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I know that I have read about this before but I'm not sure how to deal with it. The mention of "suspension motion frequency" confuses me!



That is something you can get into as you get more in depth with information and wish to better understand all the interactions of the systems. Its not a prerequisite to setting up your car now.

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As far as frequency goes, I'm trying to think of a really good example...



A porpoising drag car is a good example of when frequencies are harmonized instead of complimentary.

I've also heard of guys setting up their cars with brand new, wiz bang, 300 different setting double adjustable shocks that do not understand the frequency situation and set all four shocks to identical settings. The net result a car that porpoises anytime it hits a highway expansion joint and produces a ride that is scary at anything over 50 mph.

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Search for "Torsion Bar Tango". It is an old article that I wrote a long time ago. It needs to be updated with pictures and illustrations but if you can wade thru it you'll get a handle on how to calculate the natural frequency for a Mopar front suspension.



This is an excellent starting point for a performance street set up. It can be found on Andy's AR Engineering site.

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After ducking under the suspension and really putting an eye ball on the torsion bar size in my Suburban.....I gotta measure thise.

After seeing that I kinda see what TC means. That and my Suburban came stock with 46mm Bilstein shocks and yes it handles well.

So Im thinking 1.24" for the Challenger



Yes, but don't forget the Suburban bars are also longer and supporting more weight, which supports the numbers in Andy's frequency article.

The origin of my comment is the fact that a 1.22 t-bar for a pre '72 B body is just shy of 400# of wheel rate. In Brand C cars, this equates to an 800# coil spring. Most street performance cars of this make are running spring rates that are starting at 600# and running upwards to 800#. Some competition cars are stepping up beyond that into the 1000# range. So the best we can ever hope to achieve with our mopars is very high end street performance.

One possible saving grace of all this is the current trend towards softer springs and bigger bars that would play into these lower available t-bar rates out there. However, these arrangements require infinitly more shock control than what is currently being offered in bolt on shocks for our mopars and would most likely require some specialized valving in a custom set up. They also need additional suspension travel, which would lead to rising ride heights , which doesn't always look great.

I think the reality in performance mopar handling is that we are ending up with moderate spring rates with moderate anti-sway rates and some pretty good shock options. This is where the Hotchkis development has landed with the best overall street/performance package. The old XV was there with their Level 1 packages before they folded. Copying either of these will lead to ver good results. Personal preference and application can also allow for adjustments up or down on the available rates out there.