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Off-Road IFS Truck Torsion Bar Basics

Posted in How To: Suspension Brakes on January 1, 2009
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Photographers: Sway-A-Way

So what are torsion bars? Basically they're straight steel bars that work like coil springs but twist for damping rather than compressing as coils do. The bars can be found in the front suspensions of IFS vehicles. They are the main load-bearing spring on some vehicles and also used to adjust ride height. The spring rate on a torsion bar is determined by its materials, its length, and its overall diameter. Torsion bars are as common as sideview mirrors and have been used on 4x4s, cars, trucks, and military vehicles since the early 20th century.

Torsion bars are relatively easy to adjust and replace, which can usually be accomplished by an amateur mechanic with moderate experience and a floor jack, some jackstands, an impact gun, and safety skills. If you plan to leave your beloved 4x4 in factory form, then there's really no reason to swap out the torsion bars. However, when it comes to adding additional weight to the vehicle like steel bumpers and winches, you should consider installing a suspension lift or performing a torsion-bar replacement. Installing aftermarket heavy-duty torsion bars is like adding spring rate, which is used to either lift a vehicle or carry heavier loads.

Replacement is better than adjusting or overrotating, which could damage the bars. Recently we teamed up with Sway-A-Way to get the skinny on torsion bars and their available applications.

What Makes A Better Torsion Bar?
Sway-A-Way's Toyota torsion bars have a smaller than factory diameter, yet still add the strength needed to endure harsh off-road abuse without excessive spring rate. Having just enough spring usually produces the best handling and control. Excessive spring rate is harder to control dampingwise; it also harms ride quality. Matching shocks with the proper rate complement the torsion bars and produce the best ride.

The main advantage of torsion bars is that they can easily be adjusted to increase ride height. Torsion-bar adjustment on some applications can be attained by the turn of a wrench. About 2 to 3 inches of lift can safely be achieved by adjustment. Many times we find enthusiasts overadjusting the preloading of the factory torsion bars; this will lead to harsh ride and actually decrease the vehicle's ability to maintain traction.

These 300M 4340 chromoly torsion bars are manufactured from better-than-OEM raw material and machined to proper specifications by CNC lathe. The splines are cut with a gear hobb machine, and the hexagonal surfaces are milled. The bars are then heat-treated to proper specifications. The race torsion bars are prestressed so no reindexing is necessary after initial installation. The 300M bars are left with a raw finish, while standard bars are powdercoated red. Sway-A-Way's torsion bars resist fatigue by more than 50 percent over factory bars. Racing or extreme applications with 300M bars often need a socket (A-arm) or adjuster modification to increase their strength and longevity. GM bars are splined via broaching the adjusters for a fine-tunable adjustment.

Damaging ToTorsion Bars
There is virtually no maintenance for torsion bars, but there are a couple of do's and don'ts in extending their longevity. Stay away from overrotating the bar to achieve lift; this induces excessive twist and can exceed the memory of the material. Overrotation also causes prematurefatigue and the eventual failure of the bars. Damage can also be a result of impact from high-speed debris or dragging the undercarriage and bars across rocks. Nicks and scrapes severely diminish the ability of the bar to twist.

{{{Pickup}}} '88-'98
Pickup HD 2500 '03-current
{{{Suburban}}}/{{{Yukon}}} XL '88-'03
{{{Tahoe}}}/Yukon '88-'03
{{{Hummer H2}}} '03-current
{{{Hummer H3}}} '05-current
LUV '72-'{{{80}}}
LUV '81-'83
Pickup/{{{Trooper}}}/Jackaroo N/A
Pickup '89-'97
{{{Rodeo}}} & {{{Amigo}}} '89-'97
Trooper '84-'91
Trooper Nov. '86-June '89
{{{Frontier}}} '86-'99
Frontier four-cylinder Sept. '97-'04
Frontier/{{{Xterra}}} V-6 '99-'04
Hardbody '86-'97
{{{Pathfinder}}} '87-'97
{{{4Runner}}} '86-'95
{{{Land Cruiser}}} Diesel N/A
Land Cruiser/FJ-{{{100}}} ?
Race Torsion Bars '86-'95/'93-'97
T100 up to '92
T100 '93-'97
Pickup/{{{Raider}}} '82-'89
Raider '{{{90}}}-'94
V-6 '90-'97
Pickup '87-'97
{{{Montero}}} '82-'89
Montero '90-'94
Pickup '90-'97

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