31" tyres on a Gen 4

I know the theory. I was looking for people with experience. I bit the bullet. 

 

Nice. Those look biiiiiiiiiig!

A little feedback.
On road, the auto now changes down earlier, seems to hunt less, i.e. it drops to third and stays there. 
fuel consumption appears to be around the same.
Off-road they performed exceptionally well. I deflated to 0.5 bar and we tackled a track that I quite possibly would not have been able to complete with 235's. On one muddy climb my Gen 4 with A/T's faired better than the twin locked SJ on 31" muds.

I do need to either lift it further or fit extended bump stops. It scrapes the top of the arches on all 4 wheels.  

2 months later and all good, although I haven't had the opportunity to go off-road again.
I have a slight issue with a fender flare that got damaged a while back off-road, every now and then it catches and I have to push it back into place.
I do miss the acceleration I had with the lower gearing.

Fuel consumption is 11.1l/100km averaged over the last 3 months. I averaged 11.2l/100km with the 235's, so very little difference.

I'm finding your experience very interesting. Notwithstanding clearance issues you are saying that the automatic gearbox actually responds better to bigger tyres than intuition would suggest? Do you happen to regularly monitor transmission temperature and if so how is that affected? Also when you mention acceleration have you been able to independently quantify the difference or is it just more of a seat of the pants feeling of being slower?

Lambert wrote:

I'm finding your experience very interesting. Notwithstanding clearance issues you are saying that the automatic gearbox actually responds better to bigger tyres than intuition would suggest? Do you happen to regularly monitor transmission temperature and if so how is that affected? Also when you mention acceleration have you been able to independently quantify the difference or is it just more of a seat of the pants feeling of being slower?

For low speed the auto box, well the torque converter will often compensate very well and you can always ride the brakes to go slower.

Trans temps are a good thing to consider, but no built in gauge on the Jimny unless it is available via the OBDII? I would think heavy technical off road, heavy towing or using in hot climates would be the main concerns here. Normal UK weather and mild off roading and short distance towing less of an issue.

I've seen vids of people with 235/75R15's on and the auto and acceleration times looked glacial. Maybe in the 18 sec region, with 31's and the same gearing I guess a juiced JBC Fastrac would give you a good run for your money....