Tyre MPG Hit

[HantsHog]

Not sure if this is in the right section but here goes ...

I bought my 3.0 '02 Terrano last year and it came with some worn Forceum ATZ tyres with about a milimetre of tread left above wear indicators. On these I was getting about 32mpg on normal road school runs, 37mpg on motorway at steady 56mph and 29mpg when towing (trailer empty or not). Usually I can get 100miles to each quarter of a tank on normal roads.

Now, I've changed all 4 tyres to Michelin Latitude Cross AT tyres and I'm now barely getting 28-30mpg on normal with about 75miles per quarter tank.

I believe the Michelins are suposed to be a better energy rated tyre.

All pressures are correct at 26psi and I had the tracking checked.

Can the increased tread depth make a big difference in mpg?

 

[Lazy-Ferret]

I was just wondering, new tyres are effectively larger than worn ones, and taking a guess of about 7mm more thread, that means the tyre is over 1/2inch bigger overall that the worn ones. Depending on your size of tyre, means it has gone from roughly a 30" to a 30.5" tyre.

Effectively you are going to travel the same mileage, but the odometer will show less miles travelled, as the new tyres will have gone round 11 times less per mile than the older warn tyre.

Also larger wheels take more power to turn....

:augie:augie

But really, something is wrong, I get 100miles out of each of the first 3 of the 1/4 tank marks, and about 60 out of the last one under normal urban driving on AT's, so you do seem to have lost a lot.

 

[Banshee]

I was just wondering, new tyres are effectively larger than worn ones, and taking a guess of about 7mm more thread, that means the tyre is over 1/2inch bigger overall that the worn ones. Depending on your size of tyre, means it has gone from roughly a 30" to a 30.5" tyre.

Effectively you are going to travel the same mileage, but the odometer will show less miles travelled, as the new tyres will have gone round 11 times less per mile than the older warn tyre.

Also larger wheels take more power to turn....

:augie:augie

But really, something is wrong, I get 100miles out of each of the first 3 of the 1/4 tank marks, and about 60 out of the last one under normal urban driving on AT's, so you do seem to have lost a lot.

Yep this sounds like a winner to me, You don't want to know my MPG since I've gone 33's :doh

 

[Mobieus_uk]

they are larger cos they got more tread on them, if we have a tyre with 1mm tread a circumference of 1000mm (easy number to work with) the diameter would be 1000mm/3.142 = 318mm, if we now look at that same tyre with 10mm tread(easy number again) that would add 20mm to our diameter 338mm, make our new circumference 338x3.142 = 1061mm (6% differance)so 30mpg could end up being 28mpg

the maths is something like that, simple answer is yes it will be different

 

[macabethiel]

As others have said the rolling radius of new tyres is larger so the odometer will under read the distance covered showing an apparent drop in m.p.g.

I noticed the same thing on my 300C when I fitted new Michelins it dropped from 34 mpg average to around the 30 mark on 18 " rims.

 

[HantsHog]

Mmm ... so I wonder if my readings were inaccurate on the old worn tyres and I wasn't getting as good mpg as I thought ... or ... its the other way around! I'll get the GPS out and measure my journey between fills. Come to think of it on old tyres my speedo was reading about 60mph against GPS 52mph but now on new tyres it's 56mph on GPS at odometer 60mph.

Sent from my Alba 10" using Tapatalk

 

[Blocky10]

I've owned my 04 3ltr auto for 2 years now. I bought it to tow our huge twin axle caravan, which it does well. It had a set of 4 matador conquerra's, 2 of which were knackered so I replaced them with the same. I'm still on the same tyre now and have done, at a guess, 15k.
I can honestly say I've never worked out mpg for this truck. I'm not brave enough! I bought it to do a specific job and without it I'd be stuck so mpg isn't a concern. It's also our only vehicle atm!
My way of thinking is, if you keep it regularly serviced, keep an eye on tyre pressures and don't carry about unneeded clutter and are easy on the fast pedal, you're doing the best you can for the best mpg. And that's good enough for me. :thumbs

 

[macabethiel]

Our Jeep & 300 C both have on board mpg readouts. interestingly when I compare the average manually the vehicle computers under read the consumption by a couple of mpg.

 

[Sweety]

Mine had road tyres on it when I bought it but replaced them with Cooper AT3's & there was no charge at all in mpg :thumbs not sure what size wheels you have but 26psi in the rears sounds a little low but tbh can't remember the pressure for 15 or 16" wheels now but the 17" are 26f & 29r but I have always ran the fronts at 27psi (15 & 17" wheels) as I have found I get very even wear at this pressure

 

[HantsHog]

Quick update ... since doing a complete fluid change, engine oil, filters, gearbox, transfer, front & rear diffs, the mpg is almost back to normal. I'm now getting 200 miles at the halfway tank indicator.

Also checked the odometer against my GPS and it is reading 2% over.