Mr. Carlos Fracaroli
Av. Alexandre de Gusmâo
Santo André, SP Brasil
Dear Mr. Fracaroli:
Please pardon the delay in responding to your letter in which you inquired about tolerances in the ambient temperature requirements of Federal motor vehicle safety standard (FMVSS) No. 119, New Pneumatic Tires for Vehicles Other Than Passenger Cars (49 CFR 571.119), and 49 CFR 575.104, Uniform Tire Quality Grading Standards. You stated that you found no such tolerances in the standards and asked how you should calibrate your laboratory if none exist, since ambient temperatures can oscillate 5 degrees Fahrenheit (F).
You are correct that the above standards do not provide for tolerances with respect to the testing temperatures of tires. All of our FMVSSs specify minimum performance requirements. Thus, manufacturers must design and build the products to meet or exceed the specified performance. Since increased temperature is generally detrimental to tire performance, manufacturers must ensure that each tire meets the required performance at the temperature specified in the standard, in this case, 95 degrees F. Given the variability in laboratory equipment as you correctly noted, however, the agency allows an ambient temperature tolerance in our compliance testing of +0F-10F. The +0F ensures that the actual temperature will never oscillate above 95F. That upper limit ensures that we do not exceed the requirements of the standard, which would invalidate the test. For your information, please find enclosed extracts from this agency's Laboratory Procedures for Tire Testing and Data Reporting, DOT publication No. TP-119-04, May, 1988, applicable to FMVSS No. 119, and Laboratory Procedures for Tire Temperature Resistance Testing, DOT publication No. TP-UTQG-H-01, May 25, 1979, applicable to the UTQGS. Both publications are available from this agency, ATTN: NAD-40.
I hope this information is helpful to you. Should you have any further questions or need additional information, please feel free to contact this office at this address or by Fax at 011-202- 366-3820.
Acting Chief Counsel