Chassis stiffening....opinions please

[Dreamcar]

So my car is down to a bare shell and will receive lots of new sheet metal over the next year. Then, I will be installing subframe connectors and torque boxes, that's guaranteed.

However, US Car Tool also has a kit the includes the connectors and tq boxes, as well as a core support brace and inner fender braces.

So, lets say my car ends up with 400-450hp or so, and I'm undecide if I want a stock look or lowered with bigger wheels. Should I spend the few extra hundred bucks for the full kit with inner fender braces and core support brace?

Although not a race car, I still want a nice ridding car. It's not a high value RT, but a well optioned numbers matching 383. I am leaning towards getting the extra braces, but would value your opinion.

[green69rt]

OK, I'm going to throw out an opinion and let the others pile on.  My opinion is "how much is enough??"   Torque boxes, subframe connectors, steering gear sector supports, on and on and on.  
If you are not racing, doing road rallys, etc, what's the point?  I think some help is a good thing but figure out what is a good design for you and where you want to spend you bucks.  Most of us don't have an unlimited budget.  We make trade offs in body stiffness, steering feel, braking, paint job, etc.  

Now for the other side, if the car is apart then this is the time to do whatever it takes.  I would think a few pieces of stiffing metal would be a fairly good investment that would cost a lot more down the road.  So...if that's you feeling then do it and don't look back.  If it doesn't turn your crank then just do what you want and get on with the project, again don't look back.

Now for what I did and plan to do.  Yes to frame rail connectors, torque boxes, sector support, better brakes, stiffer torsion bars, stiff LCA and tubular UCAs.   Stage two FF steering box and that's about it.  No to the radiator support and inner fender braces.  No huge disc brake conversion, normal 8 3/4 rear with the old track pac springs.  New bushings everywhere and new hardware (cheap stuff) where ever I could afford it.  Finally some nice wheel and tires and I'm done!

Edit...forgot to say that I'm looking at a similiar setup as you, mild 440, auto (maybe 400-450 HP range.)

[Dreamcar]

OK, I'm going to throw out an opinion and let the others pile on.  My opinion is "how much is enough??"   Torque boxes, subframe connectors, steering gear sector supports, on and on and on.  
If you are not racing, doing road rallys, etc, what's the point?  I think some help is a good thing but figure out what is a good design for you and where you want to spend you bucks.  Most of us don't have an unlimited budget.  We make trade offs in body stiffness, steering feel, braking, paint job, etc.  

Now for the other side, if the car is apart then this is the time to do whatever it takes.  I would think a few pieces of stiffing metal would be a fairly good investment that would cost a lot more down the road.  So...if that's you feeling then do it and don't look back.  If it doesn't turn your crank then just do what you want and get on with the project, again don't look back.

Now for what I did and plan to do.  Yes to frame rail connectors, torque boxes, sector support, better brakes, stiffer torsion bars, stiff LCA and tubular UCAs.   Stage two FF steering box and that's about it.  No to the radiator support and inner fender braces.  No huge disc brake conversion, normal 8 3/4 rear with the old track pac springs.  New bushings everywhere and new hardware (cheap stuff) where ever I could afford it.  Finally some nice wheel and tires and I'm done!

Edit...forgot to say that I'm looking at a similiar setup as you, mild 440, auto (maybe 400-450 HP range.)

What did you mean by "sector support"?

You nailed it when you said the car is apart, so now is the time. Looks like we are going to have a similar builds because I too am upgrading to disks (but nothing extreme), .96 TBs (likely), tubular UCAs (maybe upgraded LCAs too), bigger sway bars, higher performance (vs my stock non-RT) rear springs and better shocks. I like the fact that most of these bolt-ons are not that much more expensive that stock replacement stuff.

The more I thought about it, and given it's all available in kit form, I'm heavily leaning towards getting the entire kit and "not looking back". I like the fact that the extra bracing is not obvious unless you look for it. I do have a limited budget, but in the end, it's just a few hundred bucks more. 

