Springer vibration at SLOW speeds...

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OckMock
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Springer vibration at SLOW speeds...

#1

Post by OckMock » Sat Aug 29, 2009 7:09 pm

All:

Im having a bit of a quandry trying to figure out a vibration problem with my springer. I have a mid-30s VL springer freshly rebuilt and am running a drum brake (relatively new drum and brake linings) on a 21" wheel with converted (to timkens) star hub wheel.

Here's my problem...

When slowing down to about 5-10mph, coming to a stop, I get a very heavy vibration coming from the front wheel and/springer. I can feel it in the handlebars. This vibration happens when I am braking with both the front and rear brakes and when ONLY applying the rear brake. I thought it might be front brake drum related, but I still feel the vibes whether or not Im applying the front brake.

-Ive checked tire pressure - to spec.
-Ive checked front wheel spokes - to spec, not loose.
-Ive checked for excessive wheel bearing play - to spec.
-Ive checked springer rocker bolts and top nuts holding springs - tight and to spec w/red loctite
-I've checked brake shackle bolts - tight and to spec.
-Everything has been greased on the springer
-Axle is tight and checks out fine.

Could this be a condition of neck bearings?
Could it be some weird harmonic thing due to a frame or crack in the forks?

What are the symptoms of shot neck bearing or frame crack(s)?

Again, this ONLY HAPPENS when Im coming to a stop...this does not do it at speed and it is not a "wobble" that causes the bars to shake...it feels more like a vibration at the wheel.

Any ideas or something Im missing???

Thanks.



james
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Re: Springer vibration at SLOW speeds...

#2

Post by james » Sat Aug 29, 2009 10:53 pm

I would start by checking both your front and rear brake drums to see of they are out of round, are there rust spots on the drum to brake surface? Sounds like a brake pulsation.
Are the drums tightened evenly on the hubs. Is there excess paint on the hub or drum making it mate together unevenly. Your not going to like what I say----take it apart again....

jim

Bosheff
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Re: Springer vibration at SLOW speeds...

#3

Post by Bosheff » Sun Aug 30, 2009 12:29 am

Is this problem you are experiencing coming after a fresh complete build-up, or front end swap or what? Please be more specific. Explain any major changes before problem presented itself. Check frame thouroughly for cracks or broken welds.

OckMock
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Re: Springer vibration at SLOW speeds...

#4

Post by OckMock » Sun Aug 30, 2009 2:41 pm

Had tins off for paint and other assorted tasks and hadnt run the bike in a few months. To be honest, when last I rode the bike before paint, I cant remember that vibration being there.

During the wait for paint, I removed the wheel, greased everything and changed a bad brake cable...thats it.

Tonight I will pull wheel and inspect everything and see if I can see if anythings up with the springer rockers yet again. Additionally I will check the drum bolts as I hadnt checked the torque on them.

I will also re-torque all of my motor mounts and see if I can examine frame for the cracks.

This really has me stumped.

john HD
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Re: Springer vibration at SLOW speeds...

#5

Post by john HD » Sun Aug 30, 2009 5:16 pm

are your brake shoes properly chamfered? the leading edges need a 45 degree bevel on them.

otherwise they may be self applying and will vibrate as you describe.

john

OckMock
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Re: Springer vibration at SLOW speeds...

#6

Post by OckMock » Sun Aug 30, 2009 5:18 pm

Yes, they are chamfered.

stroker93
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Re: Springer vibration at SLOW speeds...

#7

Post by stroker93 » Sun Aug 30, 2009 7:19 pm

It seems that you have a good grasp of the drum breaks and such,,,I've messed with springers over the years (straightening,,removing derakes,,legnthening,,ect) what is te rake??A differnt wheel will change the trail,,,if it only happens with braking ,,use the motor too rapidly slow you down to see if symptoms are still present,,,could it be a vibration in the rear leg caused by sudden slowing of inertia in front wheel????..
Dave

OckMock
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Re: Springer vibration at SLOW speeds...

#8

Post by OckMock » Sun Aug 30, 2009 9:13 pm

As i said above...it happens with front brake applied and when NOT applied, as Im rolling to a stop...it happens either way.

james
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Re: Springer vibration at SLOW speeds...

#9

Post by james » Fri Sep 11, 2009 1:07 pm

I'm curious, did you find the problem?

jim

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Re: Springer vibration at SLOW speeds...

#10

Post by FlatHeadSix » Fri Sep 11, 2009 4:37 pm

Could it be some weird harmonic thing ?
Gabin,
Its not a weird harmoinic thing, it IS a harmonic thing, plain and simple.

All springers by their very nature (springs under tension) will have harmonic vibration, the trick is being able to control it. Those springs are similar to a guitar string and they can be tuned so that they "sing" or "ring" together in harmony instead of working against each other. With the bike sitting still in your garage, not running, you can "pop" the end of the handlebar with the heel of your hand and then place your fingertips lightly on the grip, you'll feel a vibration until the harmonic waves die down. If its real quiet in your shop you should even hear it hum. In your case something is "plucking" your springs and setting up an unharmonius vibration because the springs are not "tuned" correctly. Anything could set this off, a rough spot in a wheel bearing, an out of balance rim, or uneven tire tread.

I would almost bet that there is no ride control or steering damper on your bike, if that is the case you will only be able to cure your problem by experimenting with the amount of tension on your springs. Try running the nuts on the spring rods up or down a little at a time and see if this changes anything. Do you have all 8 springs installed?, are they the original type of springs for a VL fork. The inner cushion springs on the VLs were straight instead of bowed and they should have an additional flat piece of spring steel inside them to keep them from rattling, there are flats milled into the spring rods to hold anti-rattle spring.

keep us posted

mike

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