Wheels, Tires, and Sidewalls

On or off-highway this is a ridiculous wheel & tire combination.

A thread on the expeditionportal.com prompted this post. A gentleman asked how much sidewall is enough as he’s planning to use 37-inch tires on 20-inch wheels on a full-size diesel pickup. He asked if it would be worth it to spend money on 17-inch wheels and tires for occasional, recreational use, while using his twenties for daily driving. My answer to his question was no, it’s probably not worth it just for vacations. Though for me, it would be very desirable to run 17-inch tires & wheels everyday. His questions spurred me to expound on this important subject as it relates to overland travel for the first time here on RoadTraveler.net.

A Sidewall Baseline For 4WDs

I’m not an advocate of tall wheels if they are not necessary, of course many trucks these days have a minimum wheel diameter of 17-inches because the brakes are so large, and wheels between 18–20 inches have become fashionable. A tall wheel simply means less tire sidewall with which to perform off-highway duties for a given tire diameter. Taller sidewalls help a truck ride above the rocks and obstacles, all of the truck, including the wheels. Low-profile tires are needlessly vulnerable to trail damage, offer less flex, and are generally less versatile. It’s often forgotten, misunderstood, or unappreciated that tires are part of a vehicle’s suspension.

Using a 16-inch wheel with a 33-inch tire offers a sidewall height of 8.5-inches, (33 –16)/2 = 8.5″, a good baseline. We could get more technical and use the static radius, but it’s easier to simply use the manufacturers’ stated diameter, and it’s close enough for this topic. The lower half is what we drive on, what matters, and it provides more or less flex depending on its height and design. Sidewall flex can be a positive or a negative depending on your truck, the terrain, and your needs and preferences. In theory, a 35-inch tire on an 18-inch wheel, a 37-inch tire on a 20-inch wheel, as well as my thirty-three on a sixteen example, all have a lower sidewall height of approx. 8.5-inches.

If we are interested in the clearance we get from a particular tire size, specific tires need to be researched using the manufacturer’s data to determine the true diameter. Some tires will be very close to their stated height, 35-inches for example, while some are a half-inch short. One half-inch less diameter means 1/4-inch less sidewall on the bottom, a difference that can easily be measured and felt depending on the sensitivity of your butt dyno.

Load Range and Tire Construction 

A taller, higher aspect ratio, more flexible sidewall is helpful for off-highway travel for both ride quality and traction. One exception being that a stiffer (and tall) sidewall may be more resistant to puncture. A shorter and/or stiffer sidewall is generally less desirable off-highway. For heavy hauling and towing, a shorter, stiffer sidewall can be helpful, as less movement and flex generates less heat. However, on several occasions I’ve successfully and safely used relatively flexible, load-range D light-truck tires with 2-ply sidewalls to haul a couple tons (didn’t exceed tire capacity or GAWR), and have also towed several tons. I’ve also traveled many hundreds of miles (if not thousands) off-highway over the last two decades, mostly on load-range D tires. Have I had sidewall cuts? Of course, but only two that immediately come to mind, and one was last year. If you are concerned about sidewall punctures, there are some excellent, flexible load-range D tires with 3-ply sidewalls in some popular sizes. Your application and performance bias will help you choose your tires. There are many excellent, heavy-duty tires to choose from these days, some in load-range C, D, and E.

I acknowledge that load-range D tires are probably a dying breed, the writing has been on the sidewall for a while. The proliferation of heavy-duty pickups, particularly diesels, over the last several years has greatly influenced the tire aftermarket. Unfortunately even half-ton trucks and lightweight Jeeps are sometimes needlessly sold with load-range E tires, my 2005 Jeep Rubicon and 2011 Tundra are perfect examples. My coil-sprung, 103-inch wheelbase, 2005 Unlimited was a nice riding Jeep, with the exception of the needlessly stiff Goodyear Wrangler MT/R in a 245/75R16E (a relatively short sidewall). I liked the way the Jeep rode with only 25-PSI in the tires. After changing to taller load-range D tires, the combination of a taller sidewall and load-range D made the Jeep ride and perform better at all pressures, on- and off-highway.

My point is that as with many things these days, it’s easy to needlessly go to extremes and forget balance. All-steel, load-range F or G, Michelin military tires are not the best choice for your 3,000-pound soft-top YJ Wrangler, or for your heavy-duty pickup.

Not all load-range E tires are created equal, some are designed to flex better than others when pressures are reduced. My experience with both the BF Goodrich KM2 and All-Terrain T/A in load-range E indicates these tires are not overly stiff and flex well.

