Date: Fri, 16 Dec 2005 21:22:19 -0800
Reply-To: Marc Sayer <marcsayer@COMCAST.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Marc Sayer <marcsayer@COMCAST.NET>
Subject: Re: removing frozen lug nuts / bolts ?
In-Reply-To: <f60d9dd738b9.43a2fa1e@gci.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Sorry, he's dead right. Torque values are generally given c&d (clean and
dry) unless otherwise stated. That's an engineering standard. Any time
you alter the coefficient of friction between components in a fastener
system that relies on torque to set clamping load, you are changing the
clamping load and fastener stretch levels. Anything that will increase
the friction between the fastener components, such as rust for example,
will lead to a decrease in clamping load and fastener stretch for a
given torque value. Conversely, any lubricant that reduces friction in
the system will lead to excessive clamping loads and fastener stretch
for a given torque value. All fasteners rely on their elasticity to
clamp the load reliably. If you stretch a fastener beyond its elastic
limits, the fastener is ruined. Using a torque value works because the
amount of stretch for that fastener is known for those conditions (i.e.
friction levels) at that torque value. The only way to know just how
much to alter the torque value when the friction value is changed (such
as when a lugnut/bolt assembly is coated with anti-seize) is to use a
stretch gauge on a handful of test subjects. Once you determine what
torque value gives the proper stretch value, you are all set, as long as
you use the exact same spec fasteners for the final assembly.
For a torque value to do what it is designed to do (in terms of
fasteners), it must be achieved under the correct circumstances. Clean
and dry (unless otherwise specified), undamaged or distorted threads,
with the original finish and material specs, and arrived at dynamically
(with the torque wrench in motion). This is the only way to ensure the
relationship between the torque value and the stretch value will remain
unaltered. And achieving the proper stretch value is the only way to
achieve the proper clamping load.
Now lots of folks have "gotten away" with all sorts of things in regards
to fasteners, but that doesn't mean it's right or safe. Folks have been
reusing rod bolts and head bolts for years when many were designed to be
single use. Most folks reuse "locknuts" even though most are designed to
be single use and many also require the use of new bolts each time as
well. And they seem to get away with it, sort of. Ever wonder why most
folks can not get the same mileage out of their rebuild that the factory
got from the original motor? This is often one of the reasons. Though it
is seldom clear as to why a fastener "gave out" or that a fastener was
responsible for a specific failure. For example, If a headbolt is
stretched beyond its elastic limit, you may not see the connection
between the "bad head gasket" and the fastener, but it's there. The bolt
may look fine, it may even torque properly, but under load, at operating
temps, it is not clamping the way the other headbolts are, and it is
causing the head and block to warp. Here's another one, brakes failing
sooner than expected? It could be the hub is being distorted because the
lugnuts are being over tightened by being torqued "wet" (lubricated)
when the spec is for dry.
Mark Tuovinen wrote:
>I respect your knowledge, particulary as it applies to vanagons. Your input when list members put forth their questions always makes sense and reflects an understanding that can only come from years of experience. However I do disagree with your opinion on the use of Anti-Seize on lug nuts or bolts. I know plenty of technicians locally that have used it without a problem for decades, I have on occasion applied it myself. Do you have any data to back up your assertion that the torque needs to be reduced when using it?
>
>Here most people remove their rims twice a year for the removal and installation of snow tires and I have NEVER seen anyone replace their lugnuts as a consumable item. I do sell more lug nuts and wheel studs in the Spring and Fall, but not a huge amount, just enough to cover the ones stripped, broken, cross threaded, or lost by the underpaid and over worked technicians employed at the local tire vendors. At the rate that you mention most people in my area would be purchasing new nuts every two years and I should be selling a lot more of them then I currently do.
>
>Again, I am not trying to offend or start a flame war, just relaying my experiences on this topic, and seeking to learn more from anothers perspective.
>
>Mark in AK
>Assistant Parts Manager
>Continental Honda
>Continental Acura
>
>P S I love the trailer hitch, just wish that summer wasn't another 5 1/2 months away so I could use it
>
>
> ----- Original Message -----
>From: Dennis Haynes <dhaynes@OPTONLINE.NET>
>Date: Friday, December 16, 2005 3:54 pm
>Subject: Re: removing frozen lug nuts / bolts ?
>To: vanagon@GERRY.VANAGON.COM
>
>
>
>>Anti- Seize on lug nuts or bolts? Now there's a recipe for disaster.
>>When using lubricants of this type, the torque needs to be reduced by
>>some 40 to 50% to keep the stud or bolt from being over stretched. Lug
>>nuts are consumables and should be replaced after 3-5 times of
>>use. The
>>German stuff seems very forgiving. The Japanese and American stuff is
>>not.
>>
>>Dennis
>>
>>
--
Marc Sayer
Journalist, Photographer, Dog Trainer (APDT member #062956)
Board member - Western States Great Dane Rescue Association
Director of Operations & Training - Deaf Dane Rescue Inc.
Springfield, OR USA
My Homepage - http://gracieland.org
Deaf Dane Rescue Homepage - http://gracieland.org/DaneRescue/
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