Tire and speedo

My stock tire is 275/55/20. Is a 275/60/20 the same tire just a little taller? If I added that tire will be Speedo be off and if so would it read that I’m going faster or slower than actual speedometer? Thank you

 

If you add larger tires you will be going faster than what your speedometer reads.

The speed increase will be the same percentage as the increase in the tire circumference.

 

Go here, and enter your old tire size, and your new tire size. It will show you how things change. You can play around with it and see how drastic or minimal a change in tire size can be.

 

You are going from a 31.9 to a 33, so an inch bigger. Long story short, not a big deal, I would worry about it. I switched from 27" to 31" and speedo was barely off, I think 2-3 mph.

Your speedometer will show slightly lower than actual speed when increasing tire size.

 

So on my lease I’ll be gaining a few miles rather than loosing some . Stock suspension, will I have any rubbing to worry about?

 

It will never be off by "2-3 MPH" though. It's a percentage. The faster you go the further off it will be. It's not a static error, it's a ratio that grows the faster you travel.

 

I always wondered about that! I had a poor-mans check on the highway (speed limit is 55, you are traveling...) and it was about 3 ish, but slower checks (20 mph limits) were always closer to 2 or less, so I just kept the range in mind while driving. Always intended to change the speedo gear, but never made it high enough on the list.

 

At least you were smart enough to wonder about it. I was oblivious to it until I started doing research about going to bigger tires. I just had to put it into simple math for my brain to get it.

Something along the lines of this:
If you increase the circumference (not the height/diameter) by 10%, then you will be traveling 10% faster than the speedometer reads. So 1 MPH becomes 1.1 MPH, 50 MPH becomes 55 MPH, and 100 MPH becomes 110 MPH. Faster you go, the more pronounced it is.

It's got to be simple for my brain to go "Ooooooh, that makes total sense." I just never thought about it until I researched it.

 

when i went from 275/55/20 to 295/55/20, the speedometer was actually spot-on.

when i had 275/55/20, my speedometer was reporting a slightly higher speed than i was actually going. when i went up to 295/55/20, the speedometer was spot-on.