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Thread: Chassis stiffening bars

  1. #1
    Supporting Member II Turbo Mopar Contributor jeff1234's Avatar
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    Chassis stiffening bars

    Hello, chassis stiffening bars go between the shock towers on our cars. My question is whether anyone has custom made a three point bar for a fwd car and if so, did it improve stiffness over the two point style?
    The only substitute for cubic inches is cubic dollars, how fast can you afford to go?

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    See me ride out of the sunset... Turbo Mopar Staff BadAssPerformance's Avatar
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    Re: Chassis stiffening bars

    You mean to tie (triangulate) to the firewall? Good question, haven't seen any b2b comparisons to a regular 2-point strut tower bar

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    Supporting Member II Turbo Mopar Contributor Dr. Johny Dodge's Avatar
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    Re: Chassis stiffening bars

    I doubt tieing into the center of the firewall would help much as it has no real strength either

    I've considered boxing in the area from the strut towers to the firewall with a piece of steel tall enough to reach from the side of the frame rail right up top the top of the towers
    a right angle at the rear to fit against the firewall and a piece behind, inside the firewall , all welded in

    and a couple of tubes run flat side to side against the firewall , one right below the cowl flange at the top and one down low enough to clear the manifolds and turbo

    also always thought the front mounts for the k frame are pathetic , until you remember they're designed to rip out if you hit something hard enough to drive everything under the floor where it's intended to go

    eh I thought I could get away with no rebar in the front of one of my cars
    - until I hit the side of a ford aerostar at about 55 kph
    89 nose popped like a paper bag right before the impact - I actually heard it (first)!!

    frame rail connectors can be lethal too as they leave the front rails no place to move backwards except up into the car
    a point to consider as my passenger rail AND the floor where it was attached moved back 3-4 inches
    it was a HARD hit- I stopped in place , the van went 40 feet sideways

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    Supporting Member II Turbo Mopar Contributor jeff1234's Avatar
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    Re: Chassis stiffening bars

    Thanks for the answers. Dr. J, Your response is very thoughtful and covered ideas I wouldn't have considered, thank you. That having been said I wonder how effective a shock tower to shock tower bar actually is. I imagine when the car leaves hard on the street (my 85 Charger) that the chassis is trying to twist, perhaps around the "A" pillar area which in turn unloads the left front drive wheel. Would this be a true explanation and if it is how would the tower to tower bar affect this. If that is not correct what might be the description of what is happening?
    The only substitute for cubic inches is cubic dollars, how fast can you afford to go?

  5. #5
    Supporting Member II Turbo Mopar Contributor Dr. Johny Dodge's Avatar
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    Re: Chassis stiffening bars

    I think looking into sway bar binding and checking the control arm bushings might be your best start
    edit
    I've read here about the end bushing mounts of the sway bar can cause one wheel to unload

    thus the end link mod

    a simple try without modding anything might be simply some bushing grease like used with poly style mounts and bushings

    easy enough to try doing the ends of the sway bar

    package should say food industry safe / silicone base


    shock tower braces are more about keeping things square while turning
    Last edited by Dr. Johny Dodge; 03-17-2019 at 05:40 AM.

  6. #6
    Supporting Member II Turbo Mopar Contributor jeff1234's Avatar
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    Re: Chassis stiffening bars

    Quote Originally Posted by Dr. Johny Dodge View Post
    I think looking into sway bar binding and checking the control arm bushings might be your best start
    edit
    I've read here about the end bushing mounts of the sway bar can cause one wheel to unload

    thus the end link mod

    a simple try without modding anything might be simply some bushing grease like used with poly style mounts and bushings

    easy enough to try doing the ends of the sway bar

    package should say food industry safe / silicone base


    shock tower braces are more about keeping things square while turning
    Thanks, that clarifies the bar. Looks like it's more about road racing/gymkana than straight line accel. I think I've seen the end link info before, I will look for it.
    The only substitute for cubic inches is cubic dollars, how fast can you afford to go?

