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Will 10Mm Extra Tyre Diameter Cause Damage To My Car????

4 posts in this topic

Hi there people, I am new to the forum! :)

Hi have recently purchased ST wheels off a 170 which have are 17" alloys with 215/45R17 Tyres.

My current Focus Ebony 1.6 has 195/60R15 Tyres.

The difference in diameter is 10mm extra tyre on the ST ones. That's all. There is a 1.67% difference in diameter between them. There offset will move 7mm closer in and 13mm outward.

Are these ST wheels suitable for my car do you reckon without doing damage to the Transmission, differential etc. The tyre garage who I asked to fit the wheels for me said to ask the ford dealer before doing it, but they swouldn't say yes or no for liability reasons.

What do you guys think. I would rather a healthy car than one that looks a bit better

Many Thanks


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Should be fine - they were fitted to an ST, after all - many have fitted them to their Focusses, only potential issue is the speedo will read a little bit lower than before

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The rolling diameter wont cause you a problem as its so close to what you have, you state the distance the wheel will come in and out so you must know old and new ET of wheels, I normally stay within 5% so your 1.67% is well in, you will also loose 5mm of wheel arch gap but also raise your car 5mm in the process, as you know all these sizes and measurements you can go out to your car with a ruler and check you will clear struts, arches and dont forget steering on full lock. because you have picked a wheel that is a standard wheel to an upgraded version of your car most of the time will fit especially if you are still running standard height suspension, but if you lower suspension you might have to play with tyre width to create a % of stretch to the tyres to clear everything.

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Well, let's suppose your tyres had 2mm of tread depth when you changed them. When you changed them, they would have about 8-10mm tread depth - an extra 6-8mm, which would increase the diameter by 12-16mm. So no, an extra 10mm will do no harm whatsoever.

I cannot comment on the other measurements (offset, etc) but if they are from the ST then they will probably fit.

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