Softail vibration
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Road Captain
Joined: Aug 2005
Posts: 685
Likes: 3
From: South central, Pa.
Softail vibration
I've done a forum search and found people talking about high speed vibrations in Softails but nobody has really said what causes it. I have an '05 Fatboy that produces a "seat in the pants" vibration at speeds above 65-70 mph. It gets so un-comfortable on a long highway trip that I can't wait to pull off on a back road somewhere. Friends of mine with softails don't have the same problem but there are other people that do.
The only time that I've ever messed with the driveline was when I put a chrome sprocket cover on it. Before I removed the wheel though, I center punched the swingarm and washer so I could get it back in alignment correctly. I don't know if that's when the problem started or not.
Last week, I decided to take the bike to a local shop with a dyno and hoped he could find the problem. He thought it could be a wheel out of balance or a bad tire. He called yesterday to tell me he made three runs on the dyno and took it out on the road a few times. He feels some vibration when he's pulling out (I never felt it there) and found it real noticeable at speeds above 65. The low end vibration should rule the tires or wheels out and both tires still look good. He checked everything else he can think of and can't find anything wrong. Since he rides a Springer without a vibration, he's as curious as I am now. I want to re-check the rear wheel alignment again and if that looks good, I might try dyna beads in both tires to see if that helps.
1: Has anyone come up with a good wheel alignment tool that I can make ?
2: Could it be internal like the clutch or something in the drive gears ?
The only time that I've ever messed with the driveline was when I put a chrome sprocket cover on it. Before I removed the wheel though, I center punched the swingarm and washer so I could get it back in alignment correctly. I don't know if that's when the problem started or not.
Last week, I decided to take the bike to a local shop with a dyno and hoped he could find the problem. He thought it could be a wheel out of balance or a bad tire. He called yesterday to tell me he made three runs on the dyno and took it out on the road a few times. He feels some vibration when he's pulling out (I never felt it there) and found it real noticeable at speeds above 65. The low end vibration should rule the tires or wheels out and both tires still look good. He checked everything else he can think of and can't find anything wrong. Since he rides a Springer without a vibration, he's as curious as I am now. I want to re-check the rear wheel alignment again and if that looks good, I might try dyna beads in both tires to see if that helps.
1: Has anyone come up with a good wheel alignment tool that I can make ?
2: Could it be internal like the clutch or something in the drive gears ?
Banned
Joined: Mar 2007
Posts: 3,706
Likes: 7
From: Woodstock, Ont , Can
RE: Softail vibration
An easy way to find out if it's wheels or powertrain vibration is to get up to speed, add about 5mph more and pull in the clutch, and idle the engine.If it still vibrates it's the wheels, if it don't it's the powertrain.
Ron
Ron
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Road Captain
Joined: Aug 2005
Posts: 685
Likes: 3
From: South central, Pa.
RE: Softail vibration
I picked the bike up today and he said my alignment was good but he added 3/4 oz. of weight to the back wheel. He didn't think it's enough to make the difference but I'm hoping that's all it needs. I didn't have time to try the four lane but did get it up to 75 on a back road for a short stretch. It seems better but I won't know for sure until I ride more distance. Your clutch suggestion is a great idea and I'll try that tomorrow. Thanks for the advice !
Tourer
Joined: Feb 2008
Posts: 494
Likes: 1
From: Paola, Kansas
RE: Softail vibration
I can't say exactly how this relates to a bike, but I know that 1/2 oz can cause a felt vibration in a car. I would assume a bike would be more sensitive. A lot of guys underestimate wheel balance.
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Road Captain
Joined: Aug 2005
Posts: 685
Likes: 3
From: South central, Pa.
RE: Softail vibration
I had it up to around 95 mph the other night and it's running smoothe again. I can take my hands off the bars now and it runs straight without me leaning a little to the right so I'm betting my problem was a combination of wheel weight and alignment.
I'm going to make an adjustable length jig that goes from the swingarm to the axle before I mess with alignment again. Any ideas on this ?
I'm going to make an adjustable length jig that goes from the swingarm to the axle before I mess with alignment again. Any ideas on this ?
Elite HDF Member
Joined: Sep 2006
Posts: 3,718
Likes: 11
From: Punta Gorda,FL
RE: Softail vibration
I have always used a piece of string to check my alignment.
Wrap it around the rear portion of the back tire, as high as you can, but at a height that will not hit anything on the bike when you stretch it to the front tire.
Either have someone straddle the bike or use a bike lift, so you can stand the bike straight up and have the front wheel straight ahead. Pull the string forward and away from the back tire just a little. Then when you have the string pulled tight, forward of the front wheel, slowly bring the string toward the front tire until it hits the forward sidewall of the rear tire. There should be an equal gap between the string and the forward and aft sidewall portion of the front tire.
You can accomplish the same thing with a long enough straight edge. I have read where some owners use a real long fluorescent light as straight edge. You also need to block up the straight edge to as high as you can, without hitting any of the bike structure.
Tom
Wrap it around the rear portion of the back tire, as high as you can, but at a height that will not hit anything on the bike when you stretch it to the front tire.
Either have someone straddle the bike or use a bike lift, so you can stand the bike straight up and have the front wheel straight ahead. Pull the string forward and away from the back tire just a little. Then when you have the string pulled tight, forward of the front wheel, slowly bring the string toward the front tire until it hits the forward sidewall of the rear tire. There should be an equal gap between the string and the forward and aft sidewall portion of the front tire.
You can accomplish the same thing with a long enough straight edge. I have read where some owners use a real long fluorescent light as straight edge. You also need to block up the straight edge to as high as you can, without hitting any of the bike structure.
Tom
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Joined: Apr 2007
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