4x4 Tires Busting Beads - Built-In Bead BreakersPosted in How To: Wheels Tires on February 1, 2006 0) (
Rim protectors, rim guards, whatever you want call them-those seemingly innocent rubber ridges present on many late-model tire sidewalls that are supposed to keep the wheels from getting scuffed-may not be the hot ticket for trail use. Whether rim guards help or hurt apparently depends largely on their positioning relative to the rim, the design of the rim itself, as well as where and how you use the vehicle.
We found tire-and-wheel combinations where rim guards didn't seem to affect the tire's ability to hold air one bit, but also combos that lost beads with amazing ease. If you like the benefits of running lower inflation pressures on the trail, this story is for you. However, if you never drive in the dirt or air down, rim guards won't hurt anything and can indeed help protect the rims when those evil curbs attack.
Our tires used to stay put on the rims though we usually run just 2 to 6 psi on the trails, but then we started experiencing lots of leaks with a particular tire-and-wheel combo, and even had a tire come off both beads. This was quite embarrassing since we were towards the front of the line on an organized run and held up the entire group for more than 10 minutes while reseating the tire.
Experimenting with bead sealer helped quite a bit, but the lesson we eventually learned was that Pit Bull tires and Weld's Outback wheels don't seem to play well together. After remounting the Pit Bull Rockers on another set of old aluminum wheels, we didn't manage to lose a bead-although we tried.
It sure looked as if the Weld wheels were at fault here, but that didn't explain losing the inner bead of a Pit Bull Growler on a bead-lock wheel the next day. Now the only common denominator was the Pit Bull tires. Something strange was going on here, we just didn't know what yet.
During a bull session with Soni Honegger, we might have stumbled across the answer to these "mysterious" bead losses, as he'd noticed gaps fore and aft of the tire's bulge between tire and rim on his new BFGoodrich Krawlers. That's when it clicked; it could well be those newfangled rim protectors that are causing the problem. What seems to be happening is that when the sidewall flexes at lower pressures, the rim protector serves as a pivot point in that stiff area of the sidewall, and gaps open up on either side of the low spot. In some cases, the result is instant air loss, while other times the rim protector only traps dirt between the tire and wheel, leading to slow leaks. Several phone calls later, an assortment of tire industry people and four-wheelers agreed that we might be on to something here.
Dennis Franklin of Franklin Tire & Suspension in Yuma, Arizona, pointed out that "Rim guards were originally used only on high-pressure industrial tires." Not quite the tires we use on the trails. Warren Guidry of Interco Tire said that some of Interco's ATV tires had rim protectors to keep cut soybean stalks and the like from getting between the tire and wheel. Again, a different scenario than our trail tires, but at least a low-pressure application.
We talked to as many tire manufacturer reps as we could raise on the phone. In the end, they all agreed, or at least admitted, that rim guards could indeed have a dark side, but whether they're good or bad wasn't quite that clear-cut. For example, BFGoodrich's Jeff Cummings had witnessed rim protectors save the sidewalls on two vehicles that had smacked into a large rock at high speed. Tom Lorden, a man who has had a lot to do with the trail tires we see today, even provided the DOT standards for resistance to bead unseating. Interesting reading, but unfortunately well beyond our means and time limits.
Our thinking was that the outside bead is the most likely to give out, since it's hard to put much force on an inside bead during normal 'wheeling. Yet we had experience with, and reports of, inside beads going out on bead-locked wheels.
Jason Bunch of Tri-County Gear had noticed vehicles struggling with anything less than 7 psi in rockcrawling competitions. Soni Honegger had lost downhill-side inner beads while traversing a snowy slope, both coming and going. And we'd lost one just going downhill. Now the common ingredients were bead-locked wheels and rim guards.
To try to figure out what was going on, we rounded up a few tires and wheels, then winched a test vehicle sideways on aggregate concrete to see how each tire-and-wheel combination would act in a severe side-load situation. We kept the pull on the winch right at the threshold of dragging the tire sideways (which takes considerable force on aggregate concrete), while airing down until the tire would let air escape-or until it was below 0.5 psi, usually. This loaded the outside bead big-time, while folding the tire onto the inside bead, showing any weaknesses with the rim protector and/or rim design. We got some surprising results.
While we only had a select few tires and wheels to work with, some things became obvious, even with our limited supply. For example, not a single tire lost the outside bead. If the tire eventually did lose air, it was always the inside bead that let it out. Not exactly what we'd expected. Less surprising, a tire that'd been on a steel rim for 20 years just wouldn't let go of the rim.
The areas where the sidewalls folded, which seems to differ between radials and bias-ply tires, is also where the gap(s) occurred that allowed air to escape. See the "Test Results" sidebar for the specifics on the tire-and-wheel combinations we tried and what happened.
It's obvious that rim guards placed close to the rim play a role, but the inside shape of the rim itself appears to be at least equally important. Consequently, bead-locked wheels can be just as susceptible to losing inner beads as are regular rims.
