I see many trucks that are intended for hardcore expeditions to places like South America and such, and almost all have relatively small tires. An example would be the Camel Trophy trucks.

If bigger tires help so much, why don't they use them?

Thanks for your input.

Roy

 

i think it has alot to do with traction. The more narror the tire the less surface area and more pressure, resulting in more traction, and also, you loose alot of torque with larger tires

 

bajataco.com has a good answr for that question. iirc, i think its under the "tires" section of his website.

 

I was just reading that writeup today...he makes a great case for the "bigger isn't always better" idea, at least when we're talking expedition style travel. It's a great site, check it out! Another I would recommend is expeditionswest.com. Good stuff....

 

Wow! That's about as detailed an article as I've ever read.

Thanks
Roy

 

i always figured that it's because they'll try to avoid getting stuck, rather than try the hardest obstacles that they can find like a lot of recreational wheelers.

 

Big tires are heavy. Maybe to minimize extra weight...

 

#1 reason is to run a relatively stock size tire primarily for availability at a majority of tire shops in undeveloped areas. Can you imagine being in the middle of the amazon in a small town trying to get a 37x12.50 15 mtr? every shop will have at least a 235 or a 31" tire.

 

I think everyone has had relavant ideas. Part of what I think is that expeditions in Africa dont really have that much hardcore wheeling. They mostly stick to the plains and such so you dont really need that big of tires

 

Also the point of the Camel Trophy Landrovers is that they are in pretty much stock form, that way it brings on more talent from the crew.

I think tire sources is a big thing too.

 

i would second the expeditionswest.com, a very cool sight, lots of good ideas

 

What about arctic expeditions? Those trucks from up north use huge tires!

 

Where flotation is key, like in sand and deep snow, fat seems like the way to go. I'm also thinking that in conditions where there's a breakable crust of ice or frozen tundra that spreading out the load with a fat tire would be a good thing. (Of course in shallow snow and ice we're back to skinny . . . . ever see the snow/ice tires they use on WRC cars?)

 

I spend alot of time in the Amazon (Manaus, Brazil) working at a biological station. They have the sweetest fleet of diesel 4 door hilux's and FJ40 style landcruisers and trucks. They all have skinny, bias ply tires with military style treads and huge winches. Everything happens on a budget down there so they only go with what works, nothing fancy. I'm going to have to start taking one home piece-by-piece in my luggage like Radar on Mash!

 

Skinny tires actually help in sand a lot more than fat ones. There are two related reasons for this. 1) As you move forward the sand builds up in front of the tire. The wider the tire, the more sand built up. 2) Most footprint (for floatation) is gained by the contact patch length (which comes form tire diam.), not width. Because of this, the skinnier tire has a large footprint with a (relativly) small mound of sand in front of it.

 

The size/weight of the vehicle is directly related to the size of tire, i thought. For instance, PSI comes into play when you are talking about construction vehicles and keeping them from sinking into soft ground...

 

That's why sand rails have skinny tires on the front. But, they put fat paddles on the back. With skinny tires on either end and significant weight I think there's a problem. Sand rails have very light front ends and usually have even lighter front ends because they hang an STI engine (if they're lucky) aft of the rear axle. When I ride my dirt bike in sand I keep my weight shifted back to keep the front tire (skinny) from sinking. I've never used a paddle tire. I assume you can make the front end pretty light pretty fast with a twist of the throttle and a paddle tire.

 

Comparing sandrails and trucks isn't really fair. For one, the power/weight ratio is way different. Also, the sandrail isn't 4wd. Finally, paddles and treaded tires are two completly different beasts. The paddles are basically shovels that grab sand from the mound forming in front, forcing it below and behind the wheel, essencially digging it's way through the little sand mountain in front of it. Treaded tires can't do this nearly to the extent the paddles do. Also...the wider the paddle tire, the wider the 'shovel', meaning more sand can be moved out of the way. If having really long paddles (like I've seen on bikes) wasn't prohbitive on larger vehicles, I'm sure those would be used instead.

 

Hmmm . . . . maybe debating the ideal sand set up for our trucks is a little too OT for this thread and I can only speak from my experience. You probably have way more experience driving a truck in sand than I do being so close to Glamis down there in SD. Interesting to think about it . . . and my personal compromise is a 33 x 10.5 AT tire. I'm going for an expedition style, all purpose rig in my truck. I've also made the observation over the years that general expedition vehicles seem to have tall skinny tires. The 33 x 10.5 AT seems to be the best all purpose tire choice for my truck.


Maybe some day we can do a race . . cough . . cough . . I mean study at a Yotatech run and see which truck is faster in deep, dry, loose, sand . . the one with "skinny" tires or the one with "fat" tires whatever those are. The winner and loser . . . cough . . . cough . . . I mean researchers can toast the result with a pint of their favorite . .

 

sounds like a socal version of top gear. lemme know when you're gonna do it so I can prop up my feet and



Seriously though, you guys would have to use the same vehicle and driver to accurately gauge the effectiveness of different tires SOOOOOO (here's the clincher)....

*drum roll please*

you should let me drive