Triumphrat

JasonS · 06-18-2007, 09:20 PM

When I was coasting down a hill the other day, I let go to ride hands free , the hill was steep enough to maintain 35 or so and the bars/wheel started to wobble left/right. It could be prevented witha light touch on the bars, but can be reliably repeated. Tire is at 5500 miles, but tread wear is even. Rear is squared off and a new set is on the way.

my guess is the weight I lost on the front wheel has me slighty out of balance, which cretaes an occilation effect... but I'd be interested in hearing other ideas....

idahotb · 06-18-2007, 10:59 PM

My '96 Sprint does the same thing, but the TBS doesn't. New tires seem to help for a while but not for very long. My theory is that it's the fairing. Once it goes a little off the line of motion, it spill air on that side like a wing or a sail. The air pressure differential moves it and the bars back the other way, across the center due to inertial, where the process starts all over again. I don't have a clue how acurate this theory is, but it works for me.

motocyco · 06-19-2007, 12:06 AM

I hope this isn't the dumbest question ever, but when you do the "no hands thing", is the bike in neutral or what? Thanks

parrycm · 06-19-2007, 01:34 AM

My 95 does it between approx 40-45, more so on closed throttle and decelerating than if I apply the throttle lock to keep the speed constant but it still happens.

I've had the head and wheel bearings checked - no problem there. I've wondered if it's a function of the wavy centre groove on the Avon Azaro ST45 but like the stiction and wear too much to try another brand. The new Storms that replace the Azaros don't have that wavy groove so I might find out next time I change.

Not detectable unless hands off so the solution is too keep the hands on.

No - not in neutral! Going through the gears with the clutch in at that speed is not good for the transmission.

[ This message was edited by: parrycm on 2007-06-18 23:37 ]

JasonS · 06-19-2007, 10:02 AM

to clarify...

I note this on closed throttle, in gear, in effect coasting against the engine braking effect.

Interesting that this effect seems to be noted by others...

Mojoinco · 06-21-2007, 05:26 AM

I have had similar things with other rides over the years, usually all are related to wear patterns. Some even made noise at certain speeds. When decellerating the front suspension will be slightly compressed, changing your rake/trail numbers making it more sensitive to changes/wear patterns. And if you are missing a balance weight, a harmonic (poor choice of word) would certainly be expected. Try rolling your tire over some powder/dirt on a flat surface. You might be surprised at the wear pattern (slight cupping of the front tire from braking) as evidenced by the light/dark spots on the tire.

dazco · 06-21-2007, 02:31 PM

I think to a degree this is normal for most any bike with any miles on it. As soon as the tire starts to waer and the entire front end starts to wear i believe it's normal. It's abnormal past a certain degree. But i think most any bike aside from new (and probably even some new ones) is going to do it to a normal degree, which from what you described IS. Mine does it too. It's a fine line, that perfect balance of everything. And i believe within the first few K miles any bike's perfect balance is going to change to a small degree at least and have the same symptom.

TonyD · 06-21-2007, 06:34 PM

According to MCN's resident 'expert', Chris Dabbs, in answer to virtually the same question Jason poses:

'A lot of bikes have a resonant frequency when any surface imperfection is enough to set off a shimmy which will get worse if you don't hold on. It is usually between 50-40 mph as you slow down because that's the time when riders ease their grip when they come off the throttle. It's a fact of life on most bikes and shouldn't impinge on your enjoyment as long as you are not in the habit of riding along with your hands crossed nonchalantly behind your head.'

[ This message was edited by: TonyD on 2007-06-21 16:35 ]

JasonS · 06-22-2007, 12:30 PM

...thanks for all the good feedback!

SaddleTramp · 06-29-2007, 04:10 PM

Quote:

On 2007-06-18 19:20, JasonS wrote:
When I was coasting down a hill the other day, I let go to ride hands free , the hill was steep enough to maintain 35 or so and the bars/wheel started to wobble left/right. It could be prevented witha light touch on the bars, but can be reliably repeated. Tire is at 5500 miles, but tread wear is even. Rear is squared off and a new set is on the way.

my guess is the weight I lost on the front wheel has me slighty out of balance, which cretaes an occilation effect... but I'd be interested in hearing other ideas....

It's normal. A motorcycle really never travels in a straight line, it constantly leans one way and then the other ...