Triumphrat

TonyD · 05-23-2007, 05:16 AM

I recently bought some bar risers, but the 8.8 grade bolts supplied are too long. I have some stainless A2 bolts that are of the right dimensions, but I have read that stainless steel bolts should not be used for high tensile applications (because they snap under stress rather than bend). The stock Triumph bolts already holding the clamp look to be stainless, but are not stamped with any indication of grade.

Could anyone advise if stainless A2-70 are suitable for use with bar clamps/risers (the torque setting would be 22Nm)?

05-23-2007, 11:31 AM

The short answer is that if the original fasteners are stainless, you're probably fine.

A slightly longer answer is that A2-70 has somewhere between 2/3-3/4 of the strength of 8.8 steel. Grade 8.8 M10 bolts will handle 45Nm, so A2-70 should be just fine w/ 22Nm if you're talking about replacing the 2 large bolts that hold the bar clamp to the top triple. If you're talking about the 4 M8 screws that hold the bar clamp together, I suspect a typo in the Haynes manual. I would torque those to 16Nm or so for stainless. (25Nm is the limit for 8.8 steel or A2-80 stainless.) Use some blue thread locker if you're worried that they won't be tight enough, or spring for some A2-80 (or A4-80) stainless bolts.

HTH,
-Kit

TonyD · 05-23-2007, 04:50 PM

Thanks, Kit. The screws in question are indeed the four M8s holding the bar clamp together. On closer inspection the originals are chrome, so may be carbon steel rather than stainless.

Haynes does specify 22Nm, but then so does the Triumph Service manual. I think I will look at sourcing higher grade screws in light of what you say about the maximum torque for 8.8/A2. I see that some US suppliers refer to 18.8 stainless, although that is not a grade I have yet found amongst UK suppliers.

05-23-2007, 05:46 PM

18-8 is almost the same as A2-70 (18-8 is SAE, A2-70 is metric). Here's a helpful link.

Cheers,
-Kit