Front sub-frame bushings
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2004-2007 Cadillac CTS-V Performance Mods Discussion, Front sub-frame bushings in Cadillac CTS-V Series Forum - 2004 - 2007; I've been on the forums a couple of years and can't say as I've ever stumbled across anything about how ...
  1. #1
    ctsv247 is offline Cadillac Owners Enthusiast
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    Front sub-frame bushings

    I've been on the forums a couple of years and can't say as I've ever stumbled across anything about how the front subframe attaches to the car or if replacing any bushings in it might make sense seeing as how literally everything else has been addressed.

    Any thoughts???

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    Revshift is offline Cadillac Owners Fanatic
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    Re: Front sub-frame bushings

    There are no front subframe bushings. The subframe bolts directly to the chassis. Metal to metal.

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    ctsv247 is offline Cadillac Owners Enthusiast
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    Re: Front sub-frame bushings

    I guess it shows that I have yet to climb under mine.....thanks for the info revshift!

    Would it make sense to tie it into subframe connectors?

  5. #4
    RyRidesMotoX is offline Cadillac Owners Enthusiast
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    Quote Originally Posted by ctsv247 View Post
    I guess it shows that I have yet to climb under mine.....thanks for the info revshift!

    Would it make sense to tie it into subframe connectors?
    Depending on how hard you push it... I know my car, if I have the windows down with my arm out the window, I can feel the frame of the door move differently than the door itself. Body flex happens. Real subframe connectors run the length of the car to shore up unibody flex. It goes from subframe to subframe completely connecting both. It makes enough sense to me that I want to do it after I get the drive train all done. But I'm also going to build my car for the road courses around here.

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    FuzzyLogic is offline Banned
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    Re: Front sub-frame bushings

    I don't think that subframe connectors are necessary to solve the problem of body flex. We need reinforcement along the center section of the body.

    The traditional answer to this problem is a roll cage, but like many people here, adding a roll cage to a four-door car is a non-starter.

  7. #6
    RyRidesMotoX is offline Cadillac Owners Enthusiast
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    Quote Originally Posted by FuzzyLogic View Post
    I don't think that subframe connectors are necessary to solve the problem of body flex. We need reinforcement along the center section of the body.

    The traditional answer to this problem is a roll cage, but like many people here, adding a roll cage to a four-door car is a non-starter.
    If you look up how good subframe connectors are done, they add strength all the way through the unibody undercarriage.

    Something like this:
    http://blog.tunedbypsi.com/wp-conten...2/DSC_5793.JPG

    Or this:
    http://marylandspeed.com/images/2004b.jpg

    Lastly:
    http://www.mustangdepot.com/OnLineCa...-SFC-01_AT.jpg

    The last one is on a mustang, but the idea is still sound lol... But seriously, the do add a ton of rigidity and strength to the frame in general.

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    FuzzyLogic is offline Banned
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    Re: Front sub-frame bushings

    Chassis brace:







    Complete BMR tubular subframe:


  9. #8
    RyRidesMotoX is offline Cadillac Owners Enthusiast
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    I get what you're saying with those. But none of those are traditional subframe connectors. The Fox body mustang guys have it down. I helped a buddy with his car. It was a rough job but it was worth it. We didn't have a lift so it was welding on our back with the car on stands and it sucked. And that was 10 years ago... Before my back really started to get bad. Regardless. A simple brace from side to side like that is more like a sway bar I would think. Because the parts that actually do the twisting aren't connected together... The front and the rear.

    Edit: think of like a tube chassis car or truck. Especially a drag car with a welded 4340 tube chassis. It doesn't bend, flex, twist, do the wild monkey dance... It just points straight (usually) down the lane and launches... HARD. Look at a chassis from a Le Mans car the P1s and stuff. Tube chassis... Excellent in corners, very tough, very rigid. The parts that grip (tires front and rear) cause the twist, they need to be connected as much as possible as one unit to make the chassis rigid. Is it uncomfortable YES the ride will suck like a hooker doing coke... But it will corner and accelerate harder.

