U Bolts

Recently installed Deaver Stage II springs and DuroBumps 4.25” bump stops with the U-bolt flip kit.

I can only get this many threads showing on my U bolts and it was a bitch to torque down to 90 ft lbs.

What do you guys think? Does this seem right?

 

I’d like a few more threads showing. Replace with longer u-bolts or leave it and keep an eye on it.

 

I did some digging on this a while back for the same reasons.

I couldn't find definitive proof that having the bolt sticking through the nut was any better than any other situation (full thread engagement of course)

General engineering dogma is three full threads protruding. That said you have 100% thread engagement and I wouldn't hesitate one lick to run it just like that.

 

I do plan to keep an eye on them. I still have to retorque at 500 miles. I don’t mind buying new U bolts but I would hate to buy them if it’s truly not necessary.

On each side of the axle I have 3 bolts with maybe 1-2 threads showing and 1 bolt that is flush with the nut.

 

You think I’m still at 100% engagement with 1 bolt on each side of the axle flush with the nut? I can’t even find a definitive answer on torque. I went with 90 ft-lbs, but I’m not sure if that’s under torqued.

 

My flip kit said ~80 ftlbs. TW says 73 ftlbs.

 

I don't like the look of those. I'd be on the lookout for longer U-bolts and the extended length nuts.

 

If you're curious why most say 3 full turns of thread showing is because the end of a bolt will have a bit of a taper to the threads, meaning those last threads don't allow full engagement in the threads of the nut.

 

I expect that one nut has some small percentage of lower holding power than the others. Still, that only affects ripping the threads off the stud, not any other strength. This is where I couldn't get definitive answers since it goes down this path of thread strength, pitch, etc.

In short I wouldn't expect that even with 1/2 or 1 less thread it drastically changes the strength in this area as I expect the bolt itself is still weaker than the thread strength. So unless you think the bolt is going to snap I wouldn't expect the threads to pull out.

 

You are good with thread engagement!
This is the Deaver sticker on my Stage 2 leaf pack

 

It's unusual. More often the U-bolts are supplied extra-long and it's up to the installer to cut them afterwards. Some mechanics will trim them flush. Safety isn't affected as long as you re-torque them after some miles. The leaf pack will compress a bit with time. Maybe an additional thread will protrude after you re-torque them.

 

When I did the 500 mile re-torque I was surprised how much I had to tighten so you should be able to grab some more exposed thread after doing that. I torqued them myself the in the install so I know they were done proper but it needed more after the break in period from flex. Looks like you have some thread locker on there too so they won't turn themselves loose. Can you retake photos after torquing again to see?

 

I'd say you're fine, as-is. Those are extra long nuts, and you're not torquing anywhere near the limit of the U-bolt/nut size. As long as there isn't play in the U-bolt (retorque at specified distances), the U-bolt will have plenty of holding strength.

FYI, the Durobump install instructions specify the torque (93 lbs) and inspection intervals.

 

I have this chart on my Deavers. I originally tried going 100 ft-lb but it would not budge, so I went with 90 ft-lbs. On my retorque I might go 95 if it will move.

 

Do you have the same setup? What did you torque to? And yeah I’ll post some pictures after I retorque.

 

Interesting, I did not get these instructions.

i’ll retorque at 93 when I hit my mileage.

 

Here are the full instructions

 

Oh yeah I remember seeing this when I was digging around online. I have a different part number and the nut is larger than 19mm so I disregarded the 93 ft-lb spec.

 

No, I have a custom Alcan pack but when I was looking for torque specs I found 90 as proper so that's what I did. I was able to re-torque to 90 again after a few hundred miles and gained a thread or two but it did have extra showing to begin with. I think you might gain a little more too possibly.