Caliper Bolts - Are they really one time use?
- Thread starter ViperJoe
- Start date
sandman
GT Owner
BlackICE
GT Owner
Only if you really use the brakes. EP would be fine in reusing them, although is should be disclosed to any new owner that will really drive the car.
BlackICE
GT Owner
The bolts retaining the shocks are also one time use. I got new ones from Torrie when I replaced them.
The caliper bolts are indeed one time use as are a number of other fasteners.
I do not think they are torque to yield though, not all one time use bolts are. These are large bolts, with an installation torque of 74ft lbs, no where near enough to yield a bolt that large. Its more likely the one time use thread loc compound factory applied to the bolt. Ford does this on many fasteners on many of its products, not just the GT. I could be wrong if the bolts are a lower yield strength steel but does not seem likely. I have no published data one way or the other, just observation and the new bolts do have blue thread loc compound on them.
I do not think they are torque to yield though, not all one time use bolts are. These are large bolts, with an installation torque of 74ft lbs, no where near enough to yield a bolt that large. Its more likely the one time use thread loc compound factory applied to the bolt. Ford does this on many fasteners on many of its products, not just the GT. I could be wrong if the bolts are a lower yield strength steel but does not seem likely. I have no published data one way or the other, just observation and the new bolts do have blue thread loc compound on them.
H
HHGT
Guest
STORMCAT
GT
The Ford manual does not say to discard after use or disassembly. If someone can show me where it says that I will retract my statement.
It clearly states this on areas that we know are one use only type of bolts i.e.... like the Trans axel coupling bolts.. If there are one time use I should be dead by now,, my calipers have been off and on for the AP brake conversion and for my Carbon Ceramic Brake project .. I can say no one has been harder on brakes than me,, :biggrin
It clearly states this on areas that we know are one use only type of bolts i.e.... like the Trans axel coupling bolts.. If there are one time use I should be dead by now,, my calipers have been off and on for the AP brake conversion and for my Carbon Ceramic Brake project .. I can say no one has been harder on brakes than me,, :biggrin
2112
Blue/white 06'
BlackICE
GT Owner
Brian here is the information that you seek I cannot say if the bolts really need replacement or not, only that the my Ford service CD says to do so.
Attachments
It has been well documented here many times that the 2005 Service Manual contains numerous errors - most of which were fixed in the 2006 Service Manual. This is yet another example.
Regarding the shocks - ALL of the bolts front and rear are completely re-useable. Please refer to the manual for proper torques specs. The nut at the lower shock mount (rear shock only) IS recommended to be replaced after it is removed.
Regarding the caliper bolts, these bolts are also re-useable.
ALL of these corrections are in the 2006 Service Manual, which SHOULD be the only manual that is used - and should certainly be the only manual referenced after the well-documented shortcomings of the 2005 Service Manual.
Regarding the shocks - ALL of the bolts front and rear are completely re-useable. Please refer to the manual for proper torques specs. The nut at the lower shock mount (rear shock only) IS recommended to be replaced after it is removed.
Regarding the caliper bolts, these bolts are also re-useable.
ALL of these corrections are in the 2006 Service Manual, which SHOULD be the only manual that is used - and should certainly be the only manual referenced after the well-documented shortcomings of the 2005 Service Manual.
STORMCAT
GT
Hey Clinton , Thanks. As Kendall states the 2006 manual is different.. I repaced brake calipers and installed new shocks, removed hubs etc,,, I have reused all of the bolts. The Nut that Kedall refers to is a nylon lock nut. Some times the nylon gets a little wore and doesn't work as good as new.. A little loc-tite can make it reusable..
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BlackICE
GT Owner
Thanks Kendall, nice to know I don't need to change them.
With the outdated information that I had I thought it was prudent to be safe rather than very sorry, so I changed the bolts. I wouldn't want any failures on a mile run! :ack
I was suspicious of the recommendation to change the lower shock bolt as it is one beefy part that 129 ft/lbs shouldn't faze.
Just FYI, the 2006 service manual also instructs that the caliper bolts are one time use. Page 206-03-5. Does not say why. I do not have a 2005 manual to compare to.
I also found it interesting that all 4 calipers are different part numbers. I would have suspected only 2.
I also found it interesting that all 4 calipers are different part numbers. I would have suspected only 2.
Empty Pockets
ex-GT Owner
'Interesting...and kinda odd alright.
(Maybe that explains why the passenger side wheels alway seem to gather more brake dust than driver's side! :lol I've never been able to figger that one out...)
Indy GT
Yea, I got one...too
Indy GT
Yea, I got one...too
Although I certainly understand why an OE would want to specify a one-time use only fastener be it for the locktite issue mentioned earlier or some perceived "safety" concern, has anyone ever seen anywhere a technical description of WHY this recommendation is made (other than to maybe sell additional fasteners although probably not a big revenue stream)? Likely not.
You may imply from a one-time-use bolt that "yielding" of the bolt material is somehow harmful to the bolt and thus its structural integrity is somehow compromised by this event; thus requiring you to throw the bolt away. I do not believe this is true.
