hood@thehut.DEC (Stupid computer tricks) (11/16/85)
I've got a wobble. In March I replaced the stock tires on my bike (84 Honda Nighthawk-S) with a pair of Dunlop Sport Elites. For the entire spring and first half of summer, I was convinced that the folks at Honda designed the bike around these tires. Steering, braking, handling, everything improved dramatically. Toward the middle of summer, I started getting a back-and-forth (right- to-left) shimmy in the handle bars from about 30 to 45 mph. Not enough to affect the ride at all, but enough to be damned annoying. As time went on, the wobble got more pronounced. It still didn't affect handling, but it did get more and more annoying. I've tried checking fork pressure, wheel balancing, rear shock adjustment, and a few other things. At the suggestion of my mechanic, I increased tire pressure from 30psi to about 35. This cut the wobble quite a bit, but still didn't eliminate the problem. (The mechanic also has a Nighthawk-S, on which he put either Metzler or Michelin soft tires, and also has a bit of a wobble now.) I talked about the problem a bit to a guy who runs a motorcycle tire store (not where I bought mine) who suggested doing all the things I checked, and also recommended against using "aerosol donkey snot" in the tires. He mentioned that sometimes he just gets a bad tire that causes wobbles for no apparent reason, but because mine didn't wobble until a couple of thousand miles, that it might not be the problem. The tires aren't showing any signs of unusual wear or anything, and everything on the bike seems to be ok. Any suggestions? Tom Hood DEC, Littleton, Mass. via whatever path works
stuart@rochester.UUCP (Stuart Friedberg) (11/18/85)
> Toward the middle of summer, I started getting a back-and-forth (right- > to-left) shimmy in the handle bars from about 30 to 45 mph. Not enough to > affect the ride at all, but enough to be damned annoying. > [...] > I've tried checking fork pressure, wheel balancing, rear shock adjustment, > and a few other things. [...] You didn't mention checking the steering head bearings. I know from sad experience that they can get incredibly loose through inattention. Of course, you probably *did* check them among the "few other things". Dumb story: The first time I drove into Pittsburgh it was the middle of the night but they had a lot of construction and traffic on the loop around the city anyway. I remember thinking "These potholes are horrible! Funny, they don't *look* so bad. It must be the arc lights they're using for the road work." After getting to a friend's house and crashing (on a couch, not the road) for the night, I went out to prep my bike for the next leg of my trip. Uh. Wow. 1 and 1/2 inches of slop at the wheel from bearings that probably hadn't been on speaking terms for 500 miles. If the wheel hadn't fallen from side to side when I turned the handlebars, I *still* wouldn't have noticed even then. Dumb, but true. I think I got to my friend's place about 30 miles from a REAL catastrophe. Now I check my steering head bearings periodically. Stu Friedberg {seismo, allegra}!rochester!stuart stuart@rochester
marauder@fluke.UUCP (Bill Landsborough) (11/21/85)
In article <1458@decwrl.UUCP> hood@thehut.DEC (Stupid computer tricks) writes: > >I've got a wobble. > >In March I replaced the stock tires on my bike (84 Honda Nighthawk-S) >with a pair of Dunlop Sport Elites. For the entire spring and first >half of summer, I was convinced that the folks at Honda designed the >bike around these tires. Steering, braking, handling, everything improved >dramatically. > >Toward the middle of summer, I started getting a back-and-forth (right- >to-left) shimmy in the handle bars from about 30 to 45 mph. Not enough to >affect the ride at all, but enough to be damned annoying. > >As time went on, the wobble got more pronounced. It still didn't affect >handling, but it did get more and more annoying. > >I've tried checking fork pressure, wheel balancing, rear shock adjustment, >and a few other things. At the suggestion of my mechanic, I increased >tire pressure from 30psi to about 35. This cut the wobble quite a bit, >but still didn't eliminate the problem. (The mechanic also has a >Nighthawk-S, on which he put either Metzler or Michelin soft tires, >and also has a bit of a wobble now.) > >I talked about the problem a bit to a guy who runs a motorcycle tire >store (not where I bought mine) who suggested doing all the things I >checked, and also recommended against using "aerosol donkey snot" in >the tires. He mentioned that sometimes he just gets a bad tire that >causes wobbles for no apparent reason, but because mine didn't wobble >until a couple of thousand miles, that it might not be the problem. > >The tires aren't showing any signs of unusual wear or anything, and >everything on the bike seems to be ok. Any suggestions? > > Tom Hood > DEC, Littleton, Mass. > via whatever path works I have had tires which were like that and what I finally found out is really strange. The tire was balanced in the round sense of rotation but was not balanced in the sense of side to side rotation! For example, picture sitting on the motorcycle and looking at the front tire. The top-left part of the tire is heavy and the bottom-right is heavy. Put this tire on a balancer and it will be balanced. But run this tire and it will wobble violently (depending on the degree of unbalance). I found it by raising up the front wheel and spinning the tire very fast (about 40mph) with a grinder motor, and then feeling the handlebars. However that might not be your problem. Some bikes have a steeper steering rake than others and they do wiggle, especially when you let go of the bars at speed. Also handlebar mounted fairings will cause a wiggle. Bill Landsborough "Love is patient and kind; love is not jealous or boastful; it is not arrogant or rude... Love bears all things, believes all things, hopes all things, endures all things." 1 Corinthians 13:4-7
ralphd@teklds.UUCP (Ralph Durtschi) (11/21/85)
> > I've got a wobble. > > Any suggestions? > Does the bike have pressurized front forks? I know of a bike that lost some air pressure in the front forks which dropped the front end a little and made the fork angle steeper. This caused the front end to wobble at certain speeds (about 40). The wobble got worse when going down hill. That was a scary crotch rocket until we put some more air in the front forks. That cured it. I can also imagine that raising the back end some how would have the same effect. Bye, Ralph "Wishin' no road rash on anyone"
spud@olivee.UUCP (John Purser) (11/21/85)
> > Toward the middle of summer, I started getting a back-and-forth (right- > to-left) shimmy in the handle bars from about 30 to 45 mph. Not enough to > affect the ride at all, but enough to be damned annoying. > > As time went on, the wobble got more pronounced. It still didn't affect > handling, but it did get more and more annoying. > I've had this problem occur with several brands of tires, and have always found it related to front tire wear. I use the front break in a big way and have found that the rubber to the rear of the tread wears more rapidly. When the tread is not symetric across the tire this wear pattern leads to the shimmy in the bars. In my experience the problem has always been in the 30mph range and more pronounced when I'm slowing down. It's never proven to be a hazard but its also not pleasant. The fix has been a new front tire. John Purser Olivetti ATC Cupertino CA. < I do know how to spell if, then, else, while, ... >
mazlack@ernie.BERKELEY.EDU (Lawrence J. &) (11/23/85)
>>I've got a wobble. >> >> >>The tires aren't showing any signs of unusual wear or anything, and >>everything on the bike seems to be ok. Any suggestions? > >I have had tires which were like that and what I finally found out is >really strange. The tire was balanced in the round sense of rotation >but was not balanced in the sense of side to side rotation! For Sounds like a wobble I've once or twice. My wobbles came after I had fixed a flat myself. The wobble came about because I didn't reseat the tire properly on the rim. Redoing it by deflating the tire and moving it around the rim a little solved the problem. ...Larry Mazlack