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    ctsv247 is offline Cadillac Owners Enthusiast
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    Re: Front sub-frame bushings

    Quote Originally Posted by RyRidesMotoX View Post
    I get what you're saying with those. But none of those are traditional subframe connectors. The Fox body mustang guys have it down. I helped a buddy with his car. It was a rough job but it was worth it. We didn't have a lift so it was welding on our back with the car on stands and it sucked. And that was 10 years ago... Before my back really started to get bad. Regardless. A simple brace from side to side like that is more like a sway bar I would think. Because the parts that actually do the twisting aren't connected together... The front and the rear.

    Edit: think of like a tube chassis car or truck. Especially a drag car with a welded 4340 tube chassis. It doesn't bend, flex, twist, do the wild monkey dance... It just points straight (usually) down the lane and launches... HARD. Look at a chassis from a Le Mans car the P1s and stuff. Tube chassis... Excellent in corners, very tough, very rigid. The parts that grip (tires front and rear) cause the twist, they need to be connected as much as possible as one unit to make the chassis rigid. Is it uncomfortable YES the ride will suck like a hooker doing coke... But it will corner and accelerate harder.
    This is the answer I was looking for. Fuzzy, you're might be right about being a little more precise with your efforts but is there a downside to capturing the entire underbody with a set of connectors? The extra 20lbs maybe?

    Thanks for doing the research and posting up the pics.

  11. #10
    FuzzyLogic is offline Banned
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    Re: Front sub-frame bushings

    Quote Originally Posted by RyRidesMotoX View Post
    I get what you're saying with those. But none of those are traditional subframe connectors. The Fox body mustang guys have it down. I helped a buddy with his car. It was a rough job but it was worth it. We didn't have a lift so it was welding on our back with the car on stands and it sucked. And that was 10 years ago... Before my back really started to get bad. Regardless. A simple brace from side to side like that is more like a sway bar I would think. Because the parts that actually do the twisting aren't connected together... The front and the rear.

    Edit: think of like a tube chassis car or truck. Especially a drag car with a welded 4340 tube chassis. It doesn't bend, flex, twist, do the wild monkey dance... It just points straight (usually) down the lane and launches... HARD. Look at a chassis from a Le Mans car the P1s and stuff. Tube chassis... Excellent in corners, very tough, very rigid. The parts that grip (tires front and rear) cause the twist, they need to be connected as much as possible as one unit to make the chassis rigid. Is it uncomfortable YES the ride will suck like a hooker doing coke... But it will corner and accelerate harder.
    The issue is that most subframe connector designs are renditions of older, Mustang-specific modifications that attack a problem that the CTS-V probably doesn't share. Analysis indicates that these products don't actually reduce chassis strain very much--by pure accident (due to the available locations to attach subframe connectors), they reinforced the floorpan, which turned out to be the real source of the problem.

    According to an interesting article that I'm having a frustrating time locating, Mustangs built in the 90's and earlier featured heavy stock seats that were bolted into a very weak floorpan. This floorpan was so weak that the seat angle was being allowed to tilt under cornering loads--increasingly so as the car got older. Drivers, noticing the difference in motion between their hands and their butts, misdiagnosed the problem as chassis flex.

    All I'm proposing is that we figure out exactly what is going on with the CTS-V, and attack the source of the problem instead of copying a design from another vehicle. You really don't want to install subframe connectors if you don't have to. If you do, you might as well replace the rear subframe bushings with steel cylinders because the subframe will no longer be able to do its job by isolating the body of the car from the drivetrain.

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    ctsv247 is offline Cadillac Owners Enthusiast
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    Re: Front sub-frame bushings

    In the absence of the instrumentation and the controlled environment needed to make such an analysis, I guess the easiest way to figure this out would be to build a full set, front to rear, side to side and start cutting pieces out of it until you start noticing a substantial difference in the behavior of the car.

    Have we ever seen a car that is too stiff?

