Over torque retaining bolts in upper link of TallboyC and others

[Man from Utopia]

There seems to be an issue with people (such as myself) snapping their upper linkage retaining bolts.

The first time I removed the upper link I snapped one of the M5 bolts (locking bolt with the tapered washer) when tightening to 100 in/pounds. The second time I set my wrench to 90 but I stopped at less then that. Everything ran fine for the rest of the season. Now this week I am giving the linkage it's scheduled maintenance and found that the one bolt was severely stretched and just shy of snapping. The trouble area seams to be the bolt that attaches the link to the rear triangle. The upper bolt made it to 100 in/p the first time and didn't look damaged. This time I am tightening all bolts in the upper and lower links to 60 in/p. Everything seems to move freely and is nice and snug. We'll see how it plays.

Here's a picture of the over stressed bolt. It's hard to see but I could really feel that it was skinny in the middle.

[DWill]

I have had the same problem with my 2012 Nomad Carbon. SC will replace the bolts but it will happen again if you use the SC spec'ed bolts.

I've changed my bolts out to stainless, so far so good. But the proof of the fix is when you remove the bolt for maintenance then re-torque it the second time.

My guess is it not the right material and/or bolt size for the application.

[Man from Utopia]

I going to look for SS at my local lomo depot.

On a side note, I noticed once I removed the upper link and had full mobility of the swing arm with the lower link still attached that there was bit of friction. So when I cleaned, regreased and reattached the lower link and tightened the pivot axles to where there was no friction or play and then installed the tightening bolts with tapered washers and tightened down to 60 in./p that there was once again some friction in the pivot. So it seems that tightening the bolts turns the pivot axle

[PerfectZero]

When I brought it in to a shop to have them drill out my snapped bolts, they put the SC replacements back in by hand to some "medium" torque without a torque wrench. So far so good.

[edley]

This is a recognized problem and there are several threads on it. I've thought about converting to stainless steel but I am afraid I will get the wrong bolt specs. If anyone has sorted this out and can post up the SS sizing - see: Standard Metric Bolt Shank Dimensions (which, for all I know isn't relevant but stops me cold) - then please let us know.

[DWill]

This is a recognized problem and there are several threads on it. I've thought about converting to stainless steel but I am afraid I will get the wrong bolt specs. If anyone has sorted this out and can post up the SS sizing - see: Standard Metric Bolt Shank Dimensions (which, for all I know isn't relevant but stops me cold) - then please let us know.

I took the SC bolts into Ababa Bolt in El Cajon Ca. They have any fastener you can possibly imagine in stock. They matched the bolt, the only issue is I had to buy a dozen of each size.

You can probably also get a match from Marshals Industrial Hardware or Grangers

One thing to keep in mind; it's not the best practice to use a SS bolt in the AL axel. I used blue loctite paste and made sure to coat the threads of the bolt completely. I also remove them to maintain the pivot every 90 days; which is probably overkill and I plan to replace the bolts and axels every 12-18 months.

[onobed]

I snapped my bolt in the lower axle of the upper link at at 8 nm. I now torque to 6 nm. This is way below spec but works fine as long as you check the bolt regularly. I am using the factory replacements which SC was kind enough to send me.

[Man from Utopia]

Stupid me...I paid $50+ for mine. I just picked up a couple SS M5s at Lowes for a buck fifty. Will try them next time.

[onobed]

Stupid me...I paid $50+ for mine. I just picked up a couple SS M5s at Lowes for a buck fifty. Will try them next time.

Hopefully you won't need to - getting my snapped bolt out was an exercise in true patience.