Oversteer vs Understeer: Which is better? (DriveTribe Article)

Discussion in 'Suspension, Brakes & Chassis' started by Roadway 5.0, Apr 14, 2019.

  1. Roadway 5.0

    Roadway 5.0 Strassejager

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    #1 Roadway 5.0, Apr 14, 2019
    Last edited: Apr 14, 2019
    This makes for a good Sunday read:

    https://drivetribe.com/p/understeer...muylRkmaF8U0fmgDeg?iid=KM33_VDFR_CmD5vsfWZgdg

    It also brings up some discussion questions:

    How “much” understeer do the S550 models have from the factory?

    If modifying swaybars only, and all else staying equal, what configurations/rates does it take to hit, say, “10%” understeer, “neutral”, or "10%" oversteer?

    Just some open-ended thoughts to get the day going.

    -Mike
     
  2. Norm Peterson

    Norm Peterson corner barstool sitter

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    #2 Norm Peterson, Apr 14, 2019
    Last edited: Apr 14, 2019
    Randy Pobst is on record as favoring understeer. Light understeer, whatever that means (I think he tried to define it a little in some issue of the SCCA's monthly magazine). My own take is that if you find oversteer too easy to come by, you'll consciously or subconsciously leave a little more margin against that happening. Either by leaving a few more hundredths of a g of tire grip unused, or by being slower/later/more gradual in your throttle application as you get back into that.

    To the best of my knowledge, understeer is still best quantified in terms of an "understeer budget", which can either be a positive number (for "understeer") or a negative one ("oversteer"). This isn't a percentage thing; it's a comparison of the totals of a number of cornering compliances (front minus rear) and ends up being expressed in degrees per g.

    Straight out of RCVD

    full.jpg

    It's probably best to assume that most or all of the individual terms are themselves somewhat variable over the range of cornering g's. IOW, not the same numbers or even numbers in the same proportions at 1.0g as at 0.25g.


    Norm
     
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  3. NightmareMoon

    NightmareMoon Well-Known Member

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    The more I drive with different swaybar, shock, and spring settings, the more I feel that as long as its reasonably close to neutral, and not biased too far in either direction, the driver can adapt. I no longer have a strong preference for over/understeer, but a car close to neutral is very rewarding because weight transfer with throttle can quickly plant the rear down, and weight transfer forward by breathing on the brakes can glue the front and get the car to turn.

    Ona road course, (and going for lap times), slight understeer is reportedly best. You can maximize your speeds on the straights be being more confident and aggressive planting the throttle to the floor earlier and harder coming out of corners.

    Slight oversteer can be a blast to drive, assuming you’ve mastered it. Its like an art form or balancing act. The car will throttle steer well mid corner, but it can be a handfull on corner exit if you arent used to it.

    The stock PP car is a little biased to understeer, but its dynamics are close enough that with a sporty alignment its not going to hold back most drivers. Later, I had a lot of fun with a mildly stiffer rear swaybar and squared tires, and the car was a little oversteery in that configuration. After a few years like that I put the stock rear bar back on and learned to drive a stiff front bar. The car definitely understeered that way but it did a number of things well. The most fun tho was with a stiffer front bar AND a mild rear bar with square tires, it seems the most balanced this way, able to understeer or oversteer based on driver inputs.
     
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  4. dmann

    dmann Well-Known Member

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    that's good feedback.
    thanks
     
  5. Dano

    Dano Well-Known Member

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    I found these two youtube video's entertaining and informative.



     
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  6. Performance nut

    Performance nut Well-Known Member

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    I prefer having my car understeer in the corners but not a significant amount, almost neutral. With a high horsepower RWD vehicle, I have unlimited supply of throttle oversteer. If your car is set for oversteer naturally, I haven't figured out how to induce understeer on the fly. Plus cars that oversteer tend to have too many "oh shit" moments for my taste. Understeer cars are more forgiving. Unless you are a perfect driver who knows his crap back and forth and back again, we all need forgiveness now and then.

