Vibration while coasting

[Minivanman]

I've got a 2006 ST1300 that's getting near 60,000 mi on it. I'll say on the outset that it has some Dunlop road Smart 3 tires. I bought them for a tour up into Canada and by 2000 mi I thought they were garbage. The problem I have may or may not be related to them. The reason I think they're garbage is because they wander all over especially at high speeds and are very fickle around tire pressure. I mention all this just because it might be related to the issue.

The issue itself is that the bike has a vibration that happens at highway speeds when I pull in the clutch or when I'm simply in the in between space between accelerating and decelerating. So when there's no pressure on the drivetrain I feel a vibration. My thought turns to something in the drive shaft or if the rear hub has rubber spacers or rubber bumpers in there. There's probably a threat on this already but I couldn't find it. But over the winter I plan to put new tires on it and address whatever this issue is and I'm curious if anyone has some thoughts on that.

On another note, I rode it this morning because my truck is in the shop. It was 35° out. Which is a little too cold even for my heated grips. And I do love this bike. It is so sweet to go get on a machine that is so smooth and powerful and comfortable and inviting to just go and go and go. So far this is absolutely my favorite motorcycle. Thanks in advance.

 

[core-aggie]

Well, I'd check for the obvious ...
Check for cupping or other odd wear
Check for any foreign object stuck in the grooves
Get tires off the ground and while spinning them, give a visual inspection
Check the wheel balance
.

 

[dwalby]

when you pull in the clutch the bike is still traveling at the same speed as just before you pulled it in, so if it were the tires you wouldn't expect anything to change if the speed didn't change.

Based on that, it sounds more like a drivetrain issue, possibly U-joint.

 

[dduelin]

I get by with 78% nitrogen.

 

[ST-Traveler]

Is the vibration in the handle bars?

 

[jfheath]

@dwalby is correct about that - but don't dismiss tyre problems in favour of drive train because when you pull the clutch in you are removing engine vibration and engine noise. Which makes tyre noise and tyre vibration more noticeable. Vibration always feels worse when you can hear it. I'd eliminate the cheapest suggestion first !

60,000 miles isn't much to be having drive train issues in my experience.

 

[core-aggie]

60,000 miles isn't much to be having drive train issues in my experience.

... agreed on that !

 

[SMSW]

Drive train, as Doug suggested, or wheel bearings on their way out. If you think the tires are garbage, replace them and see if the vibes follow them. You might also have the tires spin balanced by someone who is competent to do that. A performance shop near me does that and is very reasonable $-wise. An independent bike shop around here also does spin balancing - these folks are around. You just have to find them.

 

[dwalby]

yeah, I was quick with the diagnosis, but if it were my bike I'd be waiting on the next tire change before tearing into anything mechanical, just to rule out a simple (and no cost) cause first. Unless the vibration is quite strong, in which case I'd probably admit its not the tires and address the drivetrain issue before it makes things worse. Not knowing how much vibration the OP is feeling, its hard to say.

 

[Jethro]

After 10 miles or so of not using brakes,pull over .Stop. Carefully feel both front & rear brake rotors for high heat.Metallic smell?Brakes dragging?(At your home base)- - Rotor Bobbi’s frozen?Just some thoughts.

 

[Igofar]

We have a winner! (Jethro)
Get a large flange bolt & nut, snug them down on the bobbins on your rotors, and spin them (air ratchet or battery operated impact) while spraying brake cleaner on them.
You'll be amazed at all the brake dust and rust that will flow out.
I bet this will fix your vibration.

