Which Tire does our Speedometer measure Speed from?

[Edmo83]

hello fellow forumers,
Simple question, hopefully someone can help me out....
after searching for it, i know about tire sizes and stuff....
but out of curiousity... which tire or tires does our dashboards take the speed calculations from. I would think the rear, basically tracking how many rotations per second etc.... based on the stock tire diameter....
anyone has the little info to help fill me in?

and this is cuz i just got a slightly smaller tires on the rims i just bought, and want to use them up before getting a more close to OEM size.

Thanks in Advance!!!

[DOHCammer]

Speed is measured at the transmission through a sensor.

[touringcamry]

^ To add to that:

The speed is measured at the trasmission. So if you put different size tires on the vehicle, the speedometer will be inaccurate. The car has no way to know what size tires that you have put on the vehicle.

[Edmo83]

Thanks, that clears it up for me.

ill just have to white out my dashboards speedo and pencil the new numbers in

Thanks for the info guys

[trickyazn]

^^ thats ghetto LOL

[skewe]

try using the miata link.

check miata.. search for it

[Edmo83]

skewe, ive been on miata tire calc religiously, but the flaw ive discovered is...tires fit differently pending rim width, so i dont really know what to trust anymore. I'm gunna start editing my dash board soon, haha, and rolling back those pesky odometer miles for a more accurate number, like 00002
Either way i realize im only off by a percent or two, no biggie

[BlackCamSe]

so thats why when my speed sensor went in my trany the odometer and speedometer were fucked up.

[touringcamry]

Originally Posted by Edmo83

skewe, ive been on miata tire calc religiously, but the flaw ive discovered is...tires fit differently pending rim width, so i dont really know what to trust anymore. I'm gunna start editing my dash board soon, haha, and rolling back those pesky odometer miles for a more accurate number, like 00002
Either way i realize im only off by a percent or two, no biggie

The only way to roll back the digital meter is to drive backwards everywhere you go.

[Edmo83]

Originally Posted by touringcamry

The only way to roll back the digital meter is to drive backwards everywhere you go.

Oh yea, forgot it is digital, lol

does driving backwards really reverse the odometer?
If it does, i think ill b driving backwards to wrok 3 days of the week from now on, lol

[Durrby]

Originally Posted by Edmo83

does driving backwards really reverse the odometer?
If it does, i think ill b driving backwards to wrok 3 days of the week from now on, lol

Someone didn't see "Ferris Bueller's Day Off"