    With that said, the base GT had a cubic shit ton of oversteer. Dear god man, I started to wonder if the damn steering wheel worked at all above 30mph. I'm exaggerating but jeez laweez it really pushed in the turns. My 2018 was better than my 2016 but still pushed. A popular combo for sway bars is having an aftermarket front that is adjustable and a PP rear. I have a GT350R front and rear sway bar with some rather stiff springs and it use to push just barely. Still troubleshooting why it doesn't anymore.
     
  7. bootlegger

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    The 2018 PP1 with magneride understeers quite a bit in stock form. Sure, you can nail the throttle to whip the tail out, but in controlled cornering you feel the tendency to understeer. Just installed the new rims and tires with a square setup yesterday (using 5mm front and 3mm rear spacers), and now the car has a tendency to oversteer. I may have to do some work to get closer to neutral. While oversteer can be fun, I feel that it is more restrictive when trying to push the car as an amateur.
     
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  8. Norm Peterson

    Norm Peterson corner barstool sitter

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    Up to what size tires and wheel widths?


    Wait until you've run up at least a couple hundred miles of gradually increasing "enthusiasm" before making this kind of evaluation.


    Norm
     
  9. bjstang

    bjstang Well-Known Member

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    #9 bjstang, Apr 16, 2019
    Last edited: Apr 16, 2019
    Just my two cents as a non-track competitor, oversteer for the win. Stock non-pp suspension with the Steeda 2-point brace and the GT350R rear stabilizer bar, (no other suspension mods). After going to a 275/19 square set-up there was too much flex in the back. The heavier bar fixed that and the trac brace reduced the tramlining.

    The drive and feel are better in IMHO than my wife’s car on curvy mountainous roads, or just cruising down the Interstate. Lowering our cars is not possible due to clearance issues in the places we like to travel, historic towns, scenic byways, etc.…

    Yes, not the same as, but I found it interesting that the 2020 EcoBoost will have the same size rear bar that I placed on my car.

     
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  10. Cardude99

    Cardude99 Well-Known Member

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    I thought it was just me. My car understeers like crazy. To me it's too much, working on trying to reduce it. Inducing oversteer with an eco is not as easy as with a GT. At least not in stock form
     
  11. bootlegger

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    19x9.5 with 285/35/19 on all 4 corners. Using 5mm spacer (to clear Brembos) in front and 3mm in back.


    It could also be that I am not used to the tires. Going from PS4 to RE71R is a big change. I know I will need to get them hotter in order to see the real balance, but my first impressions are that I went from mild understeer to oversteer.
     
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  12. BmacIL

    BmacIL Enginerd

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    You also flattened out the rake of the car while doing so, going from a 27.0" front, 27.7" rear to a 26.9" all around. The rear of the car dropped almost 3/8", while the front hardly any. This means less static weight on the front of the car, with more or less the same weight transfer.
     
  13. bootlegger

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    Wonder what it would feel like going with larger spacers in the rear. I imagine that would make things more neutral, but I am guessing I would need proper spacers with longer studs.
     
  14. OP
    OP
    Roadway 5.0

    Roadway 5.0 Strassejager

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    I’m 100% on your side. I suppose it’s a track-king versus street-carver situation, but for what I like to experience in my drive a larger rear bar with the stock PP front bar produces exactly the dynamic I enjoy. Turns are flat, and where I steer I go...telepathically.

    Interesting the stats on the new 2020 EcoBoost. I’m curious to the PP2’s sway bar sizes as well, though I can’t seem to find the specifics.
     
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  15. Norm Peterson

    Norm Peterson corner barstool sitter

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    The CG did move rearward, but I don't think that the amount it moved could be by enough to matter. I'm seeing 46.0% rear weight become something like 46.05% (gaining around 2 lbs) - it's a side view geometric solution involving fairly shallow triangles and arcs drawn about the front stub axle.

    It's easy to assume that changes in the relation between front and rear ride height are due to "weight" moving around, but we know that didn't happen. The sprung mass just rotated slightly about the front axle.


    Norm
     
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