[HPP]

Part of the improvement in modern cars is the redesigned monocoque structure that provides a greater amount of resistance to deflection. By making the uni-body structure more solid, you allow the suspension work more effectively, irregardless of your power levels. IMO, chassis stiffening is as important in a six banger restoration as a solidly built big block. By firming up the chassis, you eliminate the flex that leads to squeaks, rattle, wind whistle, and moisture seeping into places it doesn't belong. It eliminates the body as an active participant in the suspension motion. 

Think if it with this analogy; our cars are put together using large panels that are spot welded into place. By comparison, how well would your coat protect you if it had no stitching in it but instead it was all buttoned together. Yes, it would all hold together and cover you adequately, but all those small gaps between spots welds, er, buttons, still allow things to flex and let weather in. Reinforcement kits eliminate the flex that opens these gaps in the car's structure.

The reason why the engine bay receives a big dose of reinforcement is because it is the one segment of the car that is only support by the chassis on 5 of its 6 sides. The hood is not a structural member. This is an important contrast to the drivers compartment and trunk areas that do have significant reinforcing on all 6 sides of the cube. The passenger compartment also gets additional assistance from the doors that lock rigidly into place.

Can you get carried away with reinforcements, sort of. There is a balance between achieving rigidity and managing weight. I think the best research was performed by XV on their four post rig. Auto Rust has done less technical work but has also spent some time demostrating the results they can produce with their kits by showing simple deflection rates.

Competition cars need a whole additional level of support beyond that requirement that gets pretty complex pretty quickly and in all reality should go beyond the simple street stiffening kits. Entire engineering white papers have been written on the competition aspect of the subject that go waaaay beyond anything most of us have ever discussed.

Most of these reinforcements can be done to a completed car with some minor disassembly and paint touch ups. Obviously its much easier if everything is apart, but being apart is not a requirement.

What did you mean by "sector support"?

The sector support is a piece that Firm Feel has that bolts to the K frame and the output shaft of the steering box. It reduces the leverage effect the steering box has on the k frame. This is a good example of a piece that is designed to be bolted into a finished car that provides an improvement. If your car is all apart, you can install gussets into the k frame its self that eliminate the same flex, but access to the areas requiring this is all but impossible with the engine installed.

[Dreamcar]

Thanks! And that's a great analogy too.

[Hard Charger]

if you are not racing the car why bother.

spirited street driving would not gain anything from those extra pieces. it will from the frame connectors.

[myk]

if you are not racing the car why bother.

spirited street driving would not gain anything from those extra pieces. it will from the frame connectors.

Real world experience says otherwise.  Just with the Fox shocks, SFC's, 18" wheels/tires and Hotchkis tubular sway bars my '69 corners as flat and as sure as my late-model Firebird, better than my late-model Mustang...

[green69rt]

Yeah, the key item here is that you now have the car apart.  Changes now are relatively cheap and easy, not so much later.  That was my thinking on my car, do more than I think is needed now but then move on.  Again I say, how much is enough???   I really have no comparison between the old 69 RT charger that I bought new in 69 and a modern car so can't say but I do expect that my old charger will not match modern car for handling and ride, etc.  Just a fact of life, but I do want to help where I can.   

[Mike DC]

if you are not racing the car why bother.

spirited street driving would not gain anything from those extra pieces. it will from the frame connectors

The factory added torque-boxing on the 4spd RTs & convertibles without adding any subframe connectors.  Heck, by the mid-70s some basic torque box plating & shock tower braces were becoming standard on all the B-bodies.  Something to think about. 

SCs are probably better for long-ways bending forces like on a dragstrip launch.  The other stuff would help more for handling.    



Really, I can't see a good reason not to take all the "low hanging fruit" steps to stiffen up these unibodies.  The parts cost & installation isn't a huge issue.  The weight & appearance drawbacks of the end results are pretty negligible too.

 

[Hard Charger]

I guess my meaning of spirited street driving differs from some of you people's.

that stuff is nice if you have the budget. I never missed having the suspension upgrades and chassis stiffening.

[comet_666]

I did steel tubing directly in line with frame and gusseted along with XV under fender braces, torque boxes and a XV lower rad support.

[comet_666]

Under fender brace...

[comet_666]

Frame ties coming through floor.

