Effect of 31" tyres on mpg

[MudSurfer]

Does anyone know what the effect on the mpg is on a 2.4 running on 31" tyres? I'm sure that my mpg is falling after I've put the 31" tyres on - but don't know if this is realted to the difference based on the speedo figure being off (by about 5mph) and this affecting the odo recording actual mileage....does any of this make sense???

[laser_jock99]

Circumference = Pi * d (where d is your wheel diameter)

'd' on factory Surf is 29.5" your Surf odometer is calibrated to this. You have increased 'd' to 31" therefore your odometer and speedo are underreading by a factor of 31/29.5

So each km your odo reads is really 1.0508474km travelled.

For 33" tyres it's 1.118km and should you dable in 35"s a whopping 1.186km! With the knobblyness of the tyres invovled (the tread depth doesn't count in tyre diameters) I reckon a 33" mud terrain tyre when new (with say a 20mm tread depth) is under reading by nearly 200m per km! In other words making the car seem 20% less efficient.

[plumb bob]

I put 31"x15x10.5 on my surf, and had the head replaced almost imedeately afterwards(and appear to have a fuel leak now) and lost about 4mpg, but with the bigger tyres on my speedo is now more accurate, in fact almost spot on.

I think my drop in fuel consumption is more likely to be because of the leak rather than the new tyres.

[BUSHWHACKER]

Does anyone know what the effect on the mpg is on a 2.4 running on 31" tyres? I'm sure that my mpg is falling after I've put the 31" tyres on - but don't know if this is realted to the difference based on the speedo figure being off (by about 5mph) and this affecting the odo recording actual mileage....does any of this make sense???

Mud tyres will lower the MPG.

[Apache]

Mud tyres will lower the MPG.

Hehe, wont they just!

[RodLeach]

My tyres come in at 31.8 inches tall an to be honest im still getting around the 25mpg figure! Obviously theres a little room for it to drop etc! but its still nothing that worring!

Why is it M/Ts lower the MPG more then? i mean obviously i could guess that the deep tread creates a drag or something but...

[Apache]

Yeah it's just drag. TBH its not that much. Air resistance is the biggest killer with a brick shaped truck. All the rest is minor!

[RodLeach]

When i got my surf it never even entered my head about "fuel economy" Its just one of those things you cant really factor in when buying any large car let alone one that shares the aero dynamic propertys of j-lo's backside!

BUT it looks cooler then j-lo's a$$ so hey!!

looks even cooler running on a set of m/ts!

[Apache]

When i got my surf it never even entered my head about "fuel economy" Its just one of those things you cant really factor in when buying any large car let alone one that shares the aero dynamic propertys of j-lo's backside!

BUT it looks cooler then j-lo's a$$ so hey!!

looks even cooler running on a set of m/ts!

And then there's that 'MMMMMMMMMMMMMMMM' sound they make. Cant beat it!

[nero279]

and the snorkel going
ffffffffffffffffssssssssssssss sssssssssssssssshhhhhhhhhhhhhh hhhhhhh

and exhaust
pphhhhhhhhhhhhhhhhhhhooooooooo oooooooooaaaaaarrrrrrrrrrrrrrr rrrr

and..................

[RodLeach]

and the snorkel going
ffffffffffffffffssssssssssssss sssssssssssssssshhhhhhhhhhhhhh hhhhhhh

and exhaust
pphhhhhhhhhhhhhhhhhhhooooooooo oooooooooaaaaaarrrrrrrrrrrrrrr rrrr

and..................

The driver singing along to his favorite tune..... "treat your mother right" by Mr T!

[Apache]

The driver singing along to his favorite tune..... "treat your mother right" by Mr T!

"Sweeeet home Alahbameeeh
Where the skies are so blue..."

[RodLeach]

"Sweeeet home Alahbameeeh
Where the skies are so blue..."

Well i spose that lays the "head turning" statements to rest!! I'd stare at someone singing that if i was next to them at the lights!!

Good tune though!

My surf makes all sorts of noises now! my exhaust gives a low end rumble that makes it sound like i pour curry in the fuel! my speakers punch out my 'eavy metal an make the side panels visibly shake! rattling the hell out of me and the truck! Then theres the squeeky belts that need changing!

[BUSHWHACKER]

When i got my surf it never even entered my head about "fuel economy" Its just one of those things you cant really factor in when buying any large car let alone one that shares the aero dynamic propertys of j-lo's backside!

BUT it looks cooler then j-lo's a$$ so hey!!

looks even cooler running on a set of m/ts!

Um, can I just say, there's absolutely nothing wrong with Ms Lopez's rear end!

Thank you.

[captain_chaos]

I run 31" on mine and haven't noticed any change in fuel consumption, think it's thrown my speedo out a little though. Towed my dad's cavalier a week ago and he insisted I was doing 40 when I was doing 35.