Got a question? The Geek
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On The Rebound
I have had a 2002 GSX-R600 for four months now. After adjusting my suspension settings I’ve noticed something interesting. I have my front rebound set to one turn out from full stiff. Good for warm daytime use but sometimes at night it gets into the low 30s and I’ve noticed that I have a lot of oversteer. Turning another half turn out corrects this. But, I am always adjusting rebound in these crazy winter days of Florida. Is this normal or am I just out of my mind?
I wouldn’t say this is normal, but not to worry; you are not out of your mind either. It’s possible that with a significant drop in temperature your GSX-R’s fork oil is thickening enough to increase rebound damping to the point that it is holding the front end down, and decreasing rake and trail to cause your oversteer. Your bike is 10 years old now, and it’s anyone’s guess as to what oil is in the front fork — especially since you just recently bought the bike. Changing it for fresh, good-quality fluid will likely give you more stable damping over that wide temperature range.
Plugging And Patching Tires
Oops. Can this tire be re...
Oops. Can this tire be re-used?
What would happen to a sportbike tire if it is plugged, patched or plug patched (a plug patch is a one-piece patch used by Firestone shops on Oahu)? And where is the data to confirm or deny the claims? Rumor is that a sportbike tire that has a nail in it should be thrown away and replaced with a new tire. My question is are the tire manufactures saying this to increase sales? Or is this really a safety issue? If it is a safety issue where is the data of catastrophic tire failure? As a reporter I have researched this topic and have not found any data stating that motorcycle tires that have been repaired suffered catastrophic failure. But I have seen firsthand tires that have been repaired by a plug and/or patch and used for drag racing, roadracing and everyday street use.
Most tire manufacturers advise that a tire can be repaired, with some restrictions. A small puncture in the tread area, not on the sidewall, can be fixed using the “plug patch” type of repair. A plug patch is just that — both a plug and a patch molded together. This requires that the tire be removed from the rim and the plug patch inserted from inside the tire. There are three things to consider when repairing a tire. One, is the tire physically damaged? If the puncture is too big, or if the tire is actually cut, it may be impossible to repair. Two, the tire must be made air-tight; and three, the exposed cords (which may be steel) must be protected from the elements. A patch will keep the tire air-tight, but leaves the actual puncture open to the elements. Water or debris can get in and lift the patch from the inside of the tire, as well as corrode or deteriorate the exposed cords. A plug repair will protect the exposed cords, but is not the greatest at sealing the tire for extended use. Provided the tire is not excessively damaged, a plug patch seals the tire in addition to protecting it from further damage.
The safety issue is that a plug repair alone, or a patch repair alone, is more subject to a sudden failure and loss of air pressure, which could easily lead to a crash. While the plug patch repair is what tire manufacturers recommend, it is also the proper repair according to the NHTSA, based on studies of tire safety — and “data of catastrophic tire failures,” I’m sure. With all that in mind, we log a lot of miles on bikes and have had our share of flat tires. Our standard procedure is to plug the tire temporarily to return to the shop, and then replace the tire as soon as possible. I don’t have any experience with a plug patch repair, but I would be comfortable with that for everyday street riding. For any kind of track use, however, I would still opt for replacement rather than any kind of repair. SR