The debate over tires.

[ZooJunkie]

I have been reading up on the recommended tires for expedition/off highway traveling. There are two school of thoughts:

1. Tall thin tires.
2. Tall fat tires.

Obviously some has advantages over the other, but for most of us here, who doesn't always hit deep, loose sand or snow, which general tire physical dimension would you prefer?

A tall thin tire with a smaller contact patch exerts more pressure per square inch underneath the tire. As a result, it can "bite" into the road better as some would argue.

A tall fat tire with a much larger contact patch will exert less pressure per square inch than the thin tire. However, because of the larger surface contact, it provides more friction, and as a result traction.

For powder snow and deep sand, a fat tire is the way to go.

So, it comes down to this...
1. Do you want to float over the surface with a fat tire?
2. Or do you want to dig into the surface for that added grip?

What general size would benefit all of us for our daily expedition vehicle?
245/75/16 vs. 265/75/16?
225/75/16 vs. 245/75/16?

I'm extremely interested in everyone's opinion on this.

 

[asteffes]

225? 245? Holy pizza cutters, Batman! While those might be fine in certain off-road conditions I sure wouldn't want tires that skinny on pavement. Your braking will suffer as you'll get a lot of ABS activity under heavy braking.

The general consensus here and elsewhere is that a 265-75-16 is an excellent all-around choice for many folks. For those who want a bit more clearance and are willing to re-gear if they carry a lot of weight or want better highway performance is a 255-85-16. These are about the tallest you can get without going crazy with a sawzall and provide excellent clearance and traction. You also don't need tremendous lift to accomodate them.

Some will argue that a 285-70-16 is the way to go. It looks cool, but isn't necessarily the ultimate in expedition/everyday tires. The highway stability is nice, and they'll probably slow you down better on pavement under heavy braking, but a quality 265 AT will work just fine, too.

 

[Scott Brady]

I would recommend starting here: Narrow tire white paper

Having owned a Trooper, the 265/75 was the best size I have run in over 100,000 miles and 5 years

 

[ZooJunkie]

Scott, I've read your article intensely before I joined the forum.
That is a great read and a wealth of information.

EDITED: OOpS used the wrong smilicon.

 

[gjackson]

A tall thin tire with a smaller contact patch exerts more pressure per square inch underneath the tire.

Only when aired up. When aired down the contact patch becomes LONGER and that's the awesome thing about tall and skinny. A long contact patch is more like a track. I've used 760R16s for most expedition work. Excellent size, and very easy to replace in almost any country.

Just my 2 cents.

cheers

 

[OverlandZJ]

Cool thread ZooJunkie! :wings:

I'v recently been considering a taller and narrower tire, currently i run a 33x12.5x15. I believe i'd like to find something in the 34x11x15 size. I need to read up on my metric sizes as i'm not familiar with how they equate.

Scott...awesome writeup, i'm sure i'll find it informative. I look fwd to others input in this thread also.

 

[upcruiser]

I ran 33x9.50 15's on both my FJ60 and on my 80 for a spell before switching to 33x12.50's. The pizza cutters were much better in snow, and in mud as well. The 12.50's have less sidewall deflection when cornering which makes things a bit less tippy feeling. The 12.50's have a hard time with driving on snowy services when flotation is not needed. I'm thinking for my next set of tires of going with 33x10.50's and finding the perfect compromise.

 

[Pskhaat]

What general size would benefit all of us for our daily expedition vehicle?
245/75/16 vs. 265/75/16?
225/75/16 vs. 245/75/16?

265/75r16 = 31.7x10.4r16
http://xepoch.com/mud/tire.cgi?w=265&a=75&r=16

or this very famous size:

235/85r16 = 31.7x9.3r16
http://xepoch.com/mud/tire.cgi?w=235&a=85&r=16

Which gives you about the same general diameter as the 265 yet keeping it nice and skinny with an 85% aspect. Also darn near the exact same size as the 7.50r16s around the World.

 

[jeff@work]

So, it comes down to this...
1. Do you want to float over the surface with a fat tire?
2. Or do you want to dig into the surface for that added grip?

What general size would benefit all of us for our daily expedition vehicle?
245/75/16 vs. 265/75/16?
225/75/16 vs. 245/75/16?

Well i'm a fan of tall and skinny, less overall weight means less wear and tear on the vehicle. On road i've found the wider tires tend to hydroplane easier, are worse in snow and ice, and throw crap all over the side of your vehicle unless you have extended fenders. I also feel a narrower tire provides better traction is most situations offroad although scotts paper describes that better than i ever could.

That said none of the tires you noted would really be considered a wide tire by most peoples standards although i guess the 265 is getting close to one...that works out to roughly a 32x10.50, for comparison a narrower tire would be a 235/85/16 which is rougly a 32x9.25. I personally went with 265's because I feel that it is narrow enough of a tire and it's the size the tire i wanted was offered in.

When i think of a wide tire i think of more along the lines of a 285/75/16 or a 305/70/16.

Anyway's that my $0.02 no refunds

 

[bigreen505]

I'm a big tall and skinny fan and I've always liked the 235/85-16 size, but for the Trooper both Scott and other well respected ExPo members have told me that I need to run 265/75 or if I had the gearing, 285/75 for Colorado conditions, so I think what is a reasonable level of tall and skinny depends on the vehicle weight and how much float you want. Or I guess more specifically, how much pressure the surface can handle or how much pressure is required to get down to a solid surface.

For example I have 31x10.50/15 on the Pathfinder, say 4800 lb. at max weight (just guessing, never weighed it). At 12 psi the tires have more than enough float to ride on soft, deep sand and pull a sail boat (probably close to 1000 lb. of boat, trailer and sloshing water on standard trailer tires). Off road I guess they are okay, I've never really thought about width, though often wished for more height.

Where they flat out suck is on road snow, particularly heavy snow (say more than 18% moisture), and light mud. That size of tires, with the Pathfinder on top of them, are simply too wide to develop enough road pressure (psi under the tread) to get down to the road surface and instead ride on about a 2" layer of compressed snow. Same holds true with deep slush; they float/hydroplane instead of cutting through.

Take the same logic to the extreme -- a road bike tire. It is tall and skinny, but too skinny to be of any value off road. Instead MTB tires are more than twice as wide and on a much smaller rim. What the bike world is starting to experiment with is taller tires, while maintaining the same width. While the jury is still out as to whether they are more efficient or not (do the benefits offset the added energy required to turn them, factoring in both added height and mass), everyone who has used them claims benefits exactly mirroring what Scott reports in his white paper.

Like Jeff, I'm not giving any refunds either.

 

[Prich1973]

I would recommend a taller, thinner tire for expedition/off highway traveling. I think it provides better grip and traction than a taller, wider tire. However, if you are traveling in powder snow or deep sand, a wider tire may be beneficial. Ultimately, it comes down to what you want and what you think will work best for your situation.