Outer Limits 4x4 Board

Hi - i have set of boring 31" s and want to get better 33"s. Got talking to some bloke shile camping and he has a set 31 for town and 33 for off road. Got talking a bit more and he stated that the bigger tyres cause the trol to use alot more fuel getting 1 k less per litre.

Now i want 33"s but not at this price as its a daily driver and im not prepared to have 2 sets (i on road 1 off road)

Can someone let me know if this is true or false and how much more fuel they have been using if any.

thanks - see you on the tracks

yes bigger tyres = more fuel

bigger tyres take more power to turn

but in saying that its not that much more

Well i beg to differ becuase i have just done a test with mine on 32's i got 18litres per 100 and with the 35 simex i get around 30 litres per 100 for the same trip

dwaynes wrote:Well i beg to differ becuase i have just done a test with mine on 32's i got 18litres per 100 and with the 35 simex i get around 30 litres per 100 for the same trip

Just curious, has the speedo been adjusted for the bigger tyres

dwaynes wrote:Well i beg to differ becuase i have just done a test with mine on 32's i got 18litres per 100 and with the 35 simex i get around 30 litres per 100 for the same trip

hiway kms you could get better economy ... Daily driving around town u won't

Sorry that should of read

but in saying that its not that much more

Well i beg to differ becuase i have just done a test with mine on 32's i got 18litres per 100 and with the 35 simex i get around 30 litres per 100 for the same trip


Also all distance was taken from the GPS not the Speedo

All in all i use roughly 12 lires more per 100 with 35's compared to 32's for the same highway trip

getting the tyres moving will use more fuel.
once moving tho, you will travel further under less rotations of the wheel, so will get further on less fuel.

so the equals, stop starting will use more fuel.
cruising will use less fuel



it depends on what kinda driving you do as to whether it will use more or less. but i would think in the end it would even itself out unless you only drive in one style

My gq uses less fuel with my bfg 33's than it does with my 31 desert duellers.

I get the same km from a tank but with the 33's i'm going 6.5% further than what the od is telling me. At 100km/h i'm only doing 143rpm less. I could see it making a difference with 3's though.

If ya can keep it around/under 100kms on 35's with 4.1s, you should in theory use less fuel. But with bigger tyres they like to roll along a bit quicker, so....

macca81 wrote:getting the tyres moving will use more fuel.
once moving tho, you will travel further under less rotations of the wheel, so will get further on less fuel.

so the equals, stop starting will use more fuel.
cruising will use less fuel



it depends on what kinda driving you do as to whether it will use more or less. but i would think in the end it would even itself out unless you only drive in one style

From my experience once you go to 35’s that theory goes out the window, you still have to keep the bigger diameter moving, if that was the case you would never need gearing.

around town I noticed that 35's use more fuel than 31's.
But on my normal home/work/home trip it hasnt made much difference. I only got slight worse economy with the 35's.
It is much nicer to drive on the 31's though. So thats why the 35's are in the shed and theres some good Road tyres on there now.

All distances where calculated using a GPS.
Oh and thats with a 91swb petrol/gas auto.

One other thing to concider... Bigger tyres usually means more aggresive tread making it harder to spin them through the air at speed. The more aggressive the tread the harder it is to turn them.. Sorta like a 10" fan with a low pitch on a 1/2hp elec motor.. put a 12" fan on with a high pitch on the same motor and the motor will burn out.. Same deal !!!
I was running 35" A/t's and went to 35's in a mud terrain pattern and that alone slowed me up heaps and I used more fuel.

I found the bigger the tyre the better for general off road touring. They seem to soak up or bounce over ruts a bit better, allmost tempted to take my 35 all terrains off ebay and keep em. they dont really like stopping, But i swear i had better economy on the hway even though it was slower up hills,etc

STIKA wrote:

macca81 wrote:getting the tyres moving will use more fuel.
once moving tho, you will travel further under less rotations of the wheel, so will get further on less fuel.

so the equals, stop starting will use more fuel.
cruising will use less fuel



it depends on what kinda driving you do as to whether it will use more or less. but i would think in the end it would even itself out unless you only drive in one style

From my experience once you go to 35’s that theory goes out the window, you still have to keep the bigger diameter moving, if that was the case you would never need gearing.

but once they are moving the engine doesnt have to work any harder than on smaller tyres, if anything it works easier because the rpm will be lower for the same road speed. the gearing is there to get you upto speed.

that big diameter might be hard to get moving, but its also harder to stop, which means its easier to keep moving. inertia comes into play to a point here aswell

Typically you will drink more the bigger you go....

Going 31 to 33 not so bad, problem is if you go BIGGER and your motor ends up reeving to low you end up labouring it at low revs sucking juice like nothing you've seen cause its struggling, this is why big tyres if you still have big diff gears can still return reasonable figures.


