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[Jhalf]

I might be missing something really simple, but when i use the calculator for tire diameter at the top of this page, it says that an increase of 1.5 percent would make the speedometer at 60 actual mph read 61.

In actuality if you have a bigger tire diameter the speedometer would say you are going slower than 60 because the tire travels less revolutions per mile.

Am i missing something? Or misreading it?

[bmw325i]

When your speedometers at 60 your actually going 61.

[Jhalf]

Doesn't the above say "Speedo will read:____ mph?"

Doesn't that seem written wrong?

Shouldn't it say "Speed when speedometer reads 60:___mph"

[Orion4]

The calculator is correct. Think of it this way: Since the new tire has a slightly larger diameter, it takes longer to make a single rotation, although you are covering slightly longer distance per rotation, therefore the speedometer system which is calculating based on number of rotations still thinks your going 60-while because of the slightly greater distance covered for the same time period you are going slightly faster.

Hope that make sense.

[Jhalf]

That makes perfect sense, Im saying with a bigger tire the that readout at should say:

Speedo @60mph will read: "59" mph not 61

[The Kingpin]

Originally Posted by Jhalf

That makes perfect sense, Im saying with a bigger tire the that readout at should say:

Speedo @60mph will read: "59" mph not 61

I agree. It should say " when spedo says 60 your actual speed is ___"

[BrazilianBimmer]

I agree that speedometer should say say 60 but in reality you would be going at 61, however if the wheel is slightly bigger the speedometer would most certainly be lying to you due to the known fact that a bigger wheel travels a slightly longer distance with each rotation than a stock. It should really say, speedometer reads 60, while you are traveling @ 59.
Does that makes sense?

[Jhalf]

Originally Posted by The Kingpin

I agree. It should say " when spedo says 60 your actual speed is ___"

Originally Posted by BrazilianBimmer

I agree that speedometer should say say 60 but in reality you would be going at 61, however if the wheel is slightly bigger the speedometer would most certainly be lying to you due to the known fact that a bigger wheel travels a slightly longer distance with each rotation than a stock. It should really say, speedometer reads 60, while you are traveling @ 59.
Does that makes sense?

Thanks guys, just making sure i wasn't going crazy