Driving on big tyres is a waste of time with the incorrect gearing. With the wrong gearing, you've got no torque and you're going to break something.
Simply put, I use THIS KIT from Protrack in Greece. The gearing is fantastic, the high range gearing is reduced by 17%, and low range is reduced by 87%. With my 33” tyres, this is a fantastic setup for the type of driving that I do.
My 33" tyres are exactly 17% larger in diameter than the original tyres, so the gearing for open road driving is just the same as it'd be with standard wheels and tyres.
Low range is so low, that the max speed in top gear is around 35kph. This can sometimes cause an issue on river tracks, or farm tracks, where we end up speeding up between tricky sections.
Recommendation
If you have 31” tyres or larger, this is a great addition to your Jimny. I’ve used 30” tyres, then 31” tyres, and am now using 33” tyres. Changing from 30” to 31” tyres was very noticeable when driving on the roads, especially seeing as my Jimny is manual. Using this gear kit with 31” tyres would mean the engine will be revving a little higher at motorway speeds, but that’s where the power is, so it’d be more drivable.
Protrack is great to deal with, but the shipping is expensive and I’m told you may require an importers licence to bring a kit in from Europe.