Unstable corner transitioning

Discussion in 'Suspension, Brakes & Chassis' started by MartinNoHo, May 10, 2020.

  1. Brian@BMVK

    [email protected] Well-Known Member

    Vehicle(s):
    2015 GT
    Joined:
    Apr 27, 2020
    Location:
    Illinois
    Posts:
    528
    Likes Received:
    379
    0   0   0
    No, the opposite.
     
    MartinNoHo and TeeLew like this.
  2. OP
    OP
    MartinNoHo

    MartinNoHo Active Member

    Vehicle(s):
    2015 Mustang V6 (2014-2020), 2018 Mustang GT Premium yellow (2020-XXXX)
    Joined:
    Jan 22, 2017
    Location:
    Los Angeles
    Posts:
    42
    Likes Received:
    0
    0   0   0
    If it isn't a bother can you explain/summarize to me how spring rates might affect handling dynamics in layman's terms, I'm curious how you came to the idea that my car is front biased and what does this mean.
     
  3. OP
    OP
    MartinNoHo

    MartinNoHo Active Member

    Vehicle(s):
    2015 Mustang V6 (2014-2020), 2018 Mustang GT Premium yellow (2020-XXXX)
    Joined:
    Jan 22, 2017
    Location:
    Los Angeles
    Posts:
    42
    Likes Received:
    0
    0   0   0
    #33 MartinNoHo, May 14, 2020
    Last edited: May 14, 2020
    Do you have a recommended read for me to better understand suspension dynamics? Cause now i'm confused as to how sway bars, springs rates, etc work together and affect vehicle dynamics, because I understand them far to simplistically. I learn from engineering explained videos on youtube, and I think its simple mainly because it's for general audience.
     
  4. Bluemustang

    Bluemustang Well-Known Member

    First Name:
    Ryan
    Vehicle(s):
    2015 Mustang Base GT
    Joined:
    Nov 6, 2015
    Location:
    Maryland
    Posts:
    3,161
    Likes Received:
    1,397
    Occupation:
    Financial
    0   0   0
    I'll let those more technically oriented answer that question as I might not use the correct terms. Again it's hard to know for sure because I don't know exactly what it is happening with the progressive rate.
    But assume you have a linear front and rear spring - just from the numbers you listed (in lb/in) it indicates a higher front ride frequency vs. the rear. There's a spreadsheet floating around that lists all the known S550 spring rates, wheel rates and corresponding ride frequencies of the different springs out there.

    Ride frequency is extremely important to vehicle dynamics and resulting handling balance, as well as the overall ride quality. Basically what I'm talking about is stiffness, roll resistance front to rear. Changing this relationship alters the handling balance and vehicle dynamics.

    Understanding the result of a change to one end of the car or the other, you have to first understand the suspension system/how it functions. There are many general norms with respect to tuning handling balance. Some may be applicable to you, some may not.

    I suggest reading some articles about tuning handling balance and ride frequencies. Also, understand the car you are working with - heavier front weight distribution, RWD and big power. MacPherson front suspension, multi-link IRS. Therefore, some general norms of tuning handling balance may not apply if you're basing it on suggestions off a another platform. A good car to look at with similar suspension system is the BMW M3. They also use MacPherson struts and a similar IRS. Also, RWD, big power and similar weight.

    You'll notice a lot of M3 guys will upgrade to a larger front sway bar. Why? To combat the poor camber control of the MacPherson strut. Front camber and front roll stiffness is your friend. The reason why the bigger rear bar doesn't work as well on this car is because 1) the IRS has a much better camber gain than the front suspension does, so it doesn't need it as much, and 2) the stiff rear bar also has drawbacks (as do all sway bars), one of which is sacrificing wheel independence. Look at it this way, you're trying to put power down to the rear wheels - the rear sway links both sides of the suspension together. Your suspension is now less independent. If you go extremely stiff you are almost turning your IRS into a straight axle. It can make the rear end more twitchy. It ultimately reduces rear grip which hurts you trying to put power down out of the corner.

    Typically, the general norm on stiffer front sway bars is that it can make the car understeer. And yes it still can. But used in the right away on this car (with enough camber and good tires), it can actually reduce understeer by combating the weakness in the MacPherson strut. The MacPherson doesn't have a way to keep the outside tire from curling into positive camber when it's pushed too far in cornering. This is why the autocross guys will run a stiffer front bar to keep that from happening. It helps to stabilize the dynamic camber angle.
     
    MartinNoHo likes this.
  5. Brian@BMVK

    [email protected] Well-Known Member

    Vehicle(s):
    2015 GT
    Joined:
    Apr 27, 2020
    Location:
    Illinois
    Posts:
    528
    Likes Received:
    379
    0   0   0
    EE's videos are pretty dumbed down. They're good, but far from complex enough to really know what's going on. Some good reading I can recommend that's not super math intensive:

    Autocross to Win - Dennis Grant (everything is applicable to far more than autocross here)
    Tune to Win - Carroll Smith
     
    MartinNoHo and TeeLew like this.
  6. TeeLew

    TeeLew Well-Known Member

    First Name:
    Tim
    Vehicle(s):
    Honda Odyssey, Toyota Tacoma, 89 GT project, 2020 Magnetic EB HPP w/ 6M
    Joined:
    Apr 27, 2020
    Location:
    So Cal
    Posts:
    188
    Likes Received:
    61
    0   0   0
    _Tune to Win_ isn't correct about everything, but it's so damned good for the late 1970's, that it might as well be. Beyond that, Carroll was just a guy that liked to make things go fast. His books are the standard by which every other car-tech book is measured.
     
