Brakes - Pull While Braking: Overview
88Chevy33Number: 88-379-5
Section: 5
Date: DEC., 1988
Subject: LEAD WHILE BRAKING
Model and Year: 1984-86 K 1-2 1987-88 V 1-2
TO: ALL CHEVROLET DEALERS
A condition described as directional lead (either right or left) while braking may be addressed on the models listed above by careful inspection, adjustment or repair of the vehicle's tires, suspension, steering or brake components.
The following procedures have been developed to systematically address the area(s) that should be inspected and adjusted.
Evaluation of a vehicle's brake performance is not intended to be made with the vehicle operator's hands removed from the steering wheel. Vehicles that exhibit directional bias under these conditions are not considered to exhibit brake lead.
Before road testing the vehicle, perform the following services:
NOTICE: Follow the service procedures in the 1988 Light Duty Service Manual unless noted differently.
Preliminary Inspection:
^ Inspect tires for excessive, uneven wear - replace if necessary
^ Equalize tire pressures.
^ Torque leaf spring-to-axle U-bolts to high limit of specification (150 ft.lbs. or 203 N-m). See Section 3C for tightening order.
^ Equalize parking brake adjustment.
^ Adjust rear service brakes to .030" running clearance.
^ Inspect and record front end alignment readings - adjust total toe to specifications (.0 " to .14 ").
Inspect caliper brake line bolt (# 34, page 5A8, Figure 4, 1988 Service Manual) for mislocation of orifice. The orifice should be located in the unthreaded part of the bolt. If the orifice is located in a threaded portion of the bolt, then the bolt must be replaced.
NOTICE: After the preceding inspections and/or adjustments have been made, the vehicle should be road tested to determine if a lead still exists. Vehicles that lead may lead either right or left when the brakes are applied.
Make all stops on a dry, level (no crown), clean roadway.
IMPORTANT!
Each applicable step must be thoroughly completed to effect a lasting repair. Failure to complete the procedure exactly as written may result in an unsatisfactory repair.
Conduct a series of 5 stops from 55 MPH bringing vehicle to a stop in 5 seconds (15 FPS Sq.). Record amount and direction of lead. Do not slide or lock wheels.
* FPS Sq or Ft/Sec2 is the measurement used for calculating the deceleration rate with a decelerometer. Use of decelerometer, when available, is the preferred method.