Tyre size and fuel consumption




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  1. #1
    Join Date
    Sep 2018
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    Klein Pella
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    Default Tyre size and fuel consumption

    I have been wondering whether someone else had a similar experience as I did, when changing tyreson my car. I have been keeping track of my cars fuel use right from collecting it new at the dealer and about once a year I put it all in an excel file and play with the data, drawing some graphs etc. And the graphs gave a good jump a year ago.
    I went from a 255/65/17 to 265/75/17 on my Pathfinder, my average fuel consumption went from 10.5 km/l to 9.5km/l which disappointed me to say the least.
    The car went in for a service the same date and I suspected something done during the service had an effect, but then I made the calculations.

    My consumption went up 9.5%, but then my actual distance covered VS the odometer went up 8.5%, so the difference is not that much, and as for the other 1%, my actual speed went from 113km/hr to 121km/h at my usual setting on the cruise control of 120, so I am traveling faster than the speed I originally worked out as the most economical in my car. The actual speed and distances worked out by taking Ave GPS measurements over 10kms before and after the Tyre change.

    This makes me question the generally accepted knowledge that bigger tires necessarily increase your consumption.

    I will try to replicate the results when I upsize the tyres of my HILUX next week and later with my Hardbody.
    Last edited by Bex; 2018/09/29 at 11:47 PM.

  2. #2
    Join Date
    Aug 2007
    Location
    Carletonville
    Age
    52
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    6,175
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    Default Re: Tyre size and fuel consumption

    Also often question how accurate the data is when using the cars odo. When I went from 245 to 31" tyres on my Sani/Hardbody, I also noticed my figures went bad, but I never took gps kms, so never worked it properly. Then I went to 33" and I had to start using the gps as a speedo as my clock was under reading by around 10km/h at 120.

    On 31s I hardly noticed my power drop due to the gearing change the tyres made, but on 33s I can feel the loss of power, and see it on my boost gauge as it averages 0.2bar more to keep the same speed. I'm not going to even bother trying to work the figures out when I go to 35s, I know its going to be bad.
    David/Hillbilly - 1997 SFA Nissan Sani 2,7 TD - 5" lift on 33" tires - Dual Transfer with 4.1 gears

    http://www.youtube.com/user/davidabcab



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