Fuel consumption

[Lewis07]

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I would say in standard size tyres, inflated to about 35 p.s.i. instead of the Toyota recommendation of just 29 p.s.i.
Will easily see you into 33 m.p.g. at similar speeds.

Gra.[/QUOTE]

I was going to ask about tyre pressures. Would you recommend running at higher pressures than specified in the handbook then?

 

[Graham]

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I would say in standard size tyres, inflated to about 35 p.s.i. instead of the Toyota recommendation of just 29 p.s.i.
Will easily see you into 33 m.p.g. at similar speeds.

Gra.

I was going to ask about tyre pressures. Would you recommend running at higher pressures than specified in the handbook then?[/QUOTE]
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Most definitely, without a shadow of a doubt.

Gra.

 

[Lewis07]

So stupid question, but why do they specify such low pressures in the book? Sorry for my ignorance on this one.

 

[cir287]

So stupid question, but why do they specify such low pressures in the book? Sorry for my ignorance on this one.

not a stupid question.

the book states a recommended pressure which has to take varying temperatures, road conditions, driving styles, load, tyre construction, wear rate, comfort, etc into account. So the pressure they recommend is a one size fits all, which by its nature will suit most people, most of the time.

Now if you are a thinking man (or woman ............ na, forget that !) you will realise that weather, temp, road conditions etc all change.

I run ~35psi most of the time except for cold winter conditions where I go back to 28-30 psi as the grip level at the higher pressure falls off a bit with less surface contact. If I was to drive accross the continent on dry roads in the summer I might go as far as 38psi.
If you experiment a bit you will get a feel for it however with current temperatures its not the best time of year to be going for higher pressures.

 

[Lewis07]

Thanks. I'll keep them as is for the time being as you say given the weather.

 

[Andrew T]

OK the reason the tyre pressures are low are to give you enough rubber (friction) on the road to let your brakes effectively stop your vehicle and give you road holding on corners, particularly in the wet.

People who over inflate are reducing the amount of rubber on the road to reduce friction (which you need) to improve their fuel efficiency or to compensate for when they are fully loaded.

The tyres are designed to run at certain pressures at certain loads and with the weight of an empty LC on 265/65 17's that pressure is 29psi more than that reduces the amount of rubber on the road. This pressure is also calculated to give you an even wear pattern and optimise your tyre life, over inflating burns out the centre tread, so you could be sacrificing tyre life over fuel economy.

Back to fuel economy well I dont see too many claiming more than 500 miles a tank (19.6gals by the way) and this gives about 25.5 mpg at best !!

I have tracked my "Slightly Modified" LC4 for the last 10,000miles and it has returned an Average of 21.3mpg

Best tankful over that period was 24.29mpg, typical on road is 21-23mpg and expect 15-18 mpg whilst offroading in low box all day.

I hope this is helpful
Cheers
A

PS remember these are cold tyre pressures and as a tyre gets hotter the pressure will increase. The increase in pressure reduces the footprint slightly but the increase in temperature increases the stickyness of the tyre.

An over inflated cold tyre has the potential to give you a blow out if it gets too hot e.g. summer motorways

 

[Andrew Brierley]

A visual check of your side walls is also a helpfull guide, looking to keep a good shape - esp due to the influence of different manufacturers, types, age of tyre, loading, ambient temperatures and road/off road use. For example, when I'm fully loaded for an overland trip (3.7T), and planning some long high speed motorway sections, I have needed to go to 40/45 to keep the typre in good shape. Same logic about a visual check applies when you need to air-down for sand work - when fully loaded I will need to maintain a higher pressure than if normally loaded to stop them going like pancakes. In short.... there is no absolute guidance on actual tyre pressures.

 

[Lewis07]

All useful stuff. Thanks.

 

[Andrew T]

when I'm fully loaded for an overland trip (3.7T), and planning some long high speed motorway sections

Andrew are you saying you load your 120 up to 3.7 tonnes?

The Gross Vehicle Weight for a 120 is 2850 kg that sounds like you are dangerously overloaded you might want to have a look at that.

 

[OG.]

