Everything you always wanted to know about LBJ bolts

[Spiker Engineering]

Thank you so much for doing this Leon! What great data.

Thanks Mike, nice to see folks appreciate this labor of love .

ARP recommends 54 pounds feet of torque for their 663 (and SS 763) bolts. Did you test at that spec? Would the reuse theory change with the correct torque spec?

I torqued them to 37 and 59 ft-lbs, just like all the others. 54 ft-lbs is going to be just a few percent below the 59 ft-lb value, you can just read it off the plot - around 7,400 lbs. That is nowhere near the yield point for these bolts, so ARP is being extremely conservative with the 54 ft-lbs callout.

How long is the Tacoma "black bolt" 90119-10933 with washer? Total clamping length is what I'm after.

The clamping length is exactly 35 mm long. The flanged bolts are 32 mm long, and the ARP (with washer) is only 28 mm.

When does the shear test happen and will you be doing that with both first use, and successive reused bolts?

I plan to torque one new bolt of each type to failure (I already did some tests in the junkyard and got some preliminary results, but the "juju" was less than ideal in the junkyard (laying in puddles of transmission fluid, people looking at me a little funny as to why I am installing bolts), and also there were not enough 3rd Gens for me to finish the tests (I could not reuse any tapped holes because the broken bolt segments were seized in place). So I'll do some more tests at home, using a double nut to represent the knuckle. I'll probably do this just for a new bolt, not for reused ones (not sure how many fresh nuts I have on hand, and they will be single use only for these tests).

The thought is to determine the maximum number of reuse cycles before retiring the bolts. I'm at 4 cycles on my current ARP bolts and I use thread locker.

I think the preload degradation curves already address this question, although of course no one knows for sure what the acceptable lower preload limit is. If it were me, I'd try really hard to make sure it stays above 7,000 lbs, which an ARP bolt with 4 reuses would not meet at 59 ft-lbs. You'd have to bump it up to about 65 ft-lbs, which you can safely do (the one that stripped at the junkyard did so at over 90 ft-lbs).

 

[Spiker Engineering]

Well, I took the plunge and upgraded to the black bolts since I had the LBJs off anyway. I also put the dust boot on there too -- seemed like a good idea. The boot is overmolded onto the two mounting washers so there is a no rubber in the way of the bolt joint itself. I also did not have any issues with the longer black bolts. Torqued to 37 ft-lb with some medium loctite.

Way to go, you are my hero and I plan to follow in your footsteps on this one.

 

[octanejunkie]

The black bolt 90119-10933 is for 01/02 4Runners with the lbj boot/protector thing that most people don't reuse. It could also be for Tacoma's too.

Assuming they are torqued to the correct spec, it would seem there's no reason they can't be used on 2000 and earlier.
Are you suggesting otherwise?

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[Bad Luck]

Assuming they are torqued to the correct spec, it would seem there's no reason they can't be used on 2000 and earlier.
Are you suggesting otherwise?

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I don't see a reason why they wouldn't work at the recommended 37 ft/lbs for 96-00 or without the dust cover. I was more of clarifying vehicle application of those bolts than disagreeing with you. I made a note to use these bolts next time the lower ball joints need replaced or the bolts get removed.

 

[JZiggy]

This is incredible work, Leon. This deep-dive technical analysis is so fun and interesting for a forum full of smart and creative people. I know that projects like this rapidly take on increasing numbers of variables, things to try, etc. I appreciate you powering through it and using your skillset and resources to develop such useful information for us.

Go Leon!! arty:

 

[binqker]

Nice job!!

so wait.. the illustration from the Service Manual states "37ftlbs". But I'm hearing torque it to 59ftlbs?

