Gear ratio Calculators?| Grassroots Motorsports forum |

fidelity101 (Forum Supporter) UltraDork
4/21/20 4:02 p.m.

Anyone have a good link or made a handy excel file?

I want to play with different rear end ratios and shift points to understand what mph they would be. A lot of the ones I see online are simply for drag racing estimations but I am looking for something a bit simpler that I can change different RPMs easily.

otherwise I am making one from a blank...

overall tire size is fixed

transmission ratios are fixed

rear end ratio has a few options

shift point/RPM will be heavily varied.

wafflenator500 New Reader
4/21/20 4:06 p.m.

This site was pretty valuable when I was playing around with my tire size changes. You should be able to just set different redline for your shift points.

http://www.bokchoys.com/differential/e46_gear_ratio_calculator.htm

Patientzero Reader
4/21/20 4:12 p.m.

http://www.wallaceracing.com/Calculators.htm

NOT A TA SuperDork
4/21/20 4:13 p.m.

I use ones here frequently http://www.wallaceracing.com/Calculators.htm

I've compared their results with dynos, strip results, Land speed race results, GPS etc. and they've been very accurate.

NOT A TA SuperDork
4/21/20 4:15 p.m.

Patient zero beat me to it! Gettin slow at the tree, must be age.

Curtis73 (Forum Supporter) MegaDork
4/21/20 4:46 p.m.

http://www.gearcal.com/

I use this one too.

fidelity101 (Forum Supporter) UltraDork
4/21/20 5:00 p.m.

wafflenator500 said:
This site was pretty valuable when I was playing around with my tire size changes. You should be able to just set different redline for your shift points.

http://www.bokchoys.com/differential/e46_gear_ratio_calculator.htm

this is perfect! I was able to play around and get a good ballpark feel.

Its hard to justify the cost for the 4.30s and finding them is rare, there is another option with two very similar ratios and cost is the same for both but it should help make up for the loss of power the car has and more useable gearing for 3rd and 4th. This car struggles sub 200hp with two 200lb people in it to reach 100mph on stage. I don't see myself going to 120 but the 60-90mph needs some boost. shifting between 3rd and 4th is more desirable than 2nd to 3rd too.

That wallace one is very helpful too, there are incredible amounts of data/calculators there!

thanks guys!

Keith Tanner MegaDork
4/21/20 5:31 p.m.

I like to build my own from scratch when I need it because it reminds me how it all works :)

RossD MegaDork
4/21/20 5:54 p.m.

https://drive.google.com/file/d/1lW4baywVA7gJS9IlkeIn-O62xxHHaI1M/view?usp=drivesdk

Heres the one I use. I think it started from someone elses from the Locost Seven world, but then I modified it to include more typical USA transmissions.

buzzboy Dork
4/21/20 6:45 p.m.

I've always used this one

http://www.americantorque.com/graph-rpm-vs-speed/

doc_speeder HalfDork
4/21/20 7:09 p.m.

I found this one a few years ago when I was trying to figure out tire size/gears/ etc for my 6.0 lq4

http://www.grimmjeeper.com/gears.html

ProDarwin UltimaDork
4/21/20 7:19 p.m.

Keith Tanner said:
I like to build my own from scratch when I need it because it reminds me how it all works :)

You mean because you lost the last one you built.

I have rebuilt spreadsheets like this way too many times.

Keith Tanner MegaDork
4/21/20 11:14 p.m.

No, seriously. Weird spreadsheets I keep. Gear ratio calculators? Good practice.

fidelity101 (Forum Supporter) UltraDork
4/22/20 8:37 a.m.

Keith Tanner said:
No, seriously. Weird spreadsheets I keep. Gear ratio calculators? Good practice.

I've done this before but I always forget to save them and the ones I do have saved I found buried in the hard drive are for other vehicles that I don't own anymore/etc