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                                                               EXHIBIT 10.21
                                 PROMISSORY NOTE

         $441,500                                    Phoenix, Arizona
                                                     December 21, 1997

         FOR VALUE RECEIVED, the undersigned, MAYNARD JENKINS (the "Payor"),
hereby promises to pay to the order of CSK AUTO CORPORATION (the "Holder"), or:
its successor or assign, at the office of CSK Auto Corporation, 645 E. Missouri
Avenue, Phoenix, Arizona 80512, Attn: James G. Bazlen, on the earlier of (i)
December 21, 2000 (the Maturity Date) and (ii) the date to which the maturity of
this Note is accelerated as provided below, the principal sum of Four Hundred
Forty-One Thousand Five Hundred Dollars ($441,500) together with any accrued and
unpaid interest thereon, in lawful money of the United States of America in
immediately available funds, and to pay interest from the date hereof on the
principal amount hereof from time to time outstanding, in like funds, at said
office. From the date hereof interest (i) shall accrue on the outstanding
principal amount hereof at a rate which shall be calculated for each quarter or
part thereof of the Holder's fiscal year, (ii) shall equal the average rate paid
by CSK Auto, Inc. under the revolving portion of its senior credit facility
during such period, and (iii) shall be payable in arrears on or prior to the
30th day after the end of each such fiscal quarter.

         The Payor hereby promises to pay interest, on demand, on any overdue
principal and, to the extent permitted by law, on any overdue interest (other
than interest added to and constituting a part of the principal hereof in
accordance with the terms hereof), and on any overdue amount under any
instrument now or hereafter evidencing or securing the indebtedness evidenced
hereby, at a rate equal to the rate of interest from time to time announced
publicly by Citibank, N.A., as its base rate plus 3% (but in no event less than
8%), calculated on the basis of the actual number of days elapsed over 365, from
the date such principal or interest was due to the date of payment.

         The Payor shall have the right at any time and from time to time on any
business day to prepay the principal amount of this Note, together with accrued
and unpaid interest thereon, in whole or in part, without penalty or premium,
upon at least three business days' prior written notice to the holder hereof,
such notice to specify the prepayment date and the principal amount hereof to be
prepaid. In the event the Payor decides not to so prepay this Note in accordance
with any such notice delivered to the holder hereof, the Payor shall so notify
the holder hereof, not less than two business days before such prepayment would
otherwise have been made.

         This Promissory Note is secured by that certain Stock Pledge Agreement,
dated as of even date herewith, between the Holder and the Payor (the "Stock
Pledge Agreement").

         In case of the happening of any of the following events ("Events of
Default"):

                  (i) default shall be made in the payment of the principal of
         or interest on this Note when and as the same shall become due and
         payable, whether at the due date thereof or at a date fixed for
         prepayment thereof or otherwise; provided, however, that in the case of
         a failure to make an interest payment an Event of Default shall not
         occur until such 


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         interest remains unpaid for 10 days following notice from the Holder
         to the Payor that such interest payment is in default;

                  (ii) a breach of any covenant contained in this Note, other
         than the covenant to pay the principal of and interest on this Note,
         which breach shall continue unremedied for thirty days after written
         notice by the holder hereof;

                  (iii) the Payor shall (a) voluntarily commence any proceeding
         or file any petition seeking relief under Title 11 of the United States
         Code or any other Federal or state bankruptcy, insolvency, liquidation
         or similar law, (b) consent to the institution of, or fail to
         controvert in a timely and appropriate manner, any such proceeding or
         the filing of any such petition, (c) apply for or consent to the
         appointment of a receiver, trustee, custodian, sequestrator or similar
         official for him or for a substantial part of his property, (d) file an
         answer admitting the material allegations of a petition filed against
         him in any such proceeding, (e) make a general assignment for the
         benefit of creditors or (f) become unable, admit in writing his
         inability or fail generally to pay his debts as they become due;

                  (iv) an involuntary proceeding shall be commenced or an
         involuntary petition shall be filed in a court of competent
         jurisdiction seeking (a) relief in respect of the Payor, or of a
         substantial part of the property of the Payor, under Title 11 of the
         United States Code or any other Federal or state bankruptcy,
         insolvency, receivership or similar law or (b) the appointment of a
         receiver, trustee, custodian, sequestrator or similar official for the
         Payor or for a substantial part of the property of the Payor; and such
         proceeding or petition shall continue undismissed for 60 days or an
         order or decree approving or ordering any of the foregoing shall
         continue unstayed and in effect for 60 days;

                  (v) an event of Default (as defined in the Stock Pledge
         Agreement) shall have occurred under the Stock Pledge Agreement;

                  (vi) Payor shall, for any reason, cease to be an employee of
         CSK Auto Corporation and the date set for repurchase of the Pledged
         Shares (as defined in the Stock Pledge Agreement) pursuant to Section
         4(a), 4(b) or 4(c) of the Stock Purchase Agreement, as the case may be,
         shall have passed;

         then, in any such event (other than an event described in paragraph
(iii) or (iv) above), the holder hereof may declare the principal amount of this
Note then outstanding to be forthwith due and payable, whereupon the principal
hereof, together with accrued and unpaid interest thereon, shall become
forthwith due and payable both as to principal and interest, without
presentment, demand, protest or any other notice of any kind, all of which are
hereby expressly waived by the Payor (to the extent permitted by law), anything
contained herein to the contrary notwithstanding; and, in any event described in
paragraph (iii) or (iv) above, the principal amount of this Note, together with
accrued and unpaid interest thereon, shall automatically become due and payable
without presentment, demand, protest or other notice of any kind, all of which
are hereby expressly waived by the Payor.