265/75R16E front , 255/85R16D rear. The sidewall difference is clear.

Tire Testing

I recently tested two sets of 33-inch tires, both the same size with reasonable 70% aspect ratios, on the same OE wheels, but with different load ratings and sidewall construction. This latest trial simply reinforced the potential differences in ride quality and overall performance between some tires with different load ranges, sidewall designs, or heights. The difference was enough that I was comfortable running considerably more PSI in the lighter, more flexible tire, but wanted to run minimal PSI in the much firmer tire to improve daily-driving ride quality, just like with the Jeep example above. Increasing PSI on a flexible tire will reduce flex and help it run cooler on-highway if desired.

One advantage to more flexible tires is there’s often less need to reduce pressures as much off-highway as with a stiffer tire. Tires that flex, conform, and ride better at a given pressure, and are sometimes so pleasant that for short drives on easy dirt roads with few rocks, there may be no need or desire to immediately lower pressures. Conversely, tires with very stiff construction can scream dump the pressure, at the first sign of anything bigger than a pebble, particularly on a firmly sprung heavy-duty pickup with no load.

Reinforcing Sidewall Lessons 

Another, older example are tests I conducted a few years ago, using two different sizes of the same tire, on two sets of Jeep Rubicon Moab wheels, on the same vehicle, with the same air pressure in both: Toyo Open Country MT LT265/75R16E vs. LT285/75R16E. Both tires have a 7-ply tread and 3-ply sidewall, are load-range E, have similar load capacities, and are very stiff designs. With 0.6″ additional lower sidewall, the taller 285s rode better on/off-road and flexed a little better when aired-down. This was experienced several times as both sets were in my fleet for a while and used on more than one 4WD. The stiff Toyo MT needs substantial deflation to obtain adequate deformation and ride quality off-highway, one of the tradeoffs for the Toyo’s very rugged design. The noticeable lack of flexibility from this otherwise excellent tire is a big negative for my all-around use. If you want a mud tire with less flex for very heavy hauling, or you don’t mind a firmer ride, the Toyo MT can be a great choice.

Flexibility and sidewall height, it matters.

Copyright © 2012 James Langan

S-K In Green Boxes

S-K 94549 3/8″ drive socket set, $138

ToolTopia.com is based in Louisiana. When I ordered my new S-K 3/8-drive socket set (#94549, $138) on Monday I figured I’d be lucky if it arrived by Friday…tomorrow. Once the FedEx shipping information was available online, I saw that tools were coming from Fresno, California. Free ground shipping had the tools in my hands in just two days. Nice.

Initial fondling was pleasurable and confidence inspiring. I like the fitted plastic case the tools come in, and the ratchet has a better feel to the clicks than anything in my modest toolbox. The ultimate test will be after use and over time, but I like them.

My friend Paul, who used to make his living turning wrenches on diesel trucks and buses, was with me when I opened this late Christmas present, liked the ratchet as well. Paul’s tool knowledge is more complete than mine. He likes the direction changing dial better than the now common lever because it doesn’t inadvertently change directions, particularly at the most inappropriate time when tucked into a tight place. I’ve experienced an inadvertent direction change many times, often with my ratcheting combination wrenches.

I was surprised that I didn’t dislike the direction change dial on the round-head-fine-toothed (RHFT) S-K ratchet like I’d anticipated. Maybe this is because the RHFT dial-actuated ratchets I used decades ago were cheap? My memory is that the dial needed to be turned 90-degree or more and were rough? The S-K ratchet needs about a quarter turn to change from on to off, and feels smooth. Again, use will determine my long-term opinion, and a more detailed review will need to develop.

S-K 19733 hex bit set.

For $16.00 extra I purchase the S-K 94549A kit that “includes” the 9-piece SAE S-K 19733 hex bit set, which ToolTopia.com sells separately for $66.00. So for $154.00 I received a pretty complete 3/8-drive socket set, and a nice hex bit set that goes from a small 5/32″ to a rather large 5/8″. Am I the only one that sees this as a very good made-in-USA value?

RoadTraveler—Rolling Forward

Copyright © 2012 James Langan

Russian winter driving tutorial.

I’ve been waiting to post this for several weeks. Our endless autumn weather in Nevada has finally changed to winter (thankfully), so I’m motivated to share and provide commentary. I had to search a while to find the original, uncut version that I viewed last month, which includes  the car driver’s and passenger’s relief and exclamations after, as well as the police toward the end.