 

[dduelin]

Vibrations attributed to tires or wheels should be apparent at speed regardless if the clutch is engaged or disengaged. A vibration caused by brake disks is usually noticed when the brakes are applied. Brake disks so out of true they cause vibration w/o brake application have nothing to do with load on the drive train and would be noticed whether or not the clutch is engaged or disengaged at speed. That would be conventional wisdom as is a vibration that is present when load is removed or applied to the drive train is likely caused by wear or failure of a drive train component. U-joint failure at 60,000 miles is rare but not unheard of. One thing I did (and do) regularly at the suggestion of acedantinne was to lightly rest my right heel against the passenger foot peg hanger when running at speed and feel for a throb or vibration that changes when throttle application is changed. Another member here that suffered U-joint failure at relatively low miles felt a vibration in the right foot peg for some time before the final failure which took out the swing arm. Another member caught impending U-joint failure when turning the rear wheel with the bike on the center stand. A "catch" was noted where the U-joint caught up during slow rotation. It would rotate but take extra effort at points during the rotation. Another thing I do often is press on the rear caliper to open the pads and remove all drag on rotor then start the COLD engine in neutral. I watch the rear wheel. Due to gearbox oil drag on the gears the rear wheel should start to turn slowly and evenly even in neutral. A rough spot in one of the U-joint needle bearings will prevent the wheel from rotating or cause uneven rotation. Don't put the bike in gear for this examination. Shaft drive bikes will make clunking drive train noises if the bike is idling in gear. Small clunking or clacking noises when running the rear wheel in gear on the center stand are normal and due to slight idle speed changes working through every bearing and gear that has play or lash so don't test the bike in gear on the center stand or else you will think the drive shaft is coming apart. Failed or disintegrating driven flange bearings can also cause an off throttle vibration and these bearings often fail at less than 30,000 miles.

 

[Al Gully]

I'd be putting my money on the triple tree bearing preload or a faulty tire.
Does your steering stem bearings feel notchy.

 

[Minivanman]

I get by with 78% nitrogen.

What do you mean ?

 

[Minivanman]

Is the vibration in the handle bars?

And the vibration is more coming from under the seat.

 

[Minivanman]

This forum is priceless. I will check the headset bearings and I can say that when I start the bike on the center stand with the back wheel up in neutral it does slowly spin the wheel. I think step one is to replace these tires. But I'll probably also take a ride in the cold just to get a refresh on what exactly I'm feeling and where. Before the snow flies. Well I have everybody here, what tires are people running besides the road smart by Dunlop?

 

[Al Gully]

Well I have everybody here, what tires are people running besides the road smart by Dunlop?

Only ran Bridgestones since 2009, T32 GT's currently, kind of the 2023 models made by them.
Never had vibrations with any of the previous compounds and like running with my cruise on, no hands on the bars and as smooth as silk at 70 mph.

 

[core-aggie]

what tires are people running besides the road smart by Dunlop?

Had a catastrophic failure with a rear "road smart" (obviously an oxymoron) years ago, so would NEVER use them again.

Not to turn this into yet ANOTHER tire thread, tire choice is all about how you ride and the roads you ride.

The weekend rider on a country ride to lunch is WAY different than the daily rider and maybe in the twisties.

 

[diferg]

The air that we breathe is 78% nitrogen

 

[Sadlsor]

The air that we breathe is 78% nitrogen

Thank you!
I was reading this initial mention by Dave about N (the chemical symbol of nitrogen) and no one caught it.
I'm no chemist, far from it, but even in my addled, brain-fogged first-cup-of-coffee statelessness of mind, I knew what he meant.
The air in Earth's atmosphere is made up of approximately 78 percent nitrogen and 21 percent oxygen. Other ingredients are just trace gases hardly worth noting.
Unless you ARE a chemist, I suppose.
I remember 78% from school, oh so long ago, when we learned a little bit about science, and not so much about transgenderism and CRT.
And also learned it from being SCUBA-certified, which was also quite long ago. Air is important to divers, so ya gotta pay attention to it.
I have the option of filling my tires with N for free at Costco with their customer air stations, but rarely do. I understand the N molecules are larger than oxygen and thus your tires lose less "air" than from standard air tanks.
But as I said, I'm no chemist, so I have been unwilling to try to prove or disprove that statement.
Good morning, everyone!