Hepco and Becker upper tank protection bars issue. Tiger 900

[Djairouks]

Originally Posted by flyingburrito

The retailers response on torque:  "   I agree 100% with you that the instructions would only benefit from having the proper torque settings provided. When replacing bolts with the higher spec ones the torque setting often drops compared to what the factory, Triumph, calls for. "


No specs provided.   Are the bolts a higher grade?    Physics changed due to long spacers and longer bolts provided.   

So many variables here.

13 years ago I worked in tech customer sales services, this is typical smokescreen reply, agreeing sligthly
with you but still not giving any more info nor solutions, when you're in trouble !
This does not really scream of good engineering and analysis...

The only crash bars I trust are outback motortek and have never had problems with them.

Hope H&B will not try to bamboozle you.

[jaredjensen]

Originally Posted by flyingburrito

THe first question asked by the retailer "Did you overtighten them"....no, I did not.

I put the same bars on last night and posted in triumphrat about the torque specs, but ended up torquing them to 30nm based on https://www.triumphrat.net/threads/torque-settings-info.6676/ and what "felt about right".  I didn't use any threadlock since the OEM bolts didn't appear to have any; I figured I'd just check them again in a few hundred miles.  Do you recall what you torqued yours to?  And please keep up posted if you hear anything more from H&B.

[jaredjensen]

I emailed H&B about the torque spec, and they pointed out the general torque guidance in the little "service info" pamphlet that was separate from the installation instructions.  They didn't tell me specifically what the torque spec is, but the M10 bolt is class 8.8 and is attaching the guard to a steel frame, so the torque would be 26 Nm according to the pamphlet.

[hawkbox]

So a grade 5 bolt then.

[jaredjensen]

Originally Posted by hawkbox

So a grade 5 bolt then.

Yep, class 8.8 and grade 5 are comparable.  I'm not sure if they've ever shipped different bolts with the bars, but mine were marked 8.8.

[flyingburrito]

So I assumed 8.8 was a grade 8....turns out the bolts H and B supplied are about a grade 5 or a little better.

I don't know what the factory bolts are rated....but the dealer said the after market bolts are not as high quality as the OEM bolts.  (I had to have the dealer remove my broken off bolts from within the frame because I did not want to risk further damage)

Checked in with the retailer....still no response/analysis from Hepco and Becker yet.

[hawkbox]

Grade 5 is still rated to like 92000psi or something but yeah they're not as tough as grade 8, course Metric used 8.8 for some reason and that confuses everyone.

[jaredjensen]

There are no markings whatsoever on my factory Torx bolts.  I imagine 8.8 is plenty strong enough or they'd have bolts shearing all the time.  Although there's probably nothing stopping you from using 10.9 and torquing them to 37 Nm (according to the H&B pamphlet), other than possibly stripping the threads in the frame.

[flyingburrito]

A design engineer from another website using similar upper bars on an 800 chimed in with this info. (My issue is with the 900 model)   

******

"I'll comment on the H&B upper bars since I run them on my '17 800xcx and have recommended them in various threads.

I'm not sure if things were modified for the 900.

I like the design mounting through the forward engine mount because it pinches the frame with the engine in between. By their nature castings are brittle and can crack under shear loads, but usually do fine in compression. Particularly for aluminum castings, I'd rather have the steel frame taking the load.

The strength of a bolt comes from it's cross-section and material so longer bolts due to the spacers shouldn't weaken things. It does however create a longer lever arm for pry forces. If the spacer or the opposite end where the nut sits isn't flat, that can also create some weird loading on the fastener.

But if these broke without a drop then they should have just been seeing varying tensile loads due to frame flex and engine vibration and heat expansion.

 Not sure if someone noted, but Metric 8.8 is close in character to a U.S. grade 5 (medium strength) and not a U.S. grade 8 (which is metric 10.9). So, they're not using real high strength bolts. Not saying that's a bad thing (other than that yours failed)."

[jaredjensen]

I'm neither a mechanic nor an engineer, but I can internet like crazy!  The installation instructions for the 800 are at https://www.motomachines.com/amfile/file/download/file_id/5940/product_id/12332/ and the design appears pretty similar, except only one M10 bolt is 110mm where the other is a bit shorter at 80mm.  If anything, the little bracket at the top under the beak looks like the weak point.

It does make sense that dropping the bike just right where the guard got levered upward/forward/backward could snap that bolt.  But if yours sheared just riding the bike, it seems more likely they were over-torqued or somehow defective.  I know you said you didn't over-torque them, but you also said you thought they were grade 8, which would have warranted higher torque.