Fuel Consumption with mud terrain tyres

Submitted: Monday, Jan 10, 2005 at 10:29
ThreadID: 19220 Views:8132 Replies:9 FollowUps:13
This Thread has been Archived
Got an interesting question which I would like to run past to see if
anyone has come across it.

GU 4.2 TD 99 with BFG All terrains 265/75 16 uses about 12.5 to 13.5L
per 100kms (consistently through its whole life).

I got two sets of rims and some months ago I fitted BFG 265/75
16 "MUD" terrains to the second set.

When using the mud terrains it uses more fuel, between one to two
litres per 100kms more fuel (consistent over several fuel tanks
now)...

Change back to A/Ts and its back to its old consumption...

Has anybody experienced this? Driving conditions are varied but the
same for both types of tyres...

I have measured the tyre diameters and mud terrains are 5 to 8mm
larger due to lugs

Has anybody experienced this? Why is it?

Will
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Reply By: flappan - Monday, Jan 10, 2005 at 10:52

Monday, Jan 10, 2005 at 10:52
Muddies would normally be heavier due to their more robust construction. The increased size , could change your speedo slightly as well. The combination would probably account or 1 or 2 lts per 100k's
AnswerID: 92149

Reply By: Member - Bradley- Monday, Jan 10, 2005 at 10:56

Monday, Jan 10, 2005 at 10:56
gday Will, Yep i have experienced the same thing, went from b'stone 693 to MTR's and went up a size as well on my jack, fuel went from 12/100 to 15/100. I put 1.5 down to the size increase and the rest down to the tyre construction and tread design, The heavier the construction and tread, the more rolling resistance and inertia you have to overcome. Eg my jack is a slug overtaking etc now but with the old tyres it was an absolute rocket. Yes i'm going to get a second set of standard size roadies for weekday use, might look a bit silly with the lift i've got, but i need the range. And if i get 50,000k out of them they will have paid for themselves, if you know what i mean.
AnswerID: 92150

Reply By: Leroy - Monday, Jan 10, 2005 at 11:31

Monday, Jan 10, 2005 at 11:31
May explain why I cant get below 13l/100km with my 3.0GU. I have BFG 285*75 !!

Leroy
AnswerID: 92158

Follow Up By: Member - Captain (WA) - Monday, Jan 10, 2005 at 12:26

Monday, Jan 10, 2005 at 12:26
Hi Leroy,

I too have 285/75's (Cooper ST's) but regularly get 11.5 l/100km on the daily grind to work (peak hour freeway driving), even had very high 10's once in a slow country drive. Unless towing or offroad, I have never even got close to 13 l/100kms. Also, i drive like I don't pay for fuel (because I don't!!!) so its not from being light on the pedal.

Just suprised to see someone getting such low economy on a 3.0TD, in fact this is the worst regular economy I have heard of! Are there any other factors that might account for this (like a large roofrack or something)?

Cheers

Captain
Its not what you drive, but how you drive it!
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FollowupID: 350969

Follow Up By: Leroy - Monday, Jan 10, 2005 at 16:21

Monday, Jan 10, 2005 at 16:21
No roof rack, steel BB and 10klb winch. only done 18k km but thought I should see better figures.

Leroy
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FollowupID: 351023

Reply By: Truckster (Vic) - Monday, Jan 10, 2005 at 11:51

Monday, Jan 10, 2005 at 11:51
For one the different size would equate to 1ltr difference...
Also they are heavier as mentioned

1ltr difference could also be the weather causing it... driving on the day, different batches of fuel, etc etc.. but since you say the AT's instantly went dropped 1ltr, I would scrap the MT's they will send you broke.. ;)~
AnswerID: 92163

Follow Up By: GUPatrol - Monday, Jan 10, 2005 at 13:24

Monday, Jan 10, 2005 at 13:24
The size difference is negligible, (makes no difference in speedo when comparing one and the other with the GPS).
It has to be the construction and pattern..

They are excellent off road!!

Will
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FollowupID: 350982

Follow Up By: flappan - Monday, Jan 10, 2005 at 13:39

Monday, Jan 10, 2005 at 13:39
But neither is 1/100 K's , 100ml for each 10 K's.

I would think , unless you are looking at metres per kph , ie 100.1 kph , you wouldn't know any different. 5 to 8 mm WILL make a difference , but , not a BIG enough difference to really notice
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FollowupID: 350985

Follow Up By: Truckster (Vic) - Monday, Jan 10, 2005 at 13:48

Monday, Jan 10, 2005 at 13:48
Yea as flappan says, your talking 1ltr here...

You think MT's are good, you should try JTs, extreme trekkers or swampers.. :)
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FollowupID: 350987

Reply By: warthog - Monday, Jan 10, 2005 at 12:52

Monday, Jan 10, 2005 at 12:52
If the tyres are a larger diameter I spose you will also be travelling further per k registered on the odo. I guess it would stand to reason that more aggressive tread = more rolling resistance ie tractor tyres make alot of noise and don't roll as efficiently as a smooth tyre.
AnswerID: 92179

Reply By: Bloke - Monday, Jan 10, 2005 at 13:17

Monday, Jan 10, 2005 at 13:17
Had a similar situation with my 3.2TD Pajero, have recently changed tyres from the factory fitted highway tread Yokohama, with which I was getting approx 10km/litre, to BFG A/T's with which I can only get 9km/litre. Figure it must have something to do with the deeper tread/more weight requiring more power to overcome the inertia??
AnswerID: 92186

Follow Up By: GUPatrol - Monday, Jan 10, 2005 at 13:36

Monday, Jan 10, 2005 at 13:36
Bloke,

I have been using BFG A/T's since the beginning but I do recall that the original tyres returned an even better fuel consumption.
The difference between the BFG A/T and BFG M/T is amazing! 1 to 2 litres in 100kms, M/T handle very poorly on road but they are excellent off road...!

