ECO-Fit DiscussionThreads discussing the pursuit of ultimate economy, hypermiling techniques & maximizing your MPG
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I bought some light 16x6.5 rims (smallest size I could find), and looked for tires specifically with pressure in mind. I settled on the Kumho Ecsta ASX's in the stock size because they are rated at 51psig. I keep them at 51, and after about 10K miles they seem fine. I don't worry about getting a flat spot in the middle because I don't slow down for corners
EDIT: 15x6.5, NOT 16x6.5. I should pay attention to my own stupid sig...
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Best tank: 518.1 miles, 47 MPG -- Best commute: 50.3 in, 45 out
'07 NHBP Sport AT
Previous owner's mods: Tint front and back, Mugen visors
Traction is improved in dry and wet conditions. Of course there is always a limit.
Not at 60+ psi it isn't. What you're probably thinking of as "improved traction" is actually quicker initial response to steering input. Push a little harder and you will discover that you actually have less total grip. This is precisely why I chose a compromise pressure of 45 psi.
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Valve stems rated at 50psig is good to know but then the questions remain:
how much can it hold and are there standards or differences in the the valve stems? (I know they can easily hold 85psig and some have said easily 100psig.)
I'm not quite understanding where all this concern over the valves is coming from. Bicycle tires -- including many that use the same Schrader valves as car tires -- are routinely inflated to 100+ lbs.
I'm not quite understanding where all this concern over the valves is coming from. Bicycle tires -- including many that use the same Schrader valves as car tires -- are routinely inflated to 100+ lbs.
Incorrect, standard automobile valves are rated to 65psi. There are also valves that are rubber with brass inserts (ie OEM Chevrolet HD truck valves) that will handle higher. Then you have bolt in valves that will hold higher ratings but still should not exceed the tire manufacturers psi.
All you guys running more than the Tire Manufacturers rating on pressure (ie 80psi), please stay away from me and my family on the road. There is a reason for these numbers and some of it probably has to do with safety. They spend alot of money in engineering as well as Honda does when they give you a recommended pressure. You may not be concerned about testing yourself but think about others......
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Incorrect, standard automobile valves are rated to 65psi.
Not incorrect at all. Perhaps it is the valve stem on a car that is rated lower, but I assure you that valve inside the stem can take 100 psi without blinking. I've done it for years as have millions of other cyclists.
Not incorrect at all. Perhaps it is the valve stem on a car that is rated lower, but I assure you that valve inside the stem can take 100 psi without blinking. I've done it for years as have millions of other cyclists.
I'm with you. testing thousands of tires on street and on track as well as run to destruct tests never had a tire stem failure. Many of these tires went well beyond 200 psi before failing, usually around the rim. but not at the stem.
The force exerted on a quarter inch area of a valve stem by 200 psi is only 50 pounds. A tire installer needs a lever and considerable force to remove an old but good stem.
The force exerted on a 15" sidewall of about 1200 lb per inch of rim so you would expect the tire to fail at the weakest point on the rim. And so you do.
back up to 65psig here and about 60K on the car. I believe that puts these tires somewhere around 14k and still doing well. Now, I need to stop being so slack and get better mpg!
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stock and lame
slow and steady wins the race
I'm back on stock wheels/tires. Yesterday, I just pumped my front tires to 42 psi, rear tires to 48 PSI. So far, there hasn't been any big changes in handling. Braking distance didn't increase by much, about 5 to 10 ft difference. I don't feel like there's any safety concerns so I guess I'll keep the setting. I'm somehow starting to believe that it's the way you drive that determines safety rather than car settings. As long as the car handles well around the 65-70 mph mark, then I shouldn't have any problems at all.
I can't comment on MPG nor tire wear because I have 2 sets of tires/wheels that I frequently change.
I'm back on stock wheels/tires. Yesterday, I just pumped my front tires to 42 psi, rear tires to 48 PSI. So far, there hasn't been any big changes in handling. Braking distance didn't increase by much, about 5 to 10 ft difference. I don't feel like there's any safety concerns so I guess I'll keep the setting. I'm somehow starting to believe that it's the way you drive that determines safety rather than car settings. As long as the car handles well around the 65-70 mph mark, then I shouldn't have any problems at all.
I can't comment on MPG nor tire wear because I have 2 sets of tires/wheels that I frequently change.
An increase in braking distance of 5 to 10 ft is very significant to safety.
However, most tires have shorter braking dustances and higher cornering speeds at 40 psi compared to 30 psi..
An increase in braking distance of 5 to 10 ft is very significant to safety.
However, most tires have shorter braking dustances and higher cornering speeds at 40 psi compared to 30 psi..
I do agree that 5 to 10 ft (2 car lengths) is significant. Just clarifying my situation.
My old car (2000 toyota corolla) had 175 width tires and weighed almost the same as a fit. The fit sport has 195 width tires, and when I inflated the 195 width tires to 42 to 48 psi, I've noticed that handling had change. But it also still handled better than the 175 width tires. So basically, I just drive with same braking distances I was driving my old car. That's the reason why I don't see such a big safety concern.
I ran 40 on my stock tires most of their life (just replaced them at 36k a few weeks ago) and they were worn evenly. The only uneven wear I had was a few months with a slow leak in the right front. I checked it one day and it was down to 28 pounds. It was more worn on the outside than the left front, so underinflation can have a serious effect on wear.
The new tires were inflated by Discount Tire at 32 lbs. I ran a few tanks through at that pressure. Just upped them to 40 Sunday. We'll see how the next few tanks are.
My '07 Sport Auto is one of the lucky ones. The worst tanks, winter mix of highway and town, are 32 MPG. Highway is generally 38+ with 44.5 being the best so far.
I finally got a good read on my MPG status. Tires are 38 psi front and 45 psi rear. Drove from California to Las Vegas at night without traffic. Throughout the whole trip, I was on Cruise control and maintained 70 mph (even uphill). The 280 mile trip took a little less than 8 gallons when I filled up in Vegas. So I can conclude that I get at least 35 mpg in that condition.
I finally got a good read on my MPG status. Tires are 38 psi front and 45 psi rear. Drove from California to Las Vegas at night without traffic. Throughout the whole trip, I was on Cruise control and maintained 70 mph (even uphill). The 280 mile trip took a little less than 8 gallons when I filled up in Vegas. So I can conclude that I get at least 35 mpg in that condition.
It's been shown that mpg is reduced when using cruise control on hilly conditions. So maybe you can do better than that.
In the recent months I've had to do a lot of driving up and down california...about 400 miles/6hrs in a day. And i've tried different driving styles and the one style that seems to dramatically increase my mpg is driving WITHOUT cruise control. Perhaps its the grapevine and also other areas where it's hilly, but even on flat stretches of the 5, i get consistently better mpg without cruise, and I even drive FASTER or get stuck in traffic. The difference in mpg I've calculated is about 4mpg on average.
Been driving in similar weather conditions and tires are 42psi front 46psi rear.
Not like I have to worry about it going below 32psig! 
-CleanMPG.com, the real Eco forums.
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