Pinch bolt torque

[Neil E.]

45 zokes on a 2011 with M6 allen screws. All screws heavily greased to prevent corrosion. Top crown with 2 screws I went 7.5 ft lbs, lower crown with 3 screws I went 5 ft lbs on each.

I know some use a different system by tightening only 2 on the lower crown. The values I'm using "feel" right for M6 screws, but I'm wondering if anyone thinks this is too much torque.

 

[pscook]

Jut remember that grease on threads decreases resistance to turning, so your effective torque is higher. Your torque is effectively doubled from a dry value using a lubricant. That being said, you put the equivalent of ~15 ft/lbs (dry) on the top and 10 on the top.

Sorry that I don't know what the best torque value is, but I do need to know.

 

[GMP]

I've been running 8Nm lower on two bolts and just snug the third, 12Nm upper, with anti-seized bolts. No slippage and good action. Torque is not doubled, but increased 20-30%, from a machinist book in the shop at work.

 

[Neil E.]

Thanks,

12 Nm upper = 8.85 ftlbs
8 Nm lower = 5.9 ftlbs (two bolts)

Sounds like I'm in the ballpark, maybe could reduce the lower slightly with all 3 bolts torqued.

 

[andoman]

Sorry to hijack:
Are those the same numbers for the SACHS forks?
I found here on the forum: 15NM top clamp bolts, 9NM center bottom, and only just snug down the other two on the bottom clamp.

 

[husley]

Me too

Sorry to hijack:
Are those the same numbers for the SACHS forks?
I found here on the forum: 15NM top clamp bolts, 9NM center bottom, and only just snug down the other two on the bottom clamp.

Yeah, what he said

 

[pscook]

I've been running 8Nm lower on two bolts and just snug the third, 12Nm upper, with anti-seized bolts. No slippage and good action. Torque is not doubled, but increased 20-30%, from a machinist book in the shop at work.

Gotcha, I was trying to remember my machinists values and seem to remember the 50% was for assembly lube as opposed to never-seize. I'll check my sources again, because I don't want to use or provide faulty information. But the reality still stands that lubrication lowers your torque value, even if I can't get the values correct.

Thanks for the values, I have to run downstairs and "adjust" some bolts. Would those torque values apply to 43mm WP forks?

 

[GMP]

The clamp is the same design so I would use the same torque. These #s are a matter of opinion, but the consensus is that the manual is wrong, values being way too tight. I've played around with the lower bolts, torque 1, snug 2, torque 2 ,snug 1, makes no obvious difference. I've also been going lower on the torque but have yet to induce slippage. Ultimately what you want is the least clamping force that will retain the fork tube. Mine have been reanodized and as such the outer tube surface is a little more rough than stock, so maybe this helps, but I have never heard of anyone else complain of slippage with low clamp torque values.

 

[andoman]

Thanks!
Makes sense. I, too, will experiment.
I like the idea of a little less torque on two bolts vice more on one.

 

[Jakobi]

Terry Hay says 3 bolts is over kill and to just run the middle one. I have done the opposite and just run the top and bottom. Snug and then slightly tighter. Definately not cranking down on them.

 

[husley]

?

Anybody actually noticed a difference in performance with less or more torque on the clamp bolts?

 

[Simmo737]

Yep. mid stroke harshness reduced, square edges like the extra flex, no change in control. It will make your suspension last longer. its a free improvement. Ride for half an hour after you've done it then do em up again, see the difference.

 

[Binni]

I had no idea what that would do or why not tighten all bolts down, now I'm gonna try this.

 

[GMP]

The problem with the three bolt clamp is its almost impossible to properly torque it. if you keep walking the torque wrench over the bolts you end up WAY too tight by the time they all click the wrench off. Too tight and you are destroying your fork uppers.

 

[Neil E.]

Good point. That is a disadvantage to the click type torque wrench. Your cummulative torque winds up higher. For this work I use an old beam style unit so I can watch the needle approach the desired value. By carefully sneaking up on it, all three bolts can be matched for torque value. Three M6 bolts spaced so closely together is overkill for this application. I redid my lower crown clamp bolts to 3.75 ft lbs each. This should be enough holding power.

This scenario started because I was hearing a light "click" from somewhere in the front suspension when moving the bike around. The sound that dry aluminum makes when two parts shift position. I went through the stem assembly without any change. Next was the crown pinch bolts; still no change. It turns out that the right axle clamp wasn't gripping the axle tight enough. The axle is probably down in tolerance and what I thought was a reasonable "hand tighten" wasn't enough force. With the clamp torqued to 7.5 ft lbs the axle is tight.

 

[GMP]

Those don't care if there a bit tight. What do you think about changing the surface texture on the clamp IDs for a higher friction coiefficient at a lower clamping force? Like I said I may have this effect already. I beat the crap out of mine and it never moves.

 

[Neil E.]

If I tracked the "noise" to the lower fork crown, I was thinking I might coat the clamp surface with blue loctite so it would hold with low torque on the bolts. Surface finish is a tricky thing at low clamp pressure. Roughness will help when there is enough pressure to get some bite. The problem is that roughness results in less surface contact, so at low clamping force maybe it would slip easier. We should get Jakobi on this since he loves to experiment with stuff.

 

[GMP]

Yeah, he can sandblast the forks and clamps with different grit and try it.

 

[Jakobi]

No more tasks for me! I'm going riding!! BRaaap Braap!

 

[STEVEV]

For the zoke's, I've always used a bit of blue loc-tite (no grease) and torqued the upper clamps. For the lower clamps I would snug them. It seemed to me the zokes were prone to easily distorting on the lower clamps even at the specified torque. These were on a Husky.