Interpretation ID: 86-5.3

TYPE: INTERPRETATION-NHTSA

DATE: 08/22/86

FROM: AUTHOR UNAVAILABLE; Stephen P. Wood for Erika Z. Jones; NHTSA

TO: Mr. J. Leon Conner

TITLE: FMVSS INTERPRETATION

TEXT:

Mr. J. Leon Conner Manager Long & Associates, Inc. P.O. Box 691 San Angelo, TX 76902

Dear Mr. Conner:

This responds to your letter seeking an interpretation of the requirements of 49 CFR S575.104, Uniform Tire Quality Grading Standards (UTQGS). Specifically, you asked wether this regulation requises the treadwear testing for a tire size to be conducted only with vehicles that specify the subject tire size either as the original equipment size or as one of the recommended optional tire sizes. The UTQGS does not contain any such provision.

The conditions and procedures to be followed in grading tires for treadwear under the UTQGS are set forth in S575.104(e). That section specifies tire loading conditions and rim dimensional requirements for the vehicles used in the treadwear testing. However, it does not specify that the vehicles used in the treadwear testing can only be used to test tire sizes recommended as either original equipment or optional tires on the vehicle when new. Accordingly, persons testing tires to determine the treadwear grade may mount the tires on any vehicle, provided that the tire and vehicle satisfy all the requirements of S575.104(e), relating to tire construction, inflation pressure, size designation, vehicle loading, and wheel alignment.

You stated in your letter that the UTQGS compliance test procedures, used by this agency for conducting its enforcement testing for treadwear grades, currently specify that tire sizes must be tested on vehicles that specify that size as either original equipment or recommended optional size. This specification may have been adopted after the following language appeared in a 1975 preamble to a final rule establishing the UTQGS:

Several commenters suggested that the rule specify all vehicles in a given convoy be identical, to reduce variations in projected treadlife...Variations in vehicle type, however, do not appear to produce significant variations in treadwear projections. Nevertheless, to minimize such variations, tires will be tested for compliance only on vehicles for which they are available as original equipment or recommended replacement options. 40 FR 23073, at 23076, May 28, 1975.

As explained above, the UTQGS regulation does not specify that the vehicles used in treadwear testing can only be used to test tire sizes recommended as either original equipment or optional tires on the vehicle. The agency's compliance test procedures are only the methods the agency itself uses to determine the appropriate treadwear grade for a tire. Persons outside the agency are not bound by any testing conditions and methods not set forth in the UTQGS itself. Such persons may, therefore, conduct their own testing in a manner different from that specified in NHTSA's compliance test procedures, provided that their testing satisfies all requirements of S575.104(e).

You also stated that the use of different vehicles for treadwear testing of tires will produce measurably different treadwear grades for the tire, even when all the vehicle factors are closely and properly controlled. As quoted above, NHTSA concluded that vehicle-to-vehicle variations "do not appear to produce significant variations in treadwear projections", when it examined this issue in 1975. However, the agency is currently reexamining the effects of vehicle-to-vehicle variations on treadwear projections, particularly with respect to front-wheel vs. rear-wheel drive vehicles and passenger cars vs. light trucks and vans. If you wish to provide some additional data on this subject, please forward the data to Mr. Barry Felrice, Associate Administrator for Rulemaking, at this address. We would be interested in analyzing whatever data form the basis for your belief that our 1975 conclusion was incorrect.

Please feel free to contact Steve Kratzke of my staff, at this address or by telephone at (202) 366-2992, if you have any further questions about our UTQGS.

Sincerely,

Erika Z. Jones Chief Counsel

Ms. Erika Jones, Chief Counsel National Highway Traffic Safety Administration Office Of Chief Counsel, NAO-30 400 Seventh Street, S.W. Washington, D.C. 20500

Subject: Uniform Tire Quality Grading Testing

Dear Ms. Jones:

We are requesting clarification of the UTQG Stnadard relative to selection of test vehicles.

The UTQG Compliance Test Procedure requires that, "the vehicles must specify the tire size to be tested as standard equipment or approved alternate for that vehicle", i.e. government compliance testing will be performed with vehicles selected in this manner. It behooves the tester then to select vehicles in the same manner it would seem.

While outdoor road testing inherently involves a large number of variables it is apparent from our accumulated CMT data that different cars do produce different wear rates for a given set of tires and conditions, even when vehicle factors (wheel alignment, wheel loads, mechanical maintenance) are closely and properly controlled. It is therefore possible to bias the candidate tire grades measurably through selection of the control tire car, the candidate tire car or both. Use of certain larger vehicles produce faster wear of the CMT tires and consequently higher grades for the candidate tire; tested in the same convoy.

If the UTQG Standard allows the tester to choose any car in which he can attain the required wheel loads, manufacturers may seek the tester who can obtain the highest grades.

Hopefully you can clarify the intent of NHTSA on this matter. If we can be of assistance in any way please do not hesitate to call on us.

Sincerely,

J. Leon Conner JLC:bf