When I change back to the A/T tyres it feels so good on the bitumen that it seems like a different car.

The other thing I noticed is that with the A/T I would sooner or later get a slight shaking on the steering wheel at 80-90kms/h not with the M/T (so far).

Will
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FollowupID: 350983

Reply By: Voxson (Adelaide) - Monday, Jan 10, 2005 at 13:54

Monday, Jan 10, 2005 at 13:54
I went through this crap months ago and i proved beyond doubt that the tread on certain muddies walks around on the road as it is having drive put through it....(exactly the same theory as riding a mountain bike with a rear shocker on the road)... The power lost through this soft spot in the drive-line is very noticable... If your car didnt have a turbo you would have noticed a loss in HP also...
This soft spot soaks up horsepower....I fitted a turbo and have bettered the fuel economy to 15litres per 100 and gained good power...Expensive tyres in my case...
AnswerID: 92194

Follow Up By: GUPatrol - Monday, Jan 10, 2005 at 14:46

Monday, Jan 10, 2005 at 14:46
Voxson,

You are spot on!! I did loose HP also, only noticeable on certain hills where 5th was borderline before and now I have to change back to 4th.
Your point is dead right as I also notice a slight difference in braking ability...

Will
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FollowupID: 350996

Follow Up By: Member - Bradley- Monday, Jan 10, 2005 at 16:46

Monday, Jan 10, 2005 at 16:46
Yeah Voxy, i remember your post a while back, and you are dead right about the 'squirm' My MTR's squirm and howl like buggery when i put the boot into it, to the point where i avoid it now if i can. I hoped to get a good all round compromise without having 2 sets , but i cant live with the lack of braking ability on the road, hopeless grip in the wet, and the squirm etc. Shame because they are not too noisy on the road. So i'm going to have to look for a set of roadies as well.
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FollowupID: 351031

Follow Up By: GUPatrol - Monday, Jan 10, 2005 at 17:06

Monday, Jan 10, 2005 at 17:06
Bradley,

That is exactly what I found, not too noisey.
In fact we were returning from a trip to the beach at xmas via a twisty road and I pointed out to my wife the squirm every time conditions changed such as up hill down hill and on turns.

Will
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FollowupID: 351039

Follow Up By: Member - Bradley- Monday, Jan 10, 2005 at 17:27

Monday, Jan 10, 2005 at 17:27
Yeah it feels like the alignment is out to buggery as well.

No way i'll get rid of them as they are awesome off road and ok for touring, but i will get some nice road biased jobs for general work, something like the bridgestone d680.
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FollowupID: 351043

Reply By: Moose - Monday, Jan 10, 2005 at 14:40

Monday, Jan 10, 2005 at 14:40
I don't know whether this theory holds water but someone once told me that part of the issue of greater fuel consumption stems from the "rougher" tyre surface having a greater air resistance ie a smoother tyre can push through the air easier than a luggy tyre. It may be another part of the equation. If this theory is correct then a narrow tyre should be more fuel efficient than a wide one (all other factors being equal).
AnswerID: 92203

Follow Up By: flappan - Monday, Jan 10, 2005 at 15:12

Monday, Jan 10, 2005 at 15:12
That may be part of it , but there are so many factors.

You could pump up an AT tyre (and probably a muddie) to around 50 psi , and you could expect to get less rolling resistance , and therefore slightly better fuel consumption.

The downside to that is dramatically increased tyre wear , and a terribly bumpy ride.

So yes , a narrow tall slick tyres , pumped up to buggery , should get good fuel efficency , but , would be a crap ride , and hopeless offroad

Its about compromise

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FollowupID: 351001

Follow Up By: Willem - Monday, Jan 10, 2005 at 16:22

Monday, Jan 10, 2005 at 16:22
I was talking to an old fella a while ago who was driving a HiAce Campervan. Had the 14inch tyres pumped up to 60psi so as to get better fuel economy..........Geez, what some people would do to save a few cents here or there.
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FollowupID: 351024

Reply By: ianmc - Monday, Jan 10, 2005 at 19:51

Monday, Jan 10, 2005 at 19:51
Willem if his tyres dont blow at 60psi they will wear out in the centre prematurely, of course depending on the load. Rough ride too!
In my ute the original 205/16 & later 225/16 use less fuel with the same rolling diameter as a set of 30X9.5X15 MS (more like AT actually)
Wider ones may last longer if tread is the same & ride & handle better due to lower pressues required & wider track/rims.
AnswerID: 92248

Follow Up By: Toy60 - Tuesday, Jan 11, 2005 at 08:04

Tuesday, Jan 11, 2005 at 08:04
Was probably a hired camper eh????
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FollowupID: 351148

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