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Fig. 8 Installing Boot in Caliper

Fig. 9 Folded Caliper Guide Pin Bushing

the caliper assembly. Flanges should be seated evenly on both sides of the bushing hole in the caliper assembly (Fig. 11).

Install the Guide Pin Sleeve into the guide bushing using the following procedure.

(1)Install the sleeve into one end of the bushing until the seal area of the bushing is past the seal groove in the sleeve (Fig. 12).

(2)Holding the convoluted end of the bushing with one hand. Push the sleeve through the bushing (Fig.

13)until the one end of the bushing is fully seated into the seal groove on the one end of the sleeve.

(3)Holding the sleeve in place work the other end of the bushing over the end of the sleeve and into the seal grove (Fig. 13). Be sure the other end of the bushing did not come out of the seal grove in the sleeve.

Fig. 10 Installing Caliper Guide Pin Sleeve Bushings

Fig. 11 Bushing Correctly Installed In Caliper

(4) When the sleeve is seated properly into the bushing. The sealed for life bushing can be held between your fingers and easily slid back and forth without the bushing seal unseating from the sleeve.

Before installing caliper assembly on vehicle, inspect braking disc. If any conditions as described in Checking Braking Disc for Runout and Thickness are present the braking disc, must be replaced or refaced. If the braking disc does not require any servicing, install caliper assembly.

5 - 52 BRAKES

Fig. 12 Installing Caliper Sleeves

Install brake hose onto caliper using banjo bolt. Torque the brake hose to caliper assembly banjo bolt to 33 NIm (24 ft. lbs.). New seal washers MUST always be used when installing brake hose to caliper.

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Fig. 13 Installed Caliper Bushing Sleeve

Bleed the brake system (see Bleeding Brake System). Pump the brake pedal several times to be sure that the vehicle has a firm pedal, before the vehicle is moved or driven.

GENERAL INFORMATION

Any servicing of the braking disc requires extreme care to maintain the braking disc within service tolerances to ensure proper brake action.

CAUTION: If the braking disk (rotor) needs to be replaced with a new part. The protective coating on the braking surfaces of the rotor MUST BE REMOVED with an appropriate solvent, to avoid contamination of the brake shoe linings.

When replacing a rotor with a new part do NOT reface the new rotor. Rotor already has the required micro finish when manufactured, only remove the protective coating.

SERVICE PROCEDURES

CHECKING BRAKING DISC FOR RUNOUT AND THICKNESS

On vehicle, braking disc (rotor) runout is the combination of the individual runout of the hub face and the runout of the disc. (The hub and disc are separable). To measure runout on the vehicle, remove the wheel and reinstall the lug nuts tightening the disc to the hub. Mount Dial Indicator, Special Tool C-3339 with Mounting Adaptor, Special Tool SP-1910 on steering arm. Dial indicator plunger should contact disc (braking surface) approximately one inch from edge of disc (See Fig. 1). Check lateral runout (both sides of disc) runout should not exceed 0.13 mm (0.005 inch).

INSPECTION DIAGNOSIS

Before refinishing or refacing a braking disc, the disc should be checked and inspected for the following conditions:

Braking surface scoring, rust, impregnation of lining material and worn ridges.

Excessive lateral rotor runout or wobble. Thickness variation (Parallelism). Dishing or distortion (Flatness).

If a vehicle has not been driven for a period of time. The discs will rust in the area not covered by the brake lining and cause noise and chatter when the brakes are applied.

Excessive wear and scoring of the disc can cause temporary improper lining contact if ridges are not removed before installation of new brake shoe assemblies.

Some discoloration or wear of the disc surface is normal and does not require resurfacing when linings are replaced.

Excessive runout or wobble in a disc can increase pedal travel due to piston knock back. This will increase guide pin bushing wear due to tendency of caliper to follow disc wobble.

Thickness variation in a disc can also result in pedal pulsation, chatter and surge due to variation in brake output. This can also be caused by excessive runout in braking disc or hub.

Dishing or distortion can be caused by extreme heat and abuse of the brakes.

