Daveperc wrote: ↑Mon Mar 25, 2019 9:22 amThe depth of a tyre , in this case 30, is a percentage of the width. As the wheel size is fixed, if you increase the width and keep the depth % the same, you have a bigger rolling radius. If the radius is bigger, then the circumference will be bigger too, so the tyre will travel further for each revolution of the wheel, ie it will indicate slightly lower speed on the speedo.
Hope that helps! There is a website somewhere which will give you the direct comparison between different tyre sizes.
Dave
Ah ok, never really looked into it in depth, but always thought the profile number was fixed instead of it being basically an "aspect ratio".
After that it's obviously clear that the distance covered 295 vs 285 is greater with each rotation.
You learn something new every day, thanks!