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View Full Version : Interesting Studebaker Disc Brake Question?



Bo Markham
06-20-2012, 06:08 AM
A fella brought in his Avanti the other day for some brake work. The disc brakes were not working right and it appeared to me something was amiss. No shims on one side and some unequally distributed on the other. We all know the book says to shim until centered. I ask the gentleman who had worked on his brakes last. He indicated some shop in his town and the name of the owner. I called these brake specialists and possed a simple question. Why is it important to follow the service manual and shim the brake caliper until it is centered correctly? Fella told me that I didn't know what I was talking about, and shiming wasn't required as the caliper would right itself as pressure equalized in the system. I'm no brake dummy, but when the professionals can't explain it, or get it right, what's an average guy to do?

Now I ask you, why is it important to follow the service manual and correctly shim the caliper? What bad things could result if you don't? I can tell you one thing that I found. Premature pad ware on the inside resulting in grooving of the rotor, which resulted in the right front pull the customer was experiencing when braking. Quick ratio steering is mighty touchy!

What say you?

bezhawk
06-20-2012, 06:35 AM
Since the pads should hit the rotors squarely and since the caliper pistons have self retracting pins, you need to shim so they hit at the same time. If you don't it will pull, you'll get uneven wear, squealing, the pistons can hit the stops if it's too off center. All sorts of maladies.

Jim B PEI
06-20-2012, 06:53 AM
The state of 'specialists' these days, tsk tsk. Give ma an old fashioned generalist every time who can read a shop manual and isn't afraid to check it out to be sure, even if he has done it for 35 years...

Johnnywiffer
06-20-2012, 09:02 AM
On all the Fieros I ever had, as well as most other cars with disk brakes, the outer pad wears 1st. In fact, many times I could have just replaced the outer pad and still had enough inner pad for many more miles.

Do they make the pads out of different materials so the outer pad wears 1st?

John

Gunslinger
06-20-2012, 09:43 AM
Many years ago I worked at an auto center and once a customer complained to the shop manager that the tech working on his car was reading the manual on how to do the work (I don't remember what was being done to the car), and asked how good was the tech if he had to look at the shop manual. The shop manager simply replied "If any of my guys DON'T refer to the manual I'll fire them!"

Mike Van Veghten
06-20-2012, 10:45 AM
Most current calipers WILL center themselves. The caliper moves on the sleeves that the attach fasteners go thru, thru the mounting ears on the caliper body. If you remove the sleeves from the caliper, youll see an o-ring between the caliper body and the steel sleeve. This is one item that does wear and when it dies...the caliper will make noise...rattling back and forth.

Now......
With calipers that have NO...centering device...yes, they should be shimmed to the center of the rotor vs. the center of the caliper.
NOT....so "they hit at the same time..." (the hydraulic system will take care of that), but to keep the pistons as centered in their bores as possible.
As the pads wear...if one (or a pair) of caliper pistons are out of their bore farther on one side than the other, the piston that is farther out of its bore, can and will start to "rock" in the caliper when there is pressure in the system.

Simple as that.
Brake fluid is just like water...remember 8th grade science...water will find it's own center, or level when two vessels are connected. The same thing happens when the pedal is pushed...each piston acts upon the brake pad "equally"...and will push the piston until there is a returning force...the rotor....NOW...all things are equal..."force" (or pressure) wise.
BUT...if the caliper isn't centered properly over the rotor...the pistons on one side will "equalize" the system, by moving to the rotor and will end ou farther out of the caliper. Wear difference will happen because of several different factors, including the side load being put onto the piston(s) that are the farthest out of the caliper.

All that is to say...YES...center the caliper over the rotor. How close...I do mine to .020" or better.

Mike

PackardV8
06-20-2012, 10:46 AM
Fixed calipers are old school and require shimming. Because shimming is time-consuming and beyond what many techs are able to do, most recent disc brake designs have calipers which can float side to side. Many have only one piston per caliper. Sometimes these get sticky and only the pad in front of the piston is putting pressure on the rotor, or the off side sticks and drags all the time.

jack vines

Mike Van Veghten
06-20-2012, 10:48 AM
Actually Jack, "fixed" calipers are "new" again.

See the...new, "radial" mounted caliper design...

Mike

doug
06-20-2012, 10:51 AM
If you are working on aircraft and the F.A.A. drops by, the maintenance manual better be used or you are in deep doo-doo.

63 R2 Hawk
06-20-2012, 11:32 AM
Find a Ferrari mechanic and he can charge you 10X$$$ for centering the Dunlop calipers, or you can refer to:
http://www.studebaker-info.org/tech/brakes/SPdb/SPDB.html
and save a lot of money.....

Bo Markham
06-20-2012, 04:22 PM
Find a Ferrari mechanic and he can charge you 10X$$$ for centering the Dunlop calipers, or you can refer to:
http://www.studebaker-info.org/tech/brakes/SPdb/SPDB.html
and save a lot of money.....

Now what does this have to do with the original question?

SN-60
06-20-2012, 05:18 PM
It's just that this mechanic did not understand this style disc brake system, and He should not have been working on it. Happens all the time though.

PackardV8
06-20-2012, 05:48 PM
Find a Ferrari mechanic and he can charge you 10X$$$ for centering the Dunlop calipers,

Now what does this have to do with the original question?
Yes, it sort of pertains, because Ferrari, Aston Martin, Jaguar and other high dollar sports cars used the fixed Dunlop calipers back in the same era as the Avanti.
No, today's Ferrari mechanic is not very likely to have seen sixty-year-old brake .
Maybe, always take the Shop Manual and point out the relevant section when paying anyone to work on a Stude.

jack vines

StudeRich
06-20-2012, 05:58 PM
On all the Fieros I ever had, as well as most other cars with disk brakes, the outer pad wears 1st. In fact, many times I could have just replaced the outer pad and still had enough inner pad for many more miles.

Do they make the pads out of different materials so the outer pad wears 1st?

John

John, this is exactally why you have this problem, you most likely have only one Hydraulic Cylinder on the Caliper: :eek:

"Fixed calipers are old school and require shimming. Because shimming is time-consuming and beyond what many techs are able to do, most recent disc brake designs have calipers which can float side to side. Many have only one piston per caliper. Sometimes these get sticky and only the pad in front of the piston is putting pressure on the rotor, or the off side sticks and drags all the time."

Quote: jack vines

bezhawk
06-20-2012, 07:05 PM
The Ferrari I just did calipers on yesterday, has Brembo 4 piston calipers. They are directly bolted to the spindle, and non floating . The pads are specific to rotation (chamfered on the leading edge), and are different thicknesses, have markings on them . One was .255, and others were marked .335. Electronic wear sensors built into front pads. Very specific mounting bolt torque.

Bo Markham
06-21-2012, 08:40 AM
Jack,

The two part question posed was, "Why is it important to follow the service manual and correctly shim the caliper"? And, "What bad things could result if you don't"? Telling some one to find a Ferrari mechanic so he can over charge them has nothing what so ever to do with the question posed. Besides that, your just about 100 % correct with your second statement, because the shop that did the work was an import shop. You'd think that professionally trained and run shops could answer the above question and should be able to get the job done, right?

Actually, your initial response was on target, premature ware, dragging, etc...... Really, I guess I'd like to know if those people that can read and do follow the prescribed procedures in the shop manual really understand the reasons behind them, and what it really means to them travelling down the road at 70 miles an hour?