Project WomBAT - CALMINI Torsion Bar Review

Nov. 01, 2005 By Dr. Sean Michael

The Product

The torsion bars on Isuzu's pre-'92 Troopers are not terribly firm. Many trucks sag or wallow under rough driving conditions. Some older Troopers look like their front ends have been lowered for drag racing! Cranking up the height control arm bolt returns some the lost height, but it does little for the inherently weak stock bars. This is particularly evident in rough terrain.

To address this problem, CALMINI offers upgraded bars featuring approximately 25% higher spring rate, with a two millimeter thicker minor (unsplined) diameter. The CALMINI bars come nicely packaged, with thick vinyl caps protecting their splined ends. The blue powder coat finish is high quality and should be long-lived.

The Install

These are the tools I used for this install:
  • 27mm socket
  • 1/2" ratchet
  • 3' cheater bar
  • floor jack (or Hi Lift in this case)
  • the factory jack
  • hammer
  • sledge hammer
  • wood for blocking under jack
  • grease gun
  • 2 floor jackstands
  • Optional Tonka truck

The day/s before your installation, soak the height control arm bolts with Liquid Wrench or a similar penetrant. Give the underside a good rinse to avoid getting a clump of dirt in your face when you're under the truck.

Apply the parking brake and block the rear tires to prevent movement, and loosen the front wheel lug nuts. Be sure to watching for stripped or stubborn studs or nuts that may need replacing, a common Isuzu woe. Jack up the front end and remove the wheels. Support the front of the frame (not the suspension) with jackstands.

Begin loosening the height control arm bolt. Soaked in penetrant, (you did apply it, didn't you?) the bolt should come out slowly but surely. If not, the cheater bar or air tools will do the trick. I needed a three foot cheater, but then I didn't heed my own advice and apply penetrant.

Once the height adjusting bolt is out, remove the height control arm. Easy, right? If not, try using a jack to lift on the torsion bar just forward of the height control arm. (Editor's Note: Torsion bars are very strong in their designed use, which is twisting moment applied only to their ends. The bars are, however, succeptible to failure if point-loaded along their lengths. The smallest nick may result in localized stress and subsequent failure. If you do use the jack here, be sure to pad its jaw with a wood block. I suggest completely unbolting the torsion bar socket from the rear of the lower A-arm and just muscling the bar out of both sockets without using the jack.)

For a better angle, tilt the jack by placing a half inch thick piece of wood under the jack's base closest to the rocker panel, pushing the bar and the arm up and in toward the middle of the undercarriage. Be careful of clearance in the tight space under the truck, and rap with a hammer on the height adjusting arm until it slides back off the torsion bar (you did apply Liquid Wrench, didn't you?).

Once the arm is off, remove the torsion bar. Easy, right? If not, try using the factory jack to lift the front suspension - only enough to unweight the torsion bar. This should give you more leeway to wiggle and shake the bar loose. Wear gloves, because the bar can come loose suddenly, and there are plenty of sharp corners just waiting to eat your knuckles.

Unused torsion bars are not side-specific, but used torsion bars take a 'set' and must be installed on the same side, twisting in the same direction, as they were when previously used.

Remove the vinyl cap, grease the splines and use a hammer to gently tap the front end of the new CALMINI torsion bar into place. I left the rear vinyl cap on the torsion bar, but a chunk of wood might offer better protection from the hammer. If the bar doesn't slide in easily, consider removing, cleaning, greasing, and reinstalling the spline socket on the lower control arm.

Lift the torsion bar, just as you did when you removed it. Grease the splines and carefully line up the height control arm with the splines, then gently tap it on with a hammer and wooden block.

Reinsert the height control arm bolt, but ONLY after greasing it. I greased one but not the other and found out just how much difference it made when I needed three feet (and more!) of the cheater bar to move the bolt. When about 3/4" of bolt was sticking up out of the control arm nut I replaced the wheels, jacked it back up and removed the jackstands. I cranked up the bolt for more height, after lifting the weight of the front end, unweighting the torsion bars. Here again, the cheater bar was a must. I made several trips to town, over railroad tracks and through rutted alleys to allow the bars to 'settle in' before I made final ride height adjustments with a tape measure, jack, and cheater bar.

