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Motorhead Memo: Tires gauged

By Kip Woodring

Last time we talked tires, we looked at some of the basic characteristics of motorcycle tires and how they are built differently because they work differently than auto tires. This time, I thought we could examine a few, shall we say, more subjective tire qualities. Let’s start with the most subjective of all—people’s opinions. Or, maybe that should be people’s foibles?

Let’s be honest—there’s a broad spectrum of tire choices; some we shouldn’t even consider and some that are likely to be superior in some way or another to whatever road rubber we currently sport on our sleds. Trouble is, more often than not, when it comes time to pick, we get opinions and prejudices in lieu of useful criteria. Your buddy might love OEM Dumbflops, another guy you ask is just as likely to favor Flameons, yet another is a big fan of Treachelers, or Bitchelins. And so it goes! Simply attitudes by and large, with not enough concrete data (pun intended) about those precious little round rubber jobbies to go on—at least, when it comes to making an objective decision. Riders interact with tires to vastly different degrees and in as many different ways as are humanly possible. That interaction is, at best, a sort of symbiotic telegraphy keeping the body talk between you and your beast sharp, clear and loud as you ride better, farther, faster and safer. Or—it’s less. Sometimes a lot less! How is it, exactly, that the same bike with the same tires can evoke such disparate opinions from riders? Cause the riders are different! Frankly, they tend to have diverse priorities, skill levels, saddle techniques, loads to carry and roads to travel.

You don’t even have to look closely at this tire to realize it’s not just worn, cracked and old—it’s friggin’ dangerous! Two things: do you suppose it’s worse to have all these cracks on the tread or the sidewall? And hopefully you can deduce that this tire has been run hard with not enough air in it. A hands-on approach and a close look is the best way to notice things like shrapnel in the tread or lumps in the walls—in your driveway and not unexpectedly alongside the road.
Tire sidewalls are recommended reading for sure, but don’t miss the fine print. Here, for instance, is a tire that’s coming up on six years old, according to the date code (fifth month of 2005)—and it looks it. Though it stills feels fine on a ride, it’s clearly due for “re-tire-ment” in spite of that. Regardless of plenty of good tread, proper pressure, and a total lack of any heat-soak problems or damage of any kind, “ozone-cracks” (or “weather-checking”) all over the sidewalls render this tire untrustworthy and potentially unsafe. To quote a friend of mine, “Getting old is bad for anything petroleum-based.” An excellent reminder—it’s better to wear a tire out by riding than let it rot in the garage… innit?

You don’t even have to look closely at this tire to realize it’s not just worn, cracked and old—it’s friggin’ dangerous! Two things: do you suppose it’s worse to have all these cracks on the tread or the sidewall? And hopefully you can deduce that this tire has been run hard with not enough air in it. A hands-on approach and a close look is the best way to notice things like shrapnel in the tread or lumps in the walls—in your driveway and not unexpectedly alongside the road.
Tire sidewalls are recommended reading for sure, but don’t miss the fine print. Here, for instance, is a tire that’s coming up on six years old, according to the date code (fifth month of 2005)—and it looks it. Though it stills feels fine on a ride, it’s clearly due for “re-tire-ment” in spite of that. Regardless of plenty of good tread, proper pressure, and a total lack of any heat-soak problems or damage of any kind, “ozone-cracks” (or “weather-checking”) all over the sidewalls render this tire untrustworthy and potentially unsafe. To quote a friend of mine, “Getting old is bad for anything petroleum-based.” An excellent reminder—it’s better to wear a tire out by riding than let it rot in the garage… innit?

So, it seems to me the secret, beyond the realization that not all tires can be all things to all riders, is to attempt to match the tire to the rider, more than the ride. Wait! Scratch that—I should have said match the rider to the tire! Let me see if I can clarify that…

First and foremost, it’s no good dissing a tire that’s been neglected or abused. A propensity towards burnouts or a lack of discipline when it comes to simple inspections and pressure checks—followed by complaints that it only lasted 4,000 miles—doesn’t mean the tire (brand) in question is no good. It means the rider is! Sorry ’bout that sad fact, but there it is.

