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| WelshGas Member Since: 01 Oct 2010 Location: Vale of Glamorgan Posts: 935   
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Ignoring the aesthetics of different tyre sizes and using standard 16" wheels.
Please humour me. A vehicles weight is distributed through the tyre footprint, so a narrow tyre has a smaller tyre footprint and hence a higher loading / sq cm. A wider tyre has a larger footprint and using the same vehicle then we would have a lower loading / sq cm. according to my calculations, using 235 and 265 tyres on the same vehicle then the loading / sq cm would be reduced by a factor of 0.89. A larger footprint would have a higher rolling friction, hence fuel consumption increases as the tyre footprint increases. Higher loading would give increased traction, useful in snow and mud. Correct? Lower loading would spread the vehicle load and hence useful in soft sand. Correct? Lower loading and increased friction would help if rock crawling or undertaking high speed manoeuvreing . Correct? Now a Defender, not being a high speed vehicle, well not if it has not been heavily modified, would seem to be best suited to narrower tyres to cope with snow, mud and wet camping fields and the like. Correct? So combining aesthetics and function a combination of 235 width tyres and spacers would tick all the boxes! Does the above make sense?  LANDYWATCH
Neighbourhood Watch for Land Rover Owners http://www.landywatch.co.uk/smf2/index.php |
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4th Feb 2013 6:01pm |
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| willy eckerslike Member Since: 15 Jun 2009 Location: North yorks Posts: 1789  
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255 85 16 makes more sense, best of both and free 1 1/2" inch lift Original Member Pie n Pea Club.
110 HCPU Tipper |
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4th Feb 2013 6:15pm |
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| macduff Member Since: 04 Nov 2012 Location: NE Posts: 119
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the 85 is a indicator of the sidewall hieght as a percentage of the tyre width (approximate as makes vary) 2023 110 P400e |
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4th Feb 2013 6:33pm |
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| WelshGas Member Since: 01 Oct 2010 Location: Vale of Glamorgan Posts: 935
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I make it 0.6 inches lift.
 LANDYWATCH
Neighbourhood Watch for Land Rover Owners http://www.landywatch.co.uk/smf2/index.php |
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4th Feb 2013 6:43pm |
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| diesel_jim Member Since: 13 Oct 2008 Location: hiding Posts: 6092 
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The "aspect ratio".... or height, as you call it (the 85 bit) is a percentage of the tyre width so a 235, the "height" is 85% of 235mm a 255, the "height" is 85% of 255mm |
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4th Feb 2013 6:43pm |
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| stevie d Member Since: 09 Nov 2009 Location: Bishops Stortford Posts: 342 
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Welshgas,
I think most people would agree that 235 tyres are the best size for a Defender for the majority of scenarios - how you want them to look is personal choice. Why not choose a rim with a big offset rather than spacers? Steve  Defender 90 TD5 Station Wagon
Discovery 3 HSE BMW 330i Coupe |
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4th Feb 2013 6:49pm |
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| Glynparry25 Member Since: 16 Feb 2009 Location: Miserable Midlands Posts: 3015 
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 good old tyre debate 
What you have said is in is right right (on paper), but all can change with conditions (real life): If you have narrower tires with a higher loading it will cut into the mud better...... what if the mud is about 2 foot deep- the tires will actively encourage the vehicle to dig in to its axles and then you are going nowhere fast...... on the other side, a lower loading with more friction is good on the road.... but if wet it will encourage the build up of water and therefore increase the chances of aquaplaning etc. Unfortunately there is no 'perfect tire' out there. I am also getting more miles per gallon with 285s than most with the 235s are so again..... real life doesn't necessarily reflects what 'should be' according on paper. Glyn   |
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4th Feb 2013 6:59pm |
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| willy eckerslike Member Since: 15 Jun 2009 Location: North yorks Posts: 1789
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True but when comparing a GG TR to a KM2 MTR its bigger than 0.6" but on paper you are correct Original Member Pie n Pea Club.
