I've been trying to find a definitive article on wheel and tyre sizes for the series 3, but so far have only found bits and pieced.
I have to ask, why do you think there is likely to be a 'definitive' answer in the first place??
I'd like to fill the arches a bit
Why?
, perhaps with wider wheels and tyres or just adding rims with a larger offset (or using spacers).
Normally when people say fill the arches, they mean the gap between the top of the tyre and the body work, are you meaning something else as you are talking width?
On a Series you are somewhat limited as to how wide you can go, else run the risk of the tyres sticking out of the arches. Which in the UK is illegal.
Here are the images of the ones I like online but I don't know the setups. Can people please post photos of their own with details about rims and tyres please? I've also added a photo of my S3 at the end with the cammo paint scheme - this is what it currently looks like.
It has 7.50 x 16 Goodyear G90s on what I think atre 5.5 rims
A 7.50 x 16 is a good size for a Series. These tend to measure 29-31" tall (some just under 32" tall). And are narrow.
Narrow is good as they generally work better off road in the UK, have less rolling resistance, which normally translates to better mpg on the road. Make the steering easier to turn and are unlikely to rub on much.
I admit standard wheels to tend to tuck the tyres in somewhat, which might be what you are meaning.
You could run some wheel spacers, but a better solution would probably be to simply buy some 8 spoke or modular rims. Most of these will move the rims out and give a wider track. However there are a lot of different rim offsets, so you'll need to research which ones you want.
If you want to keep the standard rim look, then spacers would be your easier option. As someone mentioned above, there are other standard rims that have a different offset. The most common being known as One Ton/1 Ton or 130 rims. These can be found fairly easily and at somewhat sensible money.
The Series 2B rims have an even deeper dish again, but these are very rare and go for silly money. So I'd say probably don't even waste your time looking for them.
If you are looking at LR standard rims, make sure you read up and understand the differences between a tubed rim and a tubeless one. Running a tubeless tyre on a tubed rim is potentially very dangerous and somewhat stupid.
Note, that making the vehicle track wider by offset rims or wheelspacers can have negative results on the steering, induce more bump steer, change the scrub radius and may affect bearing wear.
None of these are reasons not to do it, but are things you should consider and understand.
As for other tyre sizes. A wider tyre might give you the look you want. A 235/85R16 is about the same height as a 7.50 x 16, but wider. So can give a chunkier look.
However note, technically 235's should not be fitted to a standard Series rim. The rim is too narrow and no tyre makers recommend 235's on a 5.5j rim.
That said, the tyre market is odd and many 7.50's (remoulds) are actually just re-stamped 235's and 7.50's can go on a 5.5j rim. Note, your G90's are actually a proper 7.50 and a lot narrower than a 235.
Wider tyres are more likely to rub parts of the vehicle. So at full steering lock you might rub the leaf springs. Which is usually why people use wider offset rims with wider tyres. To preserve the turning circle. But as said earlier, on a Series you can easily end up with the tyres outside the body work. You could fit Defender style wheel spats or some other arch extension to cover the tyre.
There are other wider tyres too. A 265/75R16. Again, similar height to a 7.50 but wider than a 235. This is a common size on late Defenders. But to keep them in the arches and retain full steering lock on a Series might be a challenge.
31.10.50R15, these are similar width to the 265's and maybe an inch shorter depending on the exact brand of tyre. And I believe would have been standard fitment in markets like the USA where 16" tyres where not the norm.
There are other bigger taller tyres as well. Someone mentioned a 9.00 x 16 earlier. This is two sizes up from a 7.50 x 16. So they are 9" wide instead of 7.5" and usually a lot taller. Land Rover actually fitted these to the One Ton variant of the 109 as standard fitment, however those have different spring hangers and mounts, which give it a couple of inch suspension lift.
Things to remember with large tyres. They weigh more, so harder to lift on and off. But also have more inertia, so more likely to break axles and/or gearboxes with them. More likely to rub and you will loose steering lock with them.
9.00 x 16 is also a rare size these days. Which means very little choice of tyre treads and can be horrendously expensive.
Sizes also vary, anywhere from 33-36" depending on make and tread pattern.
A 255/85R16 might be an interesting size to look at. Somewhat rare, but mainstream for lots of tyre makers like BFG, Maxxis, Toyo, etc. These are slightly wider than a 235, but not as wide as a 265. They are however just over 33" tall, giving them a heigh advantage of 1-2"+ over most 235/265/7.50 tyres.
