Tire pressure is important!
#32
12-12-2007, 06:05 PM
Re: Tire pressure is important!
GaryG
#33
12-13-2007, 07:40 AM
Re: Tire pressure is important!
For me, I have a feel when everything is rolling right and can tell if I have a low tire (44psi). It's almost like dragging an anchor you can't hear. I think I started out at around 40psi from the factory. It may have been cold at the KC plant when they shipped my FEH to me in warm Jupiter in January '05.
When I seen I could get 40mpg tanks within my first few fills, I was hooked on the challenge to maintain and improve my mileage. I cranked the tires up to 44psi and it stayed there for a year. I thought exceeding the max sidewall would take any liability away from the tire company and put it on myself back then. I was at the time exceeding 45mpg tanks and satisfied with that results.
During one of the test I was working with Wayne Gerdes on in my FEH, I crank the tires up to 52psi. I didn't lower them back down after the test and thought I'd try and see how much a difference it would make on a tank. You can see by my Miles To Empty on this sig page the results. After hitting a 53mpg tank, I'm convinced that 50psi is an acceptable risk I'm willing to take. Wear has slowed down on my tires and I feel my FWD FEH handles best here in So. FL. We get heavy rain at times and my tires hold the road in cornering and hard stops better I think then they did with 40psi.
BTW, I've had a tire that leaks air from the day I got my FEH. I can tell when one tire is below 44psi just by the drop in mileage and the drag when coasting in neutral. Neutral coasting is most likely the reason I can tell the tires need air right away. When I go EV on the downside of a big bridge, I can tell how my speed increases as I often have to go from "N" to "L" for regen to stay under 40mph.
All the top Hypermilers all agree that tire pressure will effect rolling resistance. Most the top hypermilers I've talked with think I should put more than 50psi in my tires, but that's my limit.
GaryG
When I seen I could get 40mpg tanks within my first few fills, I was hooked on the challenge to maintain and improve my mileage. I cranked the tires up to 44psi and it stayed there for a year. I thought exceeding the max sidewall would take any liability away from the tire company and put it on myself back then. I was at the time exceeding 45mpg tanks and satisfied with that results.
During one of the test I was working with Wayne Gerdes on in my FEH, I crank the tires up to 52psi. I didn't lower them back down after the test and thought I'd try and see how much a difference it would make on a tank. You can see by my Miles To Empty on this sig page the results. After hitting a 53mpg tank, I'm convinced that 50psi is an acceptable risk I'm willing to take. Wear has slowed down on my tires and I feel my FWD FEH handles best here in So. FL. We get heavy rain at times and my tires hold the road in cornering and hard stops better I think then they did with 40psi.
BTW, I've had a tire that leaks air from the day I got my FEH. I can tell when one tire is below 44psi just by the drop in mileage and the drag when coasting in neutral. Neutral coasting is most likely the reason I can tell the tires need air right away. When I go EV on the downside of a big bridge, I can tell how my speed increases as I often have to go from "N" to "L" for regen to stay under 40mph.
All the top Hypermilers all agree that tire pressure will effect rolling resistance. Most the top hypermilers I've talked with think I should put more than 50psi in my tires, but that's my limit.
GaryG
#34
12-13-2007, 08:17 AM
Re: Tire pressure is important!
Using "L" for regen is the key to my mileage. It takes away much of the fuel needed to to turn the small generator to charge the HV battery. When you let off that accelerator in "L", fuel is almost cut from the ICE. NOW, your not only getting hard regen, but your reducing fuel consumption. Next, you accelerate at the lowest RPM you can before your next Fake Shift again to go EV. At the bounces of the tach, shift to "N" for a coast or "D" to maintain speed in EV. I've heard some here say to accelerate up to 3,500 RPM's, that's just foolish IMO. I say accelerate at 1,800 RPM's if you can, but many times I accelerate at 1,500 RPM's. Think about what I'm saying! At 1,500 RPM's, your accelerating 25% less than at 2,000 RPM's. At 3,000 RPM's, you have doubled your gas consumption and are at a bad area of the torque curve of the Atkinson Cycle engine we have. The slow acceleration allows time for the small generator to build more of a charge in the HV battery at the least fuel consumption for longer EV mode.
GaryG
GaryG
#35
12-13-2007, 08:35 AM
Re: Tire pressure is important!
Using "L" for regen is the key to my mileage. It takes away much of the fuel needed to to turn the small generator to charge the HV battery. When you let off that accelerator in "L", fuel is almost cut from the ICE. NOW, your not only getting hard regen, but your reducing fuel consumption. Next, you accelerate at the lowest RPM you can before your next Fake Shift again to go EV. At the bounces of the tach, shift to "N" for a coast or "D" to maintain speed in EV. I've heard some here say to accelerate up to 3,500 RPM's, that's just foolish IMO. I say accelerate at 1,800 RPM's if you can, but many times I accelerate at 1,500 RPM's. Think about what I'm saying! At 1,500 RPM's, your accelerating 25% less than at 2,000 RPM's. At 3,000 RPM's, you have doubled your gas consumption and are at a bad area of the torque curve of the Atkinson Cycle engine we have. The slow acceleration allows time for the small generator to build more of a charge in the HV battery at the least fuel consumption for longer EV mode.
GaryG
GaryG
#36
12-13-2007, 08:41 AM
Re: Tire pressure is important!
Try it out. Go under recommended psi by a few pounds and then go to MAX. Do an emergency stop from say 50mph and judge for yourself.
#37
12-13-2007, 09:49 AM
Re: Tire pressure is important!
For NASCAR and other racing tires where the working temp of the tire is in the mid 200 degrees Farenheit, a dry gas makes a big difference in the delta between cold and operating temp tires.
For street tires, not so much.
For street tires, not so much.
#38
12-13-2007, 10:23 AM
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Re: Tire pressure is important!
Changing from 35psi to 45psi will net you 2-3 MPG right away.
This is a tip that everyone can do, and takes very little effort.
I just lowered my fronts to 35psi due to all the ice in the mid-west where I drive. Rears are at 40psi for winter. 8 months a year, I'll run 45psi in all four.
See signature for more info!
-John
This is a tip that everyone can do, and takes very little effort.
I just lowered my fronts to 35psi due to all the ice in the mid-west where I drive. Rears are at 40psi for winter. 8 months a year, I'll run 45psi in all four.
See signature for more info!
-John
#39
12-13-2007, 11:15 AM
Re: Tire pressure is important!
I went from 35 to 44psi at the first of last March. Looking back at my mileage by month, I went from 30.5mpg to 34.8mpg (Feb / March). Some of that jump was probably due to warmer temperatures, but not all. My monthly averages have been 35-37mpg ever since.
-- Rick
-- Rick
#40
12-13-2007, 11:45 AM
Re: Tire pressure is important!
I have a feeling you will all just tell me to try it and see what I think, but will anyone quantify "slightly rougher ride" going from say 35 to 45 psi? Is the difference in ride really noticeable? Compromise and go to 40? Put 35 in the front and 40 in the back? 
OK, I moved up to 37 front, and 40 in the rear, we'll see if there is any improvement, everything else being the same...
OK, I moved up to 37 front, and 40 in the rear, we'll see if there is any improvement, everything else being the same...
Last edited by leoashton; 12-14-2007 at 06:07 PM.
