Understanding wheel offset?

[Paul70]

Recently bought a set of VWR wheels (18x8 ET45) for winter use that have Michelin 225 40 tyres.

There is a subtle change in the car’s stance, which I like and want to retain when I put the Belvederes back on in spring. The Belvederes are narrower at 7.5 and have an offset of ET49 so I am looking to understand the spacer width required to keep the track width the same?

The obvious answer would be 8 (49-45)x2 so 4mm spacers either side but not sure if the wider rim changes this even though the tyres are the same width?

Appreciate the feedback.

Paul.

[SRGTD]

There’s a really useful calculator on www.willtheyfit.com. If you input the details of your winter wheels and your Belvederes it will calculate the critical figures for you.

According to the calculator, your winter wheels (8J x 18” ET45) will protrude an extra 10.4mm compared to your 7.5J x 18” ET49 Belvedere alloys.

So based on the above, it looks as if you would need 10 mm spacers with the Belvederes to give a similar stance to your winter wheels.

Link to the calculator below - I’ve pre-filled the details of your Belvederes and winter wheels, based on the figures in your post. Results of the calculations are lower down the web page on the left, once you’ve opened the link.

https://www.willtheyfit.com/index.php?width=225&aspect=40&diameter=18&wheelwidth=7.5&offset=49&width2=225&aspect2=40&wheel_size=18&wheel_width=8&offset2=45

Don’t forget that you’ll need longer wheel bolts once you’ve fitted spacers.

[Paul70]

Brilliant, thanks very much SRGTD. I thought it seemed more than 4 mm 

[rajb]

I’ve used willtheyfit over the years to help but ultimately the lower the number the further they’ll protrude.