Seems to me, no matter how old or new, bad or good a tire is, the quickest way to kill it (or yourself) is to ignore it (and/or the suspension it works through). I read somewhere that of the 6.9 million new cars put on the road last year, 5.1 million of them will run around on under-inflated tires this year… duh! S’pose motorcycle jockeys are any better? Look, anyone who has seen what low pressure, burnouts or any other form of “heat soaking” does to a tire would realize that these “stupid owner tricks” really cause the troubles. This sounds more like potentially lethal “pilot error” to me than any real flaw in tires. Yet no one faithfully checks for pressure, damage, cracking and/or blems pre-ride as often as they should. Well, almost no one…

You don’t need to look much further than a race track to see the value of—for lack of a better way to say it—“getting to know” the nature of tires and the lavish attention that entails. Road race tires get “warmers” and dirt track tires get extra grooves cut into them, to name just a couple examples of special treatment afforded by folks who bet their livelihood and lives on tire performance. Carcasses are ministered to and inflation pressures are checked and changed like some religious ritual, as well. If you accept that treating the tires on your ride almost as attentively is a good idea, you would not be wrong! Sure, a racer has different priorities, more extreme demands and works his tires far closer to their limits than you or I are ever likely to do, but the premise holds true. Most poor tire performance issues regardless of brand or fitment predominantly come down to cheesy (if any) interactions on the part of the responsible party—the rider!

Of course, a little informal introduction (or crass generalization) can help you get to know your tires too. It makes those all-important future interactions with them a little easier and more useful.

Meet your maker(s)!
Dunlop tires have been OEM on Harley-Davidsons for 20–25 years. With the exception of the “407” series (mostly bigger sizes) for late-model touring bikes, their line-up of tires for Big Twins and Sportsters has remained remarkably the same over the years. They have come up with plenty of new tires for new applications (like V-Rods and XR1200s). But, if you allow that traditional Harley chassis’ (FL, Dyna, Softail, XL and FXR) haven’t changed much in that time either, you’re onto all that’s good and/or bad about these tires.

Like most products designed for mass consumption, Dunlops work pretty well under most conditions for 80–90 percent of all riders. They remain the default choice for those who are either indifferent or unwilling to seek out tires that match any out-of-the-ordinary needs they might have. Whether you really need anything other than Dunlops to enhance your overall experience depends largely on where you exist on the bell curve of riding behavior. Bell curves, you’ll recall, are those nifty charts they use to determine the median bulge and the extremes on either tiny end of the curve. Applied to tires, I’d hazard that one extreme would be the lightly-loaded, gently-ridden, always vertical sleds that could probably get along nicely with recycled hockey pucks for tires. At the other extreme, one could picture some trailer-haulin’, overburdened, leaned-till-the-sparks-fly, oughta-be-runnin’-gumball-slicks Dresser (complete with 300-pound passenger)—on a race track! The vast majority of us are more middle of the road, let alone the curve. We won’t ever get within half a “g” of noticing subtle characteristics of different skins and neither know nor care that a lot of things have been learned about motorcycle tire design in the last couple of decades. Which way you roll (almost literally) should be a major factor in your tire choice and there are plenty of options to accommodate you (including Dunlops)!

Avon Tyres, as their preferred spelling should indicate, are British in origin. Wet weather, high speeds, great response and good handling tend to be priorities of riders in the UK and in areas of the world with similar weather and riding conditions. Based on those criteria as well as others, these are damn fine alternatives to Dunlops for riders in, say, the Pacific Northwest, as long as you remember one critical thing: Avons for H-Ds must be kept at their recommended (firm) air pressures at all times. Virtually anyone who has tried Avons and not had a good experience with them has either poorly assessed their tire desires, or simply doesn’t own (or can’t use) a tire gauge.

Metzeler tires have an excellent track record with touring bikes, which is to say they offer great traction and wear properties for heavy bikes that like to travel at high speeds. (Let’s see—German autobahns and alpine roads—yeah, that’s the idea!) I don’t honestly know if these tires are all that superior in performance to others, but they have a reputation for doing it all—longer—than most others. Mileage matters to touring types, so it follows as night the day, that’s one major reason they are such a popular alternative for heavy-duty cruising.

Michelin tires are surprising in more ways than one, and they are also OEM to Harley. The reason why has more to do with a strike at Dunlop than anything else. Seems for months, a couple years back, there were no H-D tires to be had from that company, so The Motor Company looked hard for an alternative—just in case. As it turned out, the strike was settled (or whatever) and Michelins weren’t fitted to scooters coming off the line, but it was a close call. And in my view a good one, partly because it shows how excellent Michelin tires really are and partly because it shows that Harley isn’t blindly committed to Dunlop as the one and only Harley tire, after all. (And, in fact, Michelin Scorcher tires are used on three of the 2010 Dyna models.) Michelins, by the way, are very French and huge advocates of stiff sidewalls (among other design features) translating into very predictable handling (more forgiving if pressures aren’t quite what they should be) as well as an ounce more prevention in the event of a blowout.

