My new wheels for my polo :)

[llai8501]

Thanks for your help btw Steve

[steveyoshi]

Tyre Rolling Diameter is the most important and brand/make of tyre is also relative as some have slight differences even in same size. Of course too wide and scrubbing can also occur.

So do the maths...

Old Wheel Diameter = 431.8mm (17")
Tyre Profile = 40% of 215mm wide = 86mm
Tyre Rolling Diameter = 431.8mm + 172mm (2 Profiles) = 603.8mm

New Wheel Diameter = 457.2mm (18")
Tyre Profile = 40% of 225mm wide = 90mm
Tyre Rolling Diameter = 457.2mm + 180mm (2 Profiles) = 637.2mm

So your tyres are more than 30mm too big in diameter... this is a fn disgrace from a Tyreshop, depending on tyre brand and type

Get it fixed and the scrubbing will very likely go.

As for tyre width...

215mm wide is 8.46"
225mm wide is 8.85"

but rim width to tyre width is not quite the same.

Most tyre shops should now the exact diameter of each tyre size in each brand and type, this is what you need to make the right choice. My diameter figures are a guide as there is a tyre bead to worry about too.


Size of original

Stock is 17x7 on 215/40/17

New is 18x7.5 on 225/40/18 but scrubbing on left rear tyre.

I'm trying to work out what sized tyre to put on the new rims

[llai8501]

So going by your calculations:

Tyre Rolling Diameter
215/40/17 = 603.8mm (original)
215/35/18 = 607.7mm (optimal)
225/35/18 = 614.7mm (alternative)
225/40/18 = 637.2mm (current)

Looks like I will ask if they can swap me with some 215/35/18 or maybe test 225/35/18. I hope they won't make me buy another set..

[ATYPIC]

So going by your calculations:

Tyre Rolling Diameter
215/40/17 = 603.8mm (original)
215/35/18 = 607.7mm (optimal)
225/35/18 = 614.7mm (alternative)
225/40/18 = 637.2mm (current)

Looks like I will ask if they can swap me with some 215/35/18 or maybe test 225/35/18. I hope they won't make me buy another set..

Get the 215/35/18. They should replace them.

[llai8501]

And they'll fit the wheels? I've been googling all morning trying to find out if the 215/35's would fit the rims

[ATYPIC]

Perfect for 18x7.5...Just make sure the tyre load rating is close to 87.

[steveyoshi]

of course they will... same width and diameter will be fine... Profile is how 'tall' the tyre is.

And once you have sorted it... never step back into that tyre place again, unless you didn't listen carefully to them in the first place.

[llai8501]

Thanks everyone. I followed their recommendations and they said it would be fine...I hope they are understanding!

[Diesel_vert]

Regardless, will I be able to fit a 35 series tyre on the wheels?

215/35 R18 and 225/35 R18 are approved fitments for a 7.5 J x 18 wheel.

And they'll fit the wheels? I've been googling all morning trying to find out if the 215/35's would fit the rims

Yes (see above reply).

Tyre Rolling Diameter
215/40/17 = 603.8mm (original)
215/35/18 = 607.7mm (optimal)
225/35/18 = 614.7mm (alternative)
225/40/18 = 637.2mm (current)

Looks like I will ask if they can swap me with some 215/35/18 or maybe test 225/35/18. I hope they won't make me buy another set..

Due to its higher load index, you'd be better off considering 225/35 R18 87V XL tyres as your primary option.

For the same reasons, it would be better to consider 215/35 R18 84V XL tyres as a last resort, but even so, there may be issues with roadworthiness in regards to the tyre's load index.

[llai8501]

So 215/35 will fit but not be road worthy?