1984-87 Honda Civic/CRX and 1986-89 Acura Integra models came with a unique torsion-bar front suspension. Because of the non-conventional nature of a torsion bar as compared to a coil spring, people at times become lost on what various bars’ diameters equate to what would be conventional spring rates. This is an important figure for determining the balance of the car and for tuning the dampers.
Between the various diameters and lengths of bars available, we were a bit lost on it ourselves, but a little poking around led us to Sway-Away’s website. As some may know, Sway-Away is one of the foremost torsion-bar producers having even produced bars for said Hondas at one point in history. We knew this convenient calculator was something we could trust!
On the page there you will find the science behind the torsion bar wheel rate calculation. You’ll also see that the effective wheel rate is the same as the spring rate taken at the end of the control arm, or what is actually the lever on which the wheel’s movement acts.
You can play with it all you like, but we have taken the liberty of making a quick chart for fast approximate reference. Some of our dimensions are approximate but the spring rates should be accurate within about 5-10% and that’s really pretty good for our purposes.
- LCA stands for “lower control arm.” Since people tune both Integras and Civic/CRX models, and sometimes Civic/CRX people put the longer Integra lower arms in their car to increase camber, we include both here. We approximate a 13.5″ length on the Civic/CRX and 14.5″ on the Integra, from the center of the torsion bar to the end of the ball joint.
- All rates are in pounds per inch of travel (lb/in), but we have a lb/in to kgf/mm charge just below.
- Not all these torsion bar diameters are actually available, but we are listing them anyway since any of them technically could be made or exist.
- The bar length will impact the wheel rate, too. The 24.3″ bar is the length of CRX and many Civic bars. Some Civics have a bar that is about 1/3″ shorter, but the rate change is fairly minor so we have omitted it to keep the chart simpler. The Mugen bars that were made long ago were shorter than the Civic/CRX ones, with an overall length of just under 22.5″. These would give the highest rate per diameter, and being the more compact bar would have the least weight (no surprise that the Mugen bar would be the ideal for performance yielding the most rate-per-weight!).
|CRX LCA||CRX LCA||CRX LCA||‘TEG LCA||‘TEG LCA||‘TEG LCA|
We work on Japanese cars at Heeltoe here, and oftentimes it becomes necessary to work in both lbs/in and kgf/mm (that’s kilogram of force per millimeter). They are different ways of saying the same thing about a spring’s rate, but we’ve offered this handy conversion chart for you to know the equivalents. This info is pulled from Tein.com’s Standardized Spring chart.
Please feel free to leave any commentary or calls for correction below! And never forget that Heeltoe is always in your corner, aiming to provide the best and most accurate info we can to help you tune your car!