What Size Coil Spring Compressor Do You Need?

Two sizes matter: spring diameter and load rating

When people ask what size compressor they need, they usually mean two separate things. The first is physical fit: do the forks or jaws wrap around your spring's coils? The second is strength: is the tool rated to hold the force the spring stores?

Fit is easy to check with a tape measure. Strength takes a little more thought, because a spring's stored load is rarely printed on it. The safe approach is to choose a tool with a rating well above what you expect, which is why heavier vehicles call for higher-rated tools.

Our coil spring compressor comparison lists both numbers for each tool, so you can check them side by side before you buy.

How to measure your spring

Measure the spring's outside diameter, not the inside. Do this with the spring off the vehicle if you can, or at the widest visible coil if it is still installed. A tape measure works, and calipers are more precise.

Some springs are conical or barrel-shaped, so the top and bottom coils differ in size. Measure both ends and make sure the tool covers the largest and smallest coil you will grip.

• Measure the outside diameter at the top coil and at the bottom coil.
• Note whether the spring is straight, tapered or barrel-shaped.
• Check the winding direction if the kit is sold in left-hand and right-hand versions.
• Write down your vehicle's weight class, since heavier vehicles usually use stiffer springs.

Fork and jaw ranges in published specs

Most strut-style compressors use interchangeable forks, each covering a band of spring diameters. The bands overlap on purpose, so you can pick the one that sits most securely on your coil.

The Amerbm 2010ATH and the aremnry 2010ASC both list three fork pairs: Gold at 2.6 to 4.9 in, Black at 3.4 to 6.3 in, and Silver at 4.9 to 8.3 in. The BILITOOLS kit lists three pairs too, covering 2.6 to 4.9 in, 3.4 to 6.5 in and 4.9 to 8.3 in.

Adjustable-jaw tools work differently. The Orion Motor Tech set lists jaws that fit springs from 0.9 to 11 in., which covers very small and very large springs with one tool. The tradeoff is its lower rating, so check the load figure as well as the range.

Compare the options by size and load

The table below uses the published specifications from our comparison page. Use it as a starting point, then confirm the numbers on the tool you are considering.

If your spring falls near the edge of a range, move up to the next fork size or choose a tool with more margin.

What about coilovers?

Coilover springs are often straight, and many are a different diameter from factory springs. That makes measuring even more important. Check the spring's outside diameter first, then see whether it sits inside one of the fork ranges above.

Many coilovers let you change ride height with threaded collars, so you may not need a compressor at all for small adjustments. You will usually need one when swapping the spring itself or working on a spring that is under heavy preload.

If your coilover spring is wider than 8.3 in, look at tools with a larger range. Our comparison page lists the Orion Motor Tech set and a CARVALAX set for springs up to 11.4 in.

Match the tool to the job

A few other specs affect how comfortable and safe the job is. Compression stroke is one: the VEVOR lists 12.8 in, which helps with long springs that need a lot of travel.

Drive type matters too. Impact-rated rods save time, but the Orion Motor Tech set warns against air or pneumatic tools, and the BILITOOLS kit recommends hand operation with a 22 mm wrench or socket. Follow the maker's instructions for the tool you own.

Fit details count as well. The BILITOOLS kit is sold for clockwise-wound springs, with a left-hand variant for counterclockwise ones, so check the winding direction before you order.

Safety before you compress anything

A compressed coil spring stores a large amount of energy. If it slips, it can cause serious injury. Treat every compression as a hazard, even with a rated tool.

Never use a tool rated below your spring's load, and do not use a tool that is bent, cracked or worn at the threads.

• Wear safety glasses or a face shield, and gloves.
• Seat the forks fully on the coil and keep them evenly spaced.
• Lubricate the threads, and tighten in small steps, alternating sides.
• Stay out of line with the spring while you compress it.
• Stop if the spring shifts, tilts or the tool binds, and release it slowly.
• Use hearing protection when running an impact wrench.

Frequently asked questions

Can one compressor fit most cars?

Often, yes. A kit with three fork sizes covering about 2.6 to 8.3 inches fits many car and SUV springs. Always measure your own spring first.

Is a higher load rating always better?

A higher rating gives more safety margin, but fit still matters. A tool must also sit securely on your spring's coils and match your drive method.

Do I need a different tool for conical springs?

Not always. Check that the forks cover both the narrow and wide ends. Some kits include a spacer to help with different upper and lower coil sizes.

Should I use an impact wrench?

Only if the tool is rated for it. Some tools allow it and others warn against it. Hand tightening in small steps gives you more control.