    54, as the only person currently pursuing this, is this something you care to take on??

  13. #12
    RyRidesMotoX is offline Cadillac Owners Enthusiast
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    Fuzzy, without copying the whole text of your response I can absolutely say you are correct. The mustangs had a terrible chassis. In most cases you can see the floorpan severely warped or even torn through the shitty thin metal in the footwells. So again you are correct. For me it would simply be a means to deny any kind of stress that could do that to the frame. And if I take it to the track and it does nothing I can just grind em off and be done with it. I would be unsure of how to test it properly between having them on and having them off... But it seems like if one was to put g meters in each corner and record the readings, one could determine the amount of flex in the chassis. I'm not going to do that. I'll just run a high speed track, get my best times, go out on the subframe connectors and then run it again with as close to the same conditions I can get. If my time improves I'd call it a marginal success. I'm almost positive, after talking with a few others via PM on here, that simply welding in a roll cage would significantly stiffen the chassis. Or at least stiffen it enough that connectors would essentially be a moot point. I only brought up the foxes as a frame of reference since those guys have a lot of experience with weaker chassis... Far weaker than I have seen from the V so far. And in one of my other responses I think I put that... The ride would be terrible but it would handle better. The reason GM didn't put them on or make a significantly stronger/more rigid chassis is simply because the ride quality would suffer. And I would venture to guess 90% of the Vs sold will not see heavy use on high performance track days. Mine eventually will. I'd like to build a GTR killer with a forged gen4 block and a procharger with a cage and connectors (the later on an as needed basis) and a bitchin suspension either KW or a local company here in Southern California that I am currently prodding to devise a coilover solution for the first gen V.

    ----------

    Quote Originally Posted by ctsv247 View Post
    Have we ever seen a car that is too stiff?
    Yea. A car can be too stiff to use comfortably on city roads. Race tracks tend to be very well maintained and smooth, with a few exceptions of course. I have ridden in a few very very rigid foxes before, and they are far less than comfortable. The chassis doesn't flex at all. Even with a good suspension on a public road its almost too stiff. But at a track day it really comes into its own.

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    nikdsctsv is offline Cadillac Owners Fanatic
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    Quantifying the results would be difficult and I would be skeptical. Would have to have a psychrometer and extremely similar conditions on the day you tested with all else with the car the same. Tires, tire pressure, driver, track, fluids, time of damn day. All would have to be recorded and similar. Then, figuring out where to mount strain gauges is a whole other task.

    So in all, you either require a rigid enough car for some serious road racing; which would just dictate a roll cage and problem solved. Or, enjoy the car as a good track day car and a comfortable daily driver. I see no benefit to any added structural rigidity to the V unless it is becoming a dedicated track car. Which again, roll cage.

    To whoever said they can feel the V flex by there arm out the window...what!? You are saying is that (assumed slow speeds since your arm is out the window) you can feel the car flex? I'd love to see this caliper/micrometer skin that you must have. Then, I dare you to consider other options, like the terrible ability of our seats to hold you in place or any other million possibilities you may have confused for your thought of "wow this car flexes."

  15. #14
    RyRidesMotoX is offline Cadillac Owners Enthusiast
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    I said I could feel the body flex. If you put your hand where the top of the door meets the frame, you can feel it. Just do a hard highway pull or do it when you are getting on a banked on ramp for a highway. You can feel it. It doesn't take a mic or any gauges to feel it. And its not super dangerous or anything its just an observation.

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    ctsv247 is offline Cadillac Owners Enthusiast
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    Re: Front sub-frame bushings

    Push a late 80's IROC hard enough and you can SEE the dash flex.....They've been buckling floorboards on f-bodies for almost 50 years and a simple set of full length subframe connectors was about all that was needed to fix them in most cases.

    This all great stuff here guys but we still haven't really made any real conclusions about what makes sense to do with our particular car. For me, I'll keep following and encouraging 54 to make something that works but in the long run, I think I'd rather have too much than not enough.

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