DIY Crawler Links: How to Size and Build Custom Links from Threaded Rod

Part of the Crawler Tools & Guides series.

Maybe you're stretching a wheelbase, correcting geometry after a tire-size change, building a micro, or you just snapped a lower link on granite and don't want to pay for a set when you only need one replacement. The classic answer has been around as long as the hobby: a piece of threaded rod inside a metal sleeve, with a rod end threaded onto each protruding end. Cheap, strong, and buildable to any length.

How long do you cut the sleeve? How much shorter (or longer) does the threaded rod need to be so the rod ends thread on far enough to be strong, but not so far they bottom out? There's a simple, repeatable formula for it, and once you've measured your rod ends one time, you can crank out links for the rest of the build without guessing.

One note before the saw comes out: this guide covers how to build a link to a target length. Figuring out what that target length should be is a geometry question... link lengths and mounting points drive your roll center, anti-squat, and instant center. If you're changing lengths to tune handling rather than just replacing a broken part, run your numbers through the Crawler Geometry Tool first and let it tell you the eye-to-eye lengths you're building to.

What you're building

Three parts per link:

• Threaded rod (all-thread) — the structural core. Runs the full length of the link and threads into both rod ends.
• Sleeve — a tube that slides over the rod and butts up against the shoulder of each rod end. It stiffens the link, protects the threads from rocks, and sets the finished length.
• Rod ends (2) — the ball joints at each end that bolt to your chassis and axle mounts.

The sleeve does more than look clean. Bare all-thread is a rock magnet — the threads catch and grind on everything. The sleeve turns the link into a smooth tube that slides off obstacles, and it locks the assembly rigid because the rod ends clamp against it.

The one measurement that matters: eye-to-eye

Every link length in crawling is measured eye-to-eye: the distance from the center of one rod-end ball to the center of the other. That's the number your geometry cares about, because the balls are the actual pivot points.

Get your target eye-to-eye one of two ways:

1. From your geometry plan — the length the geometry tool (or your measurements of a known-good setup) says you need.
2. From the truck — set the axle where you want it at ride height, and measure center-of-mounting-hole to center-of-mounting-hole.

Measure your rod ends — this is where builds go wrong

Here's the nuance that old forum threads argue about endlessly: there is no universal “cut it X mm shorter” number, because rod ends differ in two dimensions, and both are in the formula:

• Center-to-shoulder (C): from the center of the ball to the flat face where the sleeve butts up. On the popular Traxxas Revo rod ends this is about 17mm — but plastic ends, aluminum ends, and micro ends are all different.
• Thread depth: how deep the internal threads go before the hole bottoms out. Measure it with calipers, a small screw, or the cut-off shaft of a Q-tip pushed in until it stops.

Measure your rod ends. Even nominally identical plastic ones vary slightly, and some aluminum ends have a hard internal stop.

The formula

With a target eye-to-eye length (E), your rod ends' center-to-shoulder (C), and a chosen thread engagement per side (T):

Sleeve length = E − (2 × C)

Threaded rod length = sleeve length + (2 × T)

That's it. The sleeve fills the space between the two rod-end shoulders; the rod spans the sleeve plus however far it reaches into each rod end.

How much thread engagement? The working range the community has settled on is 7–10mm per side for standard 4mm/8-32 links. The mechanical floor is about 1–1.5× the rod diameter (roughly 6–8mm for 4mm or 8-32 rod), and since most crawler rod ends are plastic or aluminum rather than steel, erring toward more engagement is cheap insurance. Two practical approaches: pick a number in that range and stick with it for the whole build, or use 70–100% of your measured thread depth. Just leave a little room before bottoming out hard — a few free threads is what gives you fine length adjustment later.

