32" to 33" gets an extra 0.5" of sidewall but it's a big %.

255/60R20 have 6" height but 3/4" of that, lies within the alloy rim and about 1" is tread. Actual effective sidewall on these is only ~ 4.25"

Adding 0.5" of sidewall with a 33" tire and still being on 20" rims equates to a 12% increase in effective side wall height.

If you drop to an 18" rim and run 33" its a 1.5" increase or 35% increase in sidewall

Staying at OEM sizes 32" and going from 20 to 18" rims gives you a 23% bump in effective sidewall height.
When you add the additional variable of tougher rubber compounds and thicker rubber in a heavier tire you have another magnifying variable that increases the trail capabilities of the vehicle.

No free lunch of course.

Drawbacks aplenty.

 

While everyone nailed the statistical and objective significance, its also simply a matter of principle. Land Rover sought to design the most technologically advanced off-road capable vehicle, spends bajillions to engineer it. Then, for no conceivable reason, makes a single, solitary, soul sucking decision to damn near negate the whole thing in production and make it a Range Rover defender instead. All it needed was a little more tire. Which additionally wouldnt be a huge issue as it could have been solved aftermarket, but then they decided to equip the vehicle with a brake set that is unnecessary for the vehicle, but is impossible to improve wheel size/tire ratio. Its perplexing, thats all.

 

And I’ll offer some counters on behalf of the choices the JLR engineers made. (Mind you, I have a deposit on a Grenadier because I may decide I’d rather go that route once it comes in and I can compare it to my Defender. So I’m not “defending” the Defender, per se.)

Rubicons and Badlands Broncos are very good vehicles in the rocks in stock form. They are also very unsophisticated on-road SUVs. They are what I would call excellent off-roading trucks that are passable on the highway.

JLR sought to build a truck that can match them off-road but with far superior on-road manners. They have succeeded on the second objective, no doubt about it. As for the first it’s a bit of a tossup. I’d put my nearly stock P400 up against my former stock Rubicon in any environment. I’d put it up against my heavily modified Rubicon in any environment except rocks too big for its tires.

The problem is, to go chasing after that last bit of supremacy off-road, i.e. to beat Jeep and Ford in every off-pavement arena, would require larger tires, and they would need to be heavier E-rated tires. That carries a serious NVH penalty from the larger size and from the tire construction. In other words, Defender would no longer be the elegant on-road machine it currently is. It wouldn’t be as bad as a Rubicon, true, but it would be the worst option JLR sells for taking down the highway. In fact, it might become something that chases away a certain percent of their client base who are used to a certain highway competence from the brand. All so we can play on 5- or 6-rated trails in Utah, instead of 4 or 5. Everywhere else the larger tires aren’t going to help anything. Unnecessary for gravel, snow, mud, ruts, slippery grass, water crossings, ice, sand. Only an advantage in big rock.

Like I said, I may decide that the compromises the Grenadier designers decided to make, with its more off-road and manual/old-school bias, are the ones I prefer; even if that’s where I land, though, I’m glad JLR went with the compromises they’ve made. I spend a whole lot more time on-highway than off.

 

Yeah The 19"+ alloy sizes was a nutty choice. Especially as there is an 18" option on the P300 and a caliper for the Disco that works with the P400 allowing 18". Approved by JLR. The majority customer base wants RR size alloys it seems.

Per the OP's thread title, the one simple change would be to allow the 18" option on the P400 and D300 via the OEM parts already up to the task and readily available. There is no trade-off. Win win for all parties. 18"s for those who want a maximally capable Defender, 22"s or 20"s for those who want the city vibe, and 19"s for those who want a good talking to.

 

The conversion i did on mine definitely convinced me that this should be a stock option for the 90. Flat cargo and flat folding jump seats. It changed the entire function of the rear area.

 

i took the request for true 33s as more of a request for changes in wheel well geometry to allow the buyer the option of fitting 33s without lift, at least that would be more than enough for me.

i will say that having both a bronco (bone stock still) and defender that even with E-load MTs (general x3) on the Defender its still far smoother and quieter on the road than the Bronco, which itself drives surprisingly well given it’s own geometry. If you have any roof rack even with a fairing you’ll probably not be able to tell a difference from OEM (assuming you run psi to match XL load and dont run at 80 psi)

i hope the grenadier works out! Even if i could sneak that one by the wife, I can’t bring myself to splash that kind of money on the first generation of any model from a brand new manufacturer.

anyways, back to the OP: to me my biggest gripe is the difficulty and complexity of customization. So as a partial fix, I’d love to see accessory switches on the dash or header, already wired into the power system with easy interfaces under the hood for our lighting upgrade convenience. maybe even 1-2 ready to go in the boot too.

 

Erroneous. There are multiple great choices in, say, a 275/60R20 (33") that are D rated and not too heavy. K02s and Toyo Open Country among them. 33" is just the minimum tire to be 'in the game' in this day and age. With optional 37s on Raptors (standard on the Braptor) and 35s now optional on Wranglers and Broncos of all varieties, 33" is really the minimum buy-in for anyone to take your offroady car seriously in my opinion.

 

I think the L663 is perfect. The 20" wheels are just right. If you want aggressive wheels, change to a 33 and add some lifts.

 

I won't be using the Defender for its off-roading capabilities (as most of the previous responses are), so my wish list is more focused on the daily driver.

Must haves on the 90:

1) Add 3rd 'swing' door on the 90 for egress to the backseat.(similar to FJ Cruiser). Current setup requires a gymnast to get into back seat. Or fix front seat angle of access to allow easier access. It takes an engineer.
2) Fix design of backseat on the 90 to allow flush mount with back deck or worse case raise the back deck six inches to be flush with seats. Seats should be flat when folded down, not angled, making them effectively useless as everything slides toward the tailgate during use.

LRJ fix these 2 issues and demand for the 90 would greatly improve. Used 90s are sitting on the market locally for months with price reductions -- its not a good sign since the market for the 110 is strong.

Nice to have:

3) Headlamp assembly enclosed and flush with nose of the car, not setback 6 inches allowing 6 inches of muck and lack on on-road aerodynamics. The headlamp washer could be bumper mounted and inset like other cars in this price range.
4) Contoured front seat options for the X and V8 options. The existing front seats are pedestrian compared to X5M and G63 competitors.
5) Option for full color body trim and bumpers on X and V8 models. its standard on the cheaper models. All the black exterior trim looks incomplete on non-black vehicle, making black the only color choice for a single color vehicle.
6) More exterior color options on the high-end models. Why is it that the V8 model for over $110K only has black, white or gray? Top price should garner all color options if buyer is willing to pay for it.
7) Option on tail gate door swing, right or left based on market. Not everywhere is the same as UK.

 

I'm not sure why adding a lift and 33"s should be a requirement for 18" rims. This makes no sense to me.