How to install an 18 inch spare wheel in a Mazda CX-3

Installing an 18 inch spare wheel in a Mazda CX-3, along with the Bose subwoofer.

In the U.K., Mazda provide a tyre repair kit which is comprised of a bottle of liquid sealant, a valve tool and a 12v compressor. There is an official spare wheel kit available at extra cost, which is a 16″ steel space-saver wheel & tyre, with pertinent accessories.

I’m not a fan of the emergency repair kit. It’s only designed to repair tyres that have a small foreign object stuck in the tread portion of the tyre. To use it, you have to deflate the tyre, extract the valve core, pour in the sealant, reinsert the valve core and re-inflate the tyre and hope for the best. You can’t get the hole repaired later by a tyre specialist, you have to replace the tyre.

The space-saver wheel & tyre isn’t ideal either. You’re advised not to use it on the front axle, you have to stick to a maximum of 50MPH, and only use it for a very short distance.

I have therefore fitted an 18″ alloy wheel with tyre in the boot as a spare. The same type of wheel and tyre as the other four on the car. These are the parts I used:

Mazda part numbers and descriptions:

  • 99652-77080 Alloy Wheel 18″
  • B001-56-170C Bolt, Jack Set
  • C236-37-790B Jack
  • LD47-37-770 Lever, Jack (This part was already included with the car)
  • LD47-69-671 Box, Extention
  • EG21-56-135 Insulator
  • DB3P-68-8F1A Board (L), Trunk
  • DB3P-68-8E1A Board (R), Trunk

Non-Mazda parts:

  • Toyo 215/50/R18 Proxes R40A 92VR Tyre, Valve & Balancing
  • M8 Stainless Steel Coupling Nut
  • M8 Threaded Rod
  • Drop of Thread Lock


Remove the luggage board and mat from the boot.

Using the wheel wrench or a 21mm socket, remove the central bolt holding the Bose subwoofer in place.

Bose subwoofer

Uncouple the connector on the subwoofer cable by squeezing the tab firmly and pulling apart.

Remove the subwoofer from the boot.

Remove the expanded polystyrene pieces from the boot.

Remove the cover from the right-hand side of the boot space and install the scissor jack with the jack bolt as per instructions in the vehicle owner’s manual. Replace the cover.

Scissor jack

Lay the insulator mat in the boot.

Insulator mat

Because the full-size wheel is deeper than a space-saver wheel, the original mounting bolt is too short. I increased it’s overall length to 200mm by adding an M8 threaded nut and a short length of M8 threaded rod, held in place by a drop of thread lock.


Place the new spare wheel into the boot with the outside face of the wheel against the insulator mat.

Feed the subwoofer cable under the tyre and up through a gap between the wheel spokes.

Put the subwoofer into the spare wheel and recouple the cable connector.

Align the subwoofer so that it’s handle is facing the rear of the car. Then put the central clamp bolt in place and tighten.

Place the new expanded polystyrene pieces around the spare wheel.

Put the towing eyes, jack lever, wheel wrench & locking wheel nut key into the cut-outs in the pieces around the spare wheel.

Spare wheel

Replace the luggage mat and luggage board.

Because a full size wheel is deeper than a space-saver wheel, you lose the ability to drop the luggage board to its lower position.


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12 Responses

  1. Tony James says:

    I’m getting my cx3 tomorrow and would like to fit this spare to my cx3 sport nav can you tell me roughly how much the bits and pieces cost to buy?

    • Julian says:

      Hi Tony,

      At the time of writing the article, the list price of the Mazda parts was £242.38 + VAT, but I negotiated a discount.

      The pieces for the mounting bolt were a few pounds. The tyre, valve and balancing was another £83.60 + VAT from a local independent tyre shop.

      I don’t know how this compares with the price for the Mazda 16″ space saver kit, but you can ask your dealer for a quote.

  2. Tony James says:

    Thanks Julian
    For your information I will compare all the options. Very pleased with my first day with the car drives very well, impressed with the amazing lights..

  3. peter spiller says:

    Thanks for this guidance Julian I have just completed it having persuaded Mazda to include a full size spare with all the jack etc in my negotiated price for the car. Couldn’t have been simpler to complete for about £3 !

  4. D Best says:

    Hi Julian,
    Thank you for taking the time to provide so much useful information.
    Do you happen to know why Mazda provide a new “trunk mat”* with their space-saver wheel kit? I assume you are just using the one you already had – or am I confused?
    (*it looks like a stiff board from the installation instructions illustration: )

    • Julian says:

      Hi Duncan,

      I didn’t buy the space-saver wheel kit, so I can’t be sure whether or not it includes a new trunk mat. It’s just a piece of black carpet material, with possibly some foam spacers stuck on the underside. I’m not using the space under the removable luggage board and so I’ve omitted the trunk mat on my vehicle.

      Regards, Jules

  5. Chris says:

    Excellent mod, plug and play, bits all fit a treat, thanks, Chris, West sussex, 2litre petrol, soul red

  6. Richard says:

    Hi Julian, thank you very much!! Recently bought this car and it is the first time I have faced this “gunge & compressor” rubbish. When I asked at the dealership why, he looked bemused:apparently it’s not a job for me, (I may break a finger nail or some such). Now sourced a full size wheel & tyre, next job to acquire the oddments you listed and so follow your excellent idiots guide

  7. peter spiller says:

    Have done mine, full sized steel spare securely fixed in place.

    • Patrick says:

      I notice you say ‘full size steel spare’ which is different to Julian’s alloy wheel fit. What size wheel and tyre did you use please?

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