Speedway Motors: When To Replace Your Torsion Bars

Speedy Bill built his company Speedway Motors around performance and became known for the famous 4X Sprint Car that he campaigned with numerous drivers across the country. Most of the drivers that sat in the Speedway Motors’ Sprinter went on to have Hall-of-Fame careers. Even after they had retired the Sprint Car, Speedway Motors stayed heavily involved in open wheel racing. The same is still true and their staff is among the most knowledgeable in the world of grassroots open wheel racing. We are reprinting a tech story written by Frank Galusha from their company blog (with permission), explaining torsion bar upkeep and maintenance.

DMI Reactor 1-1/8 x 30-inch Sprint Torsion Bar: Part # 9402395. Available at Speedway Motors.

The Original Post:

Does a torsion bar go bad? Why does the car sag when I twist a torsion bar in the opposite direction? How often should we change or replace torsion bars?

These are all common questions about torsion bars. Here are some good insights about what is truly happening. Very rarely will a bar “go bad.” It will take an extreme force to break or ruin a bar, so unless a tube gets bent with the bar inside or you are in a violent crash it is likely that your torsion bars are still good. If you are uncertain, have your torsion bars dyno tested for that peace of mind.

Ruining a torsion bar from twisting it the opposite direction is just a myth. Think of it this way, the function of a bar is to twist until it meets resistance, at which point the resistance acts as your spring. Once you have twisted the bar in a certain direction it will not actually return to a relaxed state, therefore it is still somewhat raveled up in the direction it has been twisted.

Torsion bars, the component that does it job almost hidden from vision, torsion bar arms, and torsion bar stops, are all very important components of the suspension and handling of Sprint Cars. Photo from Bobby Kimbrough.

Whether it is accidental or intentional that you put a torsion bar in a different torsion tube, sometimes a bar will get twisted in the opposite direction. When you do this you may notice the car sags and does not maintain the original attitude from where it was originally set after first hitting the track. Here is what happens- the bar first must unwind from the direction it has previously been twisted, pass its’ relaxed state, then wind back up in the opposite direction until it meets resistance again.

It only takes one session of being under a load to meet resistance by twisting it the opposite way. Once this happens, one will just need to re-block or reset ride heights at this point and all will be fine. Again, bring any torsion bars in to be dyno tested if there is any uncertainty.

These components work hard during a season of racing and torsion bars do require changing as the spring rate migrates. Photo from Bobby Kimbrough.

Some people have a predetermined life expectancy for a torsion bar and it is commonly believed that a bar will get softer over time, or lose spring rate rather. The fact of the matter is, they actually work harder over time and tend to gain spring rate. With that said, the difference you gain over a long period of time is minimal, so you should feel a great deal of consistency with your bars over the course of one season. On the contrary, the more a bar gets used, the more the rates migrate from its original rate or spring rate when it was new. Though changes tend to be minimal over time, replacing bars between seasons should be just fine to keep consistency.

If you are interested in getting your current bars checked out by our suspension experts, give us a call and we will get your torsion bars to our suspension team to be dyno tested!

Article Sources

About the author

Bobby Kimbrough

Bobby grew up in the heart of Illinois, becoming an avid dirt track race fan which has developed into a life long passion. Taking a break from the Midwest dirt tracks to fight evil doers in the world, he completed a full 21 year career in the Marine Corps.
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