There are certainly other excellent choices for replacement rubber on hogs, notably Pirelli, which has consistently pursued the high-end of the market (like Ferrari on the car side and Ducati on the bike side), but sadly overlooked by most Harley riders. Bridgestone, the largest tire company on Earth, also has suitable rubber and there’s no end of lesser-known brands that would serve quite well for most of us (60/70th percentile riders in particular). There are also some well-kept secrets in the market, one of the best being Dunlop 404-series tires, which are Harley tires that simply don’t say Harley on ’em! (That makes them just as good and a hell of lot cheaper, but don’t say I told you so.) Learning just a few of these secrets can often influence your—ah—“perspective” a great deal.

Hysterical hysteresis
For instance, would it interest you to know that Dunlop tires are actually made by Goodyear? Yeah, the blimp guys. Goodyear is also a partner with a Japanese company called Sumitomo. Hence, “Asian” Dunlops are actually manufactured by Sumitomo, whereas “Euro/American” tires can be made here, there—and everywhere else. This brings to mind another critical bit of insight that has been banished from our consciousness by legislation and lobbying—namely, how much real rubber is present in the compounds of our tires! Once upon a time, there was a separate dollar amount shown as part of the tire price, which was the excise tax on natural rubber. For what it’s worth, back then it was common knowledge that “British” Dunlops (for example) carried almost twice the excise tax of their Japanese counterparts. It was equally obvious to the go-fast crowd of the era that even though these Dunlops were supposed to be identical (K181) models, the differences in traction (especially on wet roads) and general handling characteristics—were night and day! The Brit tire was vastly superior on all fronts, save wear and longevity, precisely because there was more natural rubber in their compound than in the Japanese versions. These days, with no real way to know, the only thing we’re left with is the none-too-scientific, but useful nonetheless, “thumbnail” test for hysteresis. (Actually, I usually use a pocket knife blade or nail file.) What you do is this: Simply press firmly into the tread of the tire you’re considering at about a 45-degree angle, then release, and see how long it takes the rubber to snap back to its original position. What you hope to learn is whether that rubber will ooze back like goo or snap back like a ball. Gooey/ slow return tends to imply the tire will grip well, even on gravel, sand and wet tarmac, the relatively soft compound working like tarpaper on the road surface. The rubber ball reaction leans more toward straight-up cruising on smooth pavement and long wear under load. It’s all relative, of course, but this simple test can foreshadow an important aspect of what to expect where the rubber meets the road. You decide what you prefer.

The more you look, the more you see… See?
Most tire articles will walk you through things to be learned from reading the gibberish on the sidewall. (You can Google it.) But one thing that comes up isn’t so easy to learn, and the other is an old wives’ tale that just won’t go away. First, among all the data on the tire, there’s a date code that tells you when the tire was manufactured. More and more folks are concerned with buying a supposedly new tire that can actually be several years old! While I don’t think it’s as big a deal as some would make of it, clearly it’s still a better idea to buy a “fresh” tire than a moldy oldie! Six years seems to be the consensus on “sell-by date.” I also figure this logic doesn’t just apply to tires still on a retailers rack. Go check the ones in your garage to be safe.

While you’re at it, if you’re one of the many that figures (or has heard from someone, perhaps an old wife) normal/proper inflation pressures should be at the maximum printed on the sidewall—please—think again! Tires generally increase pressure from internal heat (once they are at operating temperature) by about 10 percent or so. If you already have ’em rock hard “cold,” you are flirting with so-called “heat soak” which kills more tires (and riders) than you’d think. Heat soak can occur from many a mistreatment—over-inflation, under-inflation, overloading, and of course the infamous burnout. What it does is trash all the good black-magic chemistry and engineering that goes into modern tires and turns a nice rubber tire into a plastic time bomb. Chunks can fly off the tread, blowouts can occur, traction qualities can vanish unexpectedly, and a host of other bad things I can’t really recall right now can and will happen to a heat-soaked tire… period! Sadly, the only dead giveaway is a ‘blued steel’ appearance on the tread surface, but that’s only an obvious indicator of the condition in its extreme. Doesn’t tell the whole story, so beware; and be aware of what the tire manufacturer tells you about proper inflation of its products.

Gauging the severity of the problem
One very good idea for our bike’s tire care is one that so far only comes standard on high-end cars and SUVs. The nice thing is, there are aftermarket kits out there (from Kisan and Doran, to name two) to add this critical capability to Harleys. Essentially, we’re talking about a wireless tire pressure monitoring (and warning) system! In the end, no matter what tire you favor, most will do the job better if you just bother to take care of them. And monitoring the most crucial equipment on the scooter is a great way to make this most important task easier. How important? Well…

Continuous 10 percent over- inflation decreases tread wear by 5 percent.

Continuous 20 percent under-inflation decreases tread wear by 25 percent.

Tire Life (not the same as tread wear as we now know) will be reduced by 30 percent if constantly under-inflated by 20 percent.

See? I’m not blowing this out of proportion, and neither should you!

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