Results 1 to 10 of 10

Thread: Taller tyres, better consumption?

  1. #1
    Join Date
    Feb 2010
    Location
    Townsville, QLD
    Posts
    2,580
    Total Downloaded
    0

    Taller tyres, better consumption?

    G’day!

    I have a query, it seems strange to me that after a significant tyre size increase, my fuel consumption has decreased! I’m not concerned, moreso dumbfounded!

    My P38 previously ran 255/60/18 all terrain tyres, I’ve gone up to a 285/75/16 mud terrain tyre.

    The best I could ever get out of a tank of LPG was 300km (GPS verified distance), having gone up to the big 285’s id expected a decrease in range, but it’s in fact gone up! Two tanks in a row on the same roads I’ve managed 325km on the odometer (360km by the GPS). As always on gas it’s pretty consistent regardless of the type of driving. The second time around I used the Bruce Highway to measure. Before the increase I’d get Townsville to Innisfail on gas before needing to fill up (virtually an empty tank). Now a few times I’ve made it all the way in to Cairns and flicked over to Petrol only 1 or 2km before the fuel station that sells gas!

    Has anyone else had the same experience?

    Cheers
    Keithy

    2002 P38 Range Rover HSE

    Sequential LPG - Redarc Charger - TPMS - Ashcroft Locker
    Wheel Carrier - Bullbar & Spotlights - 285/75/16 BFG KM3’s
    On Board Solar - Stainless Snorkel - 2” Suspension Lift

  2. #2
    Join Date
    Mar 2007
    Location
    Warwick Qld
    Posts
    1,977
    Total Downloaded
    0
    Quote Originally Posted by Keithy P38 View Post
    G’day!

    I have a query, it seems strange to me that after a significant tyre size increase, my fuel consumption has decreased! I’m not concerned, moreso dumbfounded!

    My P38 previously ran 255/60/18 all terrain tyres, I’ve gone up to a 285/75/16 mud terrain tyre.

    The best I could ever get out of a tank of LPG was 300km (GPS verified distance), having gone up to the big 285’s id expected a decrease in range, but it’s in fact gone up! Two tanks in a row on the same roads I’ve managed 325km on the odometer (360km by the GPS). As always on gas it’s pretty consistent regardless of the type of driving. The second time around I used the Bruce Highway to measure. Before the increase I’d get Townsville to Innisfail on gas before needing to fill up (virtually an empty tank). Now a few times I’ve made it all the way in to Cairns and flicked over to Petrol only 1 or 2km before the fuel station that sells gas!

    Has anyone else had the same experience?

    Cheers
    Keithy
    Sounds about right for bitumen running with a V8. Less powerful motors can struggle to turn the bigger wheels as efficiently, needing more throttle to maintain the same speed.
    You may notice the opposite when off-road in heavy going, as it takes a bit more oomph to get the wheels turning.
    -----
    You have the right to remain silent. Anything you say will be misquoted, then used against you.
    -----

    1999 Disco TD5 ("Bluey")
    1996 Disco 300 TDi ("Slo-Mo")
    1995 P38A 4.6 HSE ("The Limo")
    1966 No 5 Trailer (ARN 173 075) soon to be camper
    -----

  3. #3
    Join Date
    Apr 2008
    Location
    Brisbane,some of the time.
    Posts
    13,641
    Total Downloaded
    0
    Higher gearing can also reduce fuel consumption(such as fitting larger tyres),although too high can have the opposite effect.

    As an example,many years ago i had a HQ ute,diff ratio was 3.55,from memory.
    I changed it to 3.08,fuel consumption went from 20MPG to around 26MPG,on a run.
    Paul

    D2,D2,D2a,D4,'09 Defender 110(sons), all moved on.

    '56 S1,been in the family since...'56
    Comes out of hibernation every few months for a run

  4. #4
    Join Date
    Jan 2011
    Location
    Gippsland
    Posts
    1,504
    Total Downloaded
    0

    Taller tyres, better consumption?

    An increase in tyre size above standard means less revolutions of the wheels per kilometre so your odometer (and speedo) are no longer accurate Taller tyres, better consumption? There are online calculators that will show the percentage error. I am 2 sizes over standard and my odometer records 900m over a measured 1000m. I need to add 10% to my odo reading when calculating fuel efficiency.
    LROCV member #131
    1999 build D2 TD5 Auto, Mantec snorkel, 2" LRA spring lift, ARB on board air, Ashcroft ATB, CMM air ram CDL shifter, swag & gold pans ....

