I have in my possession a pair of NEW 44" long, 1.16" diameter bars! (And there was much rejoicing!)
I have not had a chance to do my torque wrench test or install them yet. Rest assured, I plan on testing them well in an effort to answer any and all questions! A big thank you to Just Suspension for stepping up to the plate!
The good news is they were able to keep to their original price of $499 a pair, custom sizes can be made for $699. Jayme has also told me they are offering free shipping to DryDock members! During the checkout process, put in the coupon code "cbodydrydock" and shipping will be free. That saves about $45 right there.
Now, here is where it get interesting. Here is an excerpt from their website describing the bars.
A Note About Spring Rates and Hex Offset
Many enthusiasts are concerned about spring rates, but fail to remember that a fun-to-drive 60-95 MPH car has very different requirements than a 150-200 MPH car. That's why we based the design for our C Body torsion bars on the Police Package cars. It's firm and sporty, but not too harsh for everyday use. The design is based on what we call the "wheel spring rate," which is essentially the total effective rate of the installed bar in the suspension. The original bars had a WSR of between 90 (stock soft ride) and 124 (police package). Chrysler recommended a WSR of 300 for circle track (NASCAR) cars back in the day. A street C Body equipped with a big-block, set up for ultimate high performace handling that is not harsh should range between 200-245 WSR. The Just Suspension wheel spring rate is in that range, but the exact number is a closely guarded secret, stored in the vault next to the formula for Coca-Cola. We're sure you'll like it, as it gives a solid, confident ride.
As an added bonus, we've given our C Body torsion bars a 0° Competition Hex-Offset as opposed to the traditional 30° Hex-Offset. The advanced 0° offset only works with higher spring rates, allowing you to run your car stock height or lower and still have the adjusting bolt and swivel in the middle of its travel. With an offset hex, you can back the adjuster all the way out and the car won't go as low, because the bar is inherently twisted.
I am very curious, as I am sure most are also, how they will ride and what impact the offset change will have. Jayme has assured me that they have ran these bars in several cars and the ride was a modern ride, like you would expect from a new car today, not harsh.
So stay tuned! I should have the torque testing done this week, and hopefully install the bars for the Show-Me Mopar Fest this weekend! It will be about a 300 mile round trip in one day, so that should provide an excellent first impression.
Joined: Tue Oct 11 2005, 01:33AM
Location: Calgary, Alberta
Posts: 5893
Many enthusiasts are concerned about spring rates, but fail to remember that a fun-to-drive 60-95 MPH car has very different requirements than a 150-200 MPH car. That's why we based the design for our C Body torsion bars on the Police Package cars. It's firm and sporty, but not too harsh for everyday use. The design is based on what we call the "wheel spring rate," which is essentially the total effective rate of the installed bar in the suspension.
Interesting article which defines Wheel Spring Rate, but I'm not sure how you apply the measurements to a T-bar suspension. However the basic mechanics must be the same. http://www.autospeed.com/cms/A_2904/article.html
The original bars had a WSR of between 90 (stock soft ride) and 124 (police package). Chrysler recommended a WSR of 300 for circle track (NASCAR) cars back in the day. A street C Body equipped with a big-block, set up for ultimate high performace handling that is not harsh should range between 200-245 WSR. The Just Suspension wheel spring rate is in that range, ...
So I assume from the first paragraph "we based the design for our C Body torsion bars on the Police Package cars" that the WSR of these bars will be around 124 or about 37% more than stock. But the above quote implies the the bars are in the 200-245 range which gives a 122% - 172% increase. If compared to the police rate, this is about double what was considered by Mopar and various police forces to be an acceptible rate. I'm thinking such a high rate would make the cars front end skip around on rough road. I also wonder how it would effect the "balance" between the front and rear suspensions.
.. but the exact number is a closely guarded secret, stored in the vault next to the formula for Coca-Cola. We're sure you'll like it, as it gives a solid, confident ride.
Why?
As an added bonus, we've given our C Body torsion bars a 0° Competition Hex-Offset as opposed to the traditional 30° Hex-Offset. The advanced 0° offset only works with higher spring rates, allowing you to run your car stock height or lower and still have the adjusting bolt and swivel in the middle of its travel. With an offset hex, you can back the adjuster all the way out and the car won't go as low, because the bar is inherently twisted.
Why? Seems to me that if this was a desirable thing, Ma mMopar could have reduced their costs by not using any offset and eliminating the need to stock different bars for left and right usage. I question that needs to be answered is, why did Mopar go to this extra expense?
My understanding of the offset twist is twofold... one, to prestress the t-bar in the direction it's going to live it's life and therefore prolong it's lifespan. Two, is to help account for a huge amount of twist that the limp stock bars would have to endure to support the front end. For easy figuring, if a stock t-bar had a rate of 100 #/in, and the front end weighed 1500#, each bar would have to move 7.5" at the wheel just to support the static weight of the car. That's a big percentage of the full range of movement, and doesn't account for the life the car will lead while moving down the average road or highway, let alone any additional load on the car. That said, the larger a bar gets, the less stress there is on the bar to support any given weight. It's also MUCH easier to produce bars with no offset...
