Tire Care
TIRE CARE
DON KOCH
A PRACTICAL PRIMER
Proper Tire Maintenance Is More Than Keeping Them Round, Inflated And Between You And The Ground.
MANY MOTORCYCLISTS, like the vast majority of car owners, regard their tires with casual disregard. If there is a tread showing on the carcass and it will hold air, then the tire can roll along for a few miles more. Tire care consists of adding sufficient air to maintain a roughly circular appearance and, for the showbike enthusiast, renewing the white lettering on the raised brand name and size designation. Proper tire selection, maintenance and replacement, however, require more detailed consideration than many motorcyclists — especially recent converts — devote to the subject.
In the area of tire selection, brand choice and tread pattern it is v~ ise to heed the wis dorn of the Ronians. who declared: J)e gustihus 11(01 est lisputaiuluui; or in rough translation. In matters of taste there is no disputing." Yet regardless of taste, a num ber of guidelines deserve mention:
oer 01 guiueiiries ueser~ e uieuuon. 1) Roadracing tires may look groovy and add to the appearance of a cafe racer, hut they are expensive: they wear vdth alarming rapidity, they are disastrous off paved surfaces and they permit a degree of traction unnecessary for most street cycles. Good touring tires wall hold traction until the center stand, footpegs and muffler scrape the road.
2) Touring tires are for city/highway driving and. in the case of universal pattern treads, limited dirt and gravel road use. The rib pattern front tire (such as an Avon Speedmaster) gives excellent steering, braking and cornering control on pavement, but it is unsuitable to dirt, sand and other loose surfaces. Universal pattern tires (such as a Dunlop K.-70) give good performance on pavement, hard packed dirt or clay and, with discretion, they allow' adequate control in softer dirt and shallow sand. The universal pattern tire is often the preferred choice of riders who generally follow the road signs but occasionally venture off the pavement.
3) "Dirt tires" include a wide range of tread patterns from relatively small and closely placed cleats to full motocross style "knobbies" that give superb traction in mud,
deep sand and a variety of other loose and slippery surfaces. Most cleat pattern tires, however, wear rapidly and when used on the pavement wear even faster. They also ride harshly and become decidedly treacherous when the road is wet.
Along with tread pattern, tire size and rim width are important in lire selection. American motorcyclists, like American car enthusiasts, tend to mount wider tires in their search for better traction and handling. On the lighter cycles and for off-the-road use. overwide tires, with the proper size tube installed, often aid stability, especially when the next larger rim size is also installed. But for touring use. oversize tires are of marginally greater value unless a rider expects to carry large loads, as a passenger plus luggage. in that case a larger rear tire is a worthwhile investment. By going from a 3.50 to 4.00 tire the load carrying capacity is increased by approximately 100 to 120 pounds. While it is true that an increase in air pressure raises the carrying capacity of a tire, it would require an additional 8 to 10 pounds of air pressure to effect a 100-
pound increase in load bearing capacity. And that great an increase both exceeds most manufacturers' recommended maximum pressures and produces a harsh ride and altered handling characteristics.
In the matter of oversize tires a special caveat is in order. Fitting larger tires will always reduce clearance with fender w'ells. fork legs, etc. Consequently it behooves a motorcyclist to check carefully all such clearances and undertake appropriate modifications (such as extending the rear shocks) when installing larger tires. The amount of fender clearance is especially critical. Reduced clearance — which must be measured at full compression on the rear shocks — increases the likelihood of mud packing between the tire and fender when driving in mud.
Motorcyclists who know better than to overload automobile tires unhesitantly subject their rear motorcycle tires to all manner of abuse. That sweet young blonde may weigh only 100 lb., but carrying her on the back of your lusty Fnglish Twin is roughly equal to placing more than 600 lb. of cement blocks in the trunk of your car. In this case you should at least raise the air pressure in your cycle tires and adjust the rear shock absorbers before carrying a passenger on your motorcycle.
On the other hand, under-inflation should be avoided like the plague; not only will it adversely affect cornering and place excessive strain in the tire carcass but it absorbs substantial horsepower and overheats tire cords, increasing the chance of a blowout. There is, however, no single correct pres-
sure. For normal one-up touring, the inflation pressure in the owner's manual is your best bet. But increased loads and high sustained speeds require increased pressures. Moreover, by carefully varying tire pressures no more than two or three pounds on either side of the manufacturer's recommendation you can tailor the characteristics of a motorcycle to suit your taste. Precise dirt and pavement handling require considerable experimentation with various combinations of pressure fore and aft. Because motorcycles rotate along the contour of their tires when cornering, they are more sensitive than cars to any change in tire pressure, which alters the shape of the tire contour.