 

[phattyduck]

This chart alone explains why Toyota specified a torque of 37 ft-lbs for the Black bolts, as opposed to 59 ft-lbs for the others - it's not that the bolt is weaker, as some have speculated, but that it reaches the same preload (or higher) at 37 ft-lbs as other bolts do at 59 ft-lbs. So, conclusion number 1 - if you use the Black bolt, do NOT torque it to 59 ft-lbs, you will yield the bolt. Torque it 37 ft-lbs and be happy.

.....

Using my spreadsheet for estimating torque to preload ratio as a function of bolt geometry and friction coefficient, the data above suggests that the friction coefficient is about 0.15 to 0.2 in all the bolts except Black; the Black bolt friction coefficient is likely below 0.1. That puts it squarely into dry film coating territory, which I think explains why it performs so well, wears so little, and has the smoothest rotation (by far) of them all.

My theory all along here is that the bolt with washer has a different acting friction diameter than the flanged bolts. Smaller head = lower torque for the same clamping force. I don't think the black bolts are coated with something magical that changes their coefficient of friction - to the contrary, I think they are specifically not coated with any friction reducing compounds, unlike the other 'color' bolts where Toyota was tweaking coatings to tweak preload in later years.

Toyota likes the flange bolts because they are cheaper, but they couldn't use them with the dust protector due to the torque that would be applied to the in-molded metal sleeve in the protector. They went to a bolt with washer and adjusted the installation torque for a (near) matched preload.

Anybody that thinks Toyota doesn't know these things and FULLY design/engineer stuff like this is deluding themselves. (I now work at a small US division of Yamaha - I see the same Kaizen stuff that Toyota pioneered many years ago)

I have the ARP bolts waiting for install in my garage - this data puts my mind at ease and I will feel quite comfortable installing them. I did overtorque at least some of the LBJ bolts during install years ago (read the nut spec, used it on the bolts!), so it is worth the piece of mind.

-Charlie

 

[phattyduck]

Nice job!!

so wait.. the illustration from the Service Manual states "37ftlbs". But I'm hearing torque it to 59ftlbs?

37 ft.lbs = bolts with loose washer, 59 ft.lbs = bolts with flange head.

-Charlie

 

[Bad Luck]

Nice job!!

so wait.. the illustration from the Service Manual states "37ftlbs". But I'm hearing torque it to 59ftlbs?

LBJ Bolts (4 per side) 90080-10066 (96-00)(59 ft/lb)(flanged bolt not for use with dust protector boot) or 90119-10933(01-02)(37 ft/lb)(bolt w/washer for use with or without dust protector boot)

 

[Spiker Engineering]

My theory all along here is that the bolt with washer has a different acting friction diameter than the flanged bolts. Smaller head = lower torque for the same clamping force.

That may be part of the story, but not all. The contact diameter on the ARP washer is 16.2 mm, and the one on Black bolt is 14.8 mm. That's only a 10% difference. Plug that it into the full torque vs preload equation (not the mickey mouse simplified online calculator), and the difference in preload at a given torque is about 4-5%. So that won't explain why the Black bolt generates almost twice the preload of the ARP bolt.

I don't think the black bolts are coated with something magical that changes their coefficient of friction - to the contrary, I think they are specifically not coated with any friction reducing compounds, unlike the other 'color' bolts where Toyota was tweaking coatings to tweak preload in later years.

We won't know for sure without an FTIR machine. But the data suggests that there is some kind of a friction reducing coating on the Black bolt. I don't think I stated that it is magical, just that it is good.

Anybody that thinks Toyota doesn't know these things and FULLY design/engineer stuff like this is deluding themselves. (I now work at a small US division of Yamaha - I see the same Kaizen stuff that Toyota pioneered many years ago)

I certainly did not mean to imply (and don't think I did) that I know more than Toyota does. In fact I am sure they did their engineering right, and designed the bolts (and torque specs) accordingly. My comment about "reverse engineering" was simply that since Toyota has not publicly shared their calculations with us (at least to my knowledge), we have to make some assumptions as to what they did and why. If you read these forums, you'll see how often people guess as to whether they should use 37 ft-lbs or 59 ft-lbs to torque these bolts, with all sorts of speculative answers. I think this data is helpful in figuring out the right answers with facts, instead of speculation.

