<SUBMISSION>
<ACCESSION-NUMBER>0001205106-09-000002
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20090313
<FILING-DATE>20090518
<DATE-OF-FILING-DATE-CHANGE>20090518
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>LEVIN EDGAR W
<CIK>0001205106
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>000-18914
<FILM-NUMBER>09836271
</FILING-VALUES>
</REPORTING-OWNER>
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>Dorman Products, Inc.
<CIK>0000868780
<ASSIGNED-SIC>3714
<IRS-NUMBER>232078856
<STATE-OF-INCORPORATION>PA
<FISCAL-YEAR-END>1207
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>3400 E WALNUT ST
<CITY>COLMAR
<STATE>PA
<ZIP>18915
<PHONE>2159971800
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>3400 E WALNUT ST
<CITY>COLMAR
<STATE>PA
<ZIP>18915
</MAIL-ADDRESS>
<FORMER-COMPANY>
<FORMER-CONFORMED-NAME>R & B INC
<DATE-CHANGED>19930328
</FORMER-COMPANY>
</ISSUER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2009-03-13</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000868780</issuerCik>
        <issuerName>Dorman Products, Inc.</issuerName>
        <issuerTradingSymbol>DORM</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001205106</rptOwnerCik>
            <rptOwnerName>LEVIN EDGAR W</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O DORMAN PRODUCTS</rptOwnerStreet1>
            <rptOwnerStreet2>3400 EAST WALNUT STREET</rptOwnerStreet2>
            <rptOwnerCity>COLMAR, PA</rptOwnerCity>
            <rptOwnerState></rptOwnerState>
            <rptOwnerZipCode>18915</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2009-03-13</value>
                <footnoteId id="F1"/>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>C</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>5000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>1.5</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>21600</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Stock Option</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>1.5</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2009-03-13</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>C</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>5000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>1.5</value>
                    <footnoteId id="F2"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2006-07-09</value>
            </exerciseDate>
            <expirationDate>
                <value>2011-07-09</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>5000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>43000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">This Form 4 is filed for the purpose of disclosing a stock option exercise which occurred on March 13, 2009 but for which no Form 4 was timely filed.</footnote>
        <footnote id="F2">The market close price of DORM (NASDAQ) on March 13, 2009 was $9.35.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Edgar W. Levin</signatureName>
        <signatureDate>2009-05-18</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
