blarson Posted August 21, 2007 Report Share Posted August 21, 2007 The longer I've been riding the more I've begun to take notice that the more rapidly I change direction the faster the rear end of my bike pitches to the side. This accompanied by a sudden tightening of the line I'm taking through the corner without any additional steering input. This characteristic displays itself only when I change direction quickly and with a fair amount of lean angle and sometimes manifests with the additional feeling of the rear end tucking under (twisting feeling). None of these odd characteristics apply at modest (street legal) cornering angles. Obviously, the amount of variables that might be contributing to this steering characteristic are indescribable within the confines of this forum. However, I'd greatly appreciate if some of the more knowledgeable individuals would take a crack at some of the possible explanations. Unfortunately, the advice I receive will be the best bet I have for figuring this out as I cannot afford any riding school until I finish my bachelors degree and make some money. That being said, here are some details(and my life story) that may help with analysis. This bike in question is a 01' ex500 that is mostly stock in hardware except for the forks being filled within the last 2000mi with 20wt oil. The tires are have only about 2000 miles on them and less than a month old they do not display any cupping or deviation from the original profile. The front is a dunlop qualifier and never feels like it's pushing unlike the pirelli sport-demon tire I had on just before. The rear is a dunlop D208SM sized one up (130x70 to 140x70) from stock. I would have never up sized the rear tire except that doing so was the only way I could put a radial tire on the bike. With these tires the bike will hold at least 10 degree more lean angle without feeling upset compared to the bias ply tires on there before. I run high 20's-low 30's for pressure in the rear and changing tire pressure does not seem to change the aforementioned handling issue. Sag is set correctly. The rear shock is past it's prime leading me to believe that it is at least in some way responsible for the tucking feeling but does not explain the sideway pitching. This bike has been my daily driver for over a year but I won't rule out rider error. That being said, I have made every effort to isolate any action on the bars by holding the bike with my lower torso to the best of my ability. My body weight is around 200 pounds wearing full gear. I am also generally riding straight up and without hanging off although the problem is still there when I hang off as well. Off throttle application is as smooth as I can make it from near the apex of the turn. The bike generally reacts smoothly when I put on the gas mid corner. I don't feel the rear tire sliding nor am I laying down any rubber. My relatively (un)educated guess is that I am experiencing a high degree of chassis flex due to increased cornering loads from the modern tires. This explains to me why the line would tighten as well as why it would pitch to the side. I think the twisting or washing out feeling might be from a combination of mis sized tire and crappy shock and unrelated to the pitching. Ohh wise ones, what do you think? Sorry for the novel. Thanks for the advice. Quote Link to comment Share on other sites More sharing options...
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