Guides
15 in-depth, start-to-finish guides that tie our calculators, finders and lookups together.
Reading a Tire Sidewall and Choosing a New Size
Decode the sidewall, work out diameter and speedometer error, and pick a size that fits.
Choosing Wheel Offset and Backspacing
Offset, backspacing and fitment: how to change wheels without rubbing.
Gear Ratios Explained: Axle, Transmission and Tire Size
How axle, transmission and tire size set rpm, and how to pick gears for towing or the strip.
Sizing an Air Compressor for Your Shop
CFM, PSI, tank size and duty cycle explained, with a method for matching a compressor to your tools.
Wiring a Garage: Subpanels, Circuits and Wire Gauge
Plan circuits, match wire gauge to breaker size and avoid voltage drop in a home shop.
Heating and Cooling a Garage Workshop
Estimate heating BTU, pick a heater type, insulate and stay safe from fumes and carbon monoxide.
Planning a Paint Job: Prep, Primer, Base and Clear
Estimate paint quantity, choose a system, and follow a prep sequence that avoids rework.
Choosing Blasting Media and Preparing Metal for Coating
Match glass bead, aluminum oxide, walnut shell, soda or steel to the job, and size the air supply.
Compression, Cam Timing and Pump Gas: Making the Combination Work
How compression, cam duration, overlap and octane interact, and how to match them.
Budgeting an Engine Rebuild: Machine Work, Parts and Surprises
Build a line-by-line rebuild budget with a cushion for surprises, and know when to walk away.
Sizing Fuel Injectors and Fuel Pumps for Your Power Goal
Calculate injector size and pump flow from horsepower, BSFC and duty cycle.
Turbo and Supercharger Basics: Boost, Pressure Ratio and Reliability
Boost to pressure ratio to horsepower, turbo versus supercharger, and what a boosted engine needs.
Buying and Budgeting a Project Car
Choose a project that fits your skills, inspect it properly and budget the whole restoration.
Torque Specs, Lug Nuts and Fasteners Done Right
Use a torque wrench correctly, tighten lug nuts in a star pattern, and understand bolt grades and thread.
Towing Basics: Hitch Classes, Tongue Weight and Ratings
Match hitch class to the trailer, set tongue weight and understand GVWR, GCWR and payload.
How to use the guides
Each guide takes one job from start to finish: the decisions to make first, the arithmetic behind them, worked examples, and the mistakes that cost people time and money. They link to the calculators, finders and lookups that do the numbers for you, so you can read a guide once to understand the whole picture and then use the tools when your own measurements are in hand.
What the guides cover
Wheels, tires and drivetrain: reading a tire sidewall, wheel offset and backspacing, gear ratios and towing basics.
Engine and fuel: compression, cam timing and pump gas, injector and fuel pump sizing, turbo and supercharger basics and budgeting an engine rebuild.
Shop and body: sizing an air compressor, wiring a garage, heating and cooling a workshop, planning a paint job and choosing blasting media.
Projects and fasteners: buying and budgeting a project car and torque specs and lug nuts.
A note on accuracy
The guides give general planning figures and explain where the numbers come from. They are not a substitute for your vehicle's service manual, a tool's instructions, the product data sheet or your local building and electrical codes. Where a job involves risk, such as electrical work, fuel systems, compressed air or abrasive blasting, the guide says so and tells you what to check. If you spot an error, please tell us through the Report an Issue form.