  5. #5
    Join Date
    Jan 2011
    Location
    Gippsland
    Posts
    1,504
    Total Downloaded
    0

    Taller tyres, better consumption?

    ........ and my fuel economy is unchanged and cumulatively averages out to 11.3L/100km exactly the same as when I was running standard size tyres.
    LROCV member #131
    1999 build D2 TD5 Auto, Mantec snorkel, 2" LRA spring lift, ARB on board air, Ashcroft ATB, CMM air ram CDL shifter, swag & gold pans ....

  6. #6
    Join Date
    Feb 2010
    Location
    Townsville, QLD
    Posts
    2,580
    Total Downloaded
    0
    Quote Originally Posted by onebob View Post
    An increase in tyre size above standard means less revolutions of the wheels per kilometre so your odometer (and speedo) are no longer accurate Taller tyres, better consumption? There are online calculators that will show the percentage error. I am 2 sizes over standard and my odometer records 900m over a measured 1000m. I need to add 10% to my odo reading when calculating fuel efficiency.
    Thanks mate!

    As you’ll see in my original post, both odometer readings were GPS verified. Where prior my odometer was pretty well spot on, it’s now 10% out roughly. I’ve accounted for these variances in my consumption figures accordingly.

    Cheers
    Keithy

    2002 P38 Range Rover HSE

    Sequential LPG - Redarc Charger - TPMS - Ashcroft Locker
    Wheel Carrier - Bullbar & Spotlights - 285/75/16 BFG KM3’s
    On Board Solar - Stainless Snorkel - 2” Suspension Lift

  7. #7
    Join Date
    Jan 2016
    Location
    Netherlands
    Posts
    880
    Total Downloaded
    0
    I have gone up from the standard size highway tyres on a P38 to 235/86R16 mud terrain's. I have found it to be more economical but I can't quantify just how much since the added weight of bars, bash plates, diff lockers, lift kit etc. has had an impact. The removal of the aerodynamic bumpers and the lift of the vehicle has also had an impact. The 235 tyres are a bit skinnier but the MT tread will not help.

    Overall on long distances without going over 130kph (the car really struggles to get past that with them huge tyres and a rtt :P) I get about 7km per liter. Seeing as how I never managed to get 8km's per when the car was bog stock I tend to think larger tyres and thus less rpm definatly made a difference.

    PS I also have a different cam in my engine (leaning towards torque) and a tornado chip, so overal too many changes I guess

    Cheers,
    -P

  8. #8
    Join Date
    Jul 2014
    Location
    west of Transylvania
    Posts
    3,534
    Total Downloaded
    0
    What i know for sure based on many live tests is that bigger tyres on mine(only 4% in diameter but 2kg more) increased the EGT with up to 150*C under heavy load and the coolant temp with 5-10*C... consumption increased as well and the ABS related systems were all mixed up ... IMO all these things are normal for any vehicle which has the VSS as part of the engine/(transmission if auto) management's overall addaptive strategy cos all the maps were ''calibrated" from factory for the recommended std dimension tyres, any external intrusion in that algorythm will mix up things one way or another
    Discovery Td5 (2000), manual, tuned

  9. #9
    Join Date
    Oct 2017
    Location
    AU
    Posts
    643
    Total Downloaded
    0
    Sometimes it's more to do with the gearing and tyre size.

    My puma defender's gearbox setup is terrible. Very difficult to hold 100km/h. And fuel consumption is not good.

    The truck is happy at 120kg/h on 6th gear and also 90 at 5th. But Not on 100km/h.
    I think if I change the the to a bigger diameter, I can get the truck sit at 100 in 5th happily

  10. #10
    Join Date
    Jan 2016
    Location
    Netherlands
    Posts
    880
    Total Downloaded
    0
    Now that the good weather is beginning up here, I have been wheeling in france this weekend and I finally have a nice long trip to comment on the consumption.

    With the cruise control on 100kp/h on the dash (which is about 10% of due to the larger tyres) I do 2200 rpm on the nose and get a consistent 13.7L/100. This number should be adjusted down by 10% as well which makes 12.5L/100 which is exactly 8km's per liter of fuel. The car was (I guess) on or just over GVM since it was fully loaded with gear and 4 people.

    The best I ever did on my standard tyres with an empty, unmodified vehicle under similar circumstances and speeds was 11.8L/100 so it's so close I think I can conclude that taller tyres have indeed improved my cruising consumption figures.

    Cheers!
    -P

Tags for this Thread

Bookmarks

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Search AULRO.com ONLY!
Search All the Web!