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 (purchased from parts department of authorised Mazda dealer):

  • 99652-77080 Alloy Wheel 18″
  • B001-56-170C Bolt, Jack Set (Holds the scissor jack into the car)
  • C236-37-790B Jack
  • LD47-37-770 Lever, Jack (This part was already included with the car)
  • LD47-69-671 Box, Extension (Wheel nut wrench & jack handle)
  • EG21-56-135 Insulator (Circular mat under the wheel)
  • DB3P-68-8F1A Board (L), Trunk (Expanded polystyrene moulding left-hand side)
  • DB3P-68-8E1A Board (R), Trunk (Expanded polystyrene moulding right-hand side)

Non-Mazda parts:

  • Toyo 215/50/R18 Proxes R40A 92VR Tyre, Valve & Balancing (From local independent tyre shop)
  • M8 Stainless Steel Coupling Nut (From Screwfix)
  • M8 Threaded Rod (From Screwfix & cut to length with a hacksaw)
  • Drop of Thread Lock or epoxy glue


Remove the luggage board and mat from the boot.

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

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 (these will be replaced with new ones).

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.

Lay the insulator mat in the boot.

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.

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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48 Responses

  1. John says:

    Great article. I am old school and am used to having a spare wheel, tend to feel nervous driving around without a spare. Your article is pretty well faultless, so thanks and well done. Feeling quite smug that I now have a proper spare and the subwoofer…woofing away.

  2. Arty says:

    Hi Julien,
    Just found your article having purchased second hand cx-3. Sounds brilliant. Is there any reason for it not to work with cheap steel wheel or different alloy?
    Still totally confused why car came with jack handle but no jack………….

    • Julian says:

      Hi Arty,

      The idea was to have a spare wheel & tyre combination that is the same as those fitted to the axles, so in the event of a puncture, I can just swap to the spare until such time as the puncture was repaired.

      If you want to use a steel wheel or different alloy, you will have to do your own checks to see if it would fit in the boot OK, and would be safe to use on the car.

      The car doesn’t come with a jack, because you don’t need to lift the wheels off the ground to use the sealant, but I think the jack lever is supplied because you can use one end of it to remove the towing eye covers.

  3. Ed1943 says:

    Hi Julian
    Just fitted 18″ spare to your info/instructions. Brilliant and many thanks for passing on this information. Just got to sort out the bolt in the morning. Off topic but why do we have two towing eyes?

    • Julian says:

      Hi Ed., glad to read that the information published a few years ago is still proving useful.

      The CX-3 comes with one short and one long towing eye (intended for getting the vehicle out of a ditch or a snow bank rather than for towing any real distance). I’m not sure why there are two lengths instead of just one long one. The CX-5 also comes with two, and its owner’s manual says that the long one is for the front of the vehicle and the short one is for the back.

  4. Ronlad says:

    Followed article by Julian to the letter and it has all worked brilliantly, converting my Mazda CX 3 Sport Black boot, which now carries a spanking new alloy spare wheel, bought from Mazda, fitted with a Toyo Proxes R52 (the same as rest of tyres on car) bought in excellent condition from ebay. The alloy I bought from Mazda is same as rest of wheels on car. Altogether it cost me £300, including jack and wheelbrace, but that is £80 cheaper than the space saver package.. Thanks Julian

  5. John mansell says:

    Hi what size space saver wheel will fit mazda xc3 tyre size215/ 50/r18 on a 69 plate thank you

    • Julian says:

      Hi John,

      If you want a space saver wheel it will be a 16″ with T145/90R16 106M or 185/60R 16 86M tyre. Available from main dealer or you can search the web for suppliers.

      • Hedgehog says:

        In a CX3 with 215/50r18, would a 16″ space saver wheel with T125/90D1698M fit as well?

        • Julian says:

          Hi Hedgehog,

          That size may be unsafe as it’s narrower than the sizes Mazda specifies, and it may also invalidate your insurance if fitted. I’d stick with either of the two specified sizes.

          • Hedgehog says:

            Hi Julian, thank you.
            T125/90 D16 98M is actually written as one of the sizes specified in the Mazda owner manual (that’s actually the same manual for all the CX-3, indipendently from the size of the mounted tyres), but, as you say, the difference in dimensions is really too much. I’ll go for a broader one.

