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Chassis Heeltoe Explains

Tech: What’s the Spring Rate of my Torsion Bars? #torsionbarhondas Content Inside!

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.

Notes:

  • 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
Diameter/
Lengths
22.5″24.3″25.7″22.5″24.3″25.7″
19mm978480847370
20mm1201091021039589
21mm145133125126114108
22mm175159150151139130
23mm209190179181165155
24mm247225212214195184
25mm291265250252230217
26mm340310293295269253
27mm396361340343313295
28mm458417393397362341
29mm527480452457416392
30mm603550518523477449
31mm687626591596543512

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.

lb/inkgf/mm
1122.0
1402.5
1683.0
1963.5
2244.0
2524.5
2805.0
3366.0
3927.0
4488.0
5049.0
56010.0
67212.0
78414.0
89616.0
100818.0
112020.0

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!

Categories
Chassis Universal Fit Blogging

BC Racing Coilovers: Implications of Ordering Custom Spring Rates

Many people are aware that BC Racing will allow you to customize your coilovers to your liking. Here are a few things to keep in mind when considering a custom BC kit.

  • Swift Springs upgrade is mandatory for rates above 18k. This is because BC does not make a wide variety of springs (length, diameter) at rates above 18k. The Swift Spring upgrade does come at an increased cost as well.
  • Off the shelf, your kit can handle spring changes of 2-4k in each direction. Beyond that will require shocks with different valving.
  • Any kit that varies in specification from its “Off the Shelf” version is considered a custom kit. These are not eligible for cancellation or return once your order has been processed, and the build time will be 2-3 weeks. You must be committed to your custom kit, so be sure to think about this before you place your order!

With this information, you see that BC Racing has a lot of flexibility and capability when it comes to building a kit tailored to your specific needs. Heeltoeauto.com is the place to go for all your BC Racing needs, from mild to wild.

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Chassis Heeltoe Explains

What is the difference between “shocks” and “struts,” and what is a “damper” and a “coilover?”

It is a major pet peeve of ours. The customer calls and says they need to replace their shocks and struts. Or just their struts. This wouldn’t be so bad but invariably the car they are calling about doesn’t happen to have any struts at all. If they are calling Heeltoe it is probably a Honda or Acura and bunches of them don’t have struts.

Then you’ve got companies like TEIN making replacements for these units they call “dampers?” And then some guy in the forums is telling you to forget it, and you need to buy “coilovers.” Huh?

Shocks and struts are both dampers. 

Shocks and struts are both types of dampers (do you say damper or dampener?) A damper is basically an absorber. The springs hold the weight of the car and allow the suspension to move as the car goes over bumps and dips. Without springs, the car would not be compliant at all. But while springs spring over thing things they should, they will keep springing long after you want them to stop. There needs to be something keep them in check. If you hit a spring it would “sproing” and shake and bounce around for a while before it comes to a rest. It is called vibration or oscillation. This is no good in a car because that means the car would bounce around up and down over the slightest of bumps and you’d have little or no control.

Where springs give compliance, dampers bring control.

Dampers (shocks and struts) keep the springs in check by allowing them only to be as springy as they need to be to provide comfort, but not so springy as to allow the car to float around and feel as though it were not connected to the ground. But really, all you really need to grab on to is the damper controls the ride, the handling, the body motion, and the response of the suspension to road inputs. A system is “under-dampened” when the damper is too weak to keep the mass of the car from bouncing around on the springs (like a Caddy). A system is “over-dampened” when the dampers are very firm and resist movement of the body, even with a softer spring in place. Some movement is needed for the suspension to work properly, or the car will slide over instead of grip the road. What you are shooting for is “critical dampening,” which is when the damper is tuned to match the spring and the mass in such a way that any given input results in the car returning to its neutral position on the spring as fast as possible without oscillating.

But now, on to the rear question: If shocks and struts are both dampers, what is the difference?

The difference between a shock and a strut is in their mounting. To understand the difference you need to “zoom out” and think of the whole suspension system.

The wheel is connected to the hub, which rides on a bearing, which is housed in a hub carrier (also known as a knuckle or an upright). The hub carrier is also the thing that the brake calipers bolt to. The hub carrier can be held to the car in a few different ways, and herein lies the difference between a shock and a strut.

A Subaru WRX has a strut. This is a front strut in a WRX (that’s a Tein FLEX damper):

What is it missing in the above picture that this TSX with a shock configuration has?

If you said UPPER CONTROL ARM, you get a gold star!

The simplest way to think of it is that if you were to take the shock out of a car, the wheel would still keep the same geometry and alignment as with it because the hub carrier is not located (positioned, held in place) by the shock; it is located with arms. There can be two, three, or even five arms holding the hub carrier in place. But the shock is not one of the things doing that job. It doesn’t move other than to compress and rebound over bumps. The mounts are rigid and the only compliance from bushings is there to provide comfort.

By contrast, if you were to take the strut out of the WRX in that pic above, the hub carrier would not be located. It would flop around and not be able to hold a wheel straight. The strut serves as both the damper AND a suspension member. It turns with the steering, so there is usually a bearing in the upper mount to allow it to spin to allow that movement.

Shock = damper. Strut = damper + suspension member.

This should help explain why you won’t ever see Skunk2 making camber-adjustable front upper arms for RSXs and Civics newer than 2001; they all have struts. And it should also explain why the upper mounts in TSXs and TLs will never have camber adjustment; moving the location of the shock mounting won’t change the alignment because you need an adjustable upper arm for that.

So, know the difference, and when talking about your car say the right thing. When someone says it wrong, you can either correct them or find someone else who is more well versed to talk to.

Hopefully, that clears things up a bit, and we’ve held on to you thus far. Now, what is a “coilover?”

Coilover is really a term that is short for “coil-over shock” or “coil-over strut.” The damper in the suspension system need not be all in one assembly like most of our customers see it. Many trucks have leaf springs in the back, and a separate shock. Likewise, the 1984-87 CRXs and Civics that Heeltoe caters to have struts in the front with a torsion bar for the spring.

The damper above is a strut because there is no upper arm, but also notice there is no coil spring! This is not a coil-over strut. Also, you’ll see a lot of cars where the rear suspension has a trailing arm, and the shock is mounted separately from a coil spring, such as on the later RL or later model Civics.

Coil-over literally means there is a coil spring and the coil is over the damper.

A stock TSX a coil-over shock suspension design.

But “coil-over” and “coilovers” are different. These days it is common that an adjustable-height suspension, one where there is a threaded spring mounting, to be called a coilover suspension. It is really nothing more than a damper and a spring, but you can adjust the height.

Aside from a pretty color, coilovers are typically shorter in overall length allowing adequate shock stroke when the car is set to lower ride heights. They usually come have all kinds of features such as adjustable ride-firmness and new upper mounts (and if you have a strut-type car, you’ll probably get camber adjustment on those upper mounts).

So, hope that clears things up for you!