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davewill
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Re: Put some air in those tires!

Sun Apr 10, 2011 7:10 pm

DarkStar wrote:...and realized that this is a lot more controversial than even trying to agree that a police officer won't pull you over for doing 5 MPH over the speed limit! :lol:
He won't...unless he wants to!

Seriously, I don't really doubt that range would improve, I just wanted to know if he had DATA to back up his 5% claim. So, it wasn't really even a disagreement anyway.
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DaveEV
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Re: Put some air in those tires!

Sun Apr 10, 2011 7:28 pm

davewill wrote:I just wanted to know if he had DATA to back up his 5% claim.
Over on the cleanmpg.com forums, you'll find many that report a 5% gain by going up to ~40psi. Many there go up to 50psi and report 10psi, but since the the gains are non-linear... It won't take long for someone to run some real tests in their LEAF.

derkraut
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Re: Put some air in those tires!

Sun Apr 10, 2011 8:34 pm

drees wrote:
davewill wrote:I just wanted to know if he had DATA to back up his 5% claim.
Over on the cleanmpg.com forums, you'll find many that report a 5% gain by going up to ~40psi. Many there go up to 50psi and report 10psi, but since the the gains are non-linear... It won't take long for someone to run some real tests in their LEAF.
I have an "06 Prius, (purchased new) now with 44K miles on the odometer. For the first 10,000 miles, I ran with 32psi (cold), and my average fuel consumption was 43.6mpg over that period. So, as an experiment I went up to 40psi (cold); and my mpg went up to 47.5mpg for the next 10k miles. At 30k miles, I went up to 42psi (cold), front and rear, still the same original tires. My mileage from 30k thru the present is 49.4mpg. I have no doubt that higher psi improves fuel economy, in the Prius.
On the downside, it does ride somewhat "stiffer", but I've noticed no real difference in handling/braking.
Looks like I might get 50k-60k+ miles out of my original (Goodyear Integrity) tires---which many Prius owners despise. When I do change, I'm going to go with the Michelin Energy Savers, which are perfect for this part of the country (no snow and very little rain).
I plan to run 40psi or so in the Leaf (if it ever arrives).
Derkraut
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DaveinOlyWA
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Re: Put some air in those tires!

Sun Apr 10, 2011 8:54 pm

Its impossible to exactly quantify any effect of any change without extensive side by side tests with two identical vehicles so all I can say is that over the past 7 years I have tracked mileage on 3 different Priuses and how they have performed and one thing. I do know without a doubt is that everything makes a difference.
Be it tire pressure wind speed and direction. Or the temperature tire pressure time of day I got gas or the amount of oil in the crankcase it all matters.

I consider tire pressure to be the greatest effect on performance other than the time of year and temperature assuming all other things are equal
2011 SL; 44,598 mi, 87% SOH. 2013 S; 44,840 mi, 91% SOH. 2016 S30; 29,413 mi, 99% SOH. 2018 S; 25,185 mi, SOH 92.23%. 2019 S Plus; 412 mi, 99.72% SOH
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aqn
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Re: Put some air in those tires!

Sun Apr 10, 2011 8:57 pm

DarkStar wrote:To each their own, however I've always ran maximum sidewall pressure in all my vehicles and only had a problem once [...] the wear was not in the center of the tires (it was the outer edges) [...]
Should I read that to mean that your running the maximum sidewall pressure has not/never resulted in more wear in the center of the tread? And to further qualify that information, how would you characterize your driving style?
That test has this interesting statement:
"Additionally our experience is that while low tire pressures increase tire rolling resistance, higher than recommended tire pressures don't reduce tire rolling resistance to the same degree."
drees wrote:Over on the cleanmpg.com forums, you'll find many that report a 5% gain by going up to ~40psi.
If it's true that running a higher pressure results in better efficiency, what causes that increase? A shorter/narrower contact patch, leading to less tire-road friction? If that's true (smaller contact patch), then shouldn't DarkStar have had tires that wear more in the middle of the tread?

Maybe it's not because of a smaller contact patch, but because the higher pressure results in less "flexy" tires and therefore smaller frictional losses?
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DaveinOlyWA
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Re: Put some air in those tires!

Sun Apr 10, 2011 9:11 pm

I have talked to or read responses from hundreds of people and all say that beyond a certain point there is no measurable. Improvement. In performance and it seems to be around 45 PSI. I run my tires at 42. If I thought I would vet better mileage by running higher PSI I would have. Done it in a heartbeat.
also I feeel little difference in ride comfort but readily notice body roll when pressures get low. Unfortunately. TPMS is set too low for my tastes.

A few times I knew my pressures were low before I was warned
2011 SL; 44,598 mi, 87% SOH. 2013 S; 44,840 mi, 91% SOH. 2016 S30; 29,413 mi, 99% SOH. 2018 S; 25,185 mi, SOH 92.23%. 2019 S Plus; 412 mi, 99.72% SOH
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Smidge204
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Re: Put some air in those tires!

