No Fixed Abode: The Dark Side of Unintended Consequences.

Jack Baruth
by Jack Baruth

To some very large degree, the automotive world as we know it today was fashioned by two major advances. The first was the implementation of effective and reliable engine control computers, which handle everything from emissions compliance to knock control silently and competently. We take it for granted now that cars start immediately, run perfectly from sea level to the top of Mount Evans, never smoke, stumble, or ping, and return real-world fuel mileage that is often triple that of their Seventies predecessors.

The second advance started around 1992 and it’s known as the “silica miracle”. Replacing some percentage of the carbon black in automotive tires with silica dramatically increases grip and tire life while reducing rolling resistance significantly. The Prius wouldn’t be nearly as amazing without low-rolling-resistance tires, and those tires couldn’t happen without silica. But it’s not just the eco-Mouseketeers who are benefiting from it. Today’s performance tires are so much better than their 1990-and-before predecessors it’s difficult for younger enthusiasts to truly understand the gap in capabilities. It was once taken for granted that performance cars like the Acura NSX or Porsche 911 ate their tires every five thousand miles and handled like they were on greased roller skates the minute the road became shiny with rain. Without silica tires, the enduro series like the 24 Hours of Lemons, ChumpCar, and AER would still have tire changes every two hours.

In fact, today’s automotive tires are so good, it’s possible to use them in ways that were never intended.

They call themselves “Darksiders” but a better word for them might be heretics. They mostly ride the big eight-hundred-pound touring bikes, the six-cylinder Gold Wings and cross-continental Beemers, and they put hundreds of thousands of miles beneath their saddles as they ride “Iron Butts” and swallow states one after another. Many of them have experienced blowouts and major problems from their touring motorcycle tires, particularly when two plus-sized people and a lot of gear are pushing the total load up to the three-quarter-ton mark. All of them are sick and tired, pun intended, of replacing rubber that costs $400 a set on what seems like a seasonal basis.

The Darksiders weren’t the first people to put automotive tires on a motorcycle. That’s been done again and again, most amusingly by the “Big Dog” choppers that had 250mm-width Goodyears on the back wheel. But they were the first people to do it because they expected, and in many cases received, tangible benefits from doing so. One Darksider puts it like so:

If you ride two up, you’ll find that the available moto tire load capacity can easily be exceeded even while remaining within the GVWR. 60-65% rear bias loading isn’t unusual with a passenger and luggage. If you add up the numbers you’ll see what I mean.

I blame this and the resulting heat on my moto tire (MT) failures. The CTs have a much higher load rating and run (in my own experience) about 40% cooler than the moto tires in similar conditions.

So for me, the safety provided by a more capable tire (cooler running/higher load capacity) and the additional safety of Run Flat (RF) capability are the two clear advantages of running a RF CT on a GL1800.

Other advantages are the smoothing/softer ride which is significantly appreciated by my wife. I have noticed marginally improved mileage but not significantly enough to make it an advantage. The biggest improvement on wear is that my CTs are replaced when the tread wears out versus when the tire deforms after failure like with the MT.

With many GoldWing tires lasting just 10,000 miles compared to the 30,000 or more from automotive tires that cost half as much to begin with, plus some additional fuel mileage, the economics of it make obvious sense. Wet-weather traction is also greatly improved, according to the reports of many Darksiders. I want to focus on that for a moment because I think it’s important, and, um, it also explains why you can’t buy any Motorola PowerPC computers or rotary-engined cars anymore.

Hee hee.

You see, while those of us who fancy ourselves scientists or engineers like to believe in the romance of the “aha” moment and the entirely new idea, the dirty truth of it is that the steady progress made by dedicated effort in a field is usually more important, and more effective, than any single inspiration. Take the rotary engine. It’s a hell of an idea and it has a lot to recommend it. The problem was that only one manufacturer kept developing it after the initial excitement faded, and that manufacturer — Mazda, obvi — couldn’t hope to match the sheer volume of engineering prowess being thrown at the piston engine over the same period of time. Thus the piston-engine tortoise catches the rotary hare.