The best way to set tyre pressures is using the chalk method. Find a straight level piece of road. Draw a chalk line across the tyre. Drive about 50 metres or so (trial and error here).
Now look at the chalk line.
If its rubbed off in the centre you're over inflated. If its rubbed off on the edges you're under inflated. Inside edge or outside edge is camber. Very simple and accurate no matter what load.

 

[Paddler Ed]

The other option for tyre pressure setting is the 4psi rule that the Aussie's use (care of Mickey Thompson and Cooper Tyres)

Start at x psi, drive for an hour (100km or so) a then check the pressure; it should be x+4 psi. If it's over that, ie +5 then the tyre was too soft (ie it got too warm) and under then tis too high (ie it didn't get warm enough). Amend the pressure by a 1/2 the difference and try again; it should cool or warm up accordingly and then you should be towards x+4. Check when you get home what x is now once it has cooled down (ie the next day) before you unload if you set it loaded, and again when you unload. You now know what to set the pressure at for the next trip. Do the same for unloaded/everyday driving and then record that and you'll be sorted hopefully!

Here's probably one of the better explanations of it; it's long, but read through it.
http://www.aawen4x4.com.au/index.ph...ticle&id=1:4psi-rule&catid=2:current&Itemid=7

And here's the Cooper tyres info:
http://www.slippersopreis.nl/mediapool/77/773779/data/bandenspanning_Cooper_tire_pressure.pdf

I know in Aus we ran about 42psi in our FJ73 when we were touring or everyday; touring it was a benefit because we were loaded, everyday because we had a freeway run to get anywhere. Off road it was about 25psi, so quite a big drop. That gave the tyres a reasonable footprint, without being excessive.

 

[Graham]

The other option for tyre pressure setting is the 4psi rule that the Aussie's use (care of Mickey Thompson and Cooper Tyres)

Start at x psi, drive for an hour (100km or so) a then check the pressure; it should be x+4 psi. If it's over that, ie +5 then the tyre was too soft (ie it got too warm) and under then it's too high (ie it didn't get warm enough). Amend the pressure by a 1/2 the difference and try again; it should cool or warm up accordingly and then you should be towards x+4. Check when you get home what x is now once it has cooled down (ie the next day) before you unload if you set it loaded, and again when you unload. You now know what to set the pressure at for the next trip. Do the same for unloaded/everyday driving and then record that and you'll be sorted hopefully!

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The 4 psi is used every where as far as I know.
It is used very much with caravans also.

It is remarkably accurate also.

Gra.

 

[Andrew Brierley]

Andrew are you saying you load your 120 up to 3.7 tonnes?

The Gross Vehicle Weight for a 120 is 2850 kg that sounds like you are dangerously overloaded you might want to have a look at that.

No, this is my 80 (but I'm still looking very closely at weight reduction!). Also looking at premium rated Profender shocks and new springs, as the Iron Man stuff just ain't up to the job...

 

[Gary Stockton]

I thought 3.7t was over the GVM??

 

[Andrew T]

It is the GVM for an 80 Is 2960kg

As I keep saying the differences between the 80 and 120 are minimal when you put them side by side.

Other than the few extra inches of width to suit the more portly classic car driver :0)

 

[Graham]

It is the GVM for an 80 Is 2960kg

As I keep saying the differences between the 80 and 120 are minimal when you put them side by side.

Other than the few extra inches of width to suit the more portly classic car driver :0)

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The differences I like are the fuel consumption differences.

Gra.

 

[Andrew T]

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The differences I like are the fuel consumption differences.

Gra.

Do you mean MPG Vs GPM ??

 

[nathanrobo]

Didn't realise the 120 was so economical

 

[Lewis07]

Somewhat late in the day I thought I'd share that with a mix of driving (mainly by the better half) and with tyres at 29 PSI I'm getting about 400+ per tank.

 

[TonyP]

Somewhat late in the day I thought I'd share that with a mix of driving (mainly by the better half) and with tyres at 29 PSI I'm getting about 400+ per tank.

At what speeds do you get that? For town driving I get about 300 miles, and only if I do motorway driving can I just about get 400. I normally sit at about 75 on motorways