In addition to the oh #@!^ moment close call and entertainment value, there are some driver control lessons we can glean. I’ll name a few.


Watching this the first time, I immediately noted how helpful it was that the semi driver did not apply his brakes. Surely slowing down before almost running over the plow truck, fishtailing across the roadway, and nearly hitting other traffic head-on would have been nice. But once he was there, in that moment, steering the tractor and continuing to pull that trailer was absolutely the right thing to do (whether it was a conscious effort or not). Attempting to slow or stop would have been normal, and not succumbing to a natural panic reaction is easier said than done. Braking hard would likely have broken lots of things and people. But mentally and physically training ourselves can help in situations like this. There are many training opportunities that help teach this lesson while off-highway. Times when using the brakes might slide, tip, roll, or upset your driving platform, instead keeping a steady throttle, or accelerating is the right thing to do.


It’s not easy to judge, but the video car doesn’t appear to be following the box truck very close, approximately 2-seconds back. Two seconds was an accepted minimum following distance under good conditions, allowing for perception and reaction, until fairly recently when 3-seconds became the new recommended minimum. Even if traction was excellent, visibility was not. When the box truck pulled to the right and started decelerating rapidly for no obvious, visible reason, the car driver—who had been looking for a place to pass—accelerated, reduced his following distance and visibility, and started passing. Once the car driver had a clear view of the doom ahead, he quickly applied his brakes and stopped. This was a good decision, the video confirms that if he had taken longer to stop, there would have been a serious collision.

Even with good decisions and reactions, there can be potentially severe physical and metal reactions to such danger. Did you hear the car engine RPM increase wildly just after the trailer almost slammed into the car (after because it was a reaction, and that takes time). My guess is that because of the uncontrollable stress and almost certain contact, the driver tensed, muscles flexed and limbs extended. I’m inclined to think the right foot that was holding the brake spilled over onto the gas pedal, his leg extending toward the floor. Normal. It’s likely that he also had the clutch pedal smashed to the floor, a good thing. Don’t get caught up on the pedals though, my point is about the involuntary reaction and tension, and the fact that the accelerator was depressed. Some severe reactions can make it very difficulty to control a vehicle, and improper use of the steering, brakes or accelerator are the big ones.


Following distance, visibility, and sight lines are critically important. In some circumstances being able to come to a quick, smooth, and complete emergency stop is a lifesaver. Luck can help, but it’s better to practice and have confidence. Discipline, focus, and skill are not only potential lifesavers, they make routine operation of machinery (not just vehicles) more enjoyable and safer.

RoadTraveler.net  Rolling Forward

Copyright © 2012 James Langan

Tool Shopping

As part of a new project I’m in the process of assembling a new travel tool kit. In the past I’d drive to my local Sears store, buy a fairly complete set of Craftsman sockets and ratchets, which would include 1/4″, 3/8″, and 1/2″ regular and deep sockets, far too few combination wrenches, and too many screwdriver bits to increase the pieces count of the kit. I’d use this as a starting point, add some adjustable wrenches, screwdrivers, and later some hex bits and be well on my way to having a fairly complete basic travel kit. Though I tend to drive newer, reliable, well-maintained vehicles, I don’t like to leave home without tools. Remote travel makes loose parts and little repairs more important.

Sears Craftsman tools are surely not the highest quality choice, but for this amateur wrench turner they have worked well most of the time, and were inexpensive enough to allow me to compile a travel kit for each of my vehicles. Unfortunately the quality, service, and selection has been in a nosedive at Sears. One reason for this is likely the competition from less expensive tools made mostly in Asia. For decades Made-In-USA was the mantra of Craftsman tools, and they were intentionally affordable, quality U.S. made tools. This is changing.

The Harbor Freight chain is a good example of very inexpensive tools made elsewhere. I’ve purchased a few tools from Harbor Freight in the past, mostly when I needed a specific tool immediately, which I’d likely not use again or often. I’ve never purchased a complete set of tools from Harbor Freight or similar outfits, though I was very close recently as the price is very attractive, and surely for many uses the tools can be good enough. However, when possible I typically prefer to buy higher quality products (not just tools), and also prefer Made-in-USA items. Depending on what one is shopping for, looking for products manufactured in the U.S. is increasingly difficult. It would be very easy to write a long digression about the reasons to buy American made, high quality products, but l will just say that I like to vote with my dollars when it’s practical.

