4Wheel Underground

04/03/2026

and the boys are putting in some work on our SD 3link swap. Pretty simple stuff to put together.

04/01/2026

03/09/2026

Another round of SuperDuty systems getting ready to ship. Can't wait!

03/03/2026

A 3rd Gen 4Runner, a 3UZ and our 3Link kit are turning this mild mannered grocery getter in to a full bodied dream machine.

02/26/2026

FJ80 all flexed out after the maiden voyage. And sporting a Diamond Axle with our 3Link.

02/25/2026

drop getting on the action.

02/24/2026

Fully trussed Chevy 1Ton D60 3link, fits like a glove

01/23/2026

Hot topic on dual-rate coilovers: the primary (bottom) spring is the only spring that truly defines handling.
In a real dual-rate setup, the bottom spring controls wheel rate, load transfer, and how the chassis behaves under braking, cornering, and acceleration. That’s the spring working through the damper during actual driving. If you change it, the car changes—immediately and noticeably.

The top spring (helper/tender) is there mainly for ride height, preload, and droop control. Once the suspension is loaded and in its operating range, it’s effectively irrelevant to handling.

Now here’s where people get confused 👇
Spring rate is meaningless without corner weight.
Two vehicles can look identical, run the same primary spring, and still need different secondary springs because their corner weights aren’t the same. Engine placement, accessories, cage, driver weight, fuel load—all of it matters. The primary spring is chosen to support and control the working load. The secondary is adjusted to achieve the correct ride height and preload for that specific corner weight.

That’s why copying someone else’s dual-rate stack just because the car “looks the same” is lazy setup. Same primary ≠ same setup

Different corner weight = different secondary needs
So again:

You tune handling with the primary spring.
You tune height and static compliance with the secondary.

The bottom spring defines the car. Everything else is just making it sit right.

01/22/2026

Just gonna leave this here for yall

12/26/2025

Last chance to save some green this year. Use code: Merry Christmas to save 15% before it's to late.

12/24/2025

Save 15% with code: Merry Christmas on everything store wide.