Changing ride height changes wheel alignment, so consider having the truck aligned.

Performance Impression

The WomBAT weighs a porcine 4800lb, yet one of the first impressions I had was that the CALMINI torsion bars were much too stiff, even harsh. Bumps and minor potholes initially produced rough bangs, and I was dreading my wife's summary of the new ride quality. I lowered tire pressure in the BFG ATs from 40psi to a more sane 35psi and headed for the DiRTI (Drainageway Ramp Travel Index) test.

The DiRTi test simulates a 20 degree ramp, following a marked tire route up an asphalt embankment. This attempt at the slope left the lead tire on the ramp some 8" further downhill than the WomBAT's previous high point. The CALMINI torsion bar's increased spring rate is potentially capable of the same travel as the stock bar. In this case, on the WomBAT, the bars allowed less effective travel, despite the 200 plus pounds of front winch and bumper. Fortunately, later adjustments of the torsion bar revealed that articulation gains could be made by lowering the front end back into the normal range of travel, preventing premature maxing out of front suspension's downward travel. As before, the vast majority of articulation continued to come from the rear leaf springs.

After the DiRTI test, I started the real dirty testing. I was surprised, as the initial ride harshness seemed to disappear as I bashed over ruts, holes, and ditches. My impression was that the torsion bars limbered up, and broke in. The ride no longer suffered the jarring blows I was feeling immediately after install, nor did the truck bounce and bottom out due to the massive bumper and winch combo. Instead, the front end just soaked up the roughness, smoothing out roads I would formerly have taken at far more cautious speeds. This improved ride was certainly due in part to decreased tire pressure, but the vast improvements in ride quality are clearly a result of CALMINI's torsion bars.

Since the installation, I have continued to be impressed with a number of handling characteristics that the torsion bars have improved. The truck bounces, dives, and wallows far less than it did with the cranked up stock bars, and rough terrain handling ability is much improved. As a result, my driving off road is much less tentative, and the approach to ruts and the like is more likely to be aggressive.

The bars are also an improvement on pavement. Whoop-t-doo pavement changes, where the stock bars used to allow the front to bottom out, are now easily handled, and steering response is more precise. The front end also rolls less because the thicker bars resist cornering compression better in sharp turns. All of these things are a boon to street driving, especially given the Trooper's less than Porsche-like handling.


Is the CALMINI torsion bar the upgrade that your WomBAT needs? The answer lies in the two factors: the type of terrain you drive, and the weight you may add over the front end. Unequivocally, these bars are required if you have, or plan to have, a winch. Even without a 100 plus pound bumper, the winch's mass will make you want these firm bars because of their increased spring rate. This will be doubly true if you thrash the truck in the kind of places where that winch will be needed.

What if you will never add more weight than say a pair of fog lamps and an ITOG sticker? Here, in particular, the decision will come down to the terrain you plan to explore, and or whether you are pleased with your truck's current ride. For most people, the Trooper's suspension, at both ends, is simply too soft. It bottoms too easily and leaves the driver flinching at every good sized dip or hole. Having driven a friends '91 with the same bars but no winch/bumper, I can say that the control is exceptional. The front end stays flatter in road turns, and mountain-road ruts no longer faze the suspension. That makes the CALMINI bars a great option for a lot of Trooper folks out there.

Please mail the Isuzu ORC Staff if you have questions or comments about this page.

CALMINI Manufacturing
Department Isuzu ORC
6951 McDivitt Dr
Bakersfield, CA 93313 U.S.A.

Phone: 1-800-345-3305
Fax 805-398-9555

For more information, email CALMINI. Newsletter
Join our Weekly Newsletter to get the latest off-road news, reviews, events, and alerts!