Same goes for the PowerPC chip, which smoked the pins off the x86 architecture when it arrived but couldn’t be sold in enough volume to justify the kind of development that x86 received. In the end, the compromised and thoroughly annoying x86 architecture beat no fewer than three other major processor designs, including Intel’s own Itanium clean-sheet design. The reason was simple: it sold in such numbers, and was so profitable, that there was more money available to improve it by degrees.

Now back to car tires. The market for automotive tires that are effective in the rain is an order of magnitude greater than the market for touring motorcycle tires that are effective in the rain. Don’t be fooled by the large motorcycle markets in other countries; what they consider to be a “motorcycle” has nothing to do with a Gold Wing. Hundreds of millions of dollars have been spent developing, testing, and perfecting the wet-weather automotive tire. The touring motorcycle tire, on the other hand, is like the Renesis engine in the RX-8; it has some good ideas, but it can’t hold its own against a fully developed, high-volume competitor.

It stands to reason, therefore, that a car tire would of course be better in the rain than a bike tire. Particularly when used in applications where the weight load is basically automotive; a GoldWing with heavy passengers weighs as much as a 1976 Civic and has a performance envelope that is considerably greater.

Naturally, not everyone is thrilled about this Darkside business and compelling arguments against it have been made. But some of these arguments fail to take into account the development gap between car and bike tires. Sure, the cornering loads are way different on a bike tire than a car tire — but what if a car tire is just so much better that it has enough reserve performance in that situation anyway? Remember when Grassroots Motorsports ran a Honda Odyssey against an E-Type around an autocross and the van won? That is the power of continuous development.

The war between the Darkside and the, um, Light Side is getting more heated. Some group rides are excluding Darksiders. Police are ticketing them. Harsh words are being exchanged and the size of various genitalia is being questioned on all sides. This will get worse before it gets better. At some point, one of the tire OEMs is going to “certify” a car tire for bike use, raise the price twenty percent, and clean up. Depend on it.

For those of you who don’t give a damn about motorcycle tires — well, you’re not reading, are you? But if you are, here’s the payoff to the car guys. Like it or not, much of the development money and effort in this business is now being thrown at things we find repugnant. SUVs. CUVs. Three-cylinder turbos, CVTs, DSGs, sliding-caliper brakes, tall wagons, battery packs, who knows what. Many of our cherished technologies and designs will fall by the wayside. The only consolation is that things will get better and there will be room for romance, excitement, enthusiasm in there somewhere.

In the end, though, the money and the market will determine what the cars of the future look like. We’ll just have to hope that we can misuse them to our own disreputable ends. You know what I’m saying, right? In the finish, we will all wind up on the dark side.

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  • Econobiker Econobiker on Aug 29, 2014

    Question: Haven't some hot rods run motorcycle tires on the front axle wheels even under comically small front fenders?

  • Rpn453 Rpn453 on Sep 11, 2014

    It's a similar story with trailer tires. They're typically poorly designed and constructed and you simply expect them to fail occasionally, yet it's a media disaster if a passenger vehicle tire ever fails while carrying the same weight at the same speed. A reliable, name-brand passenger vehicle tire with the same load rating is usually cheaper than the no-name Chinese trailer tire alternative anyway.

  • Tassos ask me if I care.
  • ToolGuy • Nice vehicle, reasonable price, good writeup. I like your ALL CAPS. 🙂"my mid-trim EX tester is saddled with dummy buttons for a function that’s not there"• If you press the Dummy button, does a narcissist show up spouting grandiose comments? Lol.
  • MaintenanceCosts These are everywhere around here. I'm not sure the extra power over a CR-V hybrid is worth the fragile interior materials and the Kia dealership experience.
  • MaintenanceCosts It's such a shame about the unusable ergonomics. I kind of like the looks of this Camaro and by all accounts it's the best-driving of the current generation of ponycars. A manual 2SS would be a really fun toy if only I could see out of it enough to drive safely.
  • ToolGuy Gut feel: It won't sell all that well as a new vehicle, but will be wildly popular in the used market 12.5 years from now.(See FJ Cruiser)