Tire pressures
I have heard and have confirmed with testing that mpg will increase by about .4 mpg or so for each PSI you increase for all 4 tires. Has anyone tested and documented this for sure? Also, has anyone calculated the point when PSI no longer increased the mpg? I know it's really not safe to exceed about 40-45 PSI in most tires and they will really begin to wear in the center at those pressures. Wondering at what PSI the increase stops.
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Re: Tire pressures
[quote="qsiguy"]I have heard and have confirmed with testing that mpg will increase by about .4 mpg or so for each PSI you increase for all 4 tires. Has anyone tested and documented this for sure? Also, has anyone calculated the point when PSI no longer increased the mpg? I know it's really not safe to exceed about 40-45 PSI in most tires and they will really begin to wear in the center at those pressures. Wondering at what PSI the increase stops.[/quote]
I wonder how much it depends on vehicle/tire size.
Used to run my 35 psi max tires at 40 and got results as you. Rode rougher though. Then wife bought suburban and those tires (285/70r16) are rated for 65 psi max. In a search for different tires and wheels I fond custom wheels to mount 19.5 real truck tires on for max life, improved hauling and those run 110 psi max.... While they are rated for the load and I could see where they'd reduce the rolling resistance I can't help but wonder how they ride?? As much as I'd like to believe they'll follow the .4 mpg for each psi, I really don't expect her mileage to increase from 10 to 28 mpg from just the tire/wheel swap! (if so they might actually be cost effective)
Tire pressures
Fran on hydrogen-boost.com has test results on his site. I convinced me to keep my tires well inflanted. I run 40-45 in my tires.
Tire pressures
I have some good tire pressure numbers one of my testers gathered in a 2006 Dodge Charger Hemi. I have them at my office so I'll post them next week when I'm back there.
Tire pressures
I have been running 60 psi in the tires on my Saturn and have noticed no ill effects on the wear pattern. I also suspect that there is a point at which increasing pressure doesn't significantly increase FE.
Tire pressures
They now are saying to replace tires every 4 years worn out or not. Compound degrades.
Do radial tires wear in the middle when over inflated, like old bias ply tires did?
Tire pressures
[quote]Do radial tires wear in the middle when over inflated, like old bias ply tires did?[/quote]
I have not noticed that pattern. I heard someone say once that radial tires aren't affected that way. The sidewalls bulge less with more pressure but the steel belts tend to keep the tread are from doing so.
Tire pressures
Real world suggestion: consider 85 series tires IE LT235/85 R16 Advantages: narrower so less rolling resisance. better in ice and snow, ok in mud. widely available and probably cheaper, yes its the old standard... I have proven this concept under the most rigorous of conditions and did not notice any loss of handling from 235/70/16 to 215/85/16. The 70 or 80 denotes the format. I have found that the proper format tire for conditions bald is as good or better than the "popular" format tire with tread. Another great technique available from Discount Tire and Peerless tire in the west is siping; many small cuts in the tires, once by razor now by machine. Once only done by racers, must do where tires were purchased to keep your tire warrany... Benefits: increases traction greatly in winter, summer cools tires much better so even softer rubvber lasts longer, Cost about 7$/tire, can be done any time, unlike studs, subject to warranty concerns. :lol:
Tire pressures
[quote="krmusher"]Iburnh2o said: Then wife bought suburban and those tires (285/70r16) are rated for 65 psi max.
Am familiar with that type of vehicle and wheels etc...
IMHO Many advantages are to be gained by first determining the format of tire size/ shape that you want... Here's what I mean: your cited tire size is part of the modern trend toward wider less fuel efficient tires that have poorer traction in ice and snow but better traction in mud. Supposedly they "handle" better.
Real world suggestion: consider 85 series tires IE LT235/85 R16 Advantages: narrower so less rolling resisance. better in ice and snow, ok in mud. widely available and probably cheaper, yes its the old standard... I have proven this concept under the most rigorous of conditions and did not notice any loss of handling from 235/70/16 to 215/85/16. The 70 or 80 denotes the format. I have found that the proper format tire for conditions bald is as good or better than the "popular" format tire with tread. Another great technique available from Discount Tire and Peerless tire in the west is siping; many small cuts in the tires, once by razor now by machine. Once only done by racers, must do where tires were purchased to keep your tire warrany... Benefits: increases traction greatly in winter, summer cools tires much better so even softer rubvber lasts longer, Cost about 7$/tire, can be done any time, unlike studs, subject to warranty concerns. :lol:[/quote]
I agree completely with you. Tall and narrow have always gotten me better mileage and traction. I still like the idea of running 19.5 truck tires, but have narrowed things down to some 225, vs the 285 that came on the truck. Though I've never had tires siped one concern with the tires I've looked at for the 19.5 wheels is lack of traction I might have to look into siping them for the added traction come winter. Thanks for the input.
