19775 From: Rick Carnevale <
[email protected]>
Date: Fri May 7, 2004 10:14am
Subject: HIGH SPEED WOBBLE!!!
OK guys, I need some help with this one. I experienced a high
speed wobble yesterday that required a laundry check, if you know
what I mean!! I have never had this problem before so I will start
at the beginning.
My bike is a 1996 SB Boss Hoss. It has had a car rear tire since
new and I never had a problem with it. It was a Bridgestone SF108.
The size was a 215/70 R15 and the speed rating was "S" which is only
rated at 112 mph. This was the factory installed tire that came with
the bike. I recently made many changes to the bike but the only
thing that I think could be causing this wobble is the rear tire that
I changed to. I now have a Uniroyal Laredo 235/70 R15 with the same
speed rating as the Bridgestone I took off. I am told that this tire
is made by Michelin and is a good tire. I am also told that Michelin
makes the best riding tire (for a car) and that maybe the sidewall is
too soft for a motorcycle application. I also replaced the front
tire with the same exact kind of tire that I had on it. A Metzeler
Marathon 880. Both tires where high speed balanced and I don't think
the problem is there either. No other changes where made to the
front end of the bike. I did change from a clutch to a single speed
auto with new style pulleys and belt but I don't think any of this
could be the problem. I plan to check the alignment of the rear
wheel to the front with a lazer line level that I just purchased but
I think I will find that to be good too. I am able to ride with no
hands and the bike tracks dead straight. Here is the other weird
thing. I can cruise the bike at 85 to 90 mph with no wobble. But if
I am accelerating with wide open throttle and I go through that speed
range, it goes into a real nasty wobble. I know for sure that the
swing arm bushings, rear shocks, and all that stuff are good because
I just had all that apart and checked everything. I even put all new
wheel bearings in both wheels. The wobble is not in the front end.
The handlebars do not shake. The whole bike seems to try to flop
from side to side. Not fun. It does not come out of the wobble by
useing the rear brakes either. I just had to hang on and let it slow
down by itself. It straightened out at around 70 mph. Everything I
have written here seems to point to the tire but I would like to hear
from others that have had some experience with this sort of thing.
Lastly the air pressure. I used to run 28 to 30 psi in the old tire
so I set this one the same. Then I read where several people said to
run around 36 psi in the rear (car) tire to PREVENT a high speed
wobble. So that is what I had in it. 36 in the rear and 46 in the
front. What is happening here??????? Puzzeled but lucky to have
not crashed!!!!!!!!!!!!!!!!
Rick