Friday took my bike (01 FLHT) to the dealership for a new rear tire. Picked the bike up and left saturday morning for a ride with the wife. Had an odd noise from rear on bumbs so I checked and this is what I found. Cracked swing arm. I am a ford senior master tech and understand that coincidences can happen. However it appears that if the tech who replaced my tire overtorqued that axle shaft nut it may have stressed the arm. Just wondering if anyone on this site has seen this happen and if you think torque or coincidence is the culprit.

 

Coincidence? I don't know. Seems suspect.

 

It seems to me that this is not necessarily an uncommon problem for early twin cam touring bikes. I remember reading about it on HTT.

 

Actually that's a well known issue.

In 2002 HD went to a beefed up swing arm due to cracks just like yours. Over on Harley Tech Talk there are more a few folks, myself included who have done swing arm change outs. My '01 Ultra is now sporting the newer '02 and later swing arm. There are whole kits with bushings out there specifically designed for this. Here is a link to an article on this:

http://www.motorcyclemetal.com/gpage14.html

The whole thing is due to poor design. While the "box" end leaves a lot of space and room inside for crushing due to over torquing, the real culprit is the design. Since the rear shock is mounted behind the axle, the axle acts like a fulcrum with the rear of the bike teetering on one side, and the front of the bike tottering on the other side. The box design compunds this by putting a lot of strain on the thin walled metal of the box and that is where the cracking is prevelant. The newer swing arms are solid metal drop outs with no box to crush. The real fix is to upgrade to a new swing arm, or weld metal support plates on top and on the bottom of the swing arm to reinforce the areas. Otherwise you are just buying the same part that is prone to cracking.

As with all disclaimers, your experience may differ. Some folks have never had a swing arm crack, and others have been through two swing arms.

Mark

 

Thank you guys for the help.

 

Sadly, that was a common problem with the 99~01 Baggers.

As has already been mentioned, the MoCo upgraded the swingarm in 2002.

 

Maybe it was just time. Better now than when you are on the road.

 

Yes the first thing I thought when I saw it was thank god it didn't completely break on the road. We would have went down for sure.

 

Just curious...Do you have a lowering kit on it?

 

Very common on the 01 and earlier bikes. Heres another fix so you have a few options.
http://www.customcycleengineering.co...ndex&cPath=192