Worked example

Say the geometry tool calls for a 59mm eye-to-eye lower link, and you're using Traxxas Revo rod ends with a 17mm center-to-shoulder:

• Sleeve = 59 − (2 × 17) = 25mm
• Pick 7.5mm engagement per side → rod = 25 + (2 × 7.5) = 40mm

A 40mm rod in a 25mm sleeve, 7.5mm buried in each rod end. Solid engagement, room to adjust, nothing bottomed out.

Rod-end quick reference

Always confirm with your own calipers, but these are the common starting points:

Rod end	Typical center-to-shoulder	Common engagement per side	Notes
Traxxas Revo large (#5347, 4mm/8-32)	~17mm	7.5–12mm	The de facto standard — strong, cheap, everywhere. Overall length ~22mm. Many builders just subtract 34mm from eye-to-eye to get sleeve length.
Traxxas 3mm long (#1942)	Shorter — measure	6–10mm	Lighter links, micros.
Aluminum M3/M4 aftermarket	Varies	Often 8mm (advertised thread depth)	Many CNC ends spec 8mm depth; some have a hard internal stop.
Plastic Axial / stock-style	Varies	Measure yourself	Usually shallower than Revo ends.
Rule of thumb (any end)	—	7–10mm/side	Minimum ≈ 1–1.5× rod diameter; don't bottom out hard.

Materials

• Threaded rod: 8-32 is the most common in the US; 4mm, M4, and M3 are all standard, with M2/M2.5 for micros and SCX24-scale builds. Stainless is worth it for strength and corrosion resistance.
• Sleeve: 1/4″ aluminum tube (K&S hobby tubing is the usual source) for 8-32/4mm rod. Also used: stainless tube, Delrin/acetal (slides over rock nicely), automotive brake line, brass, carbon. You want a snug slip fit over the rod — minimal slop.
• Rod ends: Traxxas Revo #5347 is the gold standard for strength and availability. Axial, SSD, RC4WD, Injora, and various M-series imports all work — whatever you pick, measure it.
• Hardware: jam nuts to match your rod (optional but recommended), blue Loctite or thin CA if you want a permanent assembly.

Build steps

1. Get your target eye-to-eye — from the geometry tool or measured on the truck at ride height.
2. Measure your rod ends: center-to-shoulder and thread depth.
3. Do the math and cut. Sleeve = E − 2C; rod = sleeve + 2T. Cut with a Dremel, hacksaw, or rotary cutoff wheel.
4. Deburr everything — seriously. Chase the rod threads with a nut before cutting (spin it off afterward to straighten the cut threads), and chamfer the sleeve ends. Sharp edges catch rocks and eat rod ends.
5. Assemble: slide the sleeve over the rod, center it, and thread a rod end onto each side until it seats against the sleeve. A drop of oil (or slight warmth on plastic ends) helps the threads start cleanly.
6. Add jam nuts if using them — snugged against the rod-end face, they lock the length and give you fine adjustment later. For a permanent link, blue Loctite or thin CA on the threads instead.
7. Install and cycle the suspension through its full travel. Check that nothing binds and the rod ends aren't at the edge of their misalignment range.

One thing worth knowing: unlike a turnbuckle, both ends of an all-thread link are the same thread direction — so spinning the assembled link does not change its length. To adjust, back off a jam nut and thread one rod end in or out. If you want on-the-truck adjustability, that's what the jam nuts are for.

The no-math shortcut for odd lengths

Replacing a bent link and can't measure eye-to-eye cleanly? Thread one rod end fully onto a scrap of rod, bolt both rod ends into their mounts on the truck (unconnected), and measure the gap between the two rod-end faces. That gap is your sleeve length; add 2× your engagement number for the rod. Same formula, measured instead of calculated.

What's next

Straight links are the foundation — but a lot of crawlers run bent lower links for ground clearance, and there's more to that than bending pipe until it fits. When and why to bend a link (and how a bad bend makes things worse) is coming up next in this series.

More setup math and calculators live on the Crawler Tools & Guides page — including the Crawler Geometry Tool for link geometry and the Gearing Calculator for drivetrain numbers.