Independent Rear Suspension

Discussion in 'Fiesta ST Chassis Upgrades' started by Ataru, Aug 23, 2013.

  1. wash

    wash Active Member

    Is that a strut?

    If so, its independent but you are kind of limited in what geometry you can get with a setup like that.

    Its one of those things, if you need what a strut can do its a good setup, like the Fiesta the twist beam works so you really don't need IRS, the neon probably worked with struts and didn't need a true 5 link.
     
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  3. Gary

    Gary New Member

    Neon rear suspension.jpg
    Yes, the Neon has struts, very similar to the fronts. The rear lateral links are adjustable for toe and it works very well for this car. Interesting how manufacturers do different things to get the same results. I had a rather large (22mm) rear sway bar on my Neon and I'm thinking that the ST probably handles better without one!
     
  4. RodMoe

    RodMoe Well-Known Member

  5. wash

    wash Active Member

    Yeah, that setup needs a rear anti-sway bar while the Fiesta twist beam does double/triple (quadruple maybe?) Duty. The strut gets to have a well defined camber curve but if you're three wheeling with a lightly loaded wheel and not much body roll, I'm not sure how much camber actually matters.

    The bushing orientation on the twist beam might give a little bit of camber gain when the beam twists but the ST beam is stiffer so maybe not. Maybe its for toe? I'm not sure but I bet it does something.

    The more I think about it, the roll center and antis are probably the biggest limitations of a twist beam but if you get what you need, lacking adjustability does not matter.
     
  6. Gary

    Gary New Member

    I put a aftermarket rear bar (in addition to a bigger front one) on my wife's Cavalier that has a twist beam and it made a huge difference. I'm thinking in this case the Cavalier axle was probably minimal to help handling. The interview with the Ford engineer said that the ST axle was upsized a bit in material thickness so probably didn't need a bar in this case. Eibach rear sway bar.JPG
     
  7. eRic

    eRic Active Member

    meh. the rear beam works for me. once you're on three wheels does it matter how you got there ;) my last pre-Fiesta vehicle was front wheel drive with an independent tri-link with strut rear suspension. the trick was to put a big bar on the rear in effect making it less independent.
     
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  8. EvoNiner

    EvoNiner Active Member

    I'm not as smart in the aspect of knowledge when it comes to suspensions or tuning, but because of this twist beam could it make my fiesta do somewhat of a "hop" through long hard sharp corners where I tend to feel the rear tire lift, drop then lift again? I understand it could just be my tires loading up, giving way, while the front stays planted, then loading up again. Am I wrong about thinking like this or no?


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  9. joe@2j-racing

    joe@2j-racing Active Member

    The twist beam is an awesome setup that gets a bad wrap because its the perspective of the media to be considered "economy". We make panhard rods for our twist beams and can run down cars that cost 10x's as much with a very stable rear. You can even throw the car into a controlled drift. Dont hate on the twist beam, it works.

    WP_20131023_003.jpg
     
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  10. ST_Rocky

    ST_Rocky Member

    Once again, another thumbs up for those ST engineers, with their attention to small details, and their willingness NOT to compromise on the handling of the ST for us true enthusiast drivers! Adding negative camber in the rear would have added better grip in the rear, causing understeer tendencies and less chance of oversteer - the safer route for the "masses", and the bean counters. Instead, they trusted us to drive it with full, proper skills and intent. They designed the Fiesta ST for US!

    And again I say, you have just got to appreciate those guys, when you hear that one video interview, and the engineer says "we allowed the traction control to be fully turned off, because we wanted to give our customers what they wanted". Wow, just plain WOW! And so why too, I was happy to get this car.
     
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  11. Cligedy

    Cligedy Active Member

    I still believe that to decrease the performance of one end to make the other end seem relatively better is a mistake. Not hatin, but improve the front instead of making the back worse.
     
  12. Smokin

    Smokin Active Member

    Really sound like an amateur.
    I've heard that around SCCA so much it makes my head spin.....
    Lots of people (like you) quote Carroll Smith when they have never read Carroll Smith.
    In fact Smith was referencing a fully tuned race prepared car where, if struggling for grip on a race track, you don't adjust the opposite end to make problem end work better. You work on the problem end to make it work better.
    Can't tell you how many times people told me I couldn't stiffen the front of my GTI and decrease understeer.
    I did and beat most of them in autocross.

    No where does Ford say they decreased the performance of the rear to make the front seem better.
    In fact they improved it.
    You tune the end you need to tune to make the handling better.
    Ford tuned the rear twist beam axle to allow the car to rotate. That has nothing to do with any mods to the front.

    (BTW, after racing F-Continental and F-Fords for 5 years, I can speak from experience.)

    FMI: http://www.amazon.com/Tune-Win-science-development-tuning/dp/0879380713/
     
  13. wash

    wash Active Member

    Carroll Smith is OK and good for some of the more practical details but it doesn't get much better than Bill Milliken's Race Car Vehicle Dynamics (SAE press) when you're talking theory.
     
  14. Cligedy

    Cligedy Active Member

    Sorry to disappoint you, but I am an amateur. By all means, decrease performance to your heart's content.
     
  15. Smokin

    Smokin Active Member

    My point was people quote what they've heard from others, not knowing the source. Remember Car Talk? Things Your Father Told You....
     
  16. wash

    wash Active Member

    I got it, I just wanted to suggest a fairly definitive reference for anyone who's serious about the topic of suspension design.

    Just like quoting Carroll Smith isn't the same as understanding his books, the depth of information in a Carroll Smith book isn't the same as Race Car Vehicle Dynamics (its over 700 pages of pretty dense text).

    Back to the other topic, beside basic suspension design which usually treats both ends separately, the whole idea of understeer/oversteer is about balancing the two ends and you can only get to neutral if the front and rear grip match.

    In a FWD car almost all of the weight is over the front wheels so they take the Lion's share of the cornering force, trying to make them keep up with a lightly loaded rear end that doesn't even have much brake torque to deal with is impossible unless its compromised some way. In the ST its high roll stiffness and less camber to balance the car.

    To improve the front, there isn't much you can do and some things like lowering the cg will help at both ends so you're still left adjusting the rear grip to balance the car unless you can drive a car with severe understeer very fast.
     
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  17. Smokin

    Smokin Active Member


    That, I learned to do in the GTI. I used to describe going through a slalom with the stock suspension GTI as a pig rooting for a truffle....
     
  18. eRic

    eRic Active Member

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  19. jasyatz

    jasyatz Member

    And is a packaging concern also. The rear seat width, wheelbase, and track width are all their sizes " because of" the twist beam. Ever been in the back of a Mini? if ou are over 5' tall it's torture. I've put 3 kids in the back of my Mazda2 and fit very comfortably. (2 over 5') If you look at the NEW Mini (R5* I forget what number they're at now) its actually more of a "medium" than a Mini.

    The Civic and the Neon are larger cars by design, and yes works quite well on both of them, as it did on the CRx and the Delsol. (but neither of the last 2 had rear seats)

    If you want to upgrade the handling on this chassis, get the best set of rear shocks you can afford, and if they're adjustable, crank them to 11!
     
    Last edited: Feb 9, 2014

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