AFAIK, the motion ratio of a T-bar is 1:1. The bar is at the pivot point of the LCA, so there's no lever action (not the right term) working against the spring like there is in a coil spring suspension. The spring RATE is measured (ideally) at the wheel, and is a true wheel rate. When I'm calculating t-bar spring rate, I always use the LCA length from the T-bar socket to the LBJ stud hole. I don't think it's exactly right, but that dimension never changes like the center of the wheel might. Besides, it's easy to convert to any other dimension if a different number is needed.
The "closely guarded secret" think is kind of silly, IMHO, as it only takes a caliper to know what the rate is. IMHO, the rate they came up with is probably a very good starting point, and is about where I'd like to be with my Fury. My OEM 0.98" bars are about 125#/in, and a 1.06" bar would be 185#/in, a 50% increase. A good start, but not what I'd buy if there were other options. I'm looking forward to seeing how these new JS bars work out with Scott's testing, and also the new Firm Feel bars that are hitting the market about now, too.
Joined: Wed Dec 06 2006, 12:50PM
Location: North Carolina
Posts: 23
Excellent observations ... can't wait to hear you guys' objective reviews. One quick point ... the steel alloy used and manufacturing process have dramatic results in the ultimate spring rate the torsion bar has. Offset/preload is yet another function that affects rate. Diameter is critical, but is not the only spec to look at. <span class='smallblacktext'>[ Edited Sun Jun 10 2007, 08:05PM ]</span>
Joined: Sun Oct 09 2005, 05:02PM
Location: ALLEN PARK, MI.
Posts: 2007
Thing that buggs me is the ZERO offset. They are saying you can still get a STOCK ride height or lower on 1/2 bolt turns in???? What makes that posiable, the thicker 1.16" bars? At 1.030", mine are 3/4 in and my upper bump rubber is 1/2" or less from my lower A arm pads. WAY TO LOW. Maybe their steel quality was better than SWAY-A-WAYS????? My "GOLDEN" bars are ZERO offset as well. Tony P.
Tony, I know that the metal used makes all the difference and that todays processes are more advanced than 40 years ago. I am moving as fast as I can on these, I am very curious myself!
Joined: Tue Oct 11 2005, 01:33AM
Location: Calgary, Alberta
Posts: 5893
Don't take my comments as being negative or closed minded towards JS bars, its just that I really don't completely follow the basic physics of how a T-bar is affected by diameter, length, offset and preload. Diameter and length seem to follow the "bigger is better" rule, but offset and preload seem to be more mystical.
Since all bars will take a set after they are used for awhile, all will end up with some offset and this will effect the adjustment range. Ma Mopar may have introduced a 30 deg offset to achieve a couple of goals. It presets the twist direction, introduces a permanent twist to the bar and makes all the bars retain their factory height adjustment even after they are put in service. A side effect introduced by the twist, is the spring rate when load is added will be greater that the spring rate as the bar is unloaded. I don't think I said that very clearly, restated, winding the bar tighter from the 30 deg point takes more force that unwinding the bar from the 30 deg point. This effect would help stop the car from bottoming out and would reduce the rebound force and probably allow the shocks do their thing. I would assume a 0 deg offset bar, after its been used for awhile would take on so set and end up with "some" offset. It maybe that modern steel is more consistent such that both bars will end up with roughly the same amount of set. As such, the advantage of a 0 deg offset is the "normal" point will produce a somewhat lower height which is desired in high speed cars. I would guess, to achieve this lower height with 30 deg offset bars would either require running with the adjustment bottomed out or would require some modification of the mounting adjustment point. Don't know if all this makes sense.
Preload, I assume, simply defines the neutral operating zone in which the bar will operate. I don't know, but assume, an objective would be to keep the whole operating range of the bar within the same direction of twist. If for example the preload only produced a small amount of twist, say clockwise, then on rebound, the bar could end up passing the zero point and start twisting counter clockwise. This is probably not a good thing. Since preload is pretty well defined by the weight of the standing car, it maybe a critical factor when determining the size of bar to use. This may also be another reason why Mopar uses a 30 deg offset which would move the preload point well into the twist so that the suspension would hit the upper stops before the bar twist could reverse. Again, I don't know if this makes sense.
What I do know, is that car manufacturer's very seldom, if every, do things the more expensive way, so using left and right bars with 30 deg offsets didn't happen without a darn good reason.
Joined: Fri Dec 22 2006, 08:41PM
Location: Warrenton, Virginia
Posts: 1366
Well, as info and an update, I got my 47" C body torsion bars from Just Suspension last week. I got my 1 1/8 " front sway from Firm Feel the other day. My mechanics are busy working on the cars their boss wants them to work on now (not THEIR customer cars, like mine was) they told me it may be quite a while before they can install my new suspension pieces. I may have it done eslewhere in the meantime if I can find someone else I trust.
Now, my car has the new ESPO rear springs. They did wonders for firming up the rear of the car. I can tell now, the car can use CONSIDERABLY more stiffening up! So these two pieces, plus maybe even a rear sway bar are needed to give the car a decent modern ride/handling combo. I'm planning on doing these upgrades one at a time now, torsion bars First! I'll let you all know what happens !drive
Tony P.
Tony P.
