Originally Posted by
precisionxt
...was wondering what the next closest value in ETACS would be to compensate for the new circumference as apposed to stock?
Go back and start reading at this post. There was a short discussion about these ETACS settings there.
One thing that the resident tire engineer (Basic) brought up was this: When calculating the circumference of a tire, you may have to use the static loaded radius of the tire...not the radius. This may explain why these circumference numbers don't make sense.
SLR Static Loaded Radius is the radius from the wheel center down to the ground, at reference load and pressure. The difference between unloaded radius and static loaded radius is called deflection. This value varies between 15-30% of the tire section height, depending on tire type.
I can tell you that if you are going to use 185-55-15s, the speedometer difference is so small it's undetectable. But I understand if you want it to be as accurate as possible.
One last comment... If you are considering Bridgestone tires, the absolute cheapest place to get them is Costco when they are running a promotion. Costco has good prices to start with...and right now they are running the best promotion of the year on these tires...$150 off a set of 4. Road hazard warranty and flat repairs are included with all tires.
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View my fuel log 2015 Mirage ES 1.2 manual: 52.2 mpg (US) ... 22.2 km/L ... 4.5 L/100 km ... 62.6 mpg (Imp)