Director, Regulations & Compliance
5355 Skylane Boulevard
Santa Rosa, CA 95403
Dear Mr. Peters:
This responds to your letter to me in which you asked whether Federal Motor Vehicle Safety Standard (FMVSS) No. 110, Tire selection and rims (49 CFR 571.110), applies to your Electricar sedan.
You explained that your Electricar sedan (Electricar), a converted Geo Prizm, is being built under NHTSA Exemption No. 92-3 for low-emission vehicles. You stated that the Electricar's speed and endurance limitations are substantially below those of internal combustion-powered vehicles. You further stated that it is your understanding that "the purpose of Standard No. 110, S4.4.2 (I assume you meant paragraph S4.2.2, since there is no S4.4.2 in the standard) is to ensure against tire failure due to prolonged operation at speeds in the range of 75 mph or higher." Thus, you interpret FMVSS No. 110 as not applying to the Electricar or other electric passenger cars "in which it is physically impossible to operate at high speeds for an extended duration." You asked this agency, therefore, to review paragraph S4.2.2 and provide you our opinion as to its applicability to your Electricar. As discussed below, the requirements of S4.2.2 are applicable to electric passenger cars.
By way of background information, the National Highway Traffic Safety Administration issues safety standards for motor vehicles and motor vehicle equipment. The agency does not provide approvals of motor vehicles or motor vehicle equipment. Instead, manufacturers are required to certify that their vehicles and equipment meet applicable safety standards.
Federal Motor Vehicle Safety Standard No. 110 specifies requirements for tire selection to prevent overloading. Section S2 of the standard provides that the standard applies to passenger cars. S4.2 of the standard specifies the following tire load limits:
S4.2.1 The vehicle maximum load on the tire shall not be greater than the applicable maximum load rating as marked on the sidewall of the tire.
S4.2.2 The vehicle normal load on the tire shall not be greater than the test load used in the high speed performance test specified in S5.5 of section 571.109 of that tire.
The test load used in the high speed performance test specified in S5.5 of Standard No. 109 is 88 percent of the tire's maximum load rating as marked on the tire sidewall.
With respect to your question whether S4.2.2 applies to electric passenger cars, the answer is yes. That section applies on its face to all passenger cars, and does not include an exception for electric passenger cars.
Your understanding that the purpose of S4.2.2 is limited to ensuring against tire failure due to prolonged operation at speeds in the range of 75 mph or higher is incorrect. The reference in that requirement to Standard No. 109's high speed performance test is for the sole purpose of specifying a load and not to indicate that the requirement is limited to high speed operation.
As indicated above, Standard No. 110 seeks to ensure that tires are not overloaded. One way Standard No. 110 does this is by requiring in S4.2.1 that the vehicle maximum load on the tire not exceed the maximum load rating of the tire. Another way Standard No. 110 does this is by limiting the vehicle normal load on the tire, so that the tire will have some reserve load carrying capacity available to handle safely cargo and other kinds of added loading the car may experience. S4.2.2 does this by limiting the normal load on a tire to 88 percent of the tire's maximum load rating, which ensures that 12 percent of the tire's load rating will be available to bear cargo and other added loads.
I hope this information is helpful to you. Should you have any further questions or need additional information, please feel free to contact Walter Myers of my staff at this address or at (202) 366-2992.
Philip R. Recht Chief Counsel Enclosure ref:110 d:2/13/95