  6. GEOFF says:

    How do l download cz 3owners manual i only have an apple i pad and at 82years old i am not computer savy

  7. Geoff says:

    When was the cx3 last updated

  8. Marco says:

    Hi, i have a civic ej9 with 14 inch spare wheel. Can you tell me the dimension of the subwoofer? Thanks

    • Julian says:

      Hi Marco,

      The top of the subwoofer has a 14 inch diameter and the main body is a bit slimmer so you should be OK fitting it into a 14 inch wheel.

  9. Paul says:

    Hi Julian, Ive just bought a second hand relatively new space saver 16in and jack from a current model Mazda 3. Am I right in assuming the existing subwoofer bolt will still fit with both the spacesaver and subwoofer in place or will a longer one be needed? Also would there be any adverse consequences if the new polystyrene inserts weren’t fitted? Or Could I perhaps trim the existing ones to fit for example?

    • Julian says:

      Hello Paul,

      The recommended space saver tyre size is T125/90D16 98M, if that’s what you’ve bought then I should think the existing retaining bolt will hold the sub and wheel in the boot without further modification.

      I don’t think you need the surrounding inserts, if you’d prefer not to buy them. You’d need to find something to wrap the wrench and towing eye hooks in to stop them rattling about in the boot.

      • Steve-t says:

        Just bought the “official spare wheel kit”, Mine is a facelift model (2018), The wheel lug nuts have been changed to 17mm so the wrench is too big, I have informed Mazda uk and new ones are being sourced. Also the original sub bolt is not long enough to secure the wheel/sub

  10. Karen says:

    Hi Julian, I’ve got mine CX3 just few days ago…. I want to fit full size wheel as well. As Steve asked where did you get your set up, from the mazda dealer or somewhere else. Can you give a link of the shop if so. Thank you.

    • Julian says:

      Hi Karen,

      I hope you’re enjoying your new purchase.

      I got the Mazda parts detailed in this post from the parts department of my local authorised Mazda dealer. I’ve edited the post to make that clear. You may also find people selling some of the parts second-hand on online auction sites or via car forums.

      The M8 threaded rod and coupler I got from Screwfix, and the tyre was supplied and fitted by a local tyre shop.

  11. Steve says:

    are all these parts available from the dealer ?

  12. Mark says:

    Re these parts are they the ones for the 16 inch space saver wheel which is the one i intend to fit.
    Also is the bolt that holds the Bose the same bolt that can be reused on the space saver wheel

    • Julian says:

      Hi Mark,

      Yes, the parts are the same as the ones you would get if you ordered the spare wheel kit from a dealer, only then you would get a 16″ space saver steel wheel.

  13. Nigel says:

    Hi Jules, I am interested in your article but would like to know if you have had any feedback as to whether the sub woofer cable can run over the top of the wheel? And in the parts list what is the Box extension used for? Regards Nigel

    • Julian says:

      Hi Nigel, I don’t think the subwoofer cable will go over the top of the wheel. I’ll have a look at the weekend, but I’ve not had any issues with the way I routed mine and it’s been that way since November 2016.

      LD47-69-671 is the wheel nut box spanner (wrench) and, by means of a hole in the handle, also acts as a winding handle for the Mazda scissor jack.

      • Julian says:

        I’ve had another look, and the wheel/tyre does not rest on the subwoofer cable, if that’s your concern.

        I haven’t tried re-routing my cable over the top of the tyre, it would probably reach OK, but I don’t think it’s a better route.

  14. ALLAN Reeling says:

    Julian, Thanks for that. Acquired a wheel, tyre and jack and made the rest.
    Personally I’m not too keen on the idea of trapping sub woofer cable under the tyre and you don’t mention the heavy plastic moulding which fits under the woofer.

    • Julian says:

      Thanks for your comments, Allan. Is the subwoofer cable long enough to go over the top of the wheel? I didn’t check.

      The reason I didn’t mention “the heavy plastic moulding” is simply because there wasn’t one in my vehicle, just the black plastic piece around the mounting hole that you can see in my picture of the insulating mat.

  15. 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?

  16. 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

  17. Chris says:

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

  18. 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

  19. 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 !

  20. 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..

  21. 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 at the parts department of my Mazda dealer was £242.38 + VAT, but I negotiated a discount.

      The pieces for the mounting bolt were a few pounds from Screwfix. 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.