[RallyeMike]

tubular UCAs (maybe upgraded LCAs too),

These are a waste of money for what you are building unless you are just trying to impress people and empty your wallet. Spend your time and money on the chassis reinforcement, sway bars, torsion bars, springs, and quality bushings, tie rod ends, and ball joints. Someone could swap your UCAs and LCAs overnight and you'd never know the difference from the driver's seat.

[myk]

I thought the aftermarket CA's helped with bumpsteer and changed the geometry of the steering to keep a better contact patch of the tire on the ground?

I guess my meaning of spirited street driving differs from some of you people's.

that stuff is nice if you have the budget. I never missed having the suspension upgrades and chassis stiffening.

When I play with other cars these days turns and twisty roads come into play as much as the straight line stuff.  I don't have the budget either but I got the parts anyway...

Comet, your car's progress is awesome.  Keep it coming...

[myk]

Oops...

[RallyeMike]

I thought the aftermarket CA's helped with bumpsteer and changed the geometry of the steering to keep a better contact patch of the tire on the ground?

Sure maybe... but The OP wants a "nice driving car, not a race car", and is "limited by budget". In sticking with the theme of the question, the Nth degree improvements of tubular arms are not worth the investment if budget is a factor. You really get very little improvement for the money compared to the investment in chassis, springs, sway bars, and shocks. For a budget project, if choosing where to wisely spend your money, tubular arms are near the end of the list.

[1974dodgecharger]

If u run a 15inch rim size and narrow tires u dont need the upper control arms from hotchkis.  Bump steer is bad and is scary and cause a wreck if u run wide tires in rear and narrow tires in front.  When i had hotchkis leaves, shocks, torsion bars with my magnums 15inch tires and 225 width front and rear the car was fine...if u want performace also get the hotchkis Upper control carms will improve your spirited driving....

I thought the aftermarket CA's helped with bumpsteer and changed the geometry of the steering to keep a better contact patch of the tire on the ground?

I guess my meaning of spirited street driving differs from some of you people's.

that stuff is nice if you have the budget. I never missed having the suspension upgrades and chassis stiffening.

When I play with other cars these days turns and twisty roads come into play as much as the straight line stuff.  I don't have the budget either but I got the parts anyway...

Comet, your car's progress is awesome.  Keep it coming...

[HPP]

 I really have no comparison between the old 69 RT charger that I bought new in 69 and a modern car so can't say but I do expect that my old charger will not match modern car for handling and ride, etc. 

Ahhh, but you can make your Charger feel modern and handle and ride as well as a new car. That is part of the point of chassis reinforcement. Make the foundation more solid so the suspension can better perform its function. The rest of the equation to make this happen has been addressed in other topics a number of times, so I won't rehash it here.

I guess my meaning of spirited street driving differs from some of you people's.
that stuff is nice if you have the budget. I never missed having the suspension upgrades and chassis stiffening.

Quite possibly. We all have different takes of stock and modified too. It doesn't take much budget if you look at what has been done and apply a little thought to it. A $400 set of custom contoured subframe connector can almost be duplicated with $60 of steel tube and some careful cutting and welding. That's a big difference in budget for nearly identical results.

I thought the aftermarket CA's helped with bumpsteer and changed the geometry of the steering to keep a better contact patch of the tire on the ground?

Sure maybe... but The OP wants a "nice driving car, not a race car", and is "limited by budget". In sticking with the theme of the question, the Nth degree improvements of tubular arms are not worth the investment if budget is a factor. You really get very little improvement for the money compared to the investment in chassis, springs, sway bars, and shocks. For a budget project, if choosing where to wisely spend your money, tubular arms are near the end of the list.

I tend to agree. "Nice driving and budget" will create a slightly different parts list than "hammer it hard and dodge the cones." Tubular arms are an expensive solution to a minor overall problem. Their original design intent was to increase positive caster, which Mopars sorely lack. You can increase caster with offset bushings for $60 compared to the $300 basic control arm price, but you also will have more limitations on that range with bushings compared to tubular arms. Of course the Hotchkis arms took geometric improvements to a whole 'nuther level with changes to anti-dive and ackerman to reduce bump steer and improve the arc of motion and add caster. However, these are incremental improvements that most won't notice independent of the whole package, unless you are really pushing you car hard and fast in corners and on rough roads.  To take the hot rodding approach of creativity and budget, you can duplicate the Hotchkis arms improvements with a pair of $40 Speedway arms and a couple of chevy truck ball joint and an aluminum block spacer. However, it will require cutting, drilling and modification to your control arm pick up points that is nearly irreversible, so that immediately scares of 99% of the people who want a budget solution.

