Mon Mar 16 17:30:00 CET 2015
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falloutboy
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Kommentare (3)
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Fahrwerk
Vibration Analysis, Part 1: Tires There have been several vibration conditions on 2014 Silverado 1500 and Sierra 1500 and 2015 Silverado, Tahoe, Suburban, Sierra, and Yukon models that have proved to be difficult to diagnose. These vibrations often occur at speeds of 35–45 mph (56–72 km/h) or 60–70 mph (96–120 km/h) and are felt in either the seat or steering wheel. Based on this information, the tires were moved from front to back on the same side. This put the highest RFV numbers on the front and the lowest on the rear of the vehicle. A second road test showed a greatly reduced tire vibration amplitude of 0.804 mg at 69 mph. (Fig. 2) Some of the vibration cases may be difficult – but with the right approach and the right tools, a successful diagnosis can be achieved quickly.
First Steps
The first step in determining the cause of a vibration is a test drive with the appropriate diagnostic equipment installed on the vehicle. If the correct tools are not used or the proper procedures are not followed, an incorrect diagnosis will result.
![]() TIP: If the vibration can be duplicated on the rack, the test should be performed a second time with the wheel and tire assemblies removed from the vehicle and the wheel nuts installed to retain the brake discs and/or brake drums. If the vibration is eliminated, focus on the wheel and tire assemblies as the source of the vibration. If the vibration is still present, focus on the vehicle driveline as the source of the vibration. Reviewing the Hunter GSP9700 Road Force Balancer results for the tire with the 2nd order disturbance showed the 1st order harmonic was below specification, but the 2nd order specification was 21 lbs. (Fig. 5) It’s important to look at all harmonic measurements when reviewing the road force measurements and not to dismiss a particular tire based on only one measurement. If present, the CH-51450 Oscilloscope Diagnostic Kit tool will display the primary vibration as a 2nd order disturbance. Be sure to use this information and look at the other harmonic measurements on the Hunter GSP9700 Road Force Balancer. The vibration was corrected by replacing and match-mounting (or vectoring) all four tires. The RFV measurements were 1 lb., 4 lbs., 4 lbs., and 7 lbs. (Fig. 6) TIP: When replacing tires, the road force should be checked before a test drive and after a test drive (minimum of 10–15 miles or 16–24 km/h). Road force on new tires will change dramatically after the tires are warmed up (as much as a 20-lb. reduction). After the test drive, the tire’s road force should be checked. If acceptable RFV cannot be achieved, first try vectoring the tire on the rim before an alternate tire is used. Refer to Bulletin #13-03-10-002: Diagnostic Tips for Difficult to Resolve Tire/Wheel Vibration Concerns. |
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