We assumed that the outside bead would let go first, for two reasons; it's hard to put much outward side load on the inner bead during regular four-wheeling, and it's usually the outer bead that ends up separated from the rim when a tire does lose air. Now we suspect that it's generally the inner bead that lets the air out, which then causes the outer bead to come loose if you don't stop immediately. Every tire and wheel we tested (that let any air out) acted that way. Also, it would explain why our old Centerlines, having virtually nothing for an outer safety bead, but with a nice, sharp machined groove on the inner bead, retains the tires extremely well. This goes against everything we believed, but based on our observations, it may mean that we should run those bead locks on the inside instead, where the cops wouldn't see them.
It's quite expensive to modify tire molds, so don't expect to see changes on tires already in production, even if it turns out that rim protectors are more evil than good on the trail. However, Pit Bull is working with Hutchison to have wheels made that will work perfectly with the Pit Bull line of tires, and it is also considering eliminating the rim guard on at least one side of the tire (it doesn't do much good on the inside, anyway).
Probably our best bet is for you readers to help sort this out. What we'd like is an e-mail from you describing which tire-and-wheel combinations you've had really good or bad luck with. We would like to know if it stays on the rim when running low pressures or if the tire tends to lose beads with ease. For this information to be useful, we'd need to know the size, make, and model of both the tire and wheel. Writing only "chrome spokes" or "aluminum directionals" won't do us much good, but "American Racing Outlaw II," for example, would. "BFGoodrich Mud-Terrain" could be either first-, second-, or current-generation, and "35-inch Swampers" could be darn near anything from Interco. Since each tire and wheel is different, we need to know which one it really is, plus what kind of vehicle you're running them on and at what pressures. If enough meaningful responses come in, we could make a listing of what works together and what doesn't, something we could all learn from. Send your input to firstname.lastname@example.org. You won't win anything, but you will help your fellow 'wheelers-and maybe yourself too.
If the tires you run are creating problems, consider removing the rim protectors (if so equipped), at least on the inside. It's easier than you'd think, especially if the tires are dismounted. Using a grooving iron is a near-must if the tire is still on the rim. However, it's also the most likely way to screw up the tire, by cutting too deep
* While the side-pull testing revealed a few tire-and-wheel combinations that may not be ideal for low-pressure trail use, we also got information about other setups that supposedly didn't work out all that well. If you're into running single-digit inflation pressures on a light vehicle, or in the low teens with something weighing 5,000 pounds or more, consider avoiding the following combos:
* BFG Krawlers on MRT composite bead-lock wheels.
* Pit Bull tires on Allied aluminum bead-lock wheels.
* Pit Bull tires on Weld Super Single-style wheels.
* Pit Bull tires on Mickey Thompson Classic II wheels.
* Super Swamper LTB tires made before 2002 on most any wheel.
* Super Swamper TSLs on Rock Crawler wheels.
* If Pit Bull tires seem overrepresented here, it's only because we had three sets of them to try, but not many other tires.
* BFG Krawlers on Trail Ready bead-lock wheels.
* BFG Krawlers on Walker Evans bead-lock wheels.
* BFG Krawlers on OMF bead-lock wheels.
* Mickey Thompson Baja Belted on American Racing Outlaw wheels.
* Super Swamper Boggers on Weld Super Single-style wheels.
* BFG Mud-Terrain KOs on Weld Super Single-style wheels.
* Goodyear MTR on MRT steel bead-lock wheels.
* Any tire that has rusted onto its steel rim over time.
Pulling at 90-degree angle on aggregate concrete until tire dragged or lost air
|TIRE||WHEEL||RIM GUARD||LOST AIR AT||COMMENTS|
|Pit Bull Growler 35x14.50-15||Allied Racing Bead lock 15x10||Inside and outside||3.5 psi||Pit Bull tires flex so well there's no real need to run less than 5 psi|
|Pit Bull Growler 35x14.50-15||Allied Racing Bead lock 15x10||Outside||1 psi||Removing the inner rim guard proved helpful on this setup.|
|Pit Bull Growler 35x14.50-15||American Eagle 15x10||N/A||Less than 1 psi||Between the rim design and removed rim guards, a trail-worthy combination.|
|Pit Bull Rocker 35x14.50-15||Centerline 15x10||Inside and outside||No loss||With a good inner safety bead the old Centerline refused to let go of the tire.|
|Super Swamper LTB 34x10.50-15||Stock CJ 15x6 steel||N/A||5 psi||These early production LTBs were hard to keep on any wheel, especially a crusty old steel one.|
|BFG Krawler 35x13.50R15||American Eagle 15x10||Inside||No loss above 2 psi||Still-wet tire lube may have helped keep the tire from losing air.|
|BFG Krawler 35x13.50R15||American Eagle 15x10||Outside||No loss above 2 psi||Rim guards on the outside seemed to make no difference in this test.|
|Cepek Fun Country 31x10.50-15||White spoke 15x8||N/A||No loss||After 20 years on rim, we would have been surprised if the tire had come off.|
|Pit Bull Mad Dog 35x14.50-15||M/T Classic II 15x10||Inside and outside||5 psi||A good tire and a good wheel but not a good combination.|