need gear ratio figuring--help

[adh383]

I currently have a 557 gear in my dirt car--- turns 7200, way to much!!!!!!!! I want it to turn max 6200 rpm's-- what gear will i ned to get it to that point? thanks--

[Scotty_S-15]

There's a few sites out there with calculators..... here is one. They also have other calcualtors........

http://www.wallaceracing.com/calcrgr.php

OK, found another calculator. Dirt car? So for this one, I guess you need to enter 0 (zero) for converter slip.

http://www.tciauto.com/Products/TechInfo/Calculators.asp#6

[adh383]

Hey Scottie--- cant use that chart because it is based on 1/4 mile time- have any idea what gear i would need? just guessing?

[Scotty_S-15]

Hey Scottie--- cant use that chart because it is based on 1/4 mile time- have any idea what gear i would need? just guessing?


* The first link is good.
* And, really, the second link is good too. They mention 1/4 mile, but what's the difference? speed is speed.
so:
Speed is just a matter of tire height, RPMs, and ratios.
Or, ratios are a matter of speed, tire height and RPMs.
etc. etc. etc.

[racer1182]

I run dirt tracks and I would try something in the 520 to low 530 range and see what rpms you are turning. Are you turning those rpms on a tacky track or a dry slick track? those are things to look at too. also 7200 isn't too bad unless that is way over your power band of the camshaft. hope this may help you.

Greg

[adh383]

Hey Scottie-- problem is. we dont run speedometers--dont know the speed------Hey Racer-- rpm's havent differed but about 200 rpm;s no matter how the track is-- and this motor has a stock bottom end in it. dont want to have GUTS all over the track-camshaft runs out at about 6500.

[Scotty_S-15]

Actually, you DO know your speed.... at least when you're not spinning the tires and throwing clay chunks all over the spectators....:naughty:
Just plug in your RPMs, tire size and gear ratio.
Bottom line is, those charts will work. But if you don't ever hookup, that's another story. Might have to take a stab like Racer said.

[pl747]

a little algebra...5.57 is to N as 7200 is to 6200. 5.57 divided by N=7200 divided by 6200.

5.57 = 7200
N 6200

7200N=34534
7200 7200

N=4.796

So a ratio of around 4.8 would be real close to run the same SPEED at 6200 as you do with the 5.57's at 7200.