Which is the best diff ratio to use in racing?

Which is the best diff ratio to use [Video]

Which diff ratio to use?

Choosing which 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 difference to your racing car’s performance.

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

But which 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”

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.

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:

Advanced Racecar Gear Shift AND Gear Ratio Optimisation Calculator

This is available at 25% discount 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.


Whenever you're ready, there are 4 ways I can help you:

  1. Get 1-1 Help From Samir – Sometimes you just need an expert race engineer to get you back on track. Get your questions answered, the best approaches made clear and your goals achieved, with my support.
  2. Master Your Tyres course [link] - Go beyond tyre pressures and guesswork. Uncover the science, tools and techniques to optimise your tyre setup, and your driving style, so you can confidently get more grip, better handling and faster lap times, on any track, in any conditions.
  3. Motorsports Data Analysis course [link] - Ever wondered what insights you might be missing? Turn the data you're already collecting into accurate, personalised guidance to help you drive faster.
  4. Get your business in front of the best motorsports eyeballs in the world by sponsoring Ahead of the Curve [link]