In a non-fatigue environment (i.e. one in which the bolt sees constant, non-varying load which the connection designer wants to strive for and can design for), the bolt is just fine being loaded into the material yield portion of the stress-strain diagram. Typical "critical" bolted connections (ones where particular attention to detail is warranted) use high strength fasteners (good, controlled and specified material properties) which have good elongation properties which enables loads into the yield portion of the stress/strain curve.
Without getting too technical and posting load/unload diagrams for bolt stresses below and above the material yield strength, the bolt will work just fine even after being loaded above the yield strength (stress) of the material. Good bolted joint engineering design practice is to torque a bolt to 90% of material “proof strength” which is roughly equivalent to 90% of material yield strength. (Ref. Shigley, ‘Mechanical Engineering Design’ for those who care). Thus “normal” (or reusable) bolts in a properly designed joint using engine oil for assembly, are already very close to loads approaching the bolt material yield strength.
Thread and head collar friction loads (which consume a large part of this initial torque before the torque can result in clamping load) are very large variables in bolt torque calculations. If the installer puts the nut on dry, with engine oil or uses “never-seize” during assembly, very large swings in the amount of actual load the initial torque produces in the fastener can and do occur. This is because the thread lubricants can significantly alter the thread friction which consumes torque before producing bolt clamp load. Thus, in reality a properly designed bolted assembly using never-seize (when torquing guidance does not specifically call out use of this assembly lubrication) torqued to specification can load a regular bolt into material yield easily without the assembler evening knowing this fact.
To be safe, one should follow the replacement instructions dictated by the OE, but it would be interesting to have the application designer state, why.
STORMCAT
GT
sahlman
Ford GT Team Alumni
Some background for you guys on the chassis bolts that corresponds to many of your comments:
None of the shock, control arms or anti-rollbar bolts are torque to yield/angle or single use bolts. I am not positive on why the manual said to replace the upper shock bolts. (I had design and release on the shocks and chassis bolt connections to the frame) If this statement changed in later manuals then I think it was an error or else FCSD decided it was unnecessary. The only reason I can think of that FCSD might have originally spec’d upper shock bolt replacement was due to threading into the aluminum casting (the control arm bolts then should have the same direction of replacement) in case the bolt coating was compromised in install or removal allowing galvanic reaction and the potential for the bolt to seize in the casting. I have not heard of any incidence of this issue in service and we reused bolts constantly in development. And I do not recall discussion on the need for replacement in service.
The caliper bolts were also standard torque spec and bolts (not torque to yield/angle) and I think the caliper bolt replacement direction in the manual may be a standard Ford statement for caliper bolts, an error or the same FCSD threading into aluminum concern. I verified it is a standard bolt with the original FGT brake design engineer.
I actually reviewed going to torque to yield for all of these bolts because it provides the most consistent torque setting and can allow for smaller bolts for weight and package. However, my detailed bolt calculations called out smaller bolts than people were used to seeing already, torque to yield is not standard practice for chassis bolts (they are for engine assembly) and this specific discussion and potential confusion is an example of why we stuck with standard torque specs and bolts.
Note- ALL chassis bolt torque specs were for dry joints, no lube, no anti-seize. As Indy GT states, any type of lubrication will change the bolt preload due to changing the thread friction when torqued to our dry spec and has a good chance of yielding the bolt.
Scott
None of the shock, control arms or anti-rollbar bolts are torque to yield/angle or single use bolts. I am not positive on why the manual said to replace the upper shock bolts. (I had design and release on the shocks and chassis bolt connections to the frame) If this statement changed in later manuals then I think it was an error or else FCSD decided it was unnecessary. The only reason I can think of that FCSD might have originally spec’d upper shock bolt replacement was due to threading into the aluminum casting (the control arm bolts then should have the same direction of replacement) in case the bolt coating was compromised in install or removal allowing galvanic reaction and the potential for the bolt to seize in the casting. I have not heard of any incidence of this issue in service and we reused bolts constantly in development. And I do not recall discussion on the need for replacement in service.
The caliper bolts were also standard torque spec and bolts (not torque to yield/angle) and I think the caliper bolt replacement direction in the manual may be a standard Ford statement for caliper bolts, an error or the same FCSD threading into aluminum concern. I verified it is a standard bolt with the original FGT brake design engineer.
I actually reviewed going to torque to yield for all of these bolts because it provides the most consistent torque setting and can allow for smaller bolts for weight and package. However, my detailed bolt calculations called out smaller bolts than people were used to seeing already, torque to yield is not standard practice for chassis bolts (they are for engine assembly) and this specific discussion and potential confusion is an example of why we stuck with standard torque specs and bolts.
Note- ALL chassis bolt torque specs were for dry joints, no lube, no anti-seize. As Indy GT states, any type of lubrication will change the bolt preload due to changing the thread friction when torqued to our dry spec and has a good chance of yielding the bolt.
Scott
FENZO
GT Owner
I saw this one Sunday morning on Horsepower TV, thought it was a decent demonstration of how different lubes can affect torque.
http://youtu.be/6-XXVk_vwKw
http://youtu.be/6-XXVk_vwKw