Vortex Rearset Failure

[fallenarch]

Every once in awhile I strip the Busa down for cleaning. Each time I get a little surprise and that's why I do it religiously! I found this today, a broken bolt on my rearset. The rearsets are fine, no damage. It does not appear that the damage came from contact with anything. I would suppose this was a bolt that I tightened too tight and the head just broke. Probably too awhile for the head to actually fall off. Now I remember why I spent all the money on the torque wrench

 

[RedBusarider]

Lucky you found it while cleaning it and not riding it. lease:

Could have been an ugly sight for both you and the bike if you had been riding it and it fell off.


Did a 260 mile run today and while I was out I thought maybe I should re-lube the chain as it's been over 600 miles and that is what the manual says to do.

 

[IG.]

Ouch! Are you saying that your rearset was being held by a single bolt, and a stub from another broken bolt? Good for you for noticing. Need to tighten probably to no more than 15-20 lb ft.

Here is what's a bit puzzling to me. Your rearsets are probably made out of 6061-T6 aluminum (hardness of around 95 Brinell) while the bolt should be made from 12.9 steel or similar (hardness of around 380 Brinell), with the latter being obviously a lot harder/stronger than the aluminum. I would imagine you would sooner strip the thread in aluminum than break the bolt's head... that is unless the bolts are made from a softer grade steel, like 10.9, 9.8, 8.8, or even 6.8 or 5.8. The hardness is usually marked on the head of the bolt. So, get the magnifying glass and a flashlight, and look carefully at the top of each bolt's head, and see what's stamped there (no need to unscrew the bolts). You may have some other letters as well which depict the manufacturer. If you discover anything lower than 12.9, and especially anything as low as 8.8 or below, then it would definitely be a good idea to replace all those bolts.

Now that I wrote this, I am thinking to myself that I also have Vortex rearsets. A year ago, I did replace the bolts with the longer ones made of 12.9 grade steel when I installed foot anchors. A quick run to the garage, looking at the original bolts under the magnifying glass, and sure enough they are made of 8.8 grade steel. And this is certainly a contributing factor to your problem!

I would speculate that you cracked the head when you over-tightened the bolt, while your weight on the peg over many rides finished the job. I would complain to Vortex. A bolt should not fail like that - it should strip the thread and in such scenario you would've noticed it right away while you were tightening the bolt. Sure a headache to fix the thread, but then you wouldn't be putting your life at risk riding with the rearset held by a single bolt.

Philosophical observation: why do I always have to get to the bottom of things? It's a curse... LOL

 

[fallenarch]

Well I talked to the guy I bought them from. He is a racer and track coach and sells stuff to support his "habit". The rearsets were new when I got/installed them. He explained that the bolts are designed to shear off in a crash where the foot peg is grounded hard as a safety precaution. I think the bolt pretty much sheared off when I over tightened them and eventually the head just fell off along the road somewhere. This brings up a bigger point about swapping parts and bolts on stuff on the bike. These things are carefully engineered (which I'm sure you realize IG with all the effort you've put into the foot anchors). When I found out my T-Rex slider mount had broken the metal was so brittle it looked like a sponge. These guys engineer this stuff to break where they want it to break.

Amazing, learn something new every day. Moral of the story is use the dam torque wrench!

 

[IG.]

Simplicity wins! Torque wrench!

Regarding the shearing of the bolts when the footpeg is grinding hard, it's hard to buy this argument. I would understand if we were talking about the bolt which holds the footpeg itself. That bolt would be stretching under heavy load of a footpeg being bent by the grinding forces. However, the two bolts in question hold two flat pieces together. It will take a significant force to shear those bolts, and the footpeg would break way before that. BTW, the bolt which holds the footpeg is usually 10 mm bolt, while the other two are 8 mm bolts. I would imagine that aluminum footpeg breaks off before anything else. At least, that was my experience from a couple of get offs. For some time, I was even carrying spare footpegs - after hitting a deer, and riding 90 miles back home without the left footpeg. Shifting was especially fun, LOL.