First thing to be aware of is that the stock tyre dia for a 109 is 32 inches. The second thing is that there are different width and diameter factory wheels. 109 wheels are 16 inch dia. Older ones (possibly yours) are 5 inch bead to bead width. 88's had an optional 15 inch dia wheel.
109 16 inch wheel got progressively wider through the years with 6 inches the widest. There is a 6-1/2" wide Defender wheel that fits Series trucks and a 7" wide Discovery I slotted steel wheel that fit Series trucks (what is under my 1960 109).
You do not want to go taller than about 33-34 inches in dia without modifying a stock 109 civilian suspension.
With that in mind you want 32 inch dia tyres that are within the tyre manufacturer's specifications to fit the bead to bead width of the rim you have or switch to.
The stock tyre size is 750/16 which is an obsolete tyre size system. The closest to that in a modern system is 235/85-16. But the 235/85-16 rim width specification is 6" to 7" bead to bead. Your rims may be narrower. If you have the old narrower wheels I recommend that you pick up a set of newer wider wheels. Ike at
pangolin4x4 should be able to set you up with used wider rims at a reasonable cost. Or considering shipping from the West cost you might do better with a new set from RN.
We all have our favorite brands of tyres, tread patterns and size so you are likely to receive different recommendations. No one tyre is best for all driving situations. So what is optimum for one person in another part of the country may not work all that well for you and where you drive.
The first decade I had my 109 I tried different tyres until I found one that fit my driving well. For the last 25 or so years my tuck has been shod with BFG Goodrich Mud Terrains. I don't feel that they are THE best tyre for any particular driving situation but they are good under a wide range of driving situations. I look at them as a very good jack of most terrains. They are good in all mud but the sticky gumbo mud that refuses to be thrown off the tyre. They are very good on all dirt surfaces. They grip well on rocks and have armored side belts that help protect them from sidewall rock cuts. Mud tyres are not the best choice for deep soft sand.
I like the BFG mud terrains because they are very good for most of the surfaces I drive on, they are reasonably quiet and have a long tread wear. I have the Disco I 7" wide steel wheels and the larger LT255/85R16 tyres. I like this combination a lot. I have run LT265/75R16 tires on the 7 inch rims in the past. This is a stock D90 tyre size requiring the 7 inch rim. The only issue I had was that under extreme articulation the inside of the rear wheels polished the inside of the inner wheel wells. No damage, just the slightest of rubs. I went to the slightly narrower taller LT255/85R16 tyres just to get a little extra ground clearance.
Originally Posted by TeriAnn
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