  7. Brian@BMVK

    [email protected] Well-Known Member

    Vehicle(s):
    2015 GT
    Joined:
    Apr 27, 2020
    Location:
    Illinois
    Posts:
    528
    Likes Received:
    379
    0   0   0
    For sure, but for getting a foundation, it's good.
     
    TeeLew likes this.
  8. TeeLew

    TeeLew Well-Known Member

    First Name:
    Tim
    Vehicle(s):
    Honda Odyssey, Toyota Tacoma, 89 GT project, 2020 Magnetic EB HPP w/ 6M
    Joined:
    Apr 27, 2020
    Location:
    So Cal
    Posts:
    188
    Likes Received:
    61
    0   0   0
    I said it clumsy, but that was my point.
     
  9. Norm Peterson

    Norm Peterson corner barstool sitter

    First Name:
    Norm
    Vehicle(s):
    '08 GT #85, '19 WRX, '01 20AE
    Joined:
    Jul 22, 2013
    Location:
    On a corner barstool not too far from I-95
    Posts:
    6,725
    Likes Received:
    2,806
    0   0   0
    "Lower" only makes a car look more race car-ish. That's not the same thing as it actually driving more like a race car. People manage to reach improper conclusions based on what they see because of such visual associations.

    The time delay to when the car takes a set is a function of the sprung mass frequency in roll. Roll takes time to happen, and there isn't much you can do about this in a lowered street-driven car other than stiffen the suspension some more. Don't ignore the shocks & struts here, and not just because stiffer springs and stiffer bars need more damping to control them. Damper forces peak before roll has fully developed and can make the car feel closer to its set before it gets all the way to a geometric definition of 'set' if they're high enough (don't go too far, though). Composure coming from appropriate levels of damping go a long way toward making the car easy to drive.


    Big heavy cars are inherently more 'deliberate' in their response to steering inputs, so you can't exactly drive them like you could a track-tuned Miata. I don't know what your corner sequence looks like, but I suspect what you're going to have to teach yourself is to have a little more patience as far as the car's inertial response times are concerned. Go back to a speed that you can comfortably stay at while focusing on the right line through those turns. Consider that you might have to write the first turn off as a "throw-away" in order to be set up properly for the second.

    I'm afraid I can't tell you how well figuring this part out as you go in only street driving is going to play out (let alone in the absence of knowledgeable instruction). Not unless you're willing to put what could amount to (literally) decades into paying close attention - all the time and at lower speeds - to what works well and what doesn't work so well. Even then, it's kind of a 'feel' or a 'rhythm' thing that different people have different aptitudes for sensing.


    Norm
     
  10. Emilbadal

    Emilbadal Well-Known Member

    First Name:
    Emil
    Vehicle(s):
    2016 V6 Auto DIB
    Joined:
    Apr 14, 2017
    Location:
    Socal
    Posts:
    170
    Likes Received:
    38
    0   0   0
    For faster weight transfer feel, thicker sway bars front and rear will help. Cradle lock out kit will help getting some vagueness out of your car handling feel. If you choose to put chassis braces on, they will help with predictability and you will feel the road more.

    As many here pointed out, public roads no matter what time of day and where it is, it’s not a good place to learn what your car’s capabilities are. It’s a disaster waiting to happen.
     
    TeeLew likes this.
  11. Ecoboosted

    Ecoboosted Well-Known Member

    Vehicle(s):
    18' Mustang GT, 19' Road Glide, 06' F-150
    Joined:
    Feb 8, 2015
    Location:
    Wisconsin
    Posts:
    1,549
    Likes Received:
    564
    0   0   0
    I have Steeda front and rear sway bars. I have the front set to the 2nd to stiffest setting out of 4 adjustable holes and rear to the softest setting out of 3 adjustable holes. Does that sound right or should I set them differently?
     
  12. SteedaTech

    SteedaTech Well-Known Member
    Diamond Sponsor


    Vehicle(s):
    2016 Mustang Q750
    Joined:
    Aug 8, 2016
    Location:
    Pompano Beach, FL
    Posts:
    1,972
    Likes Received:
    1,404
    0   0   0
    I would start off with the softest setting front and rear and tune from there.

    Steeda Tech
     
  13. Ecoboosted

    Ecoboosted Well-Known Member

    Vehicle(s):
    18' Mustang GT, 19' Road Glide, 06' F-150
    Joined:
    Feb 8, 2015
    Location:
    Wisconsin
    Posts:
    1,549
    Likes Received:
    564
    0   0   0
    I’ve tried all settings front and back except the front at the stiffest settings because I have the magnaride suspension.

    When I had the front set to the 3rd stiffest and rear to the stiffest setting after a while I heard some creaking and the car seemed twitchy on high speed back roads. I adjusted the front to 2nd softest setting and rear to middle setting. For a long time but after reading Bluemustang’s post I set the rear to the softest setting to see if it will be more compliant on the same back roads vs the settings I just had them on. Will see if it rides better.
     
Loading...

Share This Page