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Here's a snip from my manual (997.1) below. Note how it says to lubricate the threads, not the "head" of the bolt. Proper installation and torque of any mechanical connection bolt always involves lubricating the threads. If you do not lube the threads, you cannot be sure what the preload of the bolt will be, and if the torque spec is based on lubrication (like the Porsche manual), then you will definitely not achieve the intended preload. This can be dangerous especially if you are driving on the track, where the bolts are exposed to cyclic loading due to cornering forces. Without achieving the defined preload, you risk exposing the bolts to metal fatigue due to the stress amplitude changes in the bolt. Lubrication of the threads ensures you reach a consistent preload in the bolt, and does not precipitate loosening. It is the friction between the head of the bolt and the clamped material that prevents loosening, not the threads - that is why Porsche says not to lubricate the head of the bolt. I hope I am not coming off as condescending, but when I saw this I wanted to clear it up because it's an important safety issue.
Thanks.
Okay. You are quite wrong. At least in the air-cooled Porsche world. Unless specifically spelled out in the Factory manual, it is assumed that all torque specs are with dry threads and no lubricant is to be used.
In the racing side, we do not use any lubricant on lug nuts. We don't use lubricant on most fasteners. If we choose to use a lubricant, we take into account that the torque spec is for dry threads and reduce the torque accordingly.
Now, maybe Porsche changed this for the water-cooled cars...but I somehow don't think they did.
Okay. You are quite wrong. At least in the air-cooled Porsche world. Unless specifically spelled out in the Factory manual, it is assumed that all torque specs are with dry threads and no lubricant is to be used.
In the racing side, we do not use any lubricant on lug nuts. We don't use lubricant on most fasteners. If we choose to use a lubricant, we take into account that the torque spec is for dry threads and reduce the torque accordingly.
Now, maybe Porsche changed this for the water-cooled cars...but I somehow don't think they did.
I have never gotten into a peeing contest on this forum, and I'm not about to start. So this is my last post to this thread. Respond away if you like.
I am not wrong. I have a BS and MS in Mechanical Engineering and I have written the fastener torqueing guidelines for two major companies in my career. Yes, you can use a "dry" torque "spec", but you are gambling. Ask a tribological engineer if you don't understand why. I don't relube studs/bolts every time I reinstall them and torque them, as long as they were originally lubed and I still see signs of the lube. But when it appears gone, I relube. And I am not trying to tell "racers" what they might have been doing is wrong - I understand the situation (and they probably replace wheel studs regularly). I was only trying to describe the factual technology behind bolt torquing. If you choose to rely on anecdotal references, that's up to you. But you really should understand enough of the technology behind something before you claim you are right and someone else is wrong.
And air cooled versus water cooled has nothing to do with it. The mechanics of bolting have not changed. Although perhaps there was an increase in awareness.
I have never gotten into a peeing contest on this forum, and I'm not about to start. So this is my last post to this thread. Respond away if you like.
I am not wrong. I have a BS and MS in Mechanical Engineering and I have written the fastener torqueing guidelines for two major companies in my career. Yes, you can use a "dry" torque "spec", but you are gambling. Ask a tribological engineer if you don't understand why. I don't relube studs/bolts every time I reinstall them and torque them, as long as they were originally lubed and I still see signs of the lube. But when it appears gone, I relube. And I am not trying to tell "racers" what they might have been doing is wrong - I understand the situation (and they probably replace wheel studs regularly). I was only trying to describe the factual technology behind bolt torquing. If you choose to rely on anecdotal references, that's up to you. But you really should understand enough of the technology behind something before you claim you are right and someone else is wrong.
And air cooled versus water cooled has nothing to do with it. The mechanics of bolting have not changed. Although perhaps there was an increase in awareness.
Out.
I don't care what you are or do.....Porsche specs are dry unless stated otherwise. If you lube a thread that Porsche provides a torque spec for but does not say to do so in the manual, you need to adjust the torque spec accordingly. And no, we are not gambling. Stop being so melodramatic.
I will even go on to say that most threaded fasteners on a race car are NOT used with a lubricant. This includes most fasteners on suspension, axle, and brake components. When LocTite is used, you certainly don't want any lubricant on the threads AND you must adjust the torque as if a lubricant were used. If you read Carroll Smith's "Prepare to Win" and "Nuts, Bolts, Fasteners & Plumbing, you will find most are installed without lubrication. Also, all torque table in the books are for dry fasteners. This idea that this is "gambling" is absurd.
Thank you steveP911 for your comments. I think that Tom Galeo (also a mechanical engineer) would agree with you.
This is what I was disagreeing with:
Originally Posted by steveP911
Proper installation and torque of any mechanical connection bolt always involves lubricating the threads.
That statement is just plain incorrect.
For example, look at the published torque values for the CV joint bolts. At least on air-cooled cars those are dry numbers. The same is true for many fasteners on an air-cooled 911. Again, Porsche specifically calls out fasteners that are to be lubricated and provides adjusted torque values for such fasteners.
Now, maybe Porsche changed this for the water-cooled cars...but I somehow don't think they did.
SteveP911 specifically stated that the manual excerpt was for a 997.1. My 997.2 manual says exactly the same. Looks like Porsche did change things when they added water cooling. Or is the section in my manual that describes the coolant level also wrong??
For example, look at the published torque values for the CV joint bolts. At least on air-cooled cars those are dry numbers. The same is true for many fasteners on an air-cooled 911. Again, Porsche specifically calls out fasteners that are to be lubricated and provides adjusted torque values for such fasteners.
Hey Scott, guess what?
I DON'T CARE.
Start your own thread.
Take home points:
1. You are a helluva driver.
2. You argue with anyone, everyone, anytime. Hint: It's exhausting.
3. Experts know things that you don't. I'm sure you are truly expert at several things and can understand.
SteveP911 specifically stated that the manual excerpt was for a 997.1. My 997.2 manual says exactly the same. Looks like Porsche did change things when they added water cooling. Or is the section in my manual that describes the coolant level also wrong??
Porsche also said to use Optimoly TA with aluminum nuts on the air-cooled cars too. I wasn't saying that SteveP911 or Porsche were wrong about what is in the manuals. What I was saying that is wrong is the statement that fasteners "ALWAYS" need to be lubricated. The example I provided was CV joint bolts. Another example is flywheel bolts. All the nuts holding my transmission together are not specified by Porsche top be lubricated. I can't think of nylock nut on my car that is specified to be lubricated. There are plenty of fasteners that Porsche says need to be lubricated. Just not all.....or even most.
Not just nuts, but Matt's nuts and their lube level. I am just thankful to have no knowledge of them in person, but I do like how they look and their assumed function.
I was going to make a Dr. Seuss rhyme, but then I got to "can" and deleted it.
Porsche also said to use Optimoly TA with aluminum nuts on the air-cooled cars too. I wasn't saying that SteveP911 or Porsche were wrong about what is in the manuals. What I was saying that is wrong is the statement that fasteners "ALWAYS" need to be lubricated. The example I provided was CV joint bolts. Another example is flywheel bolts. All the nuts holding my transmission together are not specified by Porsche top be lubricated. I can't think of nylock nut on my car that is specified to be lubricated. There are plenty of fasteners that Porsche says need to be lubricated. Just not all.....or even most.
All you need to do is follow the instructions on what to lube and which lube to use. That's a good life lesson.
10-30-2022, 04:16 PM
