Hoop Dreams
Why are many aftermarket wheels labeled as racetrack only? Wouldn't a carbon or magnesium rim work just as well in the canyons as it would on the track? And why do racebikes have smaller wheels than stock bikes? How do the smaller hoops affect performance?
Vince Davis
Los Angeles, CA
The main benefit of lighter aftermarket wheels-quicker steering-is just as important and evident on a twisty road as it is on the track. For long-term use on the street, however, a wheel must cope with potholes, curbs, water, dirt and neglect. Racing wheels designed to perform on the track are made as light as possible; their construction makes them susceptible to bending or breaking over a pothole you wouldn't encounter on the track, they don't have dust seals to keep debris out of the bearings, and their finish is too thin to withstand the elements for a long period of time. For this reason the manufacturers recommend them for track use only.
Switching to a smaller-diameter wheel also reduces weight and improves steering quickness. But while that may explain the original widespread use of 16-inch front wheels in the early '80s, there is much more to consider when it comes to wheel size. Tire manufacturers juggle overall diameter, width and profile to achieve specific dimensions for the tire's contact patch, and changing the height of the tire's sidewall-by using a larger or smaller wheel diameter-within those constraints will change the balance of stiffness and compliance in the tire's carcass. Currently most top-level race tires are 16.5 inches in diameter, but 17-inch and 16-inch diameters-as well as a variety of rim widths-are experimented with. It's doubtful we'll see 16.5-inch wheels on streetbikes, as there are too many hazards associated with having rim sizes just a half-inch apart.
Overheating Blackbird
During the day when I'm going to work my '99 CBR1100XX warms up properly, but when I get into heavy traffic or I'm stopping and going many times the bike tends to get very hot. The fans kick on and the temperature stabilizes, but when I come to a stop or turn off the bike antifreeze comes out of the reservoir's overflow tube. What could be the problem and how can I fix it? I have been asked if I've overfilled the reservoir, but I haven't put any in the bike since I bought it a year ago.
Rick Salinas
McAllen, TX
Excessive overflow from the reservoir on a regular basis is an indication that either the cooling system is under too much pressure or that coolant is pushing past the cap at normal pressure. Check the easy things first, as it could be a simple matter of air in the system or a leaking cap. When your bike is cold fill the radiator, check the seal on the cap and have it pressure-tested. If "very hot" is hotter than usual, check the thermostat as well. Fill the reservoir to the full line and bleed the system according to the service manual. Usually it's the cap or thermostat that's the culprit, but a blown head gasket could also be overpressurizing the system; if you still have trouble, plan on having a look inside the engine.
Who Needs Oil?
I live in Minnesota, so I'm storing my bike for the winter. What would be the downside to draining the oil and leaving it dry for the duration of its storage time instead of wasting oil I will have to change in the spring? Is rust an issue? I mean, after all, the oil is just sitting in the sump, isn't it? Is it protecting anything during long periods of non-use?
Kris Skellenger
via SR mail
One of the benefits of changing the oil prior to storage is that the fresh oil distributed through the engine when it's run for a brief time flushes the old, contaminated oil from the bearings and surfaces. Simply draining the old oil and leaving the engine to sit over the winter means everything inside is still coated with the old oil. Leaving your bike with oil in the crankcase, you won't have to worry about someone starting it in the spring with no oil, either. It's not absolutely necessary to change the oil again in the spring; the new, clean oil will not go bad over the winter while it sits in your engine. It may collect some condensation, but this will burn off on the first long ride.
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