Thread: Tyres again... 255/85R16 on a defender 90?

Originally Posted by Toxic_Avenger

I'm after info regarding tyre sizing for my 2012 90.Would love to hear from those who have 'been there / done that'. I'm looking ton fit a 255/85/R16 (33") tyre to the 90.

Details regarding my vehicle below:

1. Stock height (no lift), original suspension with 35,000km on the ODO.
2. Bullbar, winch and rear bar- contributes to extra weight, suspension sag
3. Dual finish alloys- 16"x7" IIRC (unsure of offset, but +35 rings a bell?)
4. I want a larger diameter M/T tyre to replace an aging and very chipped set of 235/85R16 Goodyear wrangler MT's that have been on the vehicle since new

The factory 235/85R16 work well, but I'm often left scrubbing the diff in a few of the ruts and tracks I drive, moreso at lower tyre pressures.
I'm not in a position to lift the vehicle yet, but am looking for something that is a little bigger.
Not sure whether to lean towards a skinny tyre or a fat tyre... my thoughts are lean towards the narrow. Not sure about the trade off of tyre diameter vs tread width in relation to accelleration / handling, but keen to know more.

From what I read in countless hours of searching is that the 90's have a different (smaller) rear spring diameter and top bracket, making more room for wider tyres (at the same rim offset) than the 110's or 130's. I've heard whisperings of some potential loss of steering lock at a 33" tyre size, but not sure if the limiting factor is tyre height or tyre width...


Keen on the BFG Mud Terrain T/A KM2's in 255/85/R16. ie a 33"x 10" on a dual finish alloy rim.
Has this combo been done before? Any feedback?

Hey mate,

This has been done before, and the short answer is yes, you should not any clearance issues.
I was so very close to doing the exact combo on my 110. I stopped short however.
I spend a lot of time out bush. 255/85x16 is one of the hardest sizes to get consistently. No one carries this size out bush. If you are intending on a lot of remote travel, the most common sizes you will be able to get if you happen to have a tyre failure are: 265/75x16 and 285/75x16.
So I ended up going with a set of 16x8 Kings Steel Wheels in 0 offset with 285/75x16 BFG KM2s.
Am I happy with them?
I wouldn't change the combo for anything else. The steering response is improved, the wider wheel track from 0 offset wheels gives a mush more confident feedback and feel when on all surfaces.
One more thing to consider, go Land Rover HD front springs, that's the setup I have on my front end, and I love it.

In reference to your question regarding skinny vs fat tyres; it depends on where you are driving mostly. If you are doing more mud driving, skinny tyres are actually better, as they cut down onto the hard surface underneath. If you are doing more sand driving, fat is the way to go, bigger footprint when you drop air pressures, and allows the tyres to sit on top of the sand.
Overall, tyre size is relevant to where you drive most commonly.

Believe it or not, the 235/85x16 is a very good compromise, as is the 255/85x16. If I didn't go bush as often as I do, then I would have fitted the 255/85x16. If you do go this way, be aware that you will be very limited to brands, and it is quite common for there to be very limited stock in Australia from time to time.

Good luck with your choice, it's not an easy one!

Here's a recent pic...

I thought I'd go old-school and do some testing to see what the limitations of the 90 are when it comes to flex...

Took a drive out to a roadside quarry / gravel storage area ond drove the closest thing I could get to:







I didn't take an accurate measurements, but eyeballing it gave the following measures (Dodgy science alert! Take measurements as a guide only):

So what you all see above is stock suspension, probably a little bit sagged / worn, but with factory sway bars and everything else intact.

What I observed:
The Diff tubes are about 35-50mm off the bump stops on the compressed corners.

On face value, what I can see at this level of compression is about 20mm space between the inner sidewalls and the coil spring brackets at this level of compression. This appears to be the limiting factor for tyre fitment on a 90. This means that going wider tyre treads will pose issues with the tyre fitment. This could be overcome with wheel spacers, or different offset rims.

From what I can see, the tire tread at the 12 o'clock position, has plenty of room before it impacts the inner guards at the amount of flex pictured (not yet on bump stops).

Clearance to the flares is off by heaps. You'd need to run some pretty wide rubber to start having issues in this area at my offset without spacers, but you'd run into issues in other areas before that...

What I expect would happen when on the bump stops:
If we suppose that the the bump stops were to compress that remaining 35-50mm and bottom out against the axle tubes, then this would bring the tread of the tyre say 2 inches closer to the innder guard- leaving approx 35mm or so to the top inner guards.

There appears to be plenty of room at the front and rear of the tyres (ie the 9 and 3 o'clock positions of the wheel).

I can't really guess what would happen in regards to the inner tyre sidewall and the coil spring bracket when on the bump stops... but I believe we'd be pushing it fine within anything much wider than a 255 width tyre using the dual finish alloys. As it stands there is approx 20mm to the coil spring bracket when running a 235 tyre. Bump this up to a 255 (and have an additional 20mm width- ie 10mm per side of the rim bead), and you will be marginally closer. This distance seems to be fairly consistent front and rear.
The biggest concern with this is that the wheels camber in (gain negative camber relative to the body) when under compression, so while the body of the vehicle is pushed away by the compressing coil to some extent, the clearances will, I believe, get closer as suspension compression increases.


If I find some time tomorrow, I might put it on the flat and jack it until I reach the bump stops. Might even remove the sway bars for giggles...

Mitch I can't comment on the D90 and 255/85 Spring hanger rubbing problem. Without knowing your offset of your rim the ideal for a 255/85 is a zero offset. Returns steering lock to the same as 235/85 if not better. Fits inside the flares and visually fills the flares and wider stance for better stability off road.

While it's correct to say a 255/85 is as rare as hens teeth in the city and worse in the country I've taken my spare tyre to more towns than I've hot dinners. They essentially go on holidays with me. The BFG km2 is a great tyre. I'm on my third set and yet to have a broken bead or flat tyre even with much abuse. Carry a second spare if you must and take it on a holiday when you go on long trips.

The MT82 gearbox is low enough geared to carry the extra ratio of the 255/85 and yes it corrects the ODO.

Do it, with the 255/85 you will appreciate the extra height and appreciate not having to turn the extra width of the 285/75. Wider tyres sap power, increase fuel burn.

MLD

They fit fine mate. And they're not that rare.

No rubbing at all on Spring hangers with a 90

Regarding tyre size availability "outbush"
Very little is available in any size let alone brand, off the shelf.
The concept of "outbush" is widely romanticised and if you genuinely find yourself "outbush" (having prepared well) in need of a tyre of any description, you will be lucky to have a choice of 2nd hand, barely usable, or retread.
Popular/typical sizes are whatever happens to be in demand.
When heading into town for business, many roadhouses on the favourite tracks buy a few 2nd hand 75% ish worn tyres to sell to hapless travellers.
If you can find a brand "x" tyre to match your brand, or importantly size "y" tyre to match your size, outside of a town without a retailer, you are simply lucky.
Even the major suppliers in Alice cant be counted on to supply on the spot.

Just get the size you want and carry a second spare if genuinely heading remote.
Whatever tyre size you are running, it is an inconvenience if you need one in the middle of nowhere.

Sage advice Strangy.
This is pretty much the story of my life living in Tamworth. Half the reason things take me so long is that the things I want are not in the town I am in.

Originally Posted by Toxic_Avenger

Sage advice Strangy.

This is pretty much the story of my life living in Tamworth. Half the reason things take me so long is that the things I want are not in the town I am in.

You will insist on living in "Land Cruiser country"