hello. I ride a 2005 s40 boulevard. Over winter I have put it through quite a bit of changes including building some hard tail struts. I went ahead and welded in an additional pipe 1” diameter 10 or 12 gauge between the swing arm and the frame for extra support. My question is how strong are the bolts that held the bottom of the shocks on. I used the stock bolts but fear them shearing off when riding. I do not think this is likely but thought I would see if anyone else has any experience here. I have added some photos of how I have the struts set up. Thank you in advance for any help. I know I have seen some info on this and it may have been covered somewhere so if I am repeating something I apologize in advance.

No problem. I have a picture attached. Thank you for the info!

Srinath, thank you for the info. Did you have any additional bracing on your Vulcan to keep the swing arm from moving? This is why I added the additional pipe between swing arm and frame so that the bike wouldn’t be able to fold up and would take a lot of the impact off the bolts, and in theory absorb it in the frame tubing. Just wondering if that extra will keep the bolts from bending.

Please tell me that passenger seat (hard to see) is just for looks. That would vastly improve your tendency to break - if the seat is just for looks. Don't be putting on a 300lb passenger on there and running down a bumpy road.
Cool.
Srinath.

Again - rigid is your enemy. If you dissipate a bump's energy over 1", that's cool for all the thin stuff you have bolted to the "shock". Dissipate it over 1/1000th of that and you can see why the loads will be 1000X as much.

Energy = force X distance. Since energy loss from hitting a bump is the same, you dissipate it over 1" like the stock shock does, all the parts get 1/1000th of where you try to dissipate it over 1 thou.

Harder and more rigid will let it run longer before it shatters when you it
that mondo bump. Softer and more flexible will let it wallow and wiggle over the same bump and feel like you're riding a bowl of jello for a few seconds and keep going like nothing happened.

Cool.
Srinath.

The lack of compliance in the swingarm may result in failures in the frame. After all, the frame has been designed with tubing and welds that assume a functioning suspension. Somethings got to give.

Thank you all for the input.  I found another post on here about struts from years ago and one member added that the top member of the frame on the left side where the strut or shock bolts in actually cracked, the bolting member on the bottom never bent but the frame cracked on top.  With this being said do you think that the lower shock mounting bolts are stronger than the frame itself?  This would be ideal in my situation because all I fear is shearing a bolt and dumping the back into a sudden death crash.  If something would bend or crack in the frame to give me warning and I could limp home I have no fears of wrecking.  Also, being as I have welded the support in would most if not all the pressure be going into the frame since the swing arm is now unable to move up or down taking all the pressure off the mounting bolts?  I called around to some shops before strutting and most seemed to say this would be no problem.  One shop claimed those shock mounting bolts are built for air craft?  I don't ride extremely hard or far.  I may do 50-100 miles a week in summer.  All highway or back road travel 70 max most of the time.  I like the way it rides the hard tail doesn't bother me I just want to ride in peace knowing I wont be splattered on the road at any second which takes all the fun out of riding in the first place.  It seems since they sell these struts for sportsters and what not they must have been tested?  But then again I could be wrong.

FunTimes54 wrote on 04/02/20 at 11:26:29:




Yea that part is wide wide off the frame to clear the pulley. That's my first danger spot. And near impossible to brace/fix IMHO without it looking like a piece of CCCrap.
Cool.
Srinath.