Routine tire maintenance also requires correct alignment of the rear wheel to prevent rapid tire wear, the removal of all oil and grease from the tire to retard the deterioration of the rubber and, in the event of high speed driving, the balancing of the tire wheel assembly both to maintain smooth handling and to promote even tread wear. With specialized equipment the balancing can be done dynamically, but a roll of solder
or lead wire, some plastic tape and a bit of patience will produce a surprisingly accurate job. The procedure requires raising the wheel to be balanced, backing off the brake shoes, disconnecting the drive chain for rear wheel balancing and determining the side of the wheel that most frequently comes to rest at the bottom. Then the wire is wrapped around spokes near the rim and at the light side of the wheel and the balance rechecked. When the tire is as likely to come to rest at one point as at any other point, then the rider can assume that he has obtained satisfactory balance. Although some motorcycles come with balance weights, the accuracy of the factory job should be checked as it is often far from perfect.
Also, when changing a tire that has been balanced, it is necessary to reinstall the tire in the same relation to the rim if the proper balance is to be preserved. Proper repositioning of the tire is simplified by marking the tire with chalk, near the valve hole in the rim and then remounting the tire with the mark in the same location.
If, at the same time, the tire is placed on the rim "upside down," its direction of rotation is reversed, thereby equalizing the uneven tread wear that front tires and misaligned rear tires frequently develop.
Tire changing is seldom a pleasant event, and this is especially true when it is needed unexpectedly. A chance encounter with a rusty nail can turn a summer afternoon into a nightmare, as I learned when the rear tire on my rigid frame Harley 74 picked up a nail somewhere east of Blanchard, Oklahoma. Given sufficient patience you can drive with a deflated tire. But getting there is no longer half the fun.
Of course, flat tires are largely unavoidable. But a well prepared motorcyclist can save himself from most of the agony that often accompanies a flat tire. The simplest solution is to purchase a pressurized can of tire sealant and carry it on the bike. The sealing goo may damage a motorcycle tube, which should then be replaced as soon as convenient. But the stuff does provide a quick, simple remedy for inconvenient flats. Alternately, a motorcyclist can carry the tools and parts needed to repair and change a tire. Even on a small cycle the requisite equipment — tire levers, a hand pump, a tube patching kit and a valve stem puller — can be stored out of sight until the need arises.
But it is crucial to have all the parts necessary to change a tire, hike many motorcyclists I usually remove the center stand from a motorcycle since it is heavy, ugly and it grounds on hard cornering. This past summer I developed a flat tire on a country road only to discover that 1 lacked the center stand needed to raise the rear tire off the ground. Consequently I had to lay my bike down on its side amid the sunflowers and grass. By the end of the afternoon my enthusiasm for motorcycles and long distance touring had diminished considerably.
Given the proper equipment an experienced motorcyclist can change tires in alarmingly few' minutes. But the right tools are essential. As any Harley-Davidson rider will tell you, not all the king's men and all the king's horses can remove a tire from an older Harley without the proper alien head wrench to extract the bolts holding the rim to the brake drum. Nor is speed alone sufficient. After quickly changing the rear tire on my new Norton this past spring 1 discovered, much to the amusement of the local gas station crowd, that Í had created another leak by carelessly puncturing the tube as I worked the tire bead under the rim.
The use of a rubber mallet to press the bead under the rim will help avoid this pitfall. Tire manufacturers build their products with a circularity measured in thousandths of an inch. Mismounting the tire on the rim (when the circular rib near the rim is not equally distant from all points along the edge of the rim) can cause an error of 0.10 in. or more, thereby distorting a tire's "roundness." The careful application of a mallet and tire spoons before a cyclist inflates the tube can often force the "high" side of the tire down into the rim and pull out the '‘low" side. But it is occasionally necessary to soap the tire sidewall liberally and drive the bike slowly with a low inflation pressure to promote even seating of the tire on the rim. Such care and patience is time consuming, but it will yield a smoother, safer ride and more uniform tire wear.