 

[phattyduck]

I certainly did not mean to imply (and don't think I did) that I know more than Toyota does. In fact I am sure they did their engineering right, and designed the bolts (and torque specs) accordingly.

Oh, no - you are definitely on the right side here! I'm talking about the people avoiding the 'black' bolts because they are 'weaker' or similar such nonsense. This information is amazing and helpful.

-Charlie

 

[Spiker Engineering]

Oh, no - you are definitely on the right side here! I'm talking about the people avoiding the 'black' bolts because they are 'weaker' or similar such nonsense. This information is amazing and helpful.

Gotcha, thanks for the clarification Charlie! BTW, I bet you can safely take those ARP bolts up to 70 or even 80 ft-lbs. We'll know more after the next round of breaking things .

 

[octanejunkie]

Gotcha, thanks for the clarification Charlie! BTW, I bet you can safely take those ARP bolts up to 70 or even 80 ft-lbs. We'll know more after the next round of breaking things .

But why would you if ARP says 54 # ft?

If <60# generates over 7K of preload then more isn't necessary better... Amirite?

Personally I would rather put less stress on the fasteners than more, and use loctite for good measure

I ordered a set of black bolts for when I retire my current ARP bolts since the 663-1004 (35mm) ARP bolts are just about double the price of the 30mm 663-1003, and I'd like to use the washers

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[Spiker Engineering]

But why would you if ARP says 54 # ft?

Well the ARP torque number means nothing without a specific application in mind, because they don't know how much preload you need, so they can't tell you how much torque you should apply. All they can tell you is the maximum torque they feel is safe to apply, which at 54 ft-lbs is about half of what this bolt can handle. But I'm sure they want to be conservative. Or, thinking about [MENTION=71960]JohnMc[/MENTION]'s question earlier, perhaps they specify that torque assuming their lube is applied? I don't know the answer, but that would be a whole different ballgame.

If <60# generates over 7K of preload then more isn't necessary better... Amirite?

More is better (to a point) when it comes to preload, unless you get close to breaking things. Think of a preloaded bolt as a rubber band to hold two things together - you want a tightly stretched rubber band rather than a loose one. And I'm not sure that 7K is what you want to shoot for, especially if wheeling - I'd shoot for closer to 9K to 10K, given the Black bolt test results.

Personally I would rather put less stress on the fasteners than more, and use loctite for good measure

A high static preload is actually much better than a low one, as it reduces the stress variation in the bolt under external loading. A lower preload causes higher stress fluctuation, and a higher risk of gapping, which is really bad.

I ordered a set of black bolts for when I retire my current ARP bolts since the 663-1004 (35mm) ARP bolts are just about double the price of the 30mm 663-1003, and I'd like to use the washers

That seems like the winning combo to me as well. I'm trying to withhold final judgement until the destructive testing, on the off chance that the ARP bolts are much stronger than the Black ones.

 

[theesotericone]

SNIP

Just sent you a donation via your site. Nice work on this and thanks for taking the time to do it.

 

[Spiker Engineering]

Just sent you a donation via your site. Nice work on this and thanks for taking the time to do it.

Thank you Matt! The support from you guys for this project makes it all worthwhile!

 

[cl4Rk]

[MENTION=636945]Spiker Engineering[/MENTION]

First of all, thank you for this amazing work!!!

Newbie question: is there any potential down side to using a super strong bolt and a higher torque spec? I guess the heart of my question is this: how strong are the threads on the knuckle, and is there any danger of the knuckle threads becoming a weak point that leads to the very failure that a using stronger bolt was meant to avoid? Honest question. I have no clue. Thanks in advance!!

 

[Spiker Engineering]

[MENTION=636945]Spiker Engineering[/MENTION]

First of all, thank you for this amazing work!!!