[myk]

I thought the aftermarket CA's helped with bumpsteer and changed the geometry of the steering to keep a better contact patch of the tire on the ground?

Sure maybe... but The OP wants a "nice driving car, not a race car", and is "limited by budget". In sticking with the theme of the question, the Nth degree improvements of tubular arms are not worth the investment if budget is a factor. You really get very little improvement for the money compared to the investment in chassis, springs, sway bars, and shocks. For a budget project, if choosing where to wisely spend your money, tubular arms are near the end of the list.

Yeah I get it.  Those Hotchkis UCA's took a big chunk out of my wallet...

[ACUDANUT]

OK, I'm going to throw out an opinion and let the others pile on.  My opinion is "how much is enough??"   Torque boxes, subframe connectors, steering gear sector supports, on and on and on.  
If you are not racing, doing road rallys, etc, what's the point?  I think some help is a good thing but figure out what is a good design for you and where you want to spend you bucks.  Most of us don't have an unlimited budget.  We make trade offs in body stiffness, steering feel, braking, paint job, etc.  

Now for the other side, if the car is apart then this is the time to do whatever it takes.  I would think a few pieces of stiffing metal would be a fairly good investment that would cost a lot more down the road.  So...if that's you feeling then do it and don't look back.  If it doesn't turn your crank then just do what you want and get on with the project, again don't look back.

Now for what I did and plan to do.  Yes to frame rail connectors, torque boxes, sector support, better brakes, stiffer torsion bars, stiff LCA and tubular UCAs.   Stage two FF steering box and that's about it.  No to the radiator support and inner fender braces.  No huge disc brake conversion, normal 8 3/4 rear with the old track pac springs.  New bushings everywhere and new hardware (cheap stuff) where ever I could afford it.  Finally some nice wheel and tires and I'm done!


Edit...forgot to say that I'm looking at a similiar setup as you, mild 440, auto (maybe 400-450 HP range.)

X2

[green69rt]

Been following this thread and noticed that someone mentioned that the "sector support" and the K frame reinforcement around the stearing box mount solve the same problem.  If so, maybe it's a place I can save a few bucks?  Are both really needed for a non racing car??

[1974dodgecharger]

I thought the aftermarket CA's helped with bumpsteer and changed the geometry of the steering to keep a better contact patch of the tire on the ground?

Sure maybe... but The OP wants a "nice driving car, not a race car", and is "limited by budget". In sticking with the theme of the question, the Nth degree improvements of tubular arms are not worth the investment if budget is a factor. You really get very little improvement for the money compared to the investment in chassis, springs, sway bars, and shocks. For a budget project, if choosing where to wisely spend your money, tubular arms are near the end of the list.

Yeah I get it.  Those Hotchkis UCA's took a big chunk out of my wallet...

they all say that MYK about hotchkis upper control arms people hate me due to price, or it gives you 2 percent performance increase, etc...the hotchkis ones are the best in the business hell even other companies agree.  What other companies then tell you that their upper control arms will do the job and you don't need that performance gained from the hotchkis stuff. 

[HPP]

Been following this thread and noticed that someone mentioned that the "sector support" and the K frame reinforcement around the stearing box mount solve the same problem.  If so, maybe it's a place I can save a few bucks?  Are both really needed for a non racing car??

IMO, no, you don't need both on a street car. If you have properly gusseted the mount, the box will no longer be able to push its self around on the K. There will be some who disagree with this, and I have not compared the two side by side, but it stands that given the large diameter of the box output casting how much flex can it produce?

[Kern Dog]

if you are not racing the car why bother.

spirited street driving would not gain anything from those extra pieces. it will from the frame connectors.
[/quote

Yeah... If you only drive 1/4 mile at a time. Guys that use the steering wheel might appreciate the upgrades.