Author Topic: Ever so slight wobble at 45 mph  (Read 9611 times)

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Offline smithr1

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Re: Ever so slight wobble at 45 mph
« Reply #25 on: November 13, 2012, 04:01:25 pm »
Oh it's a Connie issue.   There are some bikes you can put cupped, unbalanced tires on a loose head bearing and it will never have a tank slap issue.   I have been listening to people with issues with the Concours doing this dance for 10 years.  The bike has to be set up correct to NOT do it.  That is the issue.
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Offline Jorge

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Re: Ever so slight wobble at 45 mph
« Reply #26 on: November 13, 2012, 04:18:43 pm »
I have the same issue while decelerating at that speed range. Never had it with the Dunlop front tire. I went to Avons (Storm 2 in front Azaro rear), and I started noticing it. I tried tightening the bearing and it was tight. As I tightened it more, I could start to feel friction.
Called my friend who recommended the Avons to me, and his has the same exact thing. In his opinion, the Avons are more likely to cause this than other tires because of their profile. Others have the issue at different levels, even with different tires and tight bearings.
I keep my hand on the bars not... at least most of the time  :)

Jorge

Offline Mcfly

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Re: Ever so slight wobble at 45 mph
« Reply #27 on: November 13, 2012, 10:14:04 pm »
This issue did start after I went from Dunlop to Avon, and it's no where's near a death wobble.
Having the right tool to adjust the stem, and doing so after 20k miles is just the right thing to do.  No loss.

I appreciate the heads up Jorge, if it's directly related to the tire, then that's a load off what's left of my mind.

I actually noticed it with my palm on the throttle rocker, and I went to adjust my
helmet visor with my left hand... there it was!  Immediately I figured I screwed up the wheel install.  :-[
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Offline ron203

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Re: Ever so slight wobble at 45 mph
« Reply #28 on: November 14, 2012, 01:59:31 am »
Mine started to do it with Avons then it went away for a while with Bridgestones, then came back. I think it was just progressive loosening over the miles. Now it's gone (for the moment).
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Offline Reaper1

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Re: Ever so slight wobble at 45 mph
« Reply #29 on: November 14, 2012, 02:54:50 am »
Mine started to do it with Avons then it went away for a while with Bridgestones, then came back. I think it was just progressive loosening over the miles. Now it's gone (for the moment).

 :bravo_2:
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Offline Bruiser

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Re: Ever so slight wobble at 45 mph
« Reply #30 on: November 17, 2012, 05:10:00 am »
I have to agree that the Dunlops made the wobble worse...Roadsmart...will never use them again. Also when I tightened the steering head bearing, I turned the nut only about 1/8 of a turn...that cured about 90% of my problem. Put the bike on the center stand and turn the handlebars to one side. Then just barely push them the other way...they should almost "flop" to their stop.
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Offline GeorgeRYoung

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Re: Ever so slight wobble at 45 mph
« Reply #31 on: November 17, 2012, 03:16:40 pm »
The input causing wobble is front wheel dynamic unbalance.

All bikes have a resonance (i.e. speed at which response to unbalance is greatest).

Wobble is a perceptible oscillation at the resonance point.

Whether the wobble is perceptible or not depends on the relative magnitudes of
1) input (the dynamic unbalance) and
2) damping (is the tire soggy or nimble? are your hands on the bar? is there sand in the steering head bearing? do you have a steering damper?)

http://web.ncf.ca/ag136/frontWheelWobble.htm

Offline Mettler1

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Re: Ever so slight wobble at 45 mph
« Reply #32 on: November 17, 2012, 07:48:53 pm »
  Gosh George, that sure is technical. Could you just tell me what screw do I turn?? :))
'94 Concours 115,000 miles-- 7th gear,2MM,KB fork brace,Over flowtubes,Stick coils,Tcro shifter,GPS,SiSF'sTorque cams,SPOOKFAK,block off plates, SS brake & clutch lines,KB risers, FENDA EXTENDA, emulators, SiSF carb Spa, Delkevic exhaust, Murphs' knee savers +grips, etc

Offline Mcfly

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Re: Ever so slight wobble at 45 mph
« Reply #33 on: November 18, 2012, 01:07:23 am »
George, after two 22 oz Winter Lagers, my brain turned to pudding after reading that page you linked to.   :o

From what I can gather, my circumstance is 'unique'?  I have a brand new Avon, that was
dynamically balanced...  Sooooo it was improperly balanced?  or
Even after dynamic balancing there's still a slight imbalance that at 45 mph causes
the wobble (with hands off the bars)... an ever so slight wobble, but still a wobble.

Steering stem gets adjusted tomorrow (yes, I got my new tool), so it will be interesting to see if there's any change.
I mean there is a chance.....
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Offline ron203

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Re: Ever so slight wobble at 45 mph
« Reply #34 on: November 18, 2012, 01:49:32 am »
 :popcorncouple:
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Offline GeorgeRYoung

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Re: Ever so slight wobble at 45 mph
« Reply #35 on: November 18, 2012, 03:24:57 am »
. . . I have a brand new Avon, that was
dynamically balanced...  Sooooo it was improperly balanced?  or
Even after dynamic balancing there's still a slight imbalance that at 45 mph causes
the wobble (with hands off the bars)... an ever so slight wobble, but still a wobble. . . .
Static balancing is you find the heavy point and stick weights on the opposite side until you can't find the heavy point any more. That's what I do. This controls the tendency of the tire to bounce up and down as you toot down the road.

