UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

(Rule 14a-101)

INFORMATION REQUIRED IN PROXY STATEMENT

SCHEDULE 14A INFORMATION

Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934

(Amendment No.  )

Filed by the Registrant   o

Filed by a Party other than the Registrant   x

Check the appropriate box:

o           Preliminary Proxy Statement

¨           Confidential, for Use of the Commission Only (as permitted by Rule14a-6(e)(2))

¨           Definitive Proxy Statement

x          Definitive Additional Materials

o           Soliciting Material Under Rule 14a-12

SUPERIOR INDUSTRIES INTERNATIONAL, INC.

(Name of Registrant as Specified in Its Charter)

GAMCO ASSET MANAGEMENT INC.

MARIO J. GABELLI

PHILIP T. BLAZEK

RYAN J. MORRIS

WALTER M. SCHENKER

(Name of Persons(s) Filing Proxy Statement, if Other Than the Registrant)

Payment of Filing Fee (Check the appropriate box):

x          No fee required.

¨           Fee computed on table below per Exchange Act Rules 14a-6(i)(1) and 0-11.

(1)           Title of each class of securities to which transaction applies:

(2)           Aggregate number of securities to which transaction applies:

(3) Per unit price or other underlying value of transaction computed pursuant to Exchange Act Rule 0-11 (set forth the amount on which the filing fee is calculated and state how it was determined):

(4)           Proposed maximum aggregate value of transaction:

(5)           Total fee paid:

¨           Fee paid previously with preliminary materials:

¨           Check box if any part of the fee is offset as provided by Exchange Act Rule 0-11(a)(2) and identify the filing for which the offsetting fee was paid previously.  Identify the previous filing by registration statement number, or the form or schedule and the date of its filing.

(1)           Amount previously paid:

(2)           Form, Schedule or Registration Statement No.:

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(4)           Date Filed:

GAMCO Asset Management Inc., together with the other participants named herein (collectively, “GAMCO”), has made a definitive filing with the Securities and Exchange Commission of a proxy statement and an accompanying BLUE proxy card to be used to solicit votes for the election of GAMCO’s slate of three highly-qualified director nominees to the Board of Directors of Superior Industries International, Inc., a California corporation (the “Company”), at the Company’s upcoming 2014 annual meeting of shareholders, or any other meeting of shareholders held in lieu thereof, and any adjournments, postponements, reschedulings or continuations thereof.

On July 18, 2014, GAMCO delivered supplementary materials to Institutional Shareholder Services Inc. (“ISS”) in connection with GAMCO’s prior discussions with ISS. The supplementary materials are attached hereto as Exhibit 1. The materials include information pertaining to the Company’s dividends and buybacks from 2007 to 2014 (Annex A) and articles chronicling the departure of Donald J. Stebbins, the Company’s President and Chief Executive Officer, from Visteon Corp. in August of 2012 (Annexes B, C, D).