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31" tyres on a Gen 4
27 Feb 2026 08:29 #263903
by saxj
I'm planning to do a trip on the Easter weekend. The trip is a high mountain very rough trail over 2 days, which is continual difficult obstacles - Baboon's pass, Lesotho.
The first time I did it I had just fitted the 235's and I had the stock gearing, and didn't experience any issues.
With the low range gearing reduction of 85%, I doubt I will have any issues with the bigger tyres.
Replied by saxj on topic 31" tyres on a Gen 4
I have an OBDII reader using SZ Viewer, which gives transmission temperature.
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.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?
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....
I'm planning to do a trip on the Easter weekend. The trip is a high mountain very rough trail over 2 days, which is continual difficult obstacles - Baboon's pass, Lesotho.
The first time I did it I had just fitted the 235's and I had the stock gearing, and didn't experience any issues.
With the low range gearing reduction of 85%, I doubt I will have any issues with the bigger tyres.
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