Spring Smasher
Setup tools for dirt racers

Change a part.
See what it does.

Engineering tools for dirt racing setups, built by a motorsports engineer. Start from the parts you have and the numbers you measure, then see what each change does before you go to the shop.

The Spring Smasher on a phone: a stacked coilover on the spring rater reading 598 lb at full extension
The tools

One toolbox for the whole car

Each tool does one job well and runs in your browser, on a phone or a computer. Nothing to install.

In testing

Spring Smasher

Your coilover on a spring rater, in software. Build it from part dimensions and see the load at every inch of travel.

  • Single or stacked springs, lockout nut, bump stop, gas
  • 443 stock springs and 445 bump stops built in
  • Target fit finds the nut settings, springs and bump stop for the loads you want
Free while in testing
Available

RaceBook

The setup logbook. Every event, session and setup in one place, on your phone at the track.

  • Tires, corner weights, shocks, springs, suspension, notes and photos
  • Tire and parts databases that count their own laps
  • Works without signal and syncs across your devices
$14.99/month or $150/year · 14-day free trial
Coming soon

Shock Dyno

Open your shock dyno files, lay shocks over each other and compare them.

  • Reads dyno spreadsheet exports
  • Force vs velocity, side by side
Coming soon

Front Geometry

The front suspension through its travel: camber, caster, bump steer and roll center.

  • Built from your own pickup points
  • See what a mount change does before you weld
Coming soon

Rear Geometry

Four-bar and birdcage rear ends: bar angles, rear steer and how they change as the rear moves.

  • Bar holes, birdcage index, J-bar and lift arm
  • Left and right sides on their own
Coming later

Late Model

The whole car in 3D: put it through a corner and watch ride heights, travel and load transfer change with your setup.

  • Springs, bars, birdcages and chains together
  • Compare two setups on the same corner
How they work

Built for comparing setups

01

Change one thing

Every tool shows the difference a change makes: a spring, a nut, a hole, a mount. Keep what you like, undo what you don't.

02

Your parts, your numbers

Start from what you measure on your own rater and your own car, or pick from published part data. Save your own parts once and use them everywhere.

03

Phone first

Made to be used in the trailer as much as at the desk. Save setups as files and share them with your crew.