Check Your U-Bolts

Are the u bolts larger diameter?

wee

 

no, uses the stock u-bolts... u loosen em enough to get the bumper stops out and replace with the sumo brackets.

 

7/8 bolts needed 1/4 to 1/2 turn to reach 60 ft-lbs

 

where in the manual (or TIS) does it state 52ft-lb's?

 

The manual lists 2 different torque specs. In the torque spec chart it lists 37ft/lbs. In the leaf spring replacement flow chart it lists 52 ft/lbs

 

That is interesting, I had not noticed that before, most likely a leftover from the 2015 manual or an oversight, interestingly on the same page the 2WD specification is the updated 52 ft-lbs.

As for where it states 52 ft-lbs:
2016 Tacoma Repair Manual (RM26L0U) > Suspension > SUSPENSION > REAR LEAF SPRING > COMPONENTS
and
2016 Tacoma Repair Manual (RM26L0U) > Suspension > SUSPENSION > REAR LEAF SPRING > INSTALLATION > 3. INSTALL REAR SPRING U BOLT > Torque: 70 N·m {714 kgf·cm, 52ft·lbf}

Interesting side note: technical instructions for the leaf spring recall have been released (2005-2011 Tacomas) and they still specify 37 ft-lbs for the updated parts.

Jeff

 

thanks Jeff, looks like I need to download more. We should setup a repository for all the TIS documents that we download.

 

@blkbelt42

 

After 3700 Miles mine are still tight

 

400 miles in. All 8 were between 35-40. Torqued to 55.

 

thx dude! says more and more about the dealer

 

Mine all took half a turn to be at 52 lbs. 198 miles on the truck.

 

I just want to say that I've seen a couple of people in the thread here torque higher than the 52 ft-lb recommendation. For future readers of the thread, I highly recommend not to go a lot higher than the recommended spec.

Bolt preload is incredibly important, especially in a u bolt setup. I guarantee toyota did not pull that torque spec from nowhere. That type of joint is in tension as well. By overdoing the preload you are effectively lowering the safety margin that toyota has used to qualify the truck as safe.

You don't know what that final margin is, and unless you guys have the loads, stress and test data to back it up, why risk it?

Even if an aftermarket vendor suggests a torque value, if you are using the TOYOTA OEM u bolts and nuts, follow Toyota's specs.

 

With all due respect theres so much fail in post dont know where to start, first wtf is a preloaded bolt ? & 1st gen ubolts are same as 2nd/3rd gen grade/thread pitch etc

 

Ok...with all due respect, if you don't know what bolt preload is, then you aren't in a position to say my post was a huge fail.

When you torque a bolt that is clamping surfaces together you induce tension in the bolt. So instead of the bolt having no load (if you are holding it in your hand), it is loaded (as if you are pulling both ends away from each other).

So in a shear joint, all is fine and dandy because your main failure mode is shear and not tension. But in a joint that will put additional tension on the bolt you are now concerned with the tension already in the bolt.

Edit: I should probably clarify that a few ft-lbs isn't what I'm talking about. What I wouldn't want to see happen is someone come in and say "oh 52? I'll just do 100 so I don't have to worry about it."

 

Tell ya what, answer this simple question & Ill listen to all the data/stats/facts you lay out... Up to 2004 Toyota had 90+ftlbs listed for value, in 2005 the value dropped to 37 ftlbs. What magic happened that would reduce that value ???

 

I don't know? I didn't and don't work as a stress engineer at toyota. I dont know what changed, i dont know what the load requirements were/are, etc. But I do work as a stress engineer at a major aerospace company and I can promise you a large part of my job is making sure bolted joints aren't going to fail.

There is a reason every bolt in the industry I work in is torqued to the exact spec given to manufacturing. It is because we qualify the integrity of the aircraft under specific load conditions. I don't work in automotive but I promise their numbers don't come out of nowhere.

It is your truck, this is simply my recommendation for people. The spec is there for a reason and multiple people get paid quite a bit of money to make sure those numbers are correct.

Again, I am NOT saying it will fail, I'm just saying you don't know what the margin of safety was when toyota qualified the joint under ALL required load conditions. So why risk it?

If someone in the automotive industry wants to chime in, I'd be happy to hear how it is done in that industry.

 

I was a certified riviter for teledyne/Ryan aeronautical, so i DO understand a little engineering, But we talking toyota trucks not aircraft & since you have no answer (no one else has).Cant really Say toyotas highly paid staff have dicked this out can we ?

 

Since it was 37ftlbs , and they decided it now requires 50 + ftlbs it tells me they,re not really sure themselves