Buick brake job reveals faulty design practices

Trouble: Brake pad wore down to metal-to-metal contact and subsequent rotor damage. No worn-pad audio warning sound generated as owner's manual specified. Observations:
1. Warning sound tab is on outer pads only; pad wear was uneven; inner pad lining wore down to metal before signal tab on outer contacted rotor. Recommendation - All pads should have tabs.
2. Brake caliper-to-steering knuckle attaching bolts are full- length threaded, coarse thread. Recommendation - Use solid shank fine thread bolts for better shear and tension strength.
3. Rotor mounting holes are oversized and share wheel studs with wheels. Recommendation - Rotor should have dedicated fasteners, be located precisely and have zero play. Dito wheel. Noted aluminum transfer to rotor indicating relative rotational movement between the two components.
#3 above deserves additional attention. The assembly is layered such that I believe it can loosen and possibly disassemble itself. I wonder if this has happened in the field. Also the wheel studs are full-length threaded, which places them in shear loading on threads, in both rotational directions, in shock loading when the rotor shifts in their oversized mounting holes when in braking or power modes. I am also concerned about the excessive tension loads on these studs as the 100 lb-ft recommended torque is far beyond that listed in reference tables, even for 150,000 psi steel, FINE THREAD, which these bolts are not. Further complex stress occurs during suspension excursions and in steering. Car makers have been building their cars like this for decades, using cheap fasteners, quick but questionable assemblies and brute force to hold things together, but that doesn't make it right. They should think solid shank, fine thread, self-locking nuts, zero play tapered splines and in general, sound engineering emphasizing the concept of fail-safe, robust design.
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On 4 Dec 2011 15:06:58 -0000, snipped-for-privacy@See.Comment.Header (Student Mechanic) wrote:

OK, that may be a good idea.

Have they proven to be a problem? If not, no reason to change.

Sorry, cannot make zero play. The tolerances are different under harsh driving conditions, heated brakes, etc. There must be an allowance for that.

You can engineer a near perfect car, but it will cost 3X or 4X the present cost. Unless you can show failures in the present design, there is no reason to change. Millions of car are made like this every year. Show me the failure numbers and we can see if your ideas make sense. Otherwise, it is engineering only for the sake of engineering. It does nothing to contribute to the economics of the product and a benefit to the consumer. It will just make cars out of reach for many of us = failure.
IMO, the main purpose of this post is for you to show off that you took a mechanical design course. Maybe you should be working on the next space shuttle design.
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***** It doesnt cost 3X or 4X to engineer and construct a car of rather good durability and performance, IMO. GM had fallen short of durability years ago.
There should be constant attention to improving the product, as in ISO, and this does not add such a cost to bringing a product to market.
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It does if you want to meet the specs of "Student Mechanic". When you specify equipment and tolerances that are normally found in the space shuttle, it adds a lot of cost. SM is suggesting change for the sake of change where it is not needed.
Most present designs are acceptable and can be tweaked to be still better, as you suggest.
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Well, that is what I thought. The designs are adequate and reasonable adherence to design and specifications would yield a pretty good car.
You know why the (overly) high rated German cars are more expensive, I am sure.
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