Hi I've just bought Fiesta ST Line 2019 with 18" alloys and got a few questions.

I wanted to replace the tyre glue and compressor with a 18" alloy first question is will it fit in the tyre well without causing any reduction in space or the carpet not sitting as it should on top of the tyre in the boot.

Next question is and bare with me, I'm new to tpms sensored tyres, how does the car know not to read the tyre pressure for the spare wheel? 

Third question.

How much am I looking at to buy the wheel brace and foam cowling for an 18" genuine Ford tyre is there anywhere expect for the obvious Ford Ebay Amazon etc that specialise in these parts doesn't have to be OEM as long as it all fits.

Cheers in advance.

A full size 18 inch alloy will barely fit in the boot. 

Buy a spacesaver if you need a spare wheel. 

Space savers are 14 inch but with high sidewalls. The diameter doesn't matter for a temporary fit and the wheel nuts are the same.

The tpms will not read the spare because it doesn't have a transducer in it.

A new spare and toolkit costs about £100 and eBay is a good place to look. 

Hello Glyn @IM1 welcome to the Ford Owners Club

You are better off just using a space saver wheel. On your model the correct size is 15" take a look at this on eBay as a good example of what you need:

https://www.ebay.co.uk/itm/GENIUINE-FORD-FIESTA-MK9-2017-2020-SPACE-SAVER-15-SPARE-WHEEL-JACK-KIT-/164131461170?var=0&mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338268676&toolid=10044&customid=CjwKCAjw2bmLBhBREiwAZ6ugo6QUQADH7oAuH5K8vLeRacaxJW0FHoo8njLfU30J6i5vJCZaJ4sjkxoCYOIQAvD_BwE

I might be worrying unnecessarily here. I know lower model fiestas often had a 175/65/14 spare but does a 14inch fit on a ST? I am wondering if it has bigger front brakes that the 14inch wheel won’t clear. It’s just a thought, I really don’t know if that is a problem or not

1 minute ago, isetta said:

but does a 14inch fit on a ST?

No it doesn't but the 15" does - see my link above

Thank you for the correction.

1 hour ago, isetta said:

but does a 14inch fit on a ST? 

OP has an ST-Line but same 15" spare, I believe.

Confusingly, every Ford price list** I've seen for the Mk 8 refers to a 15" spacesaver as a factory option for the 18" wheel cars, but still says it has a 175/65x14 tyre which obviously can't be right!😀

**Edit: except the latest for the facelift which doesn't mention a tyre size for the spare.

It normally recommends you fit the space saver on the back and rotate the remaining wheels, so there is no issue with clearance over front ST brakes anyway as it's always going on the back.