keithjh Posted May 3, 2012 Share Posted May 3, 2012 Hi All, I have just about finished a conversion to auto on a 110. What size tyres would anyone suggest? Oh I have used the Defender Transfer Box, not the Disco. Keith Quote Link to comment Share on other sites More sharing options...
western Posted May 3, 2012 Share Posted May 3, 2012 235/85R16 or 265/75R16 would do the job very well. Quote Link to comment Share on other sites More sharing options...
GBMUD Posted May 3, 2012 Share Posted May 3, 2012 I have a 90 with the same engine, auto and transfer box and I find the 235s work very well. The torque converter locks up at 45mph which then drops it to 1900rpm, if you had larger tyres I think that the gearing would end up too tall once the TC locks up. 4th gear on the auto is slightly taller than 5th on the manual box so cruising speeds of 65-70 are easy enough at about 2500rpm. ...of course, I do not know for sure that the rev counter is accurate, it is driven by the alternator and seems about right. Quote Link to comment Share on other sites More sharing options...
Boydie Posted May 4, 2012 Share Posted May 4, 2012 Agreed --- I've just gone through the same process of selecting either the 225/75R16 of the larger diameter 235/85R16 tyre profile for my 300TDi Discovery. Do the math and the 235/85R16profile is around 2 1/2" larger in diameter than the 225/75R16's are. The net result is an increase in rolling circumferance by about 8% which is simply too high for the auto box to happily cope with, if you could come up with a tyre with an aspect ratio of 80% that would be ideal but short of re-capps and retreads there isnt any such tyre. With the 85% profile the ZF4HP22 just wont want to change up into 4th (overdrive) gear and when it does it will only be for a short period and the 300Tdi will be labouring. The other thing to consider is that the 235 width is right at the limit for the standard alloy rim width. Quote Link to comment Share on other sites More sharing options...
Boydie Posted May 4, 2012 Share Posted May 4, 2012 Just a thought, are the differentials in the Defender lower geared than the Discovery? if they are then you could well be able to use the bigger 235/85R16 tyres. Quote Link to comment Share on other sites More sharing options...
Retroanaconda Posted May 4, 2012 Share Posted May 4, 2012 No, but the transfer box has a lower high range of 1.4:1 rather than 1.2:1 so there is a difference there. Quote Link to comment Share on other sites More sharing options...
tacr2man Posted May 4, 2012 Share Posted May 4, 2012 I have a 90 with 265/75r16 behind discovery 300tdiauto (edc) with original disco transfer box , and that is at limit of usability for high gearing approx 57mph at 2000 which is what i want good for relaxed (?) m/way cruise solo . If I was going to tow much I would have gone to 1.4 transfer . Quote Link to comment Share on other sites More sharing options...
Boydie Posted May 5, 2012 Share Posted May 5, 2012 So there you have it, if you have retained the Defender transfer box you should be okay for the 85 profile, but it will only be marginal. added to this as I said, the 235 tyre width is at the limit for the standard ally rims. Its your call but to be safe stick to the 225's Quote Link to comment Share on other sites More sharing options...
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