With that said my 35inch BFG AT and Cooper STT both return about 5 litres per 100 more than 31 AT's.

if u changed the ratio's to suit 35 ie the same revs for at 110kmh as they do on 31? i get 9.5 km to the litre on 31 now (qg swb)how much do u think the fuel usage drop?

going with the resistance theory, more agressive tread also means more friction on the road surface. more friction = more force to spin = more fuel used. if you had 35" road pattern and 35" simex pedes, you'd still use way more fuel with the pedes as the tread creates more friction which means more force required to turn them. add to that the more force required to get them moving and they would also be a shipload heavier too. it's not just one factor, its a combination.

simple...
obviously the larger the tires the more contact with ground, therefor more tire rpm/engine rpm and uses more fuel when stop starting because larger shit takes longer to speed up

i think in the end it will come down to whether the vehicle is driven on long highway stints, or doing town work with lots of stop starting...

bigger tyres take less rpm to keep at a high speed.
smaller tyres take less effort to move

Depends also on the vehicle an d the amount of extra load created, if the vehicle is EFI and running in closed loop still then on the cruise the economy should inprove, the additional load at lower RPm means less manifld vacuum and reduced pumping loss in the engine. If the load of the big tyre is such that the car is going out of closed loop then it would use more fuel, the same applies to a carby in regards to at how much manifold vacuum the power enrichment occurs.
If the vehicle used to cruise at 20 inches and now cruises at 15 inches but power enrichment dosent occur untill 10 inches of vac then the economy at cruise should improve as the air fuel ratio has not changed but the number of strokes has. However every time ou take off the vacuum will drop quicker, causing enrichment, due to the extra load and hurt the stop start economy.
This is why late model cars cruise at such low revs and put off power enrichment as much as possible.
It would hurt a small engine much more than a large one, 35's on a Suzi would mean the engine vacuum would drop to the point that the engine would be continuously in power enricment for example.

Joel

macca81 wrote:

STIKA wrote:

macca81 wrote:getting the tyres moving will use more fuel.
once moving tho, you will travel further under less rotations of the wheel, so will get further on less fuel.

so the equals, stop starting will use more fuel.
cruising will use less fuel



it depends on what kinda driving you do as to whether it will use more or less. but i would think in the end it would even itself out unless you only drive in one style

From my experience once you go to 35’s that theory goes out the
window, you still have to keep the bigger diameter moving, if that was the case you would never need gearing.

but once they are moving the engine doesnt have to work any harder than on smaller tyres, if anything it works easier because the rpm will be lower for the same road speed. the gearing is there to get you upto speed.

that big diameter might be hard to get moving, but its also harder to stop, which means its easier to keep moving. inertia comes into play to a point here aswell

You still havr to keep them moving, in my last 60 series you struggled to maintan 5th gear with 35

Only stating what i have found from experience

STIKA wrote:

macca81 wrote:

STIKA wrote:

macca81 wrote:getting the tyres moving will use more fuel.
once moving tho, you will travel further under less rotations of the wheel, so will get further on less fuel.

so the equals, stop starting will use more fuel.
cruising will use less fuel



it depends on what kinda driving you do as to whether it will use more or less. but i would think in the end it would even itself out unless you only drive in one style

From my experience once you go to 35’s that theory goes out the
window, you still have to keep the bigger diameter moving, if that was the case you would never need gearing.

but once they are moving the engine doesnt have to work any harder than on smaller tyres, if anything it works easier because the rpm will be lower for the same road speed. the gearing is there to get you upto speed.

that big diameter might be hard to get moving, but its also harder to stop, which means its easier to keep moving. inertia comes into play to a point here aswell

You still havr to keep them moving, in my last 60 series you struggled to maintan 5th gear with 35

Only stating what i have found from experience

True becuuse your in a rev range that is too low to spin em effecinetly

The answer is "hell yes".

im getting 12L/100km in my gq ute with td42 with 35" cooper st's. 13/100 loaded.
what would i expect to see with some 31's or 33's?

i think the big tyres affect a petrol much more than a diseasal. anyone?

i have had 31s i got 11l/100km
33s 12.5l/100km
35s 13.5/100km
35s are silverston extreams
3.3 td swb patrol so really it seams to depend on driving style and vehicle

steven101 wrote:simple...
obviously the larger the tires the more contact with ground, therefor more tire rpm/engine rpm and uses more fuel when stop starting because larger shit takes longer to speed up

add width of the bigger rubber and you get more wind drag etc.

I'll add some fuel here...
more aggressive tires use more than HT's.

bogged wrote:I'll add some fuel here...
more aggressive tires use more than HT's.

I'd certainly agree as the dyno figures are lower with agressive tyres and no other vehicle changes, high speed turbulance around big lugs. A WRX with treaded tyres make 20-30 less kw than on slick on the dyno due to movement of air over the tyre.
And the greater the speed the greater the loss

Joel

PGS 4WD wrote:

bogged wrote:I'll add some fuel here...
more aggressive tires use more than HT's.

I'd certainly agree as the dyno figures are lower with agressive tyres and no other vehicle changes, high speed turbulance around big lugs. A WRX with treaded tyres make 20-30 less kw than on slick on the dyno due to movement of air over the tyre.
And the greater the speed the greater the loss

Joel

Its funny, but its true even on the dyno the drag holds it back...

YES a had 33s on my gq deisle and was getting 550 to a tank now with 35 get 420