Rear Sway Bar

Discussion in 'Gen 2 Prius Accessories & Modifications' started by wayside, Sep 14, 2008.

  1. wayside

    wayside New Member

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    This is a Hotchkis rear sway bar from a 2006 Pontiac Vibe.

    hotchkis_sway.jpg

    We took it out of my brother in laws car this afternoon and it looked like it may fit in the Prius. 2 bolts out, 2 bolts in (didn't even have to jack up the car) and sure enough it fit in perfect. Man what a difference in the handling with almost zero sacrifice in ride comfort.

    The part was for an 02-UP TOYOTA MATRIX 2WD / COROLLA / PONTIAC VIBE.
     
  2. ibmindless

    ibmindless Member

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    Is it a larger diameter? Tell us more about the handling!
     
  3. wayside

    wayside New Member

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    This particular bar is 27mm and is hollow. It weighs quite a bit more than the stock bar but it makes a substantial difference in corner handling. The car stays a lot more level when turning and makes it feel a lot more stable.

    Possibly worth mentioning, I installed a BT Stiffing plate at the same time.
     
  4. Boo

    Boo Boola Boola Member

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    Thanks for the info wayside.

    For comparison, the Standard Prius has a 19.1 mm diameter rear stabilizer bar, and the Touring has a 20 mm diameter bar.
     
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  5. NeoPrius

    NeoPrius Member

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    Subscribing...
     
  6. Rokeby

    Rokeby Member

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    So what's the big deal? I have one already, it came with the car. It's tucked up
    inside the U-shaped rear suspension cross piece thingy (axle?) -- I just went
    out with a flashlight and checked.

    It's not like adding the front strut tower brace is it? It seems an equivalent
    piece for the rear suspension would be taking up space inside the the car,
    roughly where the tonneau cover cross bar is.

    Could the suspension-smart members explain the dynamics of how/why
    this oversize bar affects the Prius' handling and or stability. I for one haven't
    a clue.
     
  7. Boo

    Boo Boola Boola Member

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    Here's a pretty good article about anti-roll bars (aka anti-sway bars and stabilizer bars). Note also that at the top of the article are links to other good articles about handling:

    Howstuffworks
     
  8. Celtic Blue

    Celtic Blue New Member

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    Assuming this is a non-touring Prius the diameter change from 19.1 to 27 mm is enormous. If I understand correctly stiffness changes to the 4th power of the diameter, so this could result in a bar that is four times stiffer. (Touring diameter is good for 20% difference from standard.)

    This radical of a change could have some adverse consequences such as early oversteer. Have you tested this yet in an area you can afford to spin it? From what I can gather lifting off the throttle in a corner in the rain could be very exciting with such a large diameter bar.
     
  9. Boo

    Boo Boola Boola Member

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    It does seem like a huge increase. I also wonder about the effects of increasing the diameter of the rear bar by so much without also increasing the front bar too.

    Howstuffworks

    In this regard, I believe that Hotchkis sells this rear bar only as part of a front and rear bars kit for the Matrix/Vibe.
     
  10. Rokeby

    Rokeby Member

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    Boo,

    thanks for the two references. Good stuff for tyros. They get bookmarked.

    Taken together, there's enough there to get an inkling of the contribution
    of sway bars in the complex, dynamic 3-D suspension equation.
     
  11. wayside

    wayside New Member

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    The main thing that I thought was cool about this "discovery" is that it opens us up to more possibilities. It's not so much the specific bar that I was psyched on as it was where it came from. I hadn't read that people were using bars from the Corolla or Matrix.

    I agree that the 27mm bar may be a bit much but I can't say for certain as I have not tested the car to the extent of trying to make it spin out.

    On our first test drive through my neighborhood I did notice that the tires were a little more stressed than they were before the mod. I cannot say if this was caused simply by the introduction of the new sway bar or the fact that I was able to take the corners faster (I guess it's kind of the same thing either way).
    On my way to work this morning I made a conscious effort to take all exit and entry ramps at the same speed and entry angle as I had prior to the mod. The result was a lot less effort in the form of steering input while maintaining speed noticeably better throughout the turns.

    I have every intention of testing this mod in a controlled environment (e.g. big empty parking lot) before pushing it any harder than I would have on the public streets.
     
  12. Celtic Blue

    Celtic Blue New Member

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    wayside,

    I'm not trying to be overly critical. I'm glad that you let us know this fits (and that itself opens up more options as you've noted.) But I did want to pass on what I gathered from looking at some sites. I would feel guilty if I remained silent and you had a nasty spin and resultant damage or injury.

    What I read is that if you overdo a sway bar mod a car will handle great up until about 8/10's, then things happen very rapidly and unpredictably.

    I put a front & rear sway bar kit, progressive rate springs, better shocks/struts, poly bushings and strut tower brace on my 240 and that made a huge difference in handling. (And as you mention, I spun it on purpose to get a feel for what happened at the limit of adhesion...and past it; ended up saving my car when a lady ran a light in front of me forcing a crazy swerve and resultant spin.) So I'm not at all opposed to doing suspension modifications or sway bars to the Prius.
     
  13. Rokeby

    Rokeby Member

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    for the record, go here to see what Hotchkis offers for the Corolla:

    Hotchkis Sport Suspension - 2003+Corolla

    As other posters have suggested, the 27mm rear bar is paired with a 29mm
    front bar, both hollow.
     
  14. wayside

    wayside New Member

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    shawn,

    I appreciate your input for sure. I have also done a few suspension upgrades in the past. One in particular was a 94 civic hatch (in 94). That car did not come with a rear sway bar, I added a rear sway and springs to that car and never had any problems (never spun it and drove pretty aggressively for about a year).

    I'm wondering if the design of our rear suspension does anything to "lessen" the effect of a given size sway bar. The way that the bar is enclosed in the rear suspension seems to cause suspicion as I have never seen a rear sway application like this.

    Any thoughts on that?
     
  15. Boo

    Boo Boola Boola Member

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    BTW, Brian of BT Tech has been working on coming out with a beefed up front sway bar for the Prius. In one of the other threads here, he's discussed it briefly. I remember him saying that he was very pleased with the improved handling and reduced body roll from the prototype bar he created. But I also recall that he should have come out with it a couple of months ago. So, I don't know what's up with it.
     
  16. drees

    drees Senior Member

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    Good find in finding another car that "shares" parts with the Prius.

    As others have mentioned, 27mm is a huge increase from stock. But then again, stock, the Prius understeers like crazy. In my past experience with sway bars, for those who are looking for better handling without going crazy, typically upgrading both the front and rear bars similar amounts works best and gives the best balance for a daily driver.

    Anyone know how big the stock Vibe bar is? I'm just guessing, but given how big the aftermarket bar is, the stock bar must be bigger than the touring bar. That should be a better compromise, especially if you don't upgrade the front bar, or a good upgrade for Touring owners.

    I wonder if the front bar fits as well? Someone go and look up some part numbers. :)
     
  17. sdtundra

    sdtundra Senior Member

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    Dang, guess i'll be spending some time at the salvage yards in Chula Vista this weekend
     
  18. Five5Six

    Five5Six New Member

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  19. Boo

    Boo Boola Boola Member

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  20. drees

    drees Senior Member

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    If we can get another confirmation that the 03-06 Corolla/Matrix rear sway bars fit, that will give us a pretty good number of choices for rear sway bars!

    Now for the fronts...
     
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