There are still a few (mostly) American made tool companies, which have traditionally been marketed from roving tool trucks, the Snap On and Mac brands come to mind but there are others. Though, as in the past, these brands can be extremely expensive for the average joe. I did some web research over the past week and learned that there are a couple other Made-In-USA auto mechanics tool companies, notably Wright and S-K.

I quickly focused on the S-K brand as I already have a few S-K tools, and S-K sets are readily available at discounted prices online. Yes, they are much more expensive than Asian or Craftsman tools if you pay retail, but they are moderately priced from online sources. Reading a couple threads on GarageJournal.com I learned that S-K declared bankruptcy and was immediately purchased by Ideal Industries in August 2010. Quoted from a 2010 press release: “Acquiring SK Hand Tools will expand our focus on American-made quality, service and value. Loyal customers can count on the SK brand being re-energized under IDEAL ownership as the premier ‘Made in USA’ line of professional tools.” http://www.idealindustries.com/whatsnew/press_releases/view.jsp?news=2010-08-23_sktool

Another thing I like about the way these S-K mechanic’s hand tools are being sold, is that I can buy smaller, yet more complete sets of tools to cover a specific need. For example, there is one very complete all metric set of 1/4″ and 3/8″ drive sockets, SK 94562. Want a nice 3/8″ drive set of SAE and metric sockets, standard and deep? The 49-piece SK 94549 has my attention, currently only $138.00 on ToolTopia.com. Are these new S-K tools as good as the other U.S. made tools with the big reputations? S-K surely thinks and says so. Some argue the reduced price compared to the big names like Snap On are due to the reduced marketing and tool truck middleman. I don’t know, but I’m about to find out. For the record, a few years ago I did buy and regularly use 1/4″, 3/8″, and 1/2″ Snap On ratchets.

Of course if I eventually buy a few S-K sets, I could easily end up with better travel tools than I have in my shop box. That’s a nice problem to have, and surely the Craftsman stuff could move into my truck and the S-K bits could become my primary tools.

RoadTraveler—Rolling Forward

Copyright © 2012 James Langan

Tire Technology 101

It these modern times with almost endless high performance, specialty tire choices for trucks, cars, and motos, it’s easy to forget how far we have progressed in just the past few decades. Prior to the 1980s there were few enthusiast, recreational off-highway truck tires.

As trucks and tires have advanced to a very high level many are now focused on the toughest tire available, thinking this is the best option. Maybe so, if you are continually puncturing your tires and/or ripping sidewalls, maybe you do need the toughest tire. However, some have forgot or never knew that the problem with light-truck tires just a few decades ago was that most were bias-ply designs and were very inflexible. They were pretty rugged as bias-ply tires tend to be, but in addition to their limiting tread designs, on-highway handling was only fair, and sidewall and tread flex, a key component of traction, was almost non-existent. Radial tire design and the specialty tires have changed this in a big way.

This comical and entertaining historic advertising movie from 1939 for the Fisk Tire Company illustrates how advanced tire technology has become and how different it was decades ago. At minute 4:00 in the video, the narrator explains how the rubber “inserts” allow the formerly continuous tread ribs to flex and act independently. This is essentially the same as what’s accomplished with the siping of modern tires, allowing tread blocks to conform and move independently, and providing biting edges for grip. Flexibility is key. If you want traction, you need flex. Most modern tires do offer a lot of flex, and flexibility is part of the reason handling, ride, and traction is so good (think radial tires). It’s important to remember and focus on the fundamental principles of traction and drivability.

Copyright © 2012 James Langan

No Dakar Rally for North America?

I’m not much of a racing fan, or even a sports fan. It’s not that I don’t appreciate the skill of athletes, I do, but it’s never been my thing to watchsports. Though a few years ago I got hooked on watching the excellent Dakar Rally video coverage on sbs.com.au. At the end of each day in early January, I would watch all the SBS videos featuring the bikes, quads, cars, and trucks.

After two days of not being able to play the 2012 productions, a Google search indicates viewers from the United States and Canada (maybe others too) are not able to view these shows. 🙁

This is probably because another network has the rights to coverage for the U.S. and Canadian markets, but I’ve yet to learn the reason or a suitable substitute for the comprehensive SBS coverage. Maybe the videos will be viewable when the race is over?

Oh well, I guess it’s time get back to doing and not spend so much time watching during the first two weeks of the year. Thanks for the butt kick forward, it’s time to get back to working [playing] with trucks and motos.

RoadTraveler – Rolling Forward

Copyright © 2012 James Langan