tyre size equivalent for disco ratio

cborrman said:

Any mathematicians / number crunchers / rubber fetishists know / can easily work out what tyre size equivalent would be needed to take a 110 tdi 300 with 265/75/16 tyres at present to the same ratio as doing the disco ratio upgrade that ashcroft offer... and that would fit without it looking like a tonka truck and handling like a greasy weasel?

The ashcroft site says: “This is a very popular gear set, especially for those with a TD5 90/110 or Tdi which revs excessively on the motorway. This gear set will enable you to raise your transfer case gearing by 15%, by replacing the gears in the exising 1.410 ratio transfer box with new 1.222 gears, as used in the Disco”.

Obviously no point if the wheels this size (tbd) need higher suspension which make the extra motoway cruising scary / silly

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bluedog333 said:

Have you thought about getting a Disco t-box from another source that may be a bit cheaper than Ashcroft’s offerings? 4/5 new tyres aren’t exactly cheap, plus you won’t affect the suspension or handing ‘qualities’.

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Turboman said:

That isn't a bad idea, if cost is the major consideration.

But it is worth remembering that a Disco transfer box only raises overall gearings, an Ashcroft box raises high range ratios, but leaves low range unchanged, with all the off road benefits that that brings.

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bluedog333 said:

Didn’t know that about The Ashcroft box! He’d have the same dilemma with upsizing his tyres only then, wouldn’t he? I.e low range wouldn’t be that low with the increase in tyre size?

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Rougharse Racing said:

The low range ratio is the SAME on all 1.6:1, 1.4:1 and 1.2:1 transfer boxes.
As others have said, fitting a Discovery Transfer box is the simplest and possibly the cheapest way of achieving Discovery ratios.

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Turboman said:

Interesting. Didn't know that, apologies to @bluedog333 for that.

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Turboman said:

That isn't a bad idea, if cost is the major consideration.

But it is worth remembering that a Disco transfer box only raises overall gearings, an Ashcroft box raises high range ratios, but leaves low range unchanged, with all the off road benefits that that brings.

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Britcyclerider said:

I bought a cheap disco 1.2 box and fitted the Ashcroft refurb kit and one piece diff centre. It's quite easy to rebuild and (almost) fun!

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Turboman said:

That isn't a bad idea, if cost is the major consideration.

But it is worth remembering that a Disco transfer box only raises overall gearings, an Ashcroft box raises high range ratios, but leaves low range unchanged, with all the off road benefits that that brings.

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mick 1986 said:

Assuming you want a 15% increase in circumference of your current tyre, then I couldn’t find a size that is compatible. The best I could get was a 9% increase. This was with 315/75/16 tyres.

Your current tyres are around 31.6” dia, the new ones would be 34.6”, so may need a lift.

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bluedog333 said:

Have you thought about getting a Disco t-box from another source that may be a bit cheaper than Ashcroft’s offerings? 4/5 new tyres aren’t exactly cheap, plus you won’t affect the suspension or handing ‘qualities’.

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cborrman said:

I am
looking at ashcroft and like it, but its the fitting I see costing more than the parts (ashcroft charge the same as four nice tyres and wheels just to fit) and was looking at new tyres / wheels anyway, but do recognise ashcroft is way to go (also makes it quieter apparently as well...)

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jamesmartin said:

fitting a 1.2 ratio aint difficult, id fit a good used one and spend the hundreds saved on other stuff,fitting the one piece diff shaft wont make any difference

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cborrman said:

yes, if nobody has a genius tyre / wheel based solution that’s the way to go having read here. Thanks all for answers, will let you know!

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cborrman said:

“qualities” lol... I have, is it a lot less work than the ashcroft route?

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bluedog333 said:

Same amount of work, the Ashcroft is only a reconditioned unit. Treat a good used one to a drop of fresh oil and away you go. There is the reassurance of a warranty with the Ashcroft box, but to be honest the t-box rarely goes wrong, so you should be ok with a 2nd hand one.

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