About Us


Officially born on March 13, 1930, the famous Rimac® Spring Tester celebrated its United States Patent Application’s 91st birthday on March 13, 2021.  Invented by Mr. John J. McGuckin of Passaic, New Jersey, and brought to life by Rinck-McIlwaine, Inc. of New York City, U.S.A. the Rimac Spring Tester held its place as the American standard in spring calibration and testing for the industry for decades.  With the designs of very few similarly intricate mechanical devices surviving as long, there are reasons the Rimac Spring Tester has remained so popular — it is easy to use, it is durable, and it is accurate.  There was also a reason it disappeared from the market:  while its design may be simple to understand, actually making the unit is an craft requiring skills only learned over time.  When the master-craftsmen faded away, so did their device.  Now the Rimac Spring Tester has been resurrected, with Specialty Auto Parts as the exclusive Rimac brand distributor, making an important tool available to professional engine-builders and serious enthusiasts alike.