Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
Somebody mentioned running the tires at the max pressure rated on the tire, minus a couple pounds for tire heat while operating. Not based on the pressure marked on the door.
This makes no sense to me. That tire can be mounted on a 1200 lb smart car, or a 3800 lb suv. Common sense says that those two vehicles will require different tire pressures based on the weight of the vehicle, not based on what the tire says.
I don't know about tire dealers in your area, but tire dealers here will weigh your vehicle and inflate to the proper pressue based on weight so that you get the best use out of the tires (i.e. tread runs flat, but is not underinflated).
Anything that can be done to limit tire tread & sidewall flex will gain gas MPG so that only leaves one form of adjusting the tire to your car.......air PSI.
Hard pumped tires (within limits of the tire) will cut rolling resistance in every case no matter the car's weight. Soft tires = better ride. Harder tires= better MPG.
To get an idea of what I'm taking about let most of the air out a bicycles tires then ride it. Feels like you're pulling twice your weight.. Now pump the tires real hard then ride. Feels like there's little weight at all for you to pedal. It's the same thing for any vehicle.
That was the first thought my wife had, but it's been consistent for months now, always about the same mileage. And the "door" over the gas cap is one with a latch on it, it can only be opened by releasing the lever inside the car.
I would definately suspect the ecu defaulting to that rich setting due to it not getting a signal from one of your car's sensors. On my car when the ecu uses the default setting to calculate air/fuel mixture it is literally a 30% decrease in mpg. I can go outside right now and unplug my o2 sensor and mpg will drop 30% instantly. Plug it back in and it's back to normal. I calclate mpg on every tank of gas so when I spot a sudden 30% mpg drop I know it's time to check why the ecu has defaulted to the rich setting by checking what sensor isn't sending a proper signal to the ecu. BTW when ecu defaults to that rich setting the car will usually run normal, you probably won't notice any drivability issues, and there is no engine damge to worry about. You're simply just wasting a lot of gas.
IIRC there is a way to make a rough evaluation using an old school dwell meter. Something like 45 degrees of dwell means the sensor is working and the system is responding - no?
That would depend upon the setting (4, 6, or 8 cyl) of the dwell meter.
45º of dwell =
50% duty cycle if meter is set to 4 cyl; (probably the correct setting)
75% duty cycle if meter is set to 6 cyl;
100% duty cycle if meter is set to 8 cyl. (obviously the wrong setting)
A 50% duty cycle is about right. (A dwell meter is just a low-pass filter consisting of a capacitor and resistor followed by a meter across the capacitor.) A good VOM, such as a Fluke, usually has a duty cycle setting.
I've heard about this testing method. I don't really know how good it is.
Somebody mentioned running the tires at the max pressure rated on the tire, minus a couple pounds for tire heat while operating. ...
Just to point out, the maximum pressure rating on the tire sidewall is the cold temperature maxium pressure. W-rated racing tires are usually inflated to 100% of the pressure rating on the sidewall if racing speeds do not exceed 150 mph. That is, the sidewall rating has already taken temperature rise into account.
Anything that can be done to limit tire tread & sidewall flex will gain gas MPG so that only leaves one form of adjusting the tire to your car.......air PSI.
Hard pumped tires (within limits of the tire) will cut rolling resistance in every case no matter the car's weight. Soft tires = better ride. Harder tires= better MPG.
To get an idea of what I'm taking about let most of the air out a bicycles tires then ride it. Feels like you're pulling twice your weight.. Now pump the tires real hard then ride. Feels like there's little weight at all for you to pedal. It's the same thing for any vehicle.
I fully understand that. But what you make up in milage you'll loose in damage to your car because you can't keep the middle 1 inch of rubber on the pavement in a turn.
There has to be a point that the tire is PROPERLY inflated and the max pressure marked on the tire is not that pressure.
I fully understand that. But what you make up in milage you'll loose in damage to your car because you can't keep the middle 1 inch of rubber on the pavement in a turn.
There has to be a point that the tire is PROPERLY inflated and the max pressure marked on the tire is not that pressure.
Each to his/her own but I'll stick to my method since it works so well for me.
Others would do well to at least try my method to decide for themselves which way is best.
Talking about tire pressure, on some cars like mine that ride a little stiff becuase they have a sport tuned or performance suspension, I inflate according to ride compliancy or to what I feel is good. In other words I rather be 1-2 lbs low than put up with a ride that is too harsh and have the car banging over every imperfection in the road. On a car where that's not an issue then I'd keep 32-34 lbs (checked on a 70 degree day with cool tires before running the car).
Talking about tire pressure, ... I inflate according to ride compliancy or to what I feel is good. ... On a car where that's not an issue then I'd keep 32-34 lbs (checked on a 70 degree day with cool tires before running the car).
I keep my pressures at 30-32 psi. My daily car is a 4 cyl Accord, and those pressures suit me fine.
To some extent, one can increase/decrease oversteer/understeer by varying air pressures between the front and rear tires. When a tire rounds a curve, it does not follow the direction in which it is pointed, but yaws or "crabs out" to the outside of the curve. The amount of yaw in a curve depends upon tire pressure and weight on the axle (in addition to suspension geometry). Increasing tire pressure reduces the yaw effect. So increasing tire pressure on the front and decreasing tire pressure on the rear reduces understeer and drives the car's handling in the direction of oversteer.
Decreasing axle weight also reduces the yaw effect. That is why front wheel drive cars, much heavier in the front than in the back, tend to understeer.
To some extent, one can increase/decrease oversteer/understeer by varying air pressures between the front and rear tires. When a tire rounds a curve, it does not follow the direction in which it is pointed, but yaws or "crabs out" to the outside of the curve. The amount of yaw in a curve depends upon tire pressure and weight on the axle (in addition to suspension geometry). Increasing tire pressure reduces the yaw effect. So increasing tire pressure on the front and decreasing tire pressure on the rear reduces understeer and drives the car's handling in the direction of oversteer.
Decreasing axle weight also reduces the yaw effect. That is why front wheel drive cars, much heavier in the front than in the back, tend to understeer.
That was some good info! So on my FWD which tends to oversteer you're saying that running a little more pressure in the back would help reduce oversteer for 'spirited' driving in turns?
Please register to post and access all features of our very popular forum. It is free and quick. Over $68,000 in prizes has already been given out to active posters on our forum. Additional giveaways are planned.
Detailed information about all U.S. cities, counties, and zip codes on our site: City-data.com.
Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
