Running 45psi for better fuel economy?

[sssstew Junior Member Find all posts View Profile Close sssstew]

In response to :-

http://www.pradopoint.com/showthread...l=1#post315813

Has anyone else found increasing the tyre pressures, up to 45psi maybe, helps with fuel economy at all?

Thanks

[wooley Avid PP Poster! Find all posts View Profile Close wooley]

In response to :-

http://www.pradopoint.com/showthread...l=1#post315813

Has anyone else found increasing the tyre pressures, up to 45psi maybe, helps with fuel economy at all?

Thanks

helps with fuel economy, but you end up paying more in physio/chiro bills.

[krypto Avid PP Poster! Find all posts View Profile Close krypto]

There is a balance at which the tyres start wearing excessively in the middle. I run around 40 in the city and 48F/52R when towing the camper. I base my tyre pressures on how hot the tyres get which is a measure of how much the tyre is deforming and that correlates directly to wear and fuel consumption.

[Brains Find all posts View Profile Close Brains]

I have always run higher tyre pressures which can help to extend tyre life but more so for the added safety. I attended a work advanced driving course run over three days. During this course it was explained that in an emergency often hard braking is utilused to avoid a collision. Tyres inflated to the cars specifications provide a stable platform for the vehicle to stay on the road and slow the vehicle down when braking. Under extreme or hard braking puts added pressure on the front tyres as a greater downward force is applied to the tyres. Much in the sense of when you add weight you increase your tyre pressures to assist in the carrying of the load driving with higher pressures will assist the stopping capability of the vehicle. I usually run around 42-44 psi for town or highway driving. This is the consensus amount a number of instructors on advanced driving courses as I have completed three over the last 13 years and all advise to run with 40psi or above.

[AJ120 Out of control poster! Find all posts View Profile Close AJ120]

helps with fuel economy, but you end up paying more in physio/chiro bills.

And paying more replacing shocks more often, and tyres probably wont wear evenly so paying more there as well.

Cheers Andrew

[Richoson Avid PP Poster! Find all posts View Profile Close Richoson]

It's all relative I don't like the ride at 40 plus psi do I run around 36 psi and the wear on the tyres, fuel economy and comfort are all balanced at that level.

See ya on the tracks, Richo.

[D4D Addicted PP Member Find all posts View Profile Close D4D]

36 x 2 blah blah padding

[gxl_d4d Advanced Member Find all posts View Profile Close gxl_d4d]

Wet grip may become a problem with 45psi. When I had the Grandtrek's I used 36psi all round. Did a few big road trips with a fully loaded car and was getting 10.5km/l. At 40psi, the Grandtreks slipped a little when cornering and going around round abouts in the wet. With the BFG's I have the same issue at 40psi. If I drop down to 38psi, the wet handling is greatly improved. I've run the BFG's at 38, 40 and 42psi and haven't noticed a measurable change if fuel economy.

Tyre suppliers have a chart that states the diameter of a tyre vs load carrying capacity. That's how they work out what pressure to use. From what I was told, the contact area with the road should be the same irrespective of load hence the need to adjust pressures when towing or loading up the vehicle. An easy way to work out the correct pressure is the inflate to the pressure recommended by the tyre installer then measure the tread contact area with the ground. Once you've loaded the vehicle, add air to get back to the unloaded contact area.

[1coolbanana Avid PP Poster! Find all posts View Profile Close 1coolbanana]

At 45psi, economy wont matter after you crash it as soon as it starts raining
For me 36 psi with BFG's unladen seems the sweet spot for comfort, ride, traction and even wear.

[krypto Avid PP Poster! Find all posts View Profile Close krypto]

Wet grip may become a problem with 45psi. When I had the Grandtrek's I used 36psi all round. Did a few big road trips with a fully loaded car and was getting 10.5km/l. At 40psi, the Grandtreks slipped a little when cornering and going around round abouts in the wet. With the BFG's I have the same issue at 40psi. If I drop down to 38psi, the wet handling is greatly improved. I've run the BFG's at 38, 40 and 42psi and haven't noticed a measurable change if fuel economy.

Tyre suppliers have a chart that states the diameter of a tyre vs load carrying capacity. That's how they work out what pressure to use. From what I was told, the contact area with the road should be the same irrespective of load hence the need to adjust pressures when towing or loading up the vehicle. An easy way to work out the correct pressure is the inflate to the pressure recommended by the tyre installer then measure the tread contact area with the ground. Once you've loaded the vehicle, add air to get back to the unloaded contact area.

A few important points.
1. Correct tyre pressure is relative to vehicle weight and tyre dimensions, and it is nearly always more than vehicle manufacturers recommendations which are biased towards comfort.
2. An over inflated tyre will always out brake an under inflated tyre in the wet. An under inflated tyre deforms under braking pressure and forms a channel for aqua planing. I have confirmed this on a skid pan during driver training. A properly inflated tyre performs best.
3. Finding the correct pressure is a often a case of trial and error. The aim is to find the pressure that gives the correct tyre temperature for the given driving conditions. An under-inflated tyre will generally heat up more than an over-inflated tyre. The heat in a tyre is generated directly as a result of tyre deformation and lower pressures result in more deformation during use. This is why tyre temperatures are measured on race car tyres.

[raydes Advanced Member Find all posts View Profile Close raydes]

Wow 45+ PSI you must feel every bump in the road. I have my ATZ 4 ribs at 35 and still think they are hard, I would rather have a comfortable ride than save $2 on fuel every 100ks ???????????? WHY ??

[Guest Close Guest]

Wet grip may become a problem with 45psi.

I was running muddies with 40psi in the rain and it was scary. Things were much safer at 32psi

An easy way to work out the correct pressure is the inflate to the pressure recommended by the tyre installer then measure the tread contact area with the ground. Once you've loaded the vehicle, add air to get back to the unloaded contact area.

Another way is if you know the weight of the car loaded and unloaded, you can calculate how much air to put in.

Say unloaded is at 2.5T, this is 2500kg = 5500lb.
Say that this load is distributed evenly over the 4 tyres, therefore each tyre will carry 5500/4 = 1375lb.
If the tyre is inflated to 40psi, then the contact area is 1375/40 = 34.4in2 (square inches)

If you add 400kg to get to GVM, i.e. 2900kg = 6380lb.
Then each tyre will carry 6380/4 = 1595lb.
For the same contact area, you will need 1595/34.4 = 46.4psi

[Peterpilot Avid PP Poster! Find all posts View Profile Close Peterpilot]

In response to :-

http://www.pradopoint.com/showthread...l=1#post315813

Has anyone else found increasing the tyre pressures, up to 45psi maybe, helps with fuel economy at all?

Thanks

I don't know what that link ^^^ has to do with tyre pressures, but I run 36psi on the road.

Some interesting reading here: http://www.pradopoint.com/showthread...=tyre+pressure

and the 4psi rule here: http://www.aawen4x4.com.au/index.php...rrent&Itemid=7

[AJ120 Out of control poster! Find all posts View Profile Close AJ120]

Say that this load is distributed evenly over the 4 tyres

If people were to weigh both front and rear axles they would notice theat the rear axle carries more load then the front, which is why I always run lower front pressures than in the rear, on or off road.

Cheers Andrew

[1coolbanana Avid PP Poster! Find all posts View Profile Close 1coolbanana]

I just recently took mine to the weigh station and with an unladen car with half tank of fuel.
This is a V6 Grande.

I got,

Front : 1250kg
Rear: 1120kg

Less on the rear but near enough to the same I would have thought?