Car tyres

You did not tell us the tire profile existing and proposed. This specification is required before making the change.

Usually, this number appears along side the width and wheel diameter. For example,

225 HR60 16.

When you go to a lower profile tire, you need a larger wheel diameter. Alternatively, a smaller wheel will require a higher profile tire.

If the tire profile is the same (i.e. 60), you are talking about a very small width reduction (5 mm). This should not matter. However, for larger changes, get a smaller width wheel.

Typically, BMW's use narrow, high-profile steel wheels and tires mounted on separete rims for winter driving in snow and ice as they handle extremely poorly under these conditions with low profile (wide) tires.

It only depends what speeds and roads you are driving. For 80 mph , 130 kmh anyone will be OK.

For Autobahn use, or taking sharp curves at 170 kmh (that is all an R-type will get), perhaps you want to think twice about any change in width

There are a few things which have to be taken into consideration when changing your tire size. If you go wider how much clearance is there, you may start to get fender rub due to a wider tire. Another major consideration is what width tire can the wheel accept? Wheels come in different diameters and widths. A small change will probably be OK but a change of 20mm or more may require a different width wheel to be able to mount the tires correctly.

If you do change the tire width be aware it may change the handling charachteristics of the car and as mentioned earlier it should be coordinated with a change in the aspect ratio (second number in tire size) or else your speedometer and odometer will be off and you could even damage your wheels if you put on a low enough profile tire. Just as a quick primer a 225/60R16 tire would be 225mm wide and (225 * 0.60) or 135mm thick, thus the entire wheel/tire combo has a radius of 338.2mm. The last number (16) is the diameter of the wheel (not the tire) in inches.

Shawn

Can I use 220 R 16 tyres in place of 225 R16.

Yes.

how much variation is acceptable in tyre width

+/- 12mm is rule of thumb, variations beyond this will have noticeable effect on appearance first. If wheel width is narrow the tire side wall may appear to bulge outward, if wheel width is wide for the tyre bead the treaded portion will appears narrower than the wheel.

If you occasionally bump the curb a narrow wheel may prevent damage because the tyre sidewall will protect the wheel from contacting the curb.