Tire size proportional to vehicle size?

[devinsixtyseven]

What do you guys think of this? In other words...33" tires are large on a Jeep, but not a Kamaz.

I've heard of people specifying tire size from wheelbase, I suspect loosely based on breakover angle. I've also heard of people doing what "looks right"...tires subjectively sized proportional to the truck.

There is definately an "upper limit" for any vehicle...I've heard people recommend capping tire size on short wheelbase vehicles until the wheelbase is stretched, and on most trucks there is an obvious "too large" size--too much rotating weight, leverage, contact patch, torque, other drama.

By the same token, there's definately a lower limit.

You guys have been all around the world and drive the full spectrum of vehicles. What have you seen that works, as far as average proportions--big trucks, little trucks, bikes, long and short wheelbases, load? I'm not talking rock crawling or high speed desert bashing, just what everyone thinks of sizing a tire proportional to a vehicle for all-around offroad use...rock, desert, snow, etc.

-Sean

PS I did read Scott's piece on aspect ratio as well as Tom Sheppard's piece on desert expeditions...

 

[etbadger]

We recently went through some of the same mental meanderings as we were due for new tires and thus had the option of changing sizes. A few of the additional issues for consideration we came up with were:

• availabilty in the areas you intend to travel
• cost (including vehicle mods to accomidate like ratio changes)
• availaiblity of other brands/treads if you are not happy with the first choice and have invested in changing the vehicle
• managability of a spare (weight, size, where can it go)

We ended up sizing up to 37" tires for our full-sized van (from 32" previously) because they are reasonably available in North America by various manufacturers, I can pick it up and move it by myself, its larger than previous and we often were scraping on departure angle by just a touch, higher load capacity than other sizes, lower pressure and softer ride than other sizes for that load capacity, radial, etc... So far we are happy with the change for our vehicle.

-e

 

[devinsixtyseven]

...and i thought it was cool to have a fridge...you have a dishwasher .

that is quite a van! looks comfy too...i got the feeling looking over your accounts of modifications that the original manufacturer never expected you'd actually use it :yikes:.

how have you found the quality to be thus far with the few 37" tires offered? all i've found that i'd be willing to run on the highway in that size are bfg and goodyear. when you say not too heavy, offhand how much does your rim/tire combo weigh? overall has it improved your vehicle such that you'd do it again, or spec that size from the beginning for a vehicle like yours?

when i saw the badger logo and the southpark cakes i figured you guys must have a good sense of humor ...when i saw the graphics on the van i immediately thought of the "badger badger badger" flash animation from a couple years back, and the "two towers" spoof that followed, with "all badger scenes fully restored" . VERY nice job on the van.

-sean

 

[calamaridog]

With larger tires you place more strain on the drivetrain and axle components, for example, even if you regear. The additional mass may be more than the components are designed to reliably manage.

Like they say, everything in moderation:friday:

 

[devinsixtyseven]

With larger tires you place more strain on the drivetrain and axle components, for example, even if you regear. The additional mass may be more than the components are designed to reliably manage.

Like they say, everything in moderation:friday:

Being addressed . :box:
Equipment aside...opinions? Voices of experience? Some of you have crossed deserts, competed in rockcrawling comps, and trekked jungles...what worked/didn't work for your vehicle--too large, too small?

 

[goodtimes]

I like to run the tallest tire that I can fit on my vehicles. Since I keep lift height relatively low (3 - 5 inches), 33 - 35" is as big as you will see on my vehicles (at least the vehicles for "all around" use). Of course this is assuming the drivetrain is up to the task.

Once tires start rubbing on stuff,they are too big.

 

[Robthebrit]

I am not sure there is a definate yes/no for tire size based on wheel base. My little 421 Unimog only has 2200mm wheelbase but has nearly 41 inch tires. Big tires are really heavy and trucks that are made for big tires have heavy axles, all that adds low weight for better CG and general stability. This shows in my 421 as it is about as far from unstable as you can get, it will go to 45 degrees in all directions and is pretty much impossible to high center.

Unsprung weight is only a problem if you drive fast or if you overload the drive train, both are common problems on small light weight trucks. Most big trucks will handle any wheels without any drivetrain problems. For my 416 wheels that are almost 46 inches high and weigh nearly 300 pounds each are not a problem.

Its not just unsprung weight that causes problems, one thing that most people overlook when adding tires that where not made for their truck is brake capacity which is seriously affected by the rotating mass of the heavy wheels.

Rob

 

[upcruiser]

I think from an aesthetic standpoint, tire size is relative to vehicle size. When it comes to functionalit though, it all depends on the intended uses. For me, I've foud 33's on my FJ80 to be a very good compromise for the varied uses I put my truck through. To my eye, 35's on 80 series look perfect though. In reality though 33's do just about everything I need to.