Fig. 1 Checking Braking Disc for Runout

If runout is in excess of the specification, check the lateral runout of the hub face. Before removing disc from hub, make a chalk mark across both the disc and one wheel stud on the high side of runout. So you'll know exactly how the disc and hub was originally mounted (Fig. 2). Remove disc from hub.

Install Dial Indicator, Special Tool C-3339 and Mounting Adaptor, Special Tool SP-1910 on steering

Fig. 2 Marking Braking Disc and Wheel Stud

knuckle. Position stem so it contacts hub face near outer diameter. Care must be taken to position stem outside the stud circle but inside the chamfer on the hub rim. Clean hub surface before checking. (See Fig. 3)

Fig. 3 Checking Hub for Runout

Runout should not exceed 0.08 mm (0.003 inch). If runout exceeds this specification, hub must be replaced. See Suspension Group 2. If hub runout does not exceed this specification, install disc on hub with chalk marks two wheel studs apart (Fig. 4). Tighten nuts in the proper sequence and torque to specifications. Finally, check runout of disc to see if runout is now within specifications.

Fig. 4 Index Braking Disc and Wheel Stud

If runout is not within specifications. Install a new braking disc or reface disc, being careful to remove as little as possible from each side of disc. Remove equal amounts from each side of disc. Do not reduce thickness below minimum thickness cast into the unmachined surface of the rotor.

Thickness variation measurements of disc should be made in conjunction with runout. Measure thickness of disc at 12 equal points with a micrometer at a radius approximately 25.4 mm (1 inch) from edge of disc (Fig. 5). If thickness measurements vary by more than 0.013 mm (0.0005 inch) disc should be removed and resurfaced (Figs. 6 and 7), or a new disc installed. If cracks or burned spots are evident in the disc, disc must be replaced.

Fig. 5 Checking Disc for Thickness

Light scoring and/or wear is acceptable. If heavy scoring or warping is evident, the disc must be refinished or replaced (See Refinishing/Refacing Braking Disc). If cracks are evident in the disc, replace the disc.

BRAKING DISC REMOVAL

(1)Raise vehicle on hoist or jackstands. Remove wheel and tire assembly.

(2)Remove caliper assembly, as described under Brake Shoe Removal in this Group, (but do not disconnect brake line). Suspend caliper from wire hook or loop to avoid strain on flexible hose.

(3)Remove braking disc from the hub.

INSTALLING BRAKING DISC

(1)Slide braking disc on hub. Clean both sides of braking disc with alcohol or suitable solvent.

(2)Install caliper assembly, as described in Brake Shoe Installation paragraph.

REFINISHING BRAKING DISC

REFACING BRAKING DISC

Refacing of the braking disc is not required each time the shoe assemblies are replaced.

If the braking disc surface is deeply scored or warped or there is a complaint of brake roughness or pulsation the rotor should be resurfaced or refaced (Figs. 6 and 7).

Fig. 6 Refacing Braking Disc

Fig. 7 Resurfacing Braking Disc (Final Finish)

When refacing a braking disc the required 0.10 mm (0.004 inch) TIR (Total Indicator Reading) and 0.013 mm (0.0005 inch) thickness variation limits MUST BE MAINTAINED. Extreme care in the operation of braking disc turning equipment is required.

The collets, shafts and adapters used on the brake lathe, and the bearing cups in the rotor MUST be clean and free from any chips or contamination.

When mounting the disc on the brake lathe, strict attention to the brake lathe manufacturer's operating instructions is required.

If the disc is not mounted properly the run-out will be worse after refacing than before refacing.

The use of a double straddle cutter (Fig. 6) that machines both sides of the disc at the same time is highly recommended.

RESURFACING BRAKING DISC

This operation can be used when the disc surface is rusty or has lining deposits.

A sanding disc attachment will remove surface contamination without removing much braking disc material.

It will generally follow variations in thickness that are in the disc.

The following chart shows the location of measurements and specifications when servicing the braking disc.

All braking discs have markings for minimum allowable thickness cast on an un-machined surface of the braking disc (Fig. 8). The thickness markings may be located on the disc as shown in (Fig. 8) or on an alternate surface.

This marking includes 0.76 mm (0.030 inch) allowable disc wear beyond the recommended 0.76 mm(0.030 inch) of disc refacing.