Torsion Bar Upgrade - Ride quality?

Looking to do a torsion bar upgrade. I have what ever came with a 72 340 challenger, .86 maybe? Thought about using the Hotchkis 1.10 bars. I am concerned about going to big and having too stiff/hard of a ride. I've read a lot of stuff on the forum about bars and some say go BIG. Then control with a good shock. I'm concerned going to 1.10 up from what I have at .86. Really considering the PST 1.03 bar seems to be a reasonable upgrade. My car is mainly a weekend cruiser. No plans at this time to drag or road race. Its just time to go through the front end as the last time it was done was in early 1990's. Not many miles since then, just a lot of time passed by.

Just wanting to get other opinions on ride quality with the bigger bars.

If you put big bars on the car then you need really good shocks. It is as simple as that. The other thing to remember about torsion bars is that the spring rate goes up with the fourth power of diameter. So bars get really stiff really quickly. A SB E body car won't need a huge bar. The 1.03 would be way stiffer than the factory put on there but not out of bounds for today's standards. Use Koni front shocks and you'll have a firm ride but it won't knock the fillings out of your teeth.

Andy hits on an important thing, Shocks need to be capable of handling the spring rate. Torsion bar and swaybar rates.

One of the reasons my 65 Cuda had KYB's was because at the time I built it, early 90's, torsion bar nd sway bar availability was limited, short of paying thru the nose for custom bars from someone like Halibrand. Find data on shock rates was even trickier, I ended up calling KYB and talking to an engineer who wanted to know why I wanted that data (trade secret?) once I explained what i was doing he got all helpful. I was able to put together a swaybar, torsion bar, shock package that all worked together.

If there were shock dynos back then I didn't know about them and probably couldn't afford one, much less buying a bunch of shocks to test them. We do live in a bit of a golden age for this stuff right now, or maybe at the end of it.

Another problem with larger torsion bars is that the chassis may not be able to handle the larger bars. Essentially the unibody becomes a spring. If subframe connectors, torque boxes, etc have been added, larger bars become more effective.
Also, larger bars can allow for lowering without bottoming. The larger the bar, the lower you can run the car.
The final factor is tires. 15" tires have more give than 17" as the tire is also acting like a spring on the surface of the road.
My Challenger used to run 1" torsion bars and Bilstein shocks, and I hated the ride. Hindsight being 20/20 I think I had it lowered too much.
Now I have 1.18" bars and QA1 single adjustable shocks. Its a very firm ride and with 15" wheels but not unpleasant (but very easy to overpower the tires). It works well for autocross with 17" wheels.
Torsion bars and shocks are part of a complete package. 1.03 like AndyF suggested is a good all around diameter. But the caveat is, over the counter parts house shocks, won't work with them, either.

If you're only concerned for a little more stiffness, weekend cruiser (non-competition autocross, etc.), small TBs such as 1.03 and 1.10 will give it to you. BUT, you'll soon realize that you could've / should've gone stiffer... such as ~1.18. Better shocks are needed... and the choices of brands are getting wider. Adjustable shocks are preferred... double-adjustable even best preferred (and worth the extra expense). Or else, Bilsteins are an excellent simple non-adjustable option.

The tires you use are a major factor... 60 series, 50, 40-35-30 sidewalls.... the shorter you go the firmer the ride as there simply becomes less sidewall to absorb bumps. The tire PSI also is a factor... try different setups until you find your comfort zone.

I've commented many times, don't be afraid of larger TBs. As soon as you install something larger than the factory size, you'll say Wow!... and then later... that you'd probably like to go larger again.

Thanks for the replies so far. In reading past posts in other threads, there were a few people commenting about one-inch bars, give or take, and poor ride quality. Figured those were due to a bad, non-clocked T-bar or the use of cheap shocks. I'm surprised the one-inch bar and the Bilstein shocks had a poor ride. It could be the low ride, not enough shock travel or hitting bump stops. With the Bilsteins not being adjustable, perhaps they are not a match with that size bar? Premium shocks seem to be a necessity what ever the choice, maybe adjustable shocks are mandatory. I am also surprised at the bigger bar, better ride comments too. Those circumstances have to be due to shock change at the same time the bar was changes and going with a premium adjustable shock over what ever was used prior.

The roads here in the Chicago area generally suck. Its the freeze/thaw cycles coupled with the salt and such used during the winter. My daily driver is a 2013 Challenger. The firm (but not overly harsh) ride there is what I would like to duplicate in the 72.

It is almost impossible to duplicate the ride of a new car in an older car just because the torsional stiffness of new cars is 2x or 3x what it was in the old cars. Maybe find some local guys who have modified their muscle cars and see what they ride like. I had big bars with cheap shocks in my Coronet and the ride was horrible. Felt like driving an empty dump truck. I finally bit the bullet and bought some Koni shocks and the difference was amazing. I like the Koni shocks since they are adjustable. The adjustment is internal so you have to unbolt the shock to make the adjustment, but the price is much less than what an external adjustable shock will cost.

I had Mopar Performance 1.0" bars and KYB shocks for several years. 275-40 and 295-45 series tires too. The ride wasn't horrible but it was not great.
I changed to 1.15" bars and Bilstein RCD shocks and while the ride stiffness did increase, the ride was actually better. Fewer rattles. The car didn't skip over the bumps in the road, it soaked them up and rode smoother.