 

[calamaridog]

I think from an aesthetic standpoint, tire size is relative to vehicle size. When it comes to functionalit though, it all depends on the intended uses. For me, I've foud 33's on my FJ80 to be a very good compromise for the varied uses I put my truck through. To my eye, 35's on 80 series look perfect though. In reality though 33's do just about everything I need to.

I agree that 35's would LOOK great on my Land Cruiser but at this time it is not worth the trade off having to regear, etc. Basically, I would rather have many other accessories first before incurring such an expense.

So to answer the question, I believe a 33" tire will offer reasonable clearance for moderate trails on most vehicles. 33's are easy to find in the states and there is a huge variety to choose from.

 

[devinsixtyseven]

One thing that most people overlook when adding tires that where not made for their truck is brake capacity which is seriously affected by the rotating mass of the heavy wheels.

Definately the number one overlooked downside to larger tires. Also being addressed, as I can already tell a difference in braking with the current tires. I drive very conservatively as a result...with the larger tires will come a larger braking system.

the other oft ignored point on larger tires is dead weight...i wouldn't run a tire i couldn't change safely myself, and size...the spare has to go somewhere, and the bigger it gets, the less safe it is riding high, both from the hit to cg and getting it down safely--i never understood the logic of putting the spare over the cab on those unicats (?), tho im sure they dont have the same cg worries as smaller vehicles.

interesting to find out a mog has an 86" wheelbase and tires that large. dimensionally that sounds a little like a sami on 33s, or an older body style, short bed/reg cab tacoma.

 

[etbadger]

Well, the dishwasher is usually me.... The thing everyone thinks is a dishwasher is our fridge.

I have been happy with the 37" tires both on and off road so far. Off-road the lower initial pressure reduces the need to air-down for minor excursions, and the impacts when dropping into a hole or hitting a rock are much softer (larger radius & lower pressure).

We went with BFG MTs this time, and for the 2k miles so far they are holding up well. I went with them based on reviews I had read in various H1 forums since this is their default tire size.

So far it seems like the size is about right for a full-size van with the use we put it to. More time will tell more of course. I also have some suspicion that the softer pressure tires can contribute to drive-train longevity in terms of reducing some of the impulse from impacts with obstacles. Whether this is a greater or lessor factor than the increase in stress due to the diameter and weight increase, I cannot say. It certainly reduces the rattling and jarring in the cab which is good for all of our electronics and bodies.

We do have a small mushroom & snake sticker on the back of the van. Most people don't notice, but a few start to laugh...

-Erik

...and i thought it was cool to have a fridge...you have a dishwasher .

that is quite a van! looks comfy too...i got the feeling looking over your accounts of modifications that the original manufacturer never expected you'd actually use it :yikes:.

how have you found the quality to be thus far with the few 37" tires offered? all i've found that i'd be willing to run on the highway in that size are bfg and goodyear. when you say not too heavy, offhand how much does your rim/tire combo weigh? overall has it improved your vehicle such that you'd do it again, or spec that size from the beginning for a vehicle like yours?

when i saw the badger logo and the southpark cakes i figured you guys must have a good sense of humor ...when i saw the graphics on the van i immediately thought of the "badger badger badger" flash animation from a couple years back, and the "two towers" spoof that followed, with "all badger scenes fully restored" . VERY nice job on the van.

-sean

 

[devinsixtyseven]

We do have a small mushroom & snake sticker on the back of the van. Most people don't notice, but a few start to laugh...

how 'bout a quick video clip from an expedition, but with "all badger scenes fully restored"?

(if ya havent seen what we're joking about, click here... and then here. then look at the van again :hehe: )

h1 forums...thanks for the tip. i think 37 is the largest "stock" tire size available due to the h1, it's difficult to find anything larger that isn't bias ply and specifically offroad that isn't also an earth mover or milspec tire, or else made in small batches and horrifically expensive.

 

[Robthebrit]

Big tires are not too hard to come by, you can get Michellin XZL's all the way up to and above 50 inchs. Lots of mog people run 365/80R20's which are about 44-45 inches tall, you can get 335's which are around 40-41 inches and 395s which are about 49 inches, all on a 20x11 inch rim. You can also get XZLs in a tall aspect, such as 16.00R20 which are 52 inches tall.

Continental also make some big tires, their MPT 80 and MPT81 tires are available on 18 and 20 inch rims in sizes from about 37 inches upto about 50 inches.

All of the above tires are really heavy (200-300 pounds) and are DOT approved but only to 50-60mph. You can expect to drop about $500 to $800 a tire if you buy new.

Rob