Has anyone here kept track of fuel consumption relative to tire pressure?
I know from experience that pressures below spec will increase fuel burn.
I've just done a 1000 mile run with the tires set at 37 and there is a small positive difference but too soon to say if spurious or significant.
Car feels a little dancier than normal and I wouldn't want to drive it like that if I was pushing it but ok for highway close to posted speed.
Last edited on Thu Oct 14th, 2004 05:03 pm by Codger
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If you over-inflate from the manuf. specification, you will get a small increase in MPG, but you can wear out the insides of the tire faster, thus negating any fuel saving with the subsuquent tire purchase.
I'm going to take it out to the track and check all points across the contact patch with the strain guage to find out what the numbers are. I have old numbers for the Pirellis using carbon paper but those were oriented towards cornering and low fuel/weights. The street tires on the car are Generals and I've just been using factory spec pressures. I'm wondering if I take the pressures up to the high side without compromising full patch contact if the slight reduction in rolling resistance will actually make a difference in fuel consumption or if I'm blowing smoke up my ass.
BTW I'm not considering the extremes of 38+ since tire wear and more importantly, braking, would be out to lunch.
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A man is not old until regrets take the place of dreams...John Barrymore
Ive been running 38lbs up front and 40lbs in the rear. Though my tires have a max psi of 42 I believe it is. Ive never had any problems from that and I run that way primarily because of all the driving I do and want to squeeze out all the mph I can. I would normally keep it around 35lbs up front and rear, but with all the highway driving I do now going to customer locations and work I went ahead and stayed with my trip pressures. When I went on long trips such as down to Florida I would boost up the front just a little just for the sake of fuel economy. Now Im running it full time because of the driving I do.
As for any documentation to better fuel mileage, I have none, but it would be good to see some documentation on that. Though I would think that you would have to do it for a long term because of the pressure fluctuations you are going to get now because of the changes in temperatures.
It does make the driving a bit more free and slightly on the loose side, but it was raining here yesterday and I didnt notice any major differences but I also wasnt pushing the edge either as I would probably be doing in storm chase.
____________________ My car is a synner! It uses Amsoil Synthetic Lubricants.
2001 Pontiac Grand Prix GTP
It whines a lot, but I like it
I run my BFG's at 36 psi front & rear. Just an aside...I've been using nitrogen instead of air for some time now. The nitrogen molecule is larger, so the tires leak less. The psi is maintained for months at a time without changing. Nitrogen also stabilizes the temp, which is especially helpful in summer high-speed driving. I check my tires weekly at Costco.
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Mr. Versatile wrote: I run my BFG's at 36 psi front & rear. Just an aside...I've been using nitrogen instead of air for some time now. The nitrogen molecule is larger, so the tires leak less. The psi is maintained for months at a time without changing. Nitrogen also stabilizes the temp, which is especially helpful in summer high-speed driving. I check my tires weekly at Costco.
Mr. V, where in the heck do you find Nitrogen to fill up your tires with and how much does that cost?
____________________ My car is a synner! It uses Amsoil Synthetic Lubricants.
2001 Pontiac Grand Prix GTP
It whines a lot, but I like it
SyntheticShield wrote: Mr. Versatile wrote: I run my BFG's at 36 psi front & rear. Just an aside...I've been using nitrogen instead of air for some time now. The nitrogen molecule is larger, so the tires leak less. The psi is maintained for months at a time without changing. Nitrogen also stabilizes the temp, which is especially helpful in summer high-speed driving. I check my tires weekly at Costco.
Mr. V, where in the heck do you find Nitrogen to fill up your tires with and how much does that cost?
I'll second that question?! I know we don't have a Costco here in the Manchester, NH area....someone correct me if I'm wrong. I know there is one in the Burlington, VT area.
This is intreguing to me with the colder weather coming up.
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Egz wrote: Don't forget, your tires are already filled with 70% nitrogen. So the gains aren't that big.
Correct you are. However, the major differences have little to do with varying temperature so much as actually loss. The temperature doesn't effect the pressure as much as the fact that oxygen escapes from the tire by diffusion far faster than nitrogen does.
RPIJG wrote: Correct you are. However, the major differences have little to do with varying temperature so much as actually loss. The temperature doesn't effect the pressure as much as the fact that oxygen escapes from the tire by diffusion far faster than nitrogen does.
Right!
Our local COSTCO is the only place I know of, off hand, that will fill tires with Nitrogen. COSTO has been using it for some time now. Since I buy my gas, (and tires), there, they let me fill'em when needed. Fortunately, that isn't too often. I check'em with my own guage, while I'm filling up, and usually they're all within 1# psi for a couple of months.
COSTO fills all the tires they sell & repair with Nitrogen. Virtually all NASCAR/Champ/Indy Car and F1 teams do also.
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I've never heard of using Nitrogen before. Fascinating. I'll have to see if there's any place around here that has it. Ahh... better living through chemistry.
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