Dynamic balancing is you spin the wheel/tire fast on a machine that measures wig-wag left and right. Then you stick weights on opposite sides until it doesn't wig-wag left and right any more. Is that what you had done? I've never done this, it's rather hard to accomplish on a frugal home setup. In your case, a small amount of uncompensated dynamic imbalance will yield a small amount of wobble.

To get rid of it, you need to increase the damping (i.e. friction). Tightening the steering head will do it (although the adjustment is critical), sticking on a steering damper will do it.

Offline GeorgeRYoung

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Re: Ever so slight wobble at 45 mph
« Reply #36 on: November 18, 2012, 03:27:28 am »
  Gosh George, that sure is technical. Could you just tell me what screw do I turn?? :))
No problem, just tighten the steering head bearing until the bars don't turn at all, then it won't wobble.

Offline Mettler1

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Re: Ever so slight wobble at 45 mph
« Reply #37 on: November 18, 2012, 04:32:23 am »
  Gosh George, that sure is technical. Could you just tell me what screw do I turn?? :))
No problem, just tighten the steering head bearing until the bars don't turn at all, then it won't wobble.

     Gotcha!!  ;)
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Offline Mcfly

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Re: Ever so slight wobble at 45 mph
« Reply #38 on: November 18, 2012, 12:29:19 pm »

Dynamic balancing is you spin the wheel/tire fast on a machine that measures wig-wag left and right. Then you stick weights on opposite sides until it doesn't wig-wag left and right any more. Is that what you had done? I've never done this, it's rather hard to accomplish on a frugal home setup. In your case, a small amount of uncompensated dynamic imbalance will yield a small amount of wobble.

I purchased the tire at a bike shop, as my old Dunlop (I wanted balanced) had a broken belt in it. 
They work primarily on Sport bikes, and use a dynamic balancing machine (he dun showed it to me). 
I probably got charged more for it too...lol.

Well I'm going to crank down that stem bearing today.  Got my new spanner and a 3 foot pipe to get
good leverage on the bugger!  >:D
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Offline Mettler1

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Re: Ever so slight wobble at 45 mph
« Reply #39 on: November 18, 2012, 02:39:48 pm »


 

 

Well I'm going to crank down that stem bearing today.  Got my new spanner and a 3 foot pipe to get
good leverage on the bugger!  >:D
    Whatever you do don't force it!!   Get a bigger hammer. >:D
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Offline ron203

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Re: Ever so slight wobble at 45 mph
« Reply #40 on: November 18, 2012, 04:26:48 pm »

Dynamic balancing is you spin the wheel/tire fast on a machine that measures wig-wag left and right. Then you stick weights on opposite sides until it doesn't wig-wag left and right any more. Is that what you had done? I've never done this, it's rather hard to accomplish on a frugal home setup. In your case, a small amount of uncompensated dynamic imbalance will yield a small amount of wobble.

I purchased the tire at a bike shop, as my old Dunlop (I wanted balanced) had a broken belt in it. 
They work primarily on Sport bikes, and use a dynamic balancing machine (he dun showed it to me). 
I probably got charged more for it too...lol.

Well I'm going to crank down that stem bearing today.  Got my new spanner and a 3 foot pipe to get
good leverage on the bugger!  >:D

Uh oh....sounds like trouble.... :TPIWWP:
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Offline DUMB A$$

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Re: Ever so slight wobble at 45 mph
« Reply #41 on: November 24, 2012, 06:57:46 pm »
I bought my bike with a Dulop on it and at 45mph I got the wobble, found the front tire was cupping for I neglected to keep the tire presser up to specs. Put on a set of Avons, wobble went away until the front tire started cupping, again because I never checked tire pressure, could hear the tire making noise in turns and knew I Had a cupped tire again. Now with a new set of Avons all is good, no wobble at 45 and turns are quiet again. I was told by the shop that mounted my tires that Avons being only 2 ply instead of 4 like other tires that they do not like to be driven on with low tire pressure. I am going to check tire pressure every weekend and keep it in specs and see for myself if this helps them last/wear longer.

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Offline Mcfly

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Re: Ever so slight wobble at 45 mph
« Reply #42 on: November 24, 2012, 11:07:26 pm »
I put my new spanner to work, and tightened up the steering head bearing.

Not much room to tighten it... I doubt I got even an eighth turn on it, and it
started to feel like it was binding.  That bad boy is as tight as it's gonna get.
(Yes I loosened the lower fork clamp bolts before I tightened)

During the test ride, the steering DID feel better, and Marty likes that.
There was a little less wobble when I went sans hands, so there was
improvement there as well.  The wobble, although there, barely exists now.

I called the shop that mounted/balanced the tire as well, and they said they'd take
a look at it this week.

So as this chapter closes, another opens, as I started smelling anti-freeze when
the fan kicks on.  Coolant level is full in the radiator and the reservoir, so I'm gonna
start by checking all hoses and clamps tomorrow... might just get all new hoses... ::)

Thanks everyone for the input!  Christmas list includes
new front springs, and a fork brace.  So I'm not done with the
front end just yet!  Hope I was a good little boy.
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