What diff ratio to use in your racecar?

What diff ratio to use [Video]

What diff ratio to use?

Choosing what diff ratio to use for your racing car is a challenge. If your racing car (and/or series) allows you to run different diff ratios, then it can make a big different to your racing car’s performance.

Get it right(er) than your competitors, and you’ll be faster – potentially much faster.

But what diff ratio should you choose? How do you select what diff ratio to use for maximum acceleration at a particular track?

Of course, if you ask around, your resident paddock cup champion will to give you a confident answer:

“The 4:4 diff is the fastest”

Paddock Cup Champion 1911

But why? What is that actually based on?

Why is that diff really the best diff for your (unique) racecar setup?

What is actually important when choosing between different final drive ratios that you may available?

Is there even a “correct” answer anyway? 🙂

Perfect Gearing

What you are after is certainty that your racecar is geared as well as it could be.

Given all the gearing options you have available, you want to know is that you have chosen the very best gearing settings possible.

If you can just change the diff ratio, then you want to make sure that you have selected the best diff for your racing car (and for the particular track you are driving.)


Good News!

There is an objective way you can get a good answer – however it does involve some Maths.

Path 1 – If you are interested in the Maths, the most of it is covered in these two previous posts:

Path 2 – If you are interested more in the concepts and what goes into the decision, then click to watch the video I put together (above or) here: https://youtu.be/OH10et2k7lA


Diff Ratio Analysis Spreadsheet

The spreadsheet that you see in the video and is behind calculations you can get here: https://gumroad.com/l/UExM

This is available FREE to our blog subscribers. Take a look around the rest of the site. If you like what you see and fancy the spreadsheet then sign up below for instant access to it – and a whole Vault of other FREE motorsports goodies.