Hi all. after trawling through several posts on tyres/rims, I am not seeing anyone really concerned with the effect on the speedo when changing tyres. I recently got a new T6.1 that came with 205/65/16 from factory and the calibrated speedo is already 3.5-4km faster than actual, so at 100km p/hr, actual speed is 96/97 km. Already behind the eight ball and putting larger tyres on, will make that effect worse. I used the website,
Alloy Wheel & Tyre Fitment Calculator. Offset, Tyre Stretch and Speedo Error | Will They Fit to enter my factory wheels in the "new" side, then worked backwards by entering a smaller 15 inch wheel on the "existing" side of the calculator. This tells me I'm already -3.77% compared to true zero for the speedo. Putting on the next size up 215/60/17 pushes the speedo error out to -6.13%... Who wants their speedo saying 100km, when the actual is 92/93km?
Now I want to also change to all terrain of some sort but its near impossible to find the right combination of size, diameter and load rating. The sticker on the driver door shows several sizes from 16's to 18's but all have load ratings above 102. I spent an hour in a tyre shop today and they couldn't find an appropriate tyre that was in the all-terrain category they would fit legally without breaking the load rating for the car or massively affecting the speedo. What are you all doing in this regard? Are you not bothered by speedo's becoming so far out?