M Y snow tires

[EllenM]

Wondering if I can use my old M3 snow tires (235/40 R19) on my new model y that came with 255/45 R19 continental m/s tires?

 

[jjgg]

Wondering if I can use my old M3 snow tires (235/40 R19) on my new model y that came with 255/45 R19 continental m/s tires?

The tire side wall heights differ a lot. Your 235/40R19 has 235*0.40 = 94 mm side wall, while 255/45R19 has 255*0.45 = 114.75 mm. So the side wall diff is 20.75 mm. Doubling that you get the tire diameter difference of 41.5 mm (about 1" 5/8). With this difference, each wheel rotation you get more than 5 inches difference in travel distance.

 

[EllenM]

As I don’t know about these things, I’m guessing that may be too big a difference and can’t safely use my smaller snow tires?

 

[jjgg]

As I don’t know about these things, I’m guessing that may be too big a difference and can’t safely use my smaller snow tires?

With a wrong tire size your speedometer and odometer can be lying to you as the minimum consequence. As for safety, you need to make sure the load and speed ratings are good. The MY is heavier than M3 but they are likely in the same load rating range give M3 is already quite heavy for its size. Still, you need to double check and confirm this with your tire spec.

 

[EllenM]

Ok. Thanks for the info and education!