Newbie question: is there any potential down side to using a super strong bolt and a higher torque spec? I guess the heart of my question is this: how strong are the threads on the knuckle, and is there any danger of the knuckle threads becoming a weak point that leads to the very failure that a using stronger bolt was meant to avoid? Honest question. I have no clue. Thanks in advance!!

[MENTION=633155]cl4Rk[/MENTION], that's a good question. There are some potential risks to using very high strength bolts with relatively weak female threads. But the 4Runner knuckle is made from forged steel, far from a soft material, so the bolt will fail well before the knuckle will (my testing to date has confirmed this, all bolts failed in tension rather than stripping of threads, except for the ARP bolt which only had a two thread engagement).

I also want to be very clear that I am not recommending using a higher preload than what Toyota recommends. I'm only determining what torque should be used for each bolt type to get to that preload. So if Toyota designed the knuckle threads to handle 10,000 lbs (based on our results), then it doesn't matter if you get to that 10,000 lbs by using a Black bolt torqued to 37 ft-lbs or a Red bolt torqued to 59 ft-lbs - the knuckle will still see the same 10,000 lbs, and there is no increased risk of damaging the threads.

There is one other valid concern with very high strength bolts, which is embrittlement. Once you get to 12.9 or higher strength bolts, that becomes a valid concern. That is one of my hesitations with the ARP bolt – if it is indeed a Class 12.9 bolt, then it has a higher risk of failure due to embrittlement. Personally, as of now, it looks to me like the Black bolt has the best of all worlds – very low friction, very low degradation with use, and the needed strength without risking embrittlement. Not clear what the ARP bolt would add to this, other than more risk.

 

[theesotericone]

I also want to be very clear that I am not recommending using a higher preload than what Toyota recommends.

This is where the failure numbers will come in handy. For most people I agree that not exceeding OEM preload is perfect. For those that wheel hard they might need to increase that preload. Every single LBJ bolt that I failed was due to shear. Repeatedly hitting big rocks with big tires causes stress that Toyota never designed the system for. That repetition eventually causes the bolts to shear in plane with the LBJ/Spindle. By increasing preload as close to the forged threads pull strength we can mitigate that. Super rare use case but it will help a lot of folks that wheel stupid shit. lol

 

[Spiker Engineering]

This is where the failure numbers will come in handy. For most people I agree that not exceeding OEM preload is perfect. For those that wheel hard they might need to increase that preload. Every single LBJ bolt that I failed was due to shear. Repeatedly hitting big rocks with big tires causes stress that Toyota never designed the system for. That repetition eventually causes the bolts to shear in plane with the LBJ/Spindle. By increasing preload as close to the forged threads pull strength we can mitigate that. Super rare use case but it will help a lot of folks that wheel stupid shit. lol

Agreed, there's lots of margin to increase preload above what Toyota recommends. Not much of a downside to it, either. And the bolt will fail in tension way before the knuckle threads will yield, provided you have 4 or more threads engaged.

Regarding bolt failures in the field, I've seen a FB post of someone having that happen, but it's not clear how they know it was a shear, rather than tensile, failure. Any chance you have pictures or remnants of failed LBJ bolt joints?

I'm having a bit of a hard time seeing how the joint can fail in shear as long as the bolts are tight. In addition to the friction force, there are two shear cones on the LBJ that should take the shear loads. What happened to these cones to let the bolts fail in shear?

My suspicion is that the bolts start to back out due to the heavy loads you describe, and allow gapping to take place. Once the joint gaps, the impact loads lead to oscillating loads in the bolts, the shear cones are no longer effective, and the bolts do in fact fail either from shear or tension.

That's why I personally think that the most critical thing in the LBJ bolts installation (aside from preloading to the right load, around 10,000 lbs or more) is to ensure the bolts don't back out. And after way too many years in the aerospace industry, I can tell you that loctite is not the best way to ensure that.