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Thread: New tyres, different size, more fuel?

  1. #1
    Join Date
    Nov 2012
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    south africa
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    9

    New tyres, different size, more fuel?

    I've a Td5 Disco 2004 and will soon need new tyres. Its got the standard issue 255/55 R18 Goodyear Wranglers on 18" mags, and I'd really like to keep the mags rather than drop to 16" ones.
    There's a good offer for 265/60 R18 Cooper AT3 tyres which I know will alter the wheel geometry a bit, but has anyone done this tyre size change and if so how has it affected fuel consumption? I'm wary of changing to bigger dia tyres if my consumption is going to shoot up.

  2. #2
    Join Date
    Nov 2012
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    penrith
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    390
    Quote Originally Posted by mr bounce View Post
    I've a Td5 Disco 2004 and will soon need new tyres. Its got the standard issue 255/55 R18 Goodyear Wranglers on 18" mags, and I'd really like to keep the mags rather than drop to 16" ones.
    There's a good offer for 265/60 R18 Cooper AT3 tyres which I know will alter the wheel geometry a bit, but has anyone done this tyre size change and if so how has it affected fuel consumption? I'm wary of changing to bigger dia tyres if my consumption is going to shoot up.
    My guess would be that it wouldn't make to much of a difference, if you do a lot of highway driving then I believe it would improve fuel economy very slightly, I can't recommend cooper discoverer at3's highly enough!!! The only and I mean only gripe I have with mine is they seem to collect an abnormally high amount of medium size pebbles/stones so you will have to get used to a clicking sound until they all fall out after sometimes up to and slightly over 50km distance not speed, after a trip down some gravel/dirt tracks but other then that exceptional tyres, RE I personally wouldn't worry to much about increased fuel consumption with such a little increase, if you we're going say 33 or 35 inch tyres I would say get ready for a shock with your fuel bill, but this is only my opinion and by no means am I saying I'm correct but in my experience its only the drastic changes that make a noticeable change, can't recommend coopers enough lol 80,000km warranty too!!! And no I don't work for coopers lol

  3. #3
    Join Date
    Jan 1970
    Location
    Melbourne
    Posts
    1,927
    That's a 5% difference. It will increase fuel usage, but it won't be too bad.
    Thanks,

    Adam

    2004 Discovery 2

    "I didn't lose my mind, I sold it on ebay."

  4. #4
    Join Date
    Mar 2012
    Location
    Sunbury
    Posts
    269
    Quote Originally Posted by disco2_dan View Post
    My guess would be that it wouldn't make to much of a difference, if you do a lot of highway driving then I believe it would improve fuel economy very slightly, I can't recommend cooper discoverer at3's highly enough!!! The only and I mean only gripe I have with mine is they seem to collect an abnormally high amount of medium size pebbles/stones so you will have to get used to a clicking sound until they all fall out after sometimes up to and slightly over 50km distance not speed, after a trip down some gravel/dirt tracks but other then that exceptional tyres, RE I personally wouldn't worry to much about increased fuel consumption with such a little increase, if you we're going say 33 or 35 inch tyres I would say get ready for a shock with your fuel bill, but this is only my opinion and by no means am I saying I'm correct but in my experience its only the drastic changes that make a noticeable change, can't recommend coopers enough lol 80,000km warranty too!!! And no I don't work for coopers lol
    Warranty only applicable in primarily capital cities. I had Cooper STT's fitted to a previous vehicle. Great tyres, handled wet & dry conditions well, sloppy mud great, not so sandy conditions. I lived in Cairns & had a minor problem with a tyre. No warranty, outside of warranty area,

  5. #5
    Join Date
    Jan 1970
    Location
    Central West NSW
    Posts
    11,051
    I found with mine, when I went from 29" to 33" that the consumption went up by 1l/100km around town and down by the same on the highway. When I changed to a more open pattern the conumption went up everywhere. At that size I'd be looking more at the tyre pattern than the size.
    Cheers
    Slunnie


    ~ Discovery II "Storm" ~ ~ Series IIa 6cyl ute ~ ~ Series II V8 ute ~


    D2Au - The Australian Discovery2 owners group with 400 members!

  6. #6
    Join Date
    Jan 1970
    Location
    Avoca Beach
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    10,496
    I often woder if people add the 5% increase in rolling diameter to the Kilometers on the odometer that they travel when they calculate fuel consumption.

    All things like rolling diameter being equal, economy should IMPROVE slightly by having a higher gearing as the engine is turning slower for a given speed.

    I found with my RRC that economy was exactly the same, as near as could be calculated with bigger tyres, after I added the 5% because the car travelled 5% further.
    Regards Philip A

  7. #7
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    Nov 2012
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    south africa
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    Many thanks to all, I'm a bit more confident now that all will go well with the Coopers.

  8. #8
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    Aug 2012
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    Mackay
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    Quote Originally Posted by PhilipA View Post
    I often woder if people add the 5% increase in rolling diameter to the Kilometers on the odometer that they travel when they calculate fuel consumption.

    All things like rolling diameter being equal, economy should IMPROVE slightly by having a higher gearing as the engine is turning slower for a given speed.

    I found with my RRC that economy was exactly the same, as near as could be calculated with bigger tyres, after I added the 5% because the car travelled 5% further.
    Regards Philip A
    Economy should improve with lower revs to a point. Depends on the power stats of your engine and how much you gear up. If you 'over gear' and the engine starts to labour then you will burn more fuel.... if you have an instantaneous fuel read out; drive at a slow speed in the correct gear then change up.... gives the same effect. I put the biggest legal tyres I could on my 07 ranger, around town and off the mark you could feel it was a bit more sluggish (notice it most when your towing a big load) but once it's moving it's pretty good. Hasn't really affected the fuel consumption.

  9. #9
    Join Date
    Mar 2011
    Location
    Country Victoria
    Posts
    19
    I just changed up from the Pirelli Scorpion 255/55 R18 on 18" mags to the 265/60 R18 Cooper AT3 tyres. With the old tyres I was getting 10.7 litres per 100 km. With the 5% increase with the new tyres I'm getting 11 litres per 100km. These figures are tracked off of GPS Km, not the (now incorrect) odometer in the vehicle. The only thing which might have an impact on the figures (and potentially drop it down again) is that it's been quite hot and the A/C has been used more that the figures (2 years worth of averages) used to calculate the 10.7 figure - which includes winter (no A/C) driving.

    Bottom line is - I was worried that it would make a big difference, but it appears that all is well. A hell of a lot quieter too!!!

  10. #10
    Join Date
    Jan 2011
    Location
    Sydney
    Posts
    71

    Scorpions

    I have twice switched to scorpions. 1st time on my TD200 from Michellins in the UK, this time from Goodyear Wranglers on our TD5 in Aus. Kept the same profile both times and in both cases the fuel consumption dropped by 5-10%.

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