Looking into replacing my space saver spare wheel with a full sized original, (Venus) some searching has thrown up wheels that are described as either "front" or "rear". From what I can see, judging by tyre sizes and from taking physical measurements, all the wheels on my car are the same size. What gives and what spare would you carry if your front and rear wheels are different sizes? Any thoughts much appreciated.

 

Different sizes is known as a "staggered" set up.
For example the XFR has 255/35ZR20 front tyres and and 285/30ZR20 rear tyres.
The only other Euro/UK X250 I know of which came stock with a staggered set up is the SV8.
That is why some wheels/tyres are described as either front or rear.
On both the XFR and SV8 a full size wheel and tyre does not fit in the spare wheel well without sticking up way too far, due mainly to the sub-woofer underneath, so they came with a "space saver" 19" spare, and so do most (all?) XFs with the high end sound system which includes a sub-woofer in the boot.
The Venus wheel is 18" and takes a 245/45R18 tyre. This combo will fit in your spare wheel well no problems providing you do not have a sub woofer, and it might even fit if you do (but I doubt it).
Easiest way to check is to remove the space saver, rip any of your four road wheels off (they will be all the same) and see if/how it fits in the spare wheel well.

 

Many thanks for that. I don't have a sub woofer in my boot and I know that the full sized wheel will fit in the well. Mine is a Euro xf so it's the "smaller" wheel then? I know the wheel measures 19.5" across (diameter). Does this sound right? Tyres are 245/45R18 on all corners.

 

As I said, without a sub-woofer it will fit for sure, but best to test fit first.

 

Just further to the above. For my clarity, when wheels are described as 18", what does the 18" relate to? As stated, my wheels are 19.5" diameter and I can't find an 18"measurement anywhere. I've sourced a replacement online but want to be sure it's the right size. Does the tyre size indicate or give a clue to the wheel size? Pardon my ignorance and confusion and thanks.

 

The "size" of the wheels as in 18", 19", 20" etc refers to their diameter, and the same with the last number on the tyre size (although it's the external diameter for the wheels and the internal diameter for the tyres).
Back in post # 3 you say you have 245/45R18 tyres and if that is correct you absolutely definitely must have 18" wheels, and if you have Venus wheels then you have 18" wheels at that is the only size they ever came in.
So I'm not sure exactly what you are measuring to come up with 19.5".

 

Many thanks for the clarification and reassurance. I measured the wheels across the external diameter, ie. outer lip to outer lip. This is where I got my 19.5".
However when I measured the internal diameter,less the lips, I got just a tad over 18". Its hard to get an exact measurement due to the design of the wheel, but I'm happy now to order my replacement online. Many thanks again.

 

So, I got my replacement wheel, refurbished from a UK company, perfect condition, at a total cost of 124 pounds sterling, including postage to Ireland. No complaints! It fits perfectly into the wheel well in the boot and I even managed to trim the tool kit down to size to get it to fit inside the rim, so everything is as it was, all snug and secure, but with the right sized wheel. I trimmed the foam tool kit holder with a coping saw. It's like a fret saw if you're unfamiliar with such things, but a fine toothed bread knife will ddo the job just as well. I had to trim back as far as either end of the wheel brace, as seen in the picture, but at least it keeps things fairly original. The boot floor liner also fits back down perfectly without any humps. Thanks for the various responses. Now I just have to sort out my intermittent speaker!