Shake During Deceleration?

[The1970's]

After riding the bike some more I'm not quite sure the steering head bearings fixed it. It seemed better at first but now is shaking again. Im heading out to check if they came loose now. But I think I'm going to settle at the conclusion that either:

The rear wheel is out of balance, or

The mismatched tires are causing it

It seems to be just below 60 mph every time when decelerating, leaving me to think it is out of balance.

[willie]

Happened upon this thread and couldn't agree more with the advice to get rid of the Dunlop tire. I had a head shake problem with an 1150ES many yrs ago. Checked everything including having the frame examined on a laser table. I was a big fan of Dunlop at the time and a fresh front Sport Elite would cure the problem, for about 500-750 miles. Then, the problem would return. I couldn't believe it would happen after so few miles but it would with every new Dunlop.

[RichDesmond]

After riding the bike some more I'm not quite sure the steering head bearings fixed it. It seemed better at first but now is shaking again. Im heading out to check if they came loose now. But I think I'm going to settle at the conclusion that either:

The rear wheel is out of balance, or

The mismatched tires are causing it

It seems to be just below 60 mph every time when decelerating, leaving me to think it is out of balance.

It's not the steering head bearings.
What you're feeling is a decel wobble, very common phenomenon. You can make it go away by tightening (actually overtightening) the steering head bearings, to the point that they start to act as a friction steering damper. Not a good solution.

Root cause is generally one (or both) of two things. The first is the front tire. Most front tires when they're worn, and some when they're brand new, will lead to it. I've had two different tires on my Strom that were horrible for the decel wobble, a Tourance and a Conti Road Attack. Went back to a Pilot Road and all was well.
The other is a worn rear shock. As the miles add up the rebound damping in the shock deteriorates and allows the rear of the bike to cycle up and down. That motion feeds forward to the front of the bike and starts the oscillation.

[The1970's]

It's not the steering head bearings.
What you're feeling is a decel wobble, very common phenomenon. You can make it go away by tightening (actually overtightening) the steering head bearings, to the point that they start to act as a friction steering damper. Not a good solution.

Root cause is generally one (or both) of two things. The first is the front tire. Most front tires when they're worn, and some when they're brand new, will lead to it. I've had two different tires on my Strom that were horrible for the decel wobble, a Tourance and a Conti Road Attack. Went back to a Pilot Road and all was well.
The other is a worn rear shock. As the miles add up the rebound damping in the shock deteriorates and allows the rear of the bike to cycle up and down. That motion feeds forward to the front of the bike and starts the oscillation.

I think you're definitly on the right track, I was talking to some of the guys over on the Honda SOHC4 forum and those bikes and particular are very sensitive to the new style tread patterns. I've ordered a Shinko 230 for the front as well. I'll report back when I get it installed

[RichDesmond]

I think you're definitly on the right track, I was talking to some of the guys over on the Honda SOHC4 forum and those bikes and particular are very sensitive to the new style tread patterns. I've ordered a Shinko 230 for the front as well. I'll report back when I get it installed

Just keep in mind that as the shock damping fades over time, the bike will exhibit this tendency more and more, until eventually it will do it to some extent no matter what tire you have.
As for tires, I think it has less to do with tread pattern and more with carcass stiffness and damping characteristics.

[wymple]

Just balance the front wheel.

[The1970's]

Just thought I'd give an update to this thread. I finally got around to installing my Shinko 230 on the front and it took care of maybe 80% of the shake but there is still just a faint wobble decelerating through 40mph. I have made sure both wheel are running true and the tires are not out of round. I have ordered some of the tire balancing beads to try out. I don't really think they will fix it but I wanted to try them anyway. I'm beginning to think that it is in the rear dampening as Rich suggested. This would make sense as to why it started when I replaced the rear tire with a stiffer sidewall tire

[chuck hahn]

1 ounce in front tire and 2 ounces in rear tires.

[red1100]

Here’s something to think about. 83 GS 1100E.If I let go of the bars I’ve got a wobble that starts at about 25-30 and would continue to a tank slapper if I let it go. Got Dunlop 404s everything solid and tight. Have a slipstreamer windshield,quick release. Checked everything numerous times but nothing was out of spec. Was going to buy new shocks ,front springs and seals and do a tear down,rebuild. On a very nice warm evening I went for a ride and left the windshield at home. Wobble gone! I even tried to force it to wobble at 50 mph and it self centered instantly. It’s the windshield causing the problem even though I measured 3 times to get it straight. As long as I hold on to the bars even,with no real force, it tracks perfectly.

[The1970's]

Here’s something to think about. 83 GS 1100E.If I let go of the bars I’ve got a wobble that starts at about 25-30 and would continue to a tank slapper if I let it go. Got Dunlop 404s everything solid and tight. Have a slipstreamer windshield,quick release. Checked everything numerous times but nothing was out of spec. Was going to buy new shocks ,front springs and seals and do a tear down,rebuild. On a very nice warm evening I went for a ride and left the windshield at home. Wobble gone! I even tried to force it to wobble at 50 mph and it self centered instantly. It’s the windshield causing the problem even though I measured 3 times to get it straight. As long as I hold on to the bars even,with no real force, it tracks perfectly.

Interesting anecdote, I still haven't completely solved my problem. Everything I have done so far seems to help a little bit but the shake is definitely still there. My bike tracks perfectly straight, so I think we are experiencing different issues. It just seems as if the suspension is bouncing at around 45 MPH. It has now started doing it when cruising and decelerating, but not when accelerating. After looking VERY carefully at the rear wheel/tire, it seems that it may be just slightly out of round. I am not sure if this is the wheel or tire causing it, but I figure I will look into it when I am ready for a new rear tire and go from there.

[red1100]

Most every “bounce” situation I’ve had has been out of round or out of balance. Had a Super gas 71 Duster start shaking the slicks at speed turned out the wheel weights were not taped and came off. I have a 53 Buick restomod that has some custom wheels,one was .015 out of round and caused a shake.

[jabcb]

+1 on the tire issue.


Some time ago my CB650 Nighthawk was fine except for a worn out front tire. Had a new front tire mounted that a local shop had in stock. It then developed the deceleration shake that seemed to be worse when going down hill. Took the bike in, had the bearings checked and a different front tire installed. Its OK again. (Since then I've read that some of the Nighthawks are picky about their tires.)


After that I tried to cause the shake to occur. Positioning my butt off to one side so that the bike is tilted a bit sometimes causes the deceleration shake.

[The1970's]

+1 on the tire issue.


Some time ago my CB650 Nighthawk was fine except for a worn out front tire. Had a new front tire mounted that a local shop had in stock. It then developed the deceleration shake that seemed to be worse when going down hill. Took the bike in, had the bearings checked and a different front tire installed. Its OK again. (Since then I've read that some of the Nighthawks are picky about their tires.)


After that I tried to cause the shake to occur. Positioning my butt off to one side so that the bike is tilted a bit sometimes causes the deceleration shake.

I'm thinking it's the rear tire, what I don't know is if I got a bad tire or if my rim is what's causing it. I can't see the rim wobble at all if I put a truing pointer on it, but I haven't taken the tire off yet to check where the bead rests, maybe there is a flake of rust or something that I missed. It is also possible that the bead has not seated properly onto the rim, once again I see no evidence of this from the outside. The only other thing I changed was that this new rear tire is a 120/90/18 vs the last one which was a 110/90/18 but I hear many other owners go with the 120 with no issue. My bike goes through rear tires fast enough for me to just wait until it's time for a new one to deal with it. I'm at maybe 50% life now. I will post an update if I find the cause.