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S197 Handling Section For everything suspension related, inlcuding brakes, tires, and wheels.

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Old 02-20-2014, 09:46 PM   #1
bigo5552000
 
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Question Chamber Bolts?

So I was reading this thread...
http://mustangforums.com/forum/s197-...-thoughts.html

What exactly are you worried about shearing, bending, rotating??? I am just curious what failure modes you are worried about?

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Old 02-21-2014, 09:34 AM   #2
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First off, it's "camber bolts" (without any "h"), which as near as I can tell are nothing more than repair industry "crash bolts" used to bring a crash-damaged vehicle into alignment (or at least a semblance of) rather than have it consigned to the nearest recycle yard.

Most, but not all, of these bolts use a reduced shank with an eccentric cam by which adjustment is obtained. Smaller shank = not as strong, which is supported by the manufacturers of these bolts specifying installation torques that are barely half of what the OE strut-knuckle fasteners call for. Overtorquing them on installation, whether by accident or carelessness means you may have yielded them, in which case you what you now have are a couple of conversation piece paperweights. This is probably a combined torsional shear and tension failure (Mohr's circle stuff).

This is not a fastener to take any chances with, because partial (or complete) suspension collapse is something you do not want to experience, especially from a cause so easily avoided. I've been there, and while it wasn't due to strut, knuckle, or strut bolt failure, suspension failure is still suspension failure, and the possible downstream consequences (loss of control, possible crash) won't care why.

A number of early-year S197s actually experienced knuckle ("spindle") failures, and the root causes included insufficient clamping force at the bolts, which allowed repeated bending in the knuckle to the point where it ultimately failed in fatigue with a full-blown crack. Whether it was improperly torqued OE bolts or crash-bolts torqued to half of OE torque is immaterial, since the problem is inadequate clamp load due to insufficient torque for the joint.

Strictly speaking, these bolts should not be considered to act in shear. The clamp load produces friction that is supposed to prevent all movement, including whatever small amounts of bolt to hole clearance exist. It may happen that a bolt goes in with all of the clearance taken up in one direction, in which case the bolt would see some direct shear as a matter of coincidence for loads in one direction (but would be of zero help against loads in the opposite direction when the suspension moves the other way).

Unless a half-torque sized camber bolt has a method for retaining its setting separate from that torque, it is at least possible for the adjustment to slip. This may already have happened in autocross settings, but hitting a bad pothole this time of year could bring about the same result (a trip to the shop for re-alignment and possible replacement of the bolt(s) that slipped.

Ford has, or at least used to have, their own full-strength version that required opening up the holes slightly in order to install it. These you can trust to the same level that you trust the original bolts that the car rolls off the production line with.

I am aware that people seem to get away with using them, but as a now-retired engineer with some understanding of how bolted joints work I can't bring myself to endorse them given the above which I see as deficiencies.

I hope the various vendors who will eventually step in will understand my position. It's been a while since I last addressed this topic.


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Last edited by Norm Peterson; 02-21-2014 at 09:38 AM.
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Old 02-21-2014, 06:32 PM   #3
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H&R Camber bolts torque to 165 lb-ft just fine. They have a smaller range of adjustment, a degree or two at most, but that's why they're strong enough to handle the full torque.
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Old 02-22-2014, 02:54 AM   #4
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Quote:
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H&R Camber bolts torque to 165 lb-ft just fine. They have a smaller range of adjustment, a degree or two at most, but that's why they're strong enough to handle the full torque.
Unless H&R is using gypsy magic there is very little chance an H&R camber bolt in an unaltered strut mounting hole will torque to Ford's 148ft/lb torque spec and retain full fastener strength and clamping force. Fasteners are well understood and the fact is for a given clamping force you need a certain amount of clamping pressure. To achieve the factory torque spec of 148ft/lb you need a certain size fastener. By reducing the fastener size you must also reduce torque values or you will damage the fastener. H&R does not give a suggested torque spec nor are they willing to tell you the maximum allowable torque value.

Correction: should read 148ft/lb for early coarse thread fasteners.
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Old 02-22-2014, 07:19 AM   #5
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Isn't that torque spec either 148 for the early coarse-thread strut bolts or (I think) 166 for the upgraded fine-thread fasteners? (I know that 129 is associated with some of the rear UCA bracket fasteners, from current "due diligences".)

FWIW, I've occasionally heard rumors of there being one aftermarket crash bolt that can be torqued to at least the lower of the above values. But so far I have been unable to personally confirm this for anybody's bolts.


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Old 02-22-2014, 09:59 AM   #6
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Oh yes over looked the misspelling! It seems the trend is since you can't torque the fastened to the desired torque spec do to yielding the fear is the bolt in turn won't have enough clamping force. Which could allow the bolt to rotate causing a loss of suspension geometry. Has there been any testing showing that the camber bolts will stretch past their elastic point causing permanent yielding or has there only been speculation?
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Old 02-22-2014, 04:30 PM   #7
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The correct torque is 166 ft-lbs for the newer production cars. The cross section of the H&R bolts is (within the error of measurement) equal to the cross section of the oem bolts at the base of the threads.
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Old 02-22-2014, 07:48 PM   #8
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There is one other thing to check, and that's whether or not the latest OE bolt design is knurled in any way. I think Terry Fair (Vorshlag) mentioned something about this.


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Old 02-22-2014, 08:56 PM   #9
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Quote:
Originally Posted by Norm Peterson View Post
There is one other thing to check, and that's whether or not the latest OE bolt design is knurled in any way. I think Terry Fair (Vorshlag) mentioned something about this.


Norm
I replaced my 2014 suspension a month ago. Build date August 2013. The bolts were not knurled on my car.
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Old 02-23-2014, 01:03 AM   #10
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Quote:
Originally Posted by Norm Peterson View Post
Isn't that torque spec either 148 for the early coarse-thread strut bolts or (I think) 166 for the upgraded fine-thread fasteners? (I know that 129 is associated with some of the rear UCA bracket fasteners, from current "due diligences".)

FWIW, I've occasionally heard rumors of there being one aftermarket crash bolt that can be torqued to at least the lower of the above values. But so far I have been unable to personally confirm this for anybody's bolts.


Norm

Yes, brain fart on my part. Sorry.
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Old 02-23-2014, 01:03 AM
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