Mon Apr 11, 2011 5:26 am

DaveinOlyWA wrote:the increase in efficiency from less rolling resistance from increasing tire pressure is not dependent upon the method of motivation.
My initial intuition agrees, but thinking about it more carefully I'm not so sure that applies to total energy consumption.

For starters, the LEAF already had low resistance tires. These should be stiffer than normal tires, so increasing the pressure would probably have less an effect overall.

Then consider the efficiency of the drivetrain. Assuming gasoline ICE is 20% tank to wheels and the LEAF is 80% battery to wheels to make the math easy...

For a particular style of driving we need 20,000 [favorite units] of energy put to the road.

ICE, 20% efficient, uses 100,000 units of energy input to get 20,000 units out. If over-inflating the tires decreases this by 5% we only need 19,000 units on the road to do the same driving, so we need 95,000 input. We save 5,000 units.

EV uses 25,000 units of energy to get the same 20,000 units to the road. Again we over-inflate and only need 19,000 units. Calculating back we now have 23,750 units input for a saving of 1,250 units total.

In other words, we saved 5% in both cases as we would expect, but for the EV we saved 5% of a much smaller margin. This is somewhat like replacing a car that gets 10MPG with one that gets 15MPG, versus replacing a car that gets 30MPG with one that gets 40MPG.
=Smidge=

DarkStar
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Re: Put some air in those tires!

Mon Apr 11, 2011 6:15 am

aqn wrote:
DarkStar wrote:To each their own, however I've always ran maximum sidewall pressure in all my vehicles and only had a problem once [...] the wear was not in the center of the tires (it was the outer edges) [...]
Should I read that to mean that your running the maximum sidewall pressure has not/never resulted in more wear in the center of the tread? And to further qualify that information, how would you characterize your driving style?
Correct, I've always had very even tire wear when running maximum sidewall pressure. The only problem I had was the one I described earlier when I was told the increased side tread wear was because I wasn't running enough pressure, I'm pretty sure it was because of the crappy tires they sold me. :D

If your driving styles are 0=mild and 10=super aggressive, when I drove my ICE I was around a 6 on most days, 7 very rarely. In the Leaf I'm driving it around a 3 to 4 as I learn about increasing my miles/kWh.
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Reserved: 04/20/10 | Ordered: 10/01/10 | EV Project Blink Installed: 03/22/11 | Delivered: 03/25/11 | VIN: 568

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arnon
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Re: Put some air in those tires!

Sat May 14, 2011 8:25 pm

Weight transfer is one of the causes of uneven wear of your tires. When you do hard cornering(outside wear). Camber is another, check your alignment. I rotate my tires to get even wear especially my working van.
I had the same problem with my new tires(working van-fully loaded-weight effects alignment) inside front tires were bald at less than 7K miles. Going down hills Grant Pass, Shasta or Blue Mountain surely fun but hard for tires and brakes.
As for Leaf, I intend to keep my tires inflated at recommended PSI(may be up a tick) especially in seattle rain. Curtianly check PSI so often when weather changes or travel up into the higher elevations. I can't drive Leaf hard so I'm not going worry about lower my PSI to compensate for heat. PSI on tires really matters.
DarkStar wrote:
aqn wrote:
DarkStar wrote:To each their own, however I've always ran maximum sidewall pressure in all my vehicles and only had a problem once [...] the wear was not in the center of the tires (it was the outer edges) [...]
Should I read that to mean that your running the maximum sidewall pressure has not/never resulted in more wear in the center of the tread? And to further qualify that information, how would you characterize your driving style?
Correct, I've always had very even tire wear when running maximum sidewall pressure. The only problem I had was the one I described earlier when I was told the increased side tread wear was because I wasn't running enough pressure, I'm pretty sure it was because of the crappy tires they sold me. :D

If your driving styles are 0=mild and 10=super aggressive, when I drove my ICE I was around a 6 on most days, 7 very rarely. In the Leaf I'm driving it around a 3 to 4 as I learn about increasing my miles/kWh.
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DarkStar
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Re: Put some air in those tires!

Sat May 14, 2011 9:01 pm

arnon wrote:Weight transfer is one of the causes of uneven wear of your tires. When you do hard cornering(outside wear). Camber is another, check your alignment. I rotate my tires to get even wear especially my working van.
I had the same problem with my new tires(working van-fully loaded-weight effects alignment) inside front tires were bald at less than 7K miles. Going down hills Grant Pass, Shasta or Blue Mountain surely fun but hard for tires and brakes.
As for Leaf, I intend to keep my tires inflated at recommended PSI(may be up a tick) especially in seattle rain. Curtianly check PSI so often when weather changes or travel up into the higher elevations. I can't drive Leaf hard so I'm not going worry about lower my PSI to compensate for heat. PSI on tires really matters.
Unfortunately after two alignments that didn't result in any changes, I changed the tire store and oddly that solved the issue. :D
Mikiko (2011 Nissan LEAF ETEC) Status:
Reserved: 04/20/10 | Ordered: 10/01/10 | EV Project Blink Installed: 03/22/11 | Delivered: 03/25/11 | VIN: 568

Oregon Electric Vehicle Association | Electric Auto Association

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