How Tight for Triple Clamp Screws?

[Kane]

Hello, I am about the install some windshield mounting brackets that attach to the two screws on the upper triple clamp where the fork tubes go through. When I retighten the screws, how crucial is the torque specification for those screws, or how tight do you go on these? I don’t have a torque wrench handy, just a basic Allen/hex wrench. 

 

Thank you

[footgoose]

I don't have the spec handy, but I will say it's not crucial. There are several bolts and plenty of surface area to grab. It IS crucial they all be tight. At my age I just have a feel for fasteners like these, so I don't look it up. Be sure to alternate tightening as you would lug nuts, so all snug up evenly.

[Kane]

Thank you!  When I took them off one was good and snug and one was only lightly snug. They are both now probably tighter than they were before, just moderately cranked-on by hand. I guess I’ll know if it’s too light when my fork tubes start riding up!

[stewgnu]

Isn’t it some where around 34nm?

 

[Chuck]

That sounds awfully tight to me. Really, pinch bolts don't take much. You are only closing the yoke by a thousandth or so. Remember when people were cracking the forks on the Stelvios by tightening the pinch bolts on the axles?

[Lucky Phil]

When in doubt use the std torque for the bolt dia and grade. The torque is there to provide the appropriate stretch to the bolt to prevent loosening, the bolt specified in the design is whats required to carry the load. So most triple clamp bolts from my experience are 8mm dia so the std torque will be 24.5 to 30nm. 

Ciao

[Lucky Phil]

13 hours ago, Chuck said:

That sounds awfully tight to me. Really, pinch bolts don't take much. You are only closing the yoke by a thousandth or so. Remember when people were cracking the forks on the Stelvios by tightening the pinch bolts on the axles?

Ohlins forks had the same issue Chuck back in 09 and were subject to a recall for new fork legs. It wasnt the bolt torque that was an issue but a fork lower manufacturing fault. Over depth bored fastener head clearance holes from memory.  

Ciao

[GuzziMoto]

The upper triple bolts aren't as crucial as the lower triple bolts. But both should be tightened the correct amount. The reason is over tightening them can distort the outer fork tubes. That would be a potentially bigger issue for the lower triple clamp pinch bolts, but both should be correctly tightened. Lacking a published spec, I would probably tighten them to around 20 ft/lbs at the most. If you are worried, put a little loc-tight (blue) on them.

[Lucky Phil]

57 minutes ago, GuzziMoto said:

The upper triple bolts aren't as crucial as the lower triple bolts. But both should be tightened the correct amount. The reason is over tightening them can distort the outer fork tubes. That would be a potentially bigger issue for the lower triple clamp pinch bolts, but both should be correctly tightened. Lacking a published spec, I would probably tighten them to around 20 ft/lbs at the most. If you are worried, put a little loc-tight (blue) on them.

Which is the 17 to 22ft/lbs (24.5 to 30nm) std torque for an 8mm bolt.

Ciao

[gstallons]

Remember , you are tightening a clamp , not holding an engine mount .

[Lucky Phil]

8 hours ago, gstallons said:

Remember , you are tightening a clamp , not holding an engine mount .

As I mentioned previously the rated torque is for the purpose of stretching the fastener to prevent it losing its tension. You dont design a piece of engineering with an 8mm bolt and then require it to be torqued to half spec. What you do is design the item to use 2 smaller fasteners so you can achieve the similar clamping force at a lower torque.

The rated torque is about the fastener and the required clamping force is about the design. 

 Ciao

[po18guy]

OK. I dragged out my official V11 Workshop Manual. It is far less specific , um, organized than, say, Japanese manuals, which seem to specify the torque of everything in one section. It enumerates most torque values on one page - but then males you search section by section for the rest. The triple clamp values are followed by the standard toque figures for (apparently) non-critical bolts and nuts.

Triple Clamp Torque Values:

Lower Triple clamp bolts      25 Nm

Upper Triple clamp bolts      25 Nm

Standard Torque Values:

Screws and nuts ø 4            3-3.5 Nm

Screws and nuts ø 5x0,8     6-7 Nm

Screws and nuts ø 6x1        8-12 Nm

Screws and nuts ø 8x1,25   25-30 Nm

Screws and nuts ø 10x1,5   45-50 Nm