Was reading through the workshop manual today to find out how much to torque the shock absorber mounting bolts (installed Bilstein shocks this AM). I noticed that for all the hardware the manual stated to discard the original nuts/bolts and replace with new. I have been seeing this in lots of places in reading through the manual. What gives with this?

I can see replacing head bolts and such, but the shock absorber bolts??? I looked up part numbers on the Internet, a full set of replacement bolts/nuts for the shocks would run you upwards of $40!

Curious minds want to know.

Steve

 

IMHO manufacturers 'Play it safe" and mechanics like the idea of using new bolts while gaining extra profit on parts mark ups. I've been using the same bolts for hundreds times in some applications and although the threads might wear out over the years, those situation are extreme.
The only bolts that require replacement after each removal are stress bolts used in some applications on the engine. To my knowledge SuperDuty don't have such.

 

Ford used stretchy head bolts (technically knows as "Torque to Yield") in a lot of applications, including the 6.0L and 6.4L diesel engines. I don't know what other engines, but I seem to recall them telling me they couldn't reuse the head bolts on my '93 T-Bird 3.8L V6.

Probably, somewhere sometime ago, a bolt broke on some important suspension part, someone got hurt, someone sued and it cost someone a lot of money. So the recommendation became to replace the bolts, to try to reduce the future liability.

 

There are applications where I like to replace an OEM bolt with a Class 10.9 or 12.9.

If they don't have to be metric, I like Grade 8's best. They aren't all that much more costly when buying bolts and nuts.

I'm fortunate to have a supplier nearby that has a great selection of all this stuff.

Pop

 

torque to yield bolts are used to get a good averge torque load on a given object...i guess the engineers did not like torque wrentches. torque to yield bolts require you to torque to a certain ft. lb and from there continue turning the fastener a certain amount of degreee's using a degree wheel or estimating it, but you can surely feel the fastener give or streach while doing so...like it is no longer tightening, just streching, it sure can be felt while doing this

 

The idea is that used bolts will not torque properly using the standards applied to new bolts. So anywhere torque value is critical, you should use a new bolt.

But, I agree with you that on shocks it is silly to throw away perfectly good used bolts. But I've never used a torque wrench on a shock bolt either. All this torque this and torque that is ridiculous, and experienced mechanics know when it matters, and when it doesn't. When it doesn't just inspect the bolts, clean the threads if they need it, and reuse.

 

Sound advice, Bill!

Reps to you!

Pop

 

I completely agree that it is not necessary to replace the shock bolts. Head bolts, for instance, rely completely on the tensile strength of the bolt to hold down the heads.

However, shock bolts are a side-force load (shear). Unless the bolts were originally tightened to yield - which deforms them - they should be fine to reuse.

 

Why do we engineers say to replace?
Some are designed to be "torque to yield" for optimal function - like head bolts. But others are not. On those, there is another reason:

Because many "mechanics" are too clueless or lazy to use torque wrenches.

Apply more torque than recommended and the bolt WILL stretch and weaken. Each time it is overtorqued, it gets weaker. Eventually it will fail (break).

If it is a critical bolt that could result in an handling or safety issue, it is a big deal.

We can't stop the idiots, but we can at least try to minimize their damage.

Things like suspension bolts tend to get WAILED on by gorillas with impact wrenches so they are more likely than most to be damaged.

 

Been wondering this myself .... I'm getting ready to replace my brake rotors and the FSM says to replace the caliper mount bolts. These bolts are pretty substantial too! I plan on reusing them ... may add a little blue loctite.

I reused my shock hardware also when I changed my shocks.

 

had to replace the bolts on my Reese rails for my 5th wheel hitch when I changed trucks. I would have replaced them even if they had not recommended it. Lot of stress and new bolts seemed like the way to go.....

 

I replaced my front pads & rotors and like you I noticed the manual instructed to replace the caliper mount bolts. So off I went to the local parts house to get the bolts. Unfortunately, the parts house didn't carry the bolts and was told it was a dealer only part. So off I went to the local dealership. Again no bolts in stock. I checked with two other dealerships and only one had two of the four bolts I needed. So I decided to go ahead and get the two bolts and keep them just in case I needed them. All three dealerships are large with heavy volume Super Duty service departments. I know they do a lot of brake service work. When I asked if they were just out of stock of the bolts the parts guy looked in the system and told me they hardly ever get a request for this particular item and it was a very low demand item. Now if the brake techs were strictly following the manual, this item would be a fairly high demand part. This tells me the service departments of the three dealerships I checked are only replacing these caliper mount bolts if the bolts are visibly damaged.

The two new bolts I obtained each had blue thread locker on the threads. So I inspected my removed bolts for damage, put blue loctite thread locker on the threads, and reinstalled them.

Just wanted to pass along my experience.

 

It has to do with the blue thread locking compound or in the case of a nut, self locking feature. And of course the lawyers so that if there is a loss of a critical bolt and subsequent accident the "I told you so" escape clause was intact.

The problem with trying to use Loctite on the bolts that had the blue thread-locker is the integrity is not guaranteed.

Keep in mind that all those torque values given in the service manuals for these types of bolts consider the OE thread locking compound or nut deformation / compound / ect. So if you are torquing a bolt where the blue thread-locker is being "reused" or after cleaning an aftermarket compound that is liquid you are actually over torquing and stressing the bolt.