110 HCPU Tipper |
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4th Feb 2013 7:22pm |
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| Glynparry25 Member Since: 16 Feb 2009 Location: Miserable Midlands Posts: 3015
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That reminds me of a review I read somewhere. There were a few guys who had bought different 33" Mud tires and some were getting rubbing on the arches and others not. In the end they measured about 5 different types and came up with some being 32" and others being 35" even though they stated 33" on the sidewall- I think only BFG and Cooper were the correct sizes. Glyn |
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4th Feb 2013 7:30pm |
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| WelshGas Member Since: 01 Oct 2010 Location: Vale of Glamorgan Posts: 935
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I have the original General Grabber TR 235/85/16 tyres but will need to renew them before next winter at the present rate of wear, have done 36,000 miles so far and they have done everything I have required of them, and they are wearing well. Just wanted to confirm that the information I had gleaned from the multitude of posts on these forums was correct.
I thought I would try spacers first before splashing out on new wheels with a different offset. I could sell the spacers if I decided to go down that route. LANDYWATCH
Neighbourhood Watch for Land Rover Owners http://www.landywatch.co.uk/smf2/index.php |
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4th Feb 2013 7:33pm |
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| Glynparry25 Member Since: 16 Feb 2009 Location: Miserable Midlands Posts: 3015
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If the GGs are everything you have wanted, I would say a better route will be to just stick with them- people are taking new ones off to fit mud tires and selling them cheap all the time
you can normally get a set of 4 on nearly new alloys for less than you can buy a set of 4 BFG tires on their own.
Glyn |
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4th Feb 2013 7:39pm |
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| SteveS Member Since: 05 Oct 2010 Location: Devon & Berkshire Posts: 388  
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In the real world you would wish to consider the effects of airing down on sand, rocks etc. Airing down a high tyre (ie one with a large aspect ratio like 0.85 when let down creates a longer elongated footprint than does say a 0.65 aspect ratio on the same width of tyre. Airing down a big footprint tyre will tend to allow a lot of rubber to 'wrap' around rocks for example.
Personally I run 285 75s which have a big contact area for normal pressure running and will air-down well as they are relatively high sidewall. I prefer the big grip lots of tread float on top approach rather than the little grip, bite through approach. This is a personal thing as some will swear by their own methods. Tyres will always be a compromise unless you have an optimised set for every condition you encounter You may also wish to consider the tread block pattern - for example an MT actually has less rubber on the road than an equivalent AT - thus the MT blocks dig into mud more and have the pattern to self clean and provide traction. Also narrow tryes that dig down into the mud will get a lot of sidewall drag against the ruts sapping power. |
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5th Feb 2013 9:23pm |
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| Peter Member Since: 04 Mar 2012 Location: Kent Posts: 153 
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Am trying to run BFG A/T's all year on my work Defender (Have BFG M/T's on play Defender - deflate by half for off road in mud) and so far apart from gloopy wet mud when towing a laden trailer they have been excellent (no spacers). Also noted on a icy road trip they are spec'ed above Euro rating for winter tyres (check they have the snowflake symbol on the sidewall - some don't). and also should do 100,000 miles.
Been impeccable in the recent snow - which surprised me as always changed to a set of BFG M/T in about October for winter tyres. So depends what you are using your vehicle for and where. BTW Defender has aerodynamics of a 2 ton brick. |
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6th Feb 2013 1:14am |
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| MrFlips Member Since: 27 May 2009 Location: Cardiff Posts: 682 
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I'm going to suggest a set of 265 BFG AT would suit your needs perfectly. They'll last for years, look factory fit, nice and quiet, will cut down as much as a 235 (ATs fill with mud anyway) and will be easy to sell on when they're running low! (Without my sensible hat on I'd say go with a set of Cooper STT 235s, they'll be fantastic offroad but perhaps slightly slippery on roundabouts in the wet...) Peter
2008 SWB Truck Cab 1952 80" Soft top |
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6th Feb 2013 2:53am |
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