Has anyone upgraded gen 4 tyres without going bigger?

It's difficult to say if the Toyo in 195 will have as much dry grip as a 215 AT or even as the Dunlops in highway tread. I can't find a dry grip rating, but wet grip is the same for Dunlop AT20 and Toyo.

Grip on dry roads comes from the rubber compound (how sticky it is) and how much rubber is in contact with the tarmac. If you have two tyres with the same compound then the wider tyre will have more contact area and on dry/clean tarmac will have more grip, it's why F1 cars use slicks in the dry.

However, in the wet or loose surface tread pattern is more important.

Robin

Mine came with the standard duellers, replaced them in short order as they weren't quite able to take me as far as I wanted. Having said that, I did manage to eventually get it stuck in such a place that I had to resort to a tractor to get close enough to pull me out. 
After that I went to 215 75 hankook rto3's ( which after 5 years and over 100,000kms are still on the vehicle and still legal !!   very disappointed they don't still make them) and was actually suprised that my on and off road comfort, grip and traction was greatly improved. The only downside was a slight increase in noise, but it was more or a pleasant whirr than a roar you get from some muddies. 
As mentioned above, 215 75 is not much bigger than standard, and the fact they come from factory with a cheaper, basic tyre I think is actually a good thing. As we have discovered even in just this thread, no two usage cases are the same, and the manufacturer specifying a particular tyre and size combo (I hate to sound cynical but some vehicle manufacturers seem to have their fingers in a few tyre manufacturing pies) and almost threatening void of warranty if not heeded like some of the higher end vehicles I have looked at can actually be detrimental. I would be suprised if most Suzuki mechanics even expected the same tyres to be on it by the time the first service came round.
There is a massive double cab ute craze in NZ, and every manufacturer is trying to cash in on it by putting out "limited edition" versions of their utes with bits of plastic and fancy wheels and tyres to try and make it look good. ( The market for these seems to be mostly city slickers who can write it off as a "work vehicle") and it annoys me that they put relatively high end tyres on them ( that of course are baked into the price) only for the customer to rip them off and swap them for something else - generally way too wide and obnoxiously loud. It think it suits Suzuki quite well to supply them with a basic tyre - this kind of thing is what allows them to market them at a relatively cheaper rate. Whether you keep using them or not once its yours I don't think they really give two hoots.

Bob9863 wrote:

Actually I think the simple way to ask the question is like this.
When people put 215's on, they all say it improves the ride and handling.

Personally I do not believe this statement is correct.

I'm one of the people who swapped out for the 215/75 tires early on so I can't answer the question, but there a couple of points I'd like to raise.

First, as is common with forum discussions, there is no "common baseline" - the brand of tire fitted as OE varies with the market, some of the folks responding had Bridgestone as their OE rubber, others had Dunlop, I fell into the latter category and the Dunlops sucked, even as a highway tread on asphalt. Not having driven on the OE Bridgestones I can't compare them but I've had Bridgestones on other vehicles that whilst they weren't the bees knees, they weren't bad, I've also had Dunlop AT20s on other vehicles and they were nothing to write home about.

Second - I'd like to think that there are few amongst us who would consider the cost of a set of five tires as "pocket change", so the decision to replace them before it's needed is not likely to be lightly made, and it wasn't for me - I didn't have the option, as I believe some people did, to have the dealer fit a different tire for a small additional fee, I had to bite the entire cost of replacement and try to sell the used tires on, I ended up giving them to a youngster who badly needed tires for his Vitara.

I've also noticed that very few of the fourth gens I see here are still on the OE rubber, not all of them have been swapped to AT tread patterns, some are still on HT, but not on the OE HT, and I should point out that none of these fourth gens have been on the road long enough to need the OE tires replaced because of wear - I have the first fourth gen of the showroom floor here, and it's just over three years old with less than 20,000 kms on it.  Quite a few of these Jimnys are never going to go off pavement, but they are already off the OE rubber.

There has to be a reason why owners are spending the money.

I'd have kept the Bridgestone HT384 II tyres if Suzuki were still fitting them to new cars.  From experience, they muddle through ok in snow.  The Dunlops, on the other hand, I didn't want at all after reading the reviews. 

www.tyrereviews.com/Tyre/Dunlop/Grandtrek-AT20.htm

Based on tests and reviews, they are almost the worst AT tyre you can buy.

My experience always swapping them in the past leads me to a conclusion, well mote of a train of thought really.
The "improvement" has less to do with the bigger tyres and more to do with the slight loss of performance. If you can't push it as hard then it will always feel better on the road.
But you can do the same thing just by driving a bit more economical. (Pretty sure saying that would be a hanging offence in Australia)
Now I could be wrong and often am, but I also noticed after 50k or so that the drive train would develop a bitvl of noise and shudder.
I want this car to say as good as possible for the next 10 years until we move, and judging by what people here have said regarding the factory size they really don't seem to be an issue.
I think my mind is made up, I will stick with my original plan, it might not improve it on the road to a really noticeable degree, but on slippery slopes and simple it will give me more offroad capabilities without compromise to keep the factory size and just go for a better off road pattern that isn't too aggressive.