  7. #7
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    Re: Chassis stiffening bars

    This front k-frame brace seemed to help durning autocross.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Re: Chassis stiffening bars

    was gonna suggest Johnny's kframe style brace. I plan on triangulating into the fire wall up top when I get back to modding my TD's as it should help with some firewall to strut tower flex an hopefully keep the firewall from cracking at the exhaust tunnel. Easiest wait to see if doing the sway bar mod works is to just remove the sway bar. I did this mod a very long time ago after the aftermaket sway bars didn't work. The car's I've put the modded sway bar on spin both tires equally without an LSD, Even with un-equal traction side to side. Both Auto and 5spd. In the straights and in the corners if it spins a tire it spins both. Tremendous grip in the corners with the power on. Love it. Probably the biggest suspension improvement on these cars.

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    Supporting Member II Turbo Mopar Contributor jeff1234's Avatar
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    Re: Chassis stiffening bars

    Is this still available, is there a downside?
    The only substitute for cubic inches is cubic dollars, how fast can you afford to go?

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    Re: Chassis stiffening bars

    The K frame brace? Just made one. Never had them for sale.
    Great stuff for great cars! Poly engine mounts and bushings at: http://www.polybushings.com

  11. #11
    Supporting Member II Turbo Mopar Contributor jeff1234's Avatar
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    Re: Chassis stiffening bars

    I see that you have both front and rear sway bars with end links. If using both is ride harshness apparent? Do you have to cut off the old rear rod sway bar. Do you have pictures of the k frame brace?
    The only substitute for cubic inches is cubic dollars, how fast can you afford to go?

  12. #12
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    Re: Chassis stiffening bars

    Do you have pictures of the k frame brace?

    Just the one I posted.

    - - - Updated - - -

    I see that you have both front and rear sway bars with end links. If using both is ride harshness apparent?
    Feels better than stock.

    Do you have to cut off the old rear rod sway bar.
    Up to you, depends on the front bar size you use.
    Great stuff for great cars! Poly engine mounts and bushings at: http://www.polybushings.com

  13. #13
    Supporting Member II Turbo Mopar Contributor jeff1234's Avatar
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    Re: Chassis stiffening bars

    [QUOTE=Johnny;1144993]Just the one I
    Correct me if I'm wrong, in the picture it appears that a tubular bar is attached between the left and right side lower control arm bolts. If this is correct, why does this stiffen an already continuous piece of steel.
    It sure looks like something I'd like to build for myself. Why are there two mounting holes on the bracket?
    The only substitute for cubic inches is cubic dollars, how fast can you afford to go?

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    Re: Chassis stiffening bars

    From my own experience:
    A 2-point strut tower brace does help out with our cars' lack of chassis stiffness. I have never tried a triangulated bar, but have thought about it quite a bit. A lot of the reason a lot of people don't go that way, I believe, is that it can change the class you are in when doing auto-cross and track events. As was pointed out, the firewall is pretty darn thin, so even if you did triangulate, there would need to be a brace added to the opposite side of the firewall to distribute the load.

    I have a buddy that made a control arm mount brace like Johnny's. He also had a strut tower brace, so kinda hard to say how much of a difference it made. I would think it would help with vibration more than anything else.

    I have never run frame connectors. I did have a car with an AutoPower roll bar in it, though. HUGE difference in the chassis stiffness of the car! It didn't even have the door bars! So, I would imagine that well designed/installed frame connectors would also make a big difference.

    A 2 point rear shock tower brace absolutely makes a difference! Regardless of whether it's held by 2 or 4 bolts, it increases the chassis stiffness significantly. I "scientifically" tested this, then ran it on the street.

    A 3 point rear shock brace only stands to work better than a 2 point, as long as it's made decently.

    As was pointed out, you are modifying the structure and load paths of the chassis. Thus, in an impact, certain designed in crush zones may not be effective or the added bracing could direct load paths to weaker points in the structure. This is basically a YMMV thing. Compared to new cars, ours are tin cans...we're still better off than a 1950's bench seat, metal dash, no seatbelt vehicle.

  15. #15
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    Re: Chassis stiffening bars

    yea my daughters caliber SRT4 is a stiff son of a ----- But it also weighs more than my Daytona.

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