A search will reveal endless discussion on the subject, but in essence you can go to just under 31" as long as you keep the width fairly narrow. 245/75/16 is a pretty good start at maintaining decent road manners and working well off road. However, if you are looking for "big and chunky" then I suspect you are doing this just for looks, in which case lift your D2 but be prepared for the ride and handling to suffer.
 
Thanks for ur help! Id be happy to keep them abit narrower if it means not doing a lift as i quite like the drive as it is. I was just abit worried of it rubbing the arches etc

What terrain are you driving?

These look nice

download (35).jpeg


Size wise would be similar to original.

https://www.ebay.co.uk/itm/x4-245-7...526321?hash=item3fc4e8bb71:g:3iIAAOSwV8ZdejCy
 
If you mostly drive on the road I would go with the BFG KO2 All Terrains. Good grip and fairly quiet on tarmac, excellent in the snow and pretty capable in anything but deep mud.
 
In that case 245/75/16 BFG KO2s would be fine (assuming you don't have 18" alloys). There are cheaper tyres, but KO2s are very robust and last a very, very long time.
 
Why are you changing to steel? LR alloys are very tough and give better suspension response than steel due to the reduced unsprung weight.
Unless you are heading off to some remote wilderness where steel can be hammered and welded back together and alloy can't, then I'm not sure why you would replace perfectly serviceable alloy rims for steel ones.
 
The steel wheels used on Defenders or D1s will not fit a D2 as the wheel nuts are different. You can buy steel modulars for about £50 each, or tatty secondhand alloys would be about the same. Or you could spend about the same refurbishing the ones you have and end up with something that looks much better - maybe even powder coat them a complimentary colour. My son's D90 is pearl white with metallic grey roof, bonnet and wheel arches, and with the boost alloys powder coated the same metallic grey.
 
The bigger issue with Defender / Disco 1 / RR Classic wheels is that the wheel stud spacing is totally different.
 

Similar threads