Tire pressures
Traction is not really an issue for me here in Phoenix. Never snows and the occational rain can be dealt with with some carefull driving. I could put some pretty narrow tires on he Toyota. It's been so long since I've driven the Toyota I can't remember how much pressure I was running in the tires.
Tire pressures
We occasionally get snow (or as RG calls it 'sky poop')
Tire pressures
I need to be informed on what you expect to get from 19.5" wheels? The context I've seen is the large wheel skinny tire set up I see on mainly cars. I think it's for handling by reducing tire flex? I've heard it rides poorly. You mentioned lack of tread selection at 19.5"? Are 85 series tires available in 17,18" etc? (20" seems to have many choices in wheels) There are online tire calculators that might show what's possible and the effects. I've also experimented with how tall you can go with out changing gearing. I've found 5-10% usually works unless you get fitment problems, easy to do these days. Above 10% its chancy as you might get out of your engines torque band. You seem to have the most fitment problems with cars and the most torque band problems with trucks. Hope this is useful... :roll:
Tire pressures
[quote="krmusher"]I need to be informed on what you expect to get from 19.5" wheels? [/quote]
[url=http://www.ricksontruck.com/why_195s.html]Rickson[/url] has the details. It's not a mod for gas mileage, so much as tire mileage. Gas mileage should improve a little but nothing huge. I'm simply looking for a tire that will last longer and we like the look. Also plan on either using custom offset on rear wheels or spacers so that the front and rear tracks line up. As it the back is 4" narrower than the front.
Tire pressures
Thanks for the link, now I see what its about! Any idea how the ride quality is?
The heights and widths are similar to the 85 series 16s with the 225 and 8 widths, must work...
Tire pressures
A little off topic, we use to live where it would snow like that all the time. Have 1 meter dumps, no biggie. I remember my dad snowmobiling and the hut was on 15ft? stilts and they still had to dig down to it.
Tire pressures
Wear depends on the particular tire, some apparently don't like it when they are run at high pressure and so wear unevenly.
From TDICLUB forum http://forums.tdiclub.com/showthread.php?t=111009&page=3
"....As to higher tire pressures, another consideration besides a narrowed contact patch is that some tire tread construction will not tolerate significantly higher pressures in terms of even treadwear. OEM TDI tires generally perform well in this respect, but not all tires do. I had a dramatic example of this; I had set of Firestone Firehawks in a correct +1 size for one of my cars. Running 40 PSI (rated @ 44 max) for 5000 miles wore the center of the tread down to the wear bars while the outer edges were not even down a 1/32" from new on all 4 tires (car had been correctly aligned right before tire installation). These tires were quite highly rated for real world treadwear according to Tirerack's owner survey (and UTOG was 500). I think this case may be unusual, but I've read reports of less dramatic uneven treadwear with other tires."
A lot here on tire rolling resistance, Crr, and how to analyse it for yourself with tests. etc.
Tire pressures
and another item from the tdiclub
http://forums.tdiclub.com/showthread.php?t=111009&page=7 ....The quote below gives a good summary"
"For example in Figure 3 below, going from the tire with the highest rolling resistance to the tire with the lowest rolling resistance within this test group can improve highway mileage by about 3.9 mpg, or about 12%, even at 25 psi, which is typically lower than the recommended tire pressure. On the other hand, going from 20 psi (low inflation) to 45 psi (maximum recommended inflation) yielded about a 1.5 to 2.0 mpg difference in the fuel economy expected from each set of tires."
See:
http://www.ecosconsulting.com/downloads/2003-01-31_600-03-001CRVOL2.pdf
Also, take a look at the presentation made by Tim J. LaClair of Michelin. He indicates that the overwhelming majority of the rolling resistance comes from the hysteresis of the tire rubber.
http://www.energy.ca.gov/transportation/tire_efficiency/documents/2002-0...
For me, the information which has been presented to the California Energy Commision gives a pretty clear picture: get those low rolling resistance tires....