Most car makers put the tyres at the pressure giving the most comfort at the expense of other factors like economy and performance.

A general rule of thumb is to have all tyres within about 10% or each other and the end carrying the most weigh has the higher pressures.

If your tyres are at 32 now and the max pressure is 44 the I would start half way at 38 and see how that feels for you.
If they are too harsh then changing back is simple enough.

By the way buy a decent pressure gauge. The ones on garage tyre air lines are notoriously inaccurate.

Keep us posted on how you are progressing.

Cheers , Pete.
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Old 02-22-2008, 05:30 PM   #8
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I bought four tires rated 44 psi this summer, after years driving on tires with max sidewall ratings of 32 and then 35 psi. The car's labels indicate 32 psi, if I recall.

I gradually increased the pressure in the new tires from 40 to 45 then 50 psi. Finally to 52 psi. When I crossed 50 psi I felt a definite change in handling, steering was much lighter. Coasting/gliding is better with higher pressures. At 52 psi I figured I could eliminate the power steering and raise my FE additionally by that. That worked out well.

I now have four snow tires on the car, rated at 35 psi. I'm running them at 42. I just completed two days of commuting, 125 mi/day, and netted just over 26 mpg which is better than last year's typical winter numbers of 22-25 mpg. Of those two days, the first had three errand legs that were about 8 mi. each, and the second day had snow on both trips. So the 26 mpg represents less than ideal conditions.

Check and adjust your tire pressure when cold. Pump to a few pounds over your target psi so the next morning when they're cold you can let some air out to hit the target precisely. Figure that hot tires will lose 4-5 psi when they cool down.
Currently getting +/- 50 mpg in fall weather. EPA is 31/39 so not too shabby. WAI, fuel cutoff switch, full belly pan, smooth wheel covers.

Now driving '97 Civic HX; tires ~ 50 psi. '89 Volvo 240 = semi-retired.
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Old 02-23-2008, 02:19 PM   #9
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I would have to say that overinflation does effect traction to some extent (atleast for MY car). Seeing as how my little wheels are only like 4inches wide to begin with, a smaller footprint and bad weather would make it pretty easy to slide. But then again, my car sucks in all weather.

Just dont get crazy and put too much in them. I dunno how much is too much, but 55 in a 44 doesnt seem unreasonable to me...i've seen 90 in 35's :S
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Old 02-23-2008, 02:25 PM   #10
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Oh, and BTW, not too stray away from topic or anything, but how do you like your tires...mainly in the "dry traction" area? I'm considering something similar for my Mustang since they are a decent bang for the buck..

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