New tires. Adjust speedometer???

[Supertrooper4]

Alright so im going from a 265/70/16 to a 265/75/16 BFG All Terrains today. Would i have to adjust the speedometer or any other gages??

 

[downpour11]

mmmmm no... you are fine

 

[Supertrooper4]

Alright you sure.. bc the guy at discount tire said i might....but hey yall know more then he does.

 

[Qyota]

The diameter of your tire will increase, so the final gear ratio is off a bit. Not by much though...maybe 2%. So yes, technically the grease monkey is right, but it won't be off so much that you'll really notice it.

 

[sportscarfan]

Alright you sure.. bc the guy at discount tire said i might....but hey yall know more then he does.

The difference is 3.3% = you'll be going 62mph when the speedo says 60.

 

[BTO]

The difference may actually correct an error you already had. Have you tested it before and after? Besides, I'd trust the folks on this forum before a tire monkey at Discount tire who may be only trying to up sell you.

 

[Supertrooper4]

really? ok thanks guys, and wait can they reset it or do i have to learn how to do it? haha and how much will my mpg go down???

 

[Qyota]

Fuel efficiency drop will be negligible. Unless you're going to a MUCH heavier tire.

You'd need some conversion hardware to tell the ECU you're going faster than it thinks. For motorcycles, there is something called a "yellow box" (and there are others) that does the conversion on the fly. Not sure this works for cable-operated speedos...but I know it works with Hall effect pickup sensors.

Basically, don't worry about it.

 

[theizzardking]

just find one of those fixed speed check stations in a school zone and keep a steady speed and check the reading against the speedo, lol
they are usually pretty accurate to +-1mph or so, haha,

 

[spongerx]

Sure you don't want to go to 285s? :naughty:

 

[jacob7071]

I went from 265/70 to 265/75 a few months ago. The difference is about 2-3% - not enough to worry about it.

If a cop pulls you over for 90, you probably can't argue that your speedometer said 88.

 

[Limited2K]

My speedo reading actually is more accurate now with 265/75 than 265/70. My GPS and the speedo agree now, whereas before 70 mph on the speedo was 68 mph according to GPS

 

[Clemsonfan15]

My speedo is reading pretty much on target now. I guess it was a little slow before I went up to 265/70/17.

 

[Supertrooper4]

ok ok, got yall, thanks again! i just got the tires on last friday.....love em!!!!

 

[10JQKA]

Sure you don't want to go to 285s? :naughty:

by what percentage would that affect the speedometer from stock?