I typically run the Hemi bars & springs in my 383 RRs if the stock stuff needs replacement, and they ride fine.
I'm not auto-crossing them or drag-racing them, though; they're just street cars.
The old cars are definitely less structurally stiff than new cars, unless stitch-welded and/or caged or reinforced (US CarTool, etc).

Are you still running the 340 small block? I have a similar setup and I found that a spring rate in the low 200's (205, 210 lbs/inch) works well. For a big block or Hemi I'd go with 240-250 lbs/inch. I'm in the process of getting larger bars for my 440 Challenger which is still using factory bars.

Thanks for the reply! I still have the 340 and am looking more at 1.03 T-bars. They have a 210lb/in rate. Not really buying the bigger is better thing for a street car. I'm in the process of gathering front end parts and the bars will likely be the last purchase as I still am unsure. The premium shock recommendation, I absolutely buy into for ride quality.

Something in the 1.030 or 1.060 range with Koni shocks will provide a newer car type of ride. It will be firm but not harsh. Should ride like a Honda Accord or a Toyota Camry. It won't handle like a BMW or Porsche, but it will be a huge improvement from the 1970s Detroit slush bucket handling, especially if you pair it with a big anti-sway bar.

I didn't chime in before because I don't have a basis of comparison to the earlier style torsion bars. Now that you posted #rate I can. I put a set of 300# bars on my Fifth Avenue with non-adjustable Bilstein shocks. Car already had police front and rear sways with a set of homemade frame ties. The ride was great and made the car corner extremely flat. This was with 15" BFG Radials on the car. The ride went to absolute pot with 18" tires. I know it's completely subjective, but I wouldn't hesitate to go as high as 300# with good shocks and tires with a good amount of sidewall.

One thing that is rarely talked about is the tires. Shorter sidewall tires increase the effective rate.

Many don;t thing about the sidewall height's effect on spring rates.

AndyF, to get the Porsche/bmw handling ability with a small block and aluminum heads - some more weight reduction too, what bar size would be ideal, 1.15? Which shocks? I put hemi springs in the back already. Will have the bigger anti sway in front and not sure on size for back yet. I want to make my e body street car handle as well as mentioned. I am going to add the hot Chris style frame rail extenders but that is pretty much it for body mods. Thanks.

Sniper -- I speak repeatedly with advice of the choice of tire size with their sidewall height having effect on ride harshness, as well as tire PSI.... see my response in previous discussion above.

The OP will ultimately have to decide on how he likes his ride and make the adjustments -- pros and cons.... compromises.

Just changing away from the factory stock setup will make major differences... and from that point... further changes can be made.

The mods you are making will improve the handling but you'll never achieve Porsche level. The car doesn't have the correct chassis or suspension design and there isn't much you can do about it. But you can build a car that looks cool and handles fairly well without breaking the bank.

If his ride is 100% street driven would you ever even be able to drive it hard enough to notice the difference (after aforementioned upgrades)?

Its hard to say as the butt dyno and how its applied to handling can be very subjective calls. Its even possible that cars can be mechanically capable of each other but one simply feels better because of geometry, alignment, seating, or any of a myriad of differences.

When I played in the GM world, street performance spring rates were around 400#, which is around 200# in the torsion bar world. Classic Mopars can easily get to that point. Then it becomes controlling the motion (shocks) and improving the geometry where ever possible. Mopars overall have better geometry than many of their contemporaries, but the shared cast/camber of the upper arm eccentrics become limits pretty quickly when chasing down really good alignment numbers.

and you are exactly right. Bigger is not better unless you’re drag or track racer. Would be nice if you could ride in one those bigger is better cars lol. My buddy went full Hotchkis, level 3 cartool for a cruiser and hates it. Whatever you decide to go with run tunable shocks. I went with 1 1/8 SB, 1.03 TB, Q-A1 Strut Rods, 11/16 tie rod ends, Qa-1 LCA and Adjustable SPC UCA,s with Adjustable Viking shocks and it rides awesome for an old car.

and that’s why he needs to go ahead and run adjustable upper UCA,s. I’m thinking I got twice the amount of adjustment out of my SPC,s then my old offset moog bushings. Can’t remember the numbers but when I get it put back together again I’ll have the alignment guy to write it down.

I think this statement is the most over looked issue when upgrading to a larger torsion bar. With a STIFF chassis, you can run larger bars and not effect the ride. I run 1.02" bars in my 6.1 Hemi Duster with the complete US Car Tool Level 2 Chassis Stiffening Kit and it's not stiff riding, but it sure doesn't lean into corners!

Actually that is incorrect "common sense" thinking.
No chassis is perfectly stiff, every chassis has spring, and factors into the final equation. A stiff(er) chassis is always preferred, as it narrows down the items that are tunable by choice and with ease.
A stiffer chassis likely needs a softer TB for equal handling characteristics, applications, same concept applies to higher tire pressures or lower profile tires.
A stiffer chassis with stiffer TB's will move the performance envelope higher, if tires, brakes, engine and driver can achieve it.

Whoa.....where the heck have you been??