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Thread: Increasing Chassis Rigidity

  1. #1

    Default Increasing Chassis Rigidity

    I realize this might be an odd question to ask here at DI but there are a few chassis fab guys here with Subaru-specific experience and if anyone could help me it would be them.

    What areas of the Impreza's chassis, specifically the GC/GM/GF, should be reinforced to increase chassis rigidity for better on-track (not off-road) performance without a roll cage?

    I am by no means an engineer of any sort but here are a few ideas I have...

    The first and most obvious is stitch welding the seams.

    Second, reinforce the strut towers. I know this can be done many different ways like "boxing in" the towers as shown below.



    Third, better brace the B-pillar. I know that aftermarket braces that run along the floor and attach to the B-pillar exist.

    Lastly, reinforce the front fender area as seen below.



    Thoughts? Ideas? Comments? Suggestions? Paging JR

    One more question but slightly off-topic. Are there any negative effects to removing the spare tire well? JR did it to Ben's track car, but it's caged.

    Last edited by Tim.Flat4; 12-17-2009 at 12:55 PM.


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  3. #2
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    Rocker panels or mad sill bars will benefit your chassis
    Alex Rademacher
    2006 to now: 14 championships (Stage Rally, RallyX, AutoX, Club Trials) and counting ...


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    Registered Member R22B's Avatar
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    I know the spare tire actually assist it in rear impact. It helps cushion some of the damage.

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    Senior Dirty Member TOI's Avatar
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    plate the frame? cage? plate the cage?


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    Registered Member $F-5$ Inc.'s Avatar
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    seam welded the entire chassis

    It is very important that the people who create the laws be subject to them.

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    Registered Member d'cheat's Avatar
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    The install of a full cage is crazy good for adding rigidity to the chassis. So, add a cage, install stiffer sub frames, and weld in cross bars between the strut towers that are tied into the cage. You really dont have to seam weld the chassis. It wont add as much rigidity as you think. Its mainly done to keep the panels from vibrating apart. There are quiet a few WRC and open class cars that are not seam welded.
    Rally Drivers Do It Sideways, Covered In Filth

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    Registered Member $F-5$ Inc.'s Avatar
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    i disagree seam wealding a chassis adds a lot of strength.drag cars that run 600+hp seam weld their chassis the help stop it from torqin. if you seam welded you chassis you WILL notice a difference!!

    It is very important that the people who create the laws be subject to them.

    "Consumption in this overdeveloped world is carried out largely as custom rather than the result of any real belief in anything." -Steven Duncombe-

    "Any society that would give up a little liberty to gain a little security will deserve neither and lose both."
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    we used to completely seam weld the drag cars i used to build to combat twist. our customer said is was a huge difference by itself. if you don't want to cage it i feel it is a must do myself

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    you said no cage....but you said a track car right? so this IS a race car, not a street car? (just clarifying)


    if yes, then I agree on stitch welding the ENTIRE car for increased rigidity.

    fender braces. I didn't want to spend $150 on aftermarket fender braces so I just seam welded the OEM ones to the frame for more rigidity.

    I'm definitely doing the strut towers ASAP.....I really really really want to tie them into the cage, I just don't know if I'll get to it.

    Do rear strut towers and weld in a permanent rear strut tower brace as well. I'm doing that myself this winter as well....it'll be my first 'test' at cage welding....nothing critical.

  11. #10

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    Not track-specific, just looking for ideas to increase tarmac performance.

  12. #11
    Registered Member d'cheat's Avatar
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    Quote Originally Posted by DN1911 View Post
    we used to completely seam weld the drag cars i used to build to combat twist. our customer said is was a huge difference by itself. if you don't want to cage it i feel it is a must do myself

    W/O a cage, seam welding will stiffen your chassis like crazy. I 100% agree with that. With a full cage properly tied in, you wont notice that much of a difference.
    Mind you, were not rwd, live axle torque monsters. They have to eliminate all twisting motions to keep even pressure on the rear tires at all times. Take a drag car on a road course, and its a little diffrent.
    Rally Drivers Do It Sideways, Covered In Filth

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    Quote Originally Posted by Tim.Flat4 View Post
    Not track-specific, just looking for ideas to increase tarmac performance.
    well, seam welding is a real pita...which is why I elected not to do it...I just didn't have an extra 80+ hrs to put in the car if I wanted to make my first rally.

    I wouldn't ever do it for a car that wasn't race-specific unless you're just really really bored.

    Don't for get all the cleaning/prep/scraping you have to do to seam weld.

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    DirtyImpreza Badass MConte05's Avatar
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    Quote Originally Posted by UP2MTNS View Post
    I wouldn't ever do it for a car that wasn't race-specific unless you're just really really bored.
    Sounds like my kinda deal!

  15. #14

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    Quote Originally Posted by UP2MTNS View Post
    well, seam welding is a real pita...which is why I elected not to do it...I just didn't have an extra 80+ hrs to put in the car if I wanted to make my first rally.

    I wouldn't ever do it for a car that wasn't race-specific unless you're just really really bored.

    Don't for get all the cleaning/prep/scraping you have to do to seam weld.
    I've seen a few documented builds that include seam welding so yes, I understand that it's a real chore.

    I'm asking these questions because I've become infatuated with Opera's S2000 and the chassis prep they did.

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    being bored and seam wealding for the win!!!

    It is very important that the people who create the laws be subject to them.

    "Consumption in this overdeveloped world is carried out largely as custom rather than the result of any real belief in anything." -Steven Duncombe-

    "Any society that would give up a little liberty to gain a little security will deserve neither and lose both."
    -Benjamin Franklin-


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