Formula for figuring out speed?>??

[180SXtc]

What is the formula for figuring out speed after 118... I have seen it before but I dont remember it and I searced but no luck.... I know its rpm x final drive ratio x tire size or something.... and can anyone tell me what the final drive is if i need to know that... and the circumference of a 215/35/zr18....

Tony

[Drunk Bastard]

Rate = Distance / Time

[007jpang]

Rate = Distance / Time

physics yo

[timmybgood]

i just saw a post a week ago or so, can't remember which board, but whoever posted it equated all the gears at various rpms, and all i remember is [email protected]=170mph, yikes?

[andrave]

my speedo doesn't work so I just keep it at the same rpm's and have my girlfriend use a stopwatch on the milemarkers.
from there its pretty simple. that tells you how many seconds it takes you to go one mile.. for instance, 60 seconds in one mile means 60 mph.

[carkid0007]

I hate college physics....I am taking it right now....and its not kewl

[Andrew Bohan]

college physics?
that's like.... 1st grade physics

[1101]

Rate = Distance / Time implies constant acceleration, wouldnt work for his problem but yeah. (it was probably a joke)
Anyways I hit up google for you

http://www.izook.com/tech/math/gearcalc.htm
Came out saying I do about 69.69 at 3000 in 5th

http://www.type2.com/library/misc/calcspd.htm
No fancy automated converter but explains the math

http://www.johnsbugshop.com/TECH_DATA.htm

To sum it up
MPH = [ (RPM x Tire Diameter(In inches) ) / (gear * rear end (4.083) * 336)]

205/60/15 diameter is
Dia = 2[(205 * .6) / 25.4] + 15

Now where the 336 came from is just escaping me; i thought it was a conversion from in/min. I'll figure it out in a second..
(1 mile / 63360 In) * ( 60 Min / 1 Hr)

EDIT it's because the diamater needs to be in cicumference meaning the above is multiplied by pi resulting which is close to 1/336.

Anyone else tell i'm procrastnating?

i'll even go farther:
1st - 3.321
2nd - 1.902
3rd - 1.308
4th - 1
5th - 0.759
Rev - 3.382

Rear - 4.083