The Test Course And Methodology
A 28-mile round-trip course was used, starting at Tire Craft in Point Pleasant and proceeding to the Garden State Parkway (north Exit 91 in Brick, New Jersey), the roadway used for the actual tests. Using the same mile-marker posts for each test run, cabin noise levels were recorded at 35, 45, 55, 65 and 70 mph. These readings were recorded with the cruise control set for the various speeds, and level sections of the Parkway (no inclines) were used with no adjacent vehicles pacing or passing when the readings were taken. The course direction changed from north to south two miles past Exit 98, where the service area plaza was used to turn around for the return leg of the course. Again readings were taken at the five speed levels using identical mile markers on level stretches of highway as previously described. At the conclusion of the test pass, the Parkway was exited at Exit 91 south, and we returned to Tire Craft so the next set of tires could be mounted prior to starting the next test pass.
All of the run-flat tires were tested on the same day, and all of the non-run-flat tires were tested the following day. The weather was dry and hot, with temperatures averaging 90 degrees for both days. The recorded sound levels for both the departure and return test passes were tabulated and averaged then entered into the charts appearing here. Two people were present in the test vehicle for all tests; the driver (Liz Benford) who set the cruise control at the appropriate mile markers and speeds, and a passenger (Tom Benford) who recorded the sound level meter readings at these points. The windows were up, the air conditioning was on the lowest fan point, and the stereo was not turned on during all testing.
The following tires were the ones used for testing. All tires tested were 245/45ZR17s for the front and 275/40ZR18s for the rear:
The chart colors correspond to the tires on the following page.
The Pit Crew
Mark Mastrojohn, the manager of Tire Craft in Point Pleasant, New Jersey, coordinated the efforts of his staff to ensure that the test tires were mounted, balanced, inflated, and changed on the test vehicles consistently and uniformly. Jason Rodger performed the alignment on the test car, Ian Bonham did the majority of the mounting, dismounting, and balancing work, and Scott "Skittles" Grande did the actual wheel-swaps on the C5 for each test.
How Loud Is Loud?
To give you some idea of just how loud a decibel is, here's a comparative "decibel ruler" from the National Institute on Deafness and Other Communication Disorders website (http://www.nidcd.nih.gov/health/education/decibel/decibel.asp):