Went to do a brake job and found out why they were dragging. Caliper pins had pulled all the threads out of the knuckle and caliper was cocked. Talked to the guy at Schwaby and he said about 90% of the brake jobs he does on that style are heli coiled. Had to special order a 9mm heli coil kit to fix. What the hell? 9mm? What an oddball size. $50 for the kit and an hour later and its all done and back on the road. Is it really that bad of a design? Are there really that many people out there that have had to fix stripped threads?
The only thing that make me nervous is that I usually lock tite heli coils in and this time I opted not to because of the heat build up. I figured it would just cook out anyway.

 

You should have used lock tite. I don't think the pins get hot enough to cook it. Even if they did why risk not putting any on? Mine are helicoil and are fine. The lock tight hadn't cooked of at all

 

NO: 05-03-99
SUBJECT: Front Brake Caliper Mounting To Steering Knuckle Thread Repair
DATE: Apr. 23, 1999
OVERVIEW:
This bulletin involves repair of the threads on the steering knuckle or brake caliper mounting adapter that are used to install and retain the front brake caliper housing in its correct operating location.

DISCUSSION:
A Brake Knuckle Thread Repair Kit has been developed to repair stripped threads on the front brake caliper mounting attachment making it no longer necessary to replace the front steering knuckle/brake caliper mounting adapter when encountering stripped threads. The following information provides the repair procedure for using the Brake Knuckle Thread Repair Kit.

DIAGNOSIS:
Place the vehicle on an appropriate hoist.
Remove the front tire/wheel assembly.
Remove the brake caliper housing assembly by loosening the mounting bolts.
NOTE: IF HIGH TORQUE IS ENCOUNTERED DURING THE MOUNTING BOLT REMOVAL, IT IS LIKELY THAT THREAD DAMAGE WILL OCCUR OR HAS OCCURRED.

Remove the caliper housing assembly and hang the housing on the frame of the vehicle using an appropriate wire hanger.
NOTE: DO NOT ALLOW THE CALIPER HOUSING TO HANG BY ITSELF FROM THE BRAKE HOSE AS DAMAGE TO THE HOSE MAY RESULT.

If the vehicle has a bolt-on brake caliper mounting adapter, remove the adapter. If the brake caliper mounts directly to the steering knuckle, remove retainers on the wheel studs and remove the rotor.
Inspect the mounting bolts and knuckle threads for damage. If either is damaged, it is likely that damage to the other has occurred as well. If damage has occurred to the threads in the form of knicks, thread pulling, or cross-threading, perform the Repair Procedure.
PARTS REQUIRED:
Qty Part No. Description
AR (1) 05016155AA Kit, Brake Knuckle Thread Repair Includes:
23/64 Drill Bit
M9 X 1.25 Tap
Heli-Coil Installation Tool
Heli-Coil Tang Break-Off Rod
(25) M9 X 1.25 Stainless Steel Heli-Coils

REPAIR PROCEDURE:
Using the 23/64 in. drill, drill through the brake caliper mounting attachment hole keeping the drillperpendicular to the knuckle.
Using the M9 X 1.25 tap, tap the drilled hole ensuring to tap the hole entirely through.
Install a Heli-Coil insert onto the installation tool (tool number 3747-9). Be sure the tang is properly engaged into the driving contour of the tool.
Install the Heli-Coil into the drilled/tapped hole by rotating the tool and exerting slight pressure onto the tool/Heli-Coil and into the drilled/tapped hole. Continue to rotate the tool until the insert is located 1/4 to 1/2 turn below the steering knuckle surface.
Back the Heli-Coil installation tool out of the installed Heli-Coil. Then, remove the tang from the Heli-Coil by breaking the tang off using the tang break-off tool. Place the break-off tool into the assembled insert until it rests on the Heli-Coil tang. Holding the tool squarely, strike the tool sharply with a hammer.
If the vehicle has a bolt-on brake caliper mounting adapter, install the adapter. Refer to the appropriate Service Manual for information regarding proper brake caliper adapter mounting information. If the brake caliper mounts directly to the steering knuckle, install the rotor.
Install the caliper using new mounting bolts p/n 04886075AA in any location that had a Heli-Coil installed. Tighten the bolts to 30 - 35 N• m (22-26 ft. lbs.).
Install the tire/wheel assembly.
Lower the vehicle.
POLICY:
Reimbursable within the provisions of the warranty.

TIME ALLOWANCE:
Labor Op. No. Description Time
05-80-20-93 Brake Caliper Mounting Support Thread Repair, Left Side 0.4 Hrs.
05-80-20-93 Brake Caliper Mounting Support Thread Repair, Right Side 0.4 Hrs.


FAILURE CODE:
Code Description
XX Service Adjustment

 

this a two parts question, yes there are that many people that have stipped out the mounting bolts, however NO it is not really a bad design.

all threads are subject to being stipped or crossed if you are not carefull and/or load the bolt up before enough threads are caught. Stripped threads are in 99% of cases, caused by carelessness or laziness not design flaws.

this is because of how threads are designed to work, they are designed to deflect when loaded, this means that the threads (which are like little shelfs wrapped around the shaft of the bolt or the inside of the hole) actually bend whe you tighten them (or load them up, its the normal force on the bolt that causes deformation) as the bolt starts in one or two threads are bearing all of the load, as they deform more threads come in contact with each other and the load supported by each thread is reduced, by ALOT. if any of these threads are damaged it takes very little to damage everything and require thread replacement (helicoil). autozone also sells a larger self tapping bolt that will do the job too withouth putting a helicoil into it.

 

Good info, thanks. I tried the self tapping bolt and they were only about .010 larger than the original ones. I also noticed in the bulletin it did not say to apply lock tite. Maybe I guessed right. I just figured if the Heli coil backs out with the bolt when I take it apart next time, I will just put another new coil in with locktite this time. I think I have 10 of them left.