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         If any payment under this Note is not made when due, whether at
maturity or by acceleration, Payor shall pay all costs of collection whether or
not suit is filed hereon, on the Stock Pledge Agreement or otherwise, including,
but not limited to, reasonable attorneys' fees and all expenses incurred in
connection with the protection or realization of any collateral.

         Payor hereby certifies and declares that all acts, conditions and
things required to be done and performed and to have happened precedent to the
creation and issuance of this Note, and to constitute this Note the legal, valid
and binding obligation of Payor, enforceable in accordance with the terms
hereof, have been done and performed and happened in due and strict compliance
with all applicable laws.

         The Payor hereby waives (to the extent permitted by law) diligence,
presentment, demand, protest and notice of any kind whatsoever except as
expressly required herein. The nonexercise by the holder of any of its rights
hereunder[or under the Stock Pledge Agreement] in any particular instance shall
not constitute a waiver thereof in that or any subsequent instance. The Holder
shall at all times have the right to proceed against any portion of the security
held herefor in such order and in such manner as the Holder may select, without
waiving any rights with respect to any other security. No delay or omission on
the part of the Holder in exercising any right hereunder [or under the Stock
Pledge Agreement] or other agreement shall operate as a waiver of such right or
of any other right under this Note.

         All prepayment of the principal hereof and interest hereon and the
respective dates thereof shall be endorsed by the holder hereof on the schedule
attached hereto and made a part hereof, or on a continuation thereof which shall
be attached hereto and made a part hereof; provided, however, that the failure
of the holder hereof to make such a notation or any error in such a notation
shall not affect the obligations of the Payor under this Note.

         This Note may be assigned, pledged, hypothecated or otherwise
transferred by the holder hereof.

         Any notice to be given hereunder shall be in writing and shall be
deemed to have been given (i) when presented personally or (ii) three business
days after being deposited in a regularly maintained receptacle for the United
States Postal Service, postage prepaid, registered or certified, return receipt
requested addressed to the respective party at the address specified herein or
such other address as any party may from time to time designate by written
notice to the other as herein required.

         The Payor irrevocably submits to the jurisdiction of the Federal and
State courts sitting in Phoenix, Arizona for the purposes of any suit, action or
other proceeding arising out of or relating to this Note. Pledgor expressly
waives any objection which he may have now or hereafter to the laying of the
venue or to the jurisdiction of any such suit, action or proceedings.

         All agreements between Payor and the holder hereof are expressly
limited so that in no contingency or event whatsoever, whether by reason of
advancement of the proceeds of the loan evidenced hereby, acceleration of
maturity of the unpaid principal balance hereof, or otherwise, shall the
interest contracted for, charged or received by the holder exceed the maximum
amount 


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permissible under applicable law. If, from any circumstance whatsoever,
interest would otherwise be payable to the holder hereof in excess of the
maximum lawful amount, then ipso facto, the interest payable to the holder shall
be reduced to the maximum amount permitted under applicable law, and the amount
of interest for any subsequent period, to the extent less than that permitted by
applicable law, shall to that extent be increased by the amount of such
reduction. If from any circumstance the holder hereof shall ever receive
anything of value deemed interest by applicable law in excess of the maximum
lawful amount, an amount equal to any excessive interest shall be applied to the
reduction of the unpaid principal balance due hereunder and not to the payment
of interest, or if such excessive interest exceeds the unpaid principal balance
due hereunder, such excess shall be refunded to Payor. All interest paid or
agreed to be paid to the holder hereof shall, to the extent permitted by
applicable law, be amortized, prorated, allocated or spread throughout the full
period until payment in full of the principal balance due hereunder (including
the period of any renewal or extension) so that interest thereon for such period
shall not exceed the maximum amount permitted by applicable law. The provisions
of this paragraph shall control all agreements between the Payor and the holder
hereof.

         Any provision of this Note that is declared invalid, illegal or
unenforceable in any jurisdiction shall not affect in any way the remaining
provisions hereof in such jurisdiction or render that or any other provision of
this Note invalid, illegal or unenforceable in any other jurisdiction.

         This Note has been executed and delivered in the State of [Arizona] and
shall be governed and construed, and all rights and obligation hereunder shall
be determined, in accordance with the laws of the State of Delaware.

         Executed and delivered by the undersigned this 21 day of December,
1997, in the State of Arizona.

         Address for notices                           Payor
         to the Payor:

                                             /s/
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                                           Maynard Jenkins

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