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I just got the December issue in the mail and was pleased to see the tire reviews. I have used both the Dunlop Q2 and Michelin Pilot Power 2CT in the past on a GSX-R750 and have no complaints on either tire. I look forward to see how you rate Michelin's upcoming tire as compared to the Q2. I have a specific question on changing tires due to local weather and riding styles. Yesterday I purchased a leftover 2011 Triumph Speed Triple that comes stock with Metzeler Racetec Interact K3 tires. I have only put a little over 100 easy miles on the bike on Sunday, but on mostly wet roads. I live in the Pacific Northwest and it will most likely rain here every day until June. I still plan on riding the bike to work, about 30 miles roundtrip, as long as temperatures are above freezing. I think I will really be wasting tread on a tire that I have read is like "a DOT-compliant track tire" and possibly creating a safety issue on cold, wet roads. Would I be better off putting on something like Michelin's Pilot Road (series 2 or 3) for the winter riding and commuting and save the Racetecs for the summer and dry roads?
Joint Base Lewis-Mchord, WA
If your riding will consist of mostly commuting on wet, cold roads, certainly it would be a good idea to switch to a more suitable tire. It's not only a matter of saving the Racetec K3s for the drier weather; something with a more elaborate tread pattern would give better performance (and safety) in the wet weather. The Racetec K3 is a very good tire, but as you say it is definitely biased toward track riding with a very sparse tread pattern. The Pilot Road 2 or 3 are Michelin's sport-touring tires and would be a good choice, and you could also consider the Pilot Power or the company's new sport tire that is due soon. From the Metzeler lineup, your options include the Sportec M5 Interact, a sport tire that offers a more suitable tread pattern for wet-weather riding and will most likely wear better than the Sportec K3. The Z8 Interact sport-touring tire would provide even more tread life and wet-weather performance.
All your dyno charts in the magazine and on the website are labeled with "corrected horsepower." What does that actually mean? I often see references to SAE horsepower, PS, BHP, STD, and now kW. Is this a lot of BS or is one horsepower not equal to another?
Lakefield, ON Canada
Horsepower is a measure of power, and there are in fact several different definitions. For measuring motorcycle output, we are dealing with mechanical horsepower, which is also referred to occasionally as imperial or international horsepower; this is defined as equal to 745.7 watts. The abbreviation PS refers to metric horsepower, which is slightly less at 735.5 watts. Historically, European manufacturers have used PS or metric horsepower, but more recently have begun using the kW (kilowatt) measurement and bypassing the horsepower ambiguity altogether. BHP refers to brake horsepower, or power measured at the crankshaft using a brake dyno. Even though the manufacturers don't use this terminology in their press material, claimed power is almost always a brake horsepower number and measured at the crankshaft (or, as we jokingly say in the office, at the spark plug).
Our SuperFlow CycleDyn dynamometer measures international horsepower at the rear wheel, which can be significantly less than crankshaft horsepower depending on losses in the drivetrain. That value is corrected for temperature, atmospheric pressure and humidity using SAE (Society of Automotive Engineers) correction factors; these alter the measurement to be equivalent to what output would be at 77 degrees Fahrenheit, zero percent humidity and 99 kPa of atmospheric pressure. STD (standard) correction factors use slightly more favorable conditions for a baseline, and STD-corrected horsepower numbers will be slightly higher than SAE-corrected values. Using a correction factor allows runs recorded at different times with varying conditions to be more accurately compared.