Front End Alignment Bolt Torque

[vegasmarauder]

Ok, I am hesitant to post yet another front end alignment thread, but I have an interesting observation to share with all of you.

The service manual specs out 111 ft/lbs of torque for the caster adjustment bolt on the lower control arm. It is the rear bolt. The front bolt is the camber adjustment bolt and is spec at 166 ft/lbs. These are a LOT of torque. I was looking under a early build 300A that just got another alignment and decided to check the bolt torque. The rear bolt was only 80 ft/lbs, and the front was just over 100 ft/lbs. I then decided to check 2 other MM's. Neither of these have any tire wear problems at 25K miles and 12K. The 25K was an early build 300A and the 12K was a December built 300B. The A had correct torque on the rears, but the fronts were only at the 100 ft/lb mark. The B had the 80 ft/lbs at the rear and 100 ft/lbs at the front.

I do not know if these were under torque from the factory, or the bolts have stretched due to the high torque settings. Oh, and just to be sure, I used 2 different torque wrenches.

So, I would say if you are cozy with your service advisor that you ask them to actually re-torque the lower arm bolts WITH A TORQUE WRENCH the next time you are in for an oil change or whatever. This are too high of values to rely on the "feel" method tightening the bolts. This may be why they keep going out of alignment. These values are up there in the semi-truck zone for fasteners. By comaprison, the 2002 CV, Marquis uses 129 ft/lbs on the caster/camber bolts, but this is a different design.

It may be something that has to be checked on a regular basis.

Just food for thought.

[Dave Compson]

After having lots of trouble with the front end (bad alignment, eating up tires, and loosing alignment) I am happy there is finally something i can hang my hat on. I hope this fixes my problem and i hope others will check their torque. Everyone knows the techs that work on our cars for the most part dont know anything about them, so make sure they are properly torquing the front ends. Maybe with this, we can put an end to our front end alignment problems.

[Warpath]

...I do not know if these were under torque from the factory, or the bolts have stretched due to the high torque settings......ask them to actually re-torque the lower arm bolts WITH A TORQUE WRENCH... This are too high of values to rely on the "feel" method tightening the bolts. This may be why they keep going out of alignment. These values are up there in the semi-truck zone for fasteners. By comaprison, the 2002 CV, Marquis uses 129 ft/lbs on the caster/camber bolts, but this is a different design.

It may be something that has to be checked on a regular basis.


Ah, a man/woman after my own heart. There are few things more important to assembling a vehicle than a torque spec. But, here are some added thoughts.

1. After a joint is torqued, it will relax and lose some of that torque. Just about everything has an effect on it and every joint it different. In other words, you could torque a bolt to 100 ft lbs, leave the vehicle alone w/o moving it, and check it again the next day and measure 80 ft lb. Its natural and unavoidable. The torque specs are set up to take that relaxation into account.
2. Every bolt stretches when torqued (it twists too). The bolt is a spring. Think of it as a chip clip holding your car together. Torque goes into stretching the bolt and to overcome friction - mostly friction. Each joint will have a different amount of friction. You can't look at a torque spec and know that the bolts is being over stretched. Usually in the US, few bolts are torqued to permanent deformation (torque to yield). The specs you see really are not out of the ordinary for bolts that size.
3. As you said, torque by feel is far too inaccurate. Most mechanics I talk to use an impact gun only. Impact guns don't always reach the torque spec either. If the bolts are not torqued to spec, they will losen and you will lose alignment. If you leave the bolts loose for too long, the bolts may break regardless of their size.
4. Once a joint is torqued, check it once more a little while later. After that, you don't have to keep checking it. However, there is nothing wrong with periodically checking it.
5. Yes, 2002s are different than 2003s. Each joint on each vehicle is also different (for the most part) than every other joint on that vehicle too. Its not always possible to generalize that one is like the other.
6. Torque specs are set with new fasteners. So, its a good idea to use new fasteners when you swap parts if possible. Also, after a while, the fasteners will corrode and mess with torquing the bolt. New fasteners eliminate that problem.

There are many books written about fasteners. What I have above is only a small taste. The most important thing to remember though is to use a torque wrench and torque to spec.

[Petrograde]

Good info Warpath.

I use a torque wrench at work almost every day. After we put a helicopter's main rotor back together and reinstall it, we do re-torques after flying it. Sometimes they loosen up, sometimes they tighten up.

I think alot of people believe once a joint is torqued, they're done. IMHO you should do re-torques until the torque has stabilized.

Do you have to? No. Will your car suffer a catastrophic failure? Probably not. But, I'm kinda picky, I work on my car like I work on aircraft. Attention to detail is what it's all about.

I haven't really looked at the front end hardware very closely. I wonder if there are holes drilled in the bolt heads for lock wire? I'll have to look later.

Tom

[Dave Compson]

Sorry, no holes down there for safety wire. But this episode has taught me lots about torque.