Thread: Tyres...how big "should" I go? NOT how big "can" I go :)

I run 31's x 10.5's on mine.
That is close to the same rolling diameter of the 245 75 R16s
I have run 245s before too.
IMO this is the maximum size for a 300tdi with standard diff ratios
And transfer gears.
Any higher and you will feel it too much on the highway...it would
be a slug up hills with a load....and mine has aftermarket intercooler and
tweeked fuel pump.

235/85 are bigger and some people have them. I was going to put some on mine but went 245/75 instead. Bigger diameter helps on sand etc, but depends what sort of 4wding you wana do. If you are talking bout putting AT tyres on then I wouldn't bother going bigger than the above. If you are looking at getting big mud tyres and want to challenge everything then can go bigger but as mentioned probably want to change ratios.

Personally I wouldn't bother. The disco is pretty capable. Id focus more on reliability and less on tyres. Get good ATs in one of mentioned sizes and drive it smart. Get a compressor and set right pressures. For bigger tyres you need to modify gears as mentioned and probably get the wheel arch guards and body lift. If i had the coin for that id get ashcroft atb back and front instead and guarantee you will be outperforming bigger tyres.

245/75 is a good size for a mostly stock d1 , but I love the look and extra stability of the 265/75's with offset rims and flares.

Originally Posted by edddo

I run 31's x 10.5's on mine.
That is close to the same rolling diameter of the 245 75 R16s
I have run 245s before too.
IMO this is the maximum size for a 300tdi with standard diff ratios
And transfer gears.
Any higher and you will feel it too much on the highway...it would
be a slug up hills with a load....and mine has aftermarket intercooler and
tweeked fuel pump.

I must be getting confused...I've gotta work on my rolling diameter math...I'm a surveyor and maths is my thing but after a day's work it just doesn't work anymore and probably won't till tomorrow.

Mine already has a tweaked injector pump and a couple of other tweaks (maybe the intercooler, I'm not sure though, have to consult previous owner) but is there a way via diff ratios to make it okay or is it just going to be slow and sluggish with bigger tyres and the 300TDI engine? It sounds like others have done this, and would prefer the extra stability of the bigger tyre too but it's not the be all and end all for me either, I am going to have to get new tyres though seeing as they are so old now so if I'm going to be buying new rubber I might as well beef them up if I can, so long as it won't wreck the drive.

Originally Posted by Fausto79

235/85 are bigger and some people have them. I was going to put some on mine but went 245/75 instead. Bigger diameter helps on sand etc, but depends what sort of 4wding you wana do. If you are talking bout putting AT tyres on then I wouldn't bother going bigger than the above. If you are looking at getting big mud tyres and want to challenge everything then can go bigger but as mentioned probably want to change ratios.

Personally I wouldn't bother. The disco is pretty capable. Id focus more on reliability and less on tyres. Get good ATs in one of mentioned sizes and drive it smart. Get a compressor and set right pressures. For bigger tyres you need to modify gears as mentioned and probably get the wheel arch guards and body lift. If i had the coin for that id get ashcroft atb back and front instead and guarantee you will be outperforming bigger tyres.

I totally agree, and my first focus is going to be on reliability and proper driving techniques, as I've said though I'm going to be changing them anyway so if I can beef them up a little bit (not too much) then I'd like too just for stability and even a bit of looks too.

I've already got a compressor and I've got a rear vacuum locker on the car, a good one (can't remember brand exactly but it's one of the good ones) so that should cover me for rear diff...does that cover me for rear diff? It's got the 2" lift too. I don't mind modding it a tiny bit if necessary but only if it's still going to drive well with slightly bigger rubber.

Hmmmm....

The quickest way to change your overall drive ratios is to acquire and fit a Defender transfer case. They have a lower geared high range. Keep your Discovery transfer case if you want to return to stock.

Great Tip thank you! Basically I'm going through the whole car in anticipation of doing some full on outback trips and the like. So everything from a reliability and performance perspective are going to be looked at from batteries and electronics, leaks, engine temp, and tyres. Tyres are just the first cab off the rank

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Originally Posted by Young Angus

I must be getting confused...I've gotta work on my rolling diameter math......

This may help:
Width (mm) Aspect Ratio (%) Rim size (") OD (mm) OD (")
245 75 16 773.9 30.5
255 70 16 763.4 30.1
265 75 16 803.9 31.6
235 85 16 805.9 31.7