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Edmunds Inside Line Suspension walkaround

Discussion in 'Racer Physics and Technical' started by Mr Whippy, Sep 7, 2010.

  1. Edmunds Inside Line do some really good suspension reviews which are really well worth reading if you enjoy suspension and trying to simulate it in Racer. Some really good information in here both of specific cars, but also from the author and their commentary on what they see!

    Cosmo pointed these out to me the other week, and I've read all of them so far, and keep finding more. I've learnt a fair bit recently just reading these.

    There seems to be no end of information to get your teeth into, from pure maths/kinematic observations, to these here which can almost give you more information on behaviour and tendancies purely from simple observation!

    Link to archive:

    Specific reviews:

    Acura ZDX:

    BMW 135Ci:


    BMW 750i:

    BMW E9x M3:

    Ford F-150 SVT:

    Ford Fiesta:

    Hyundai Genesis Coupe:

    Nissan 370Z:

    Nissan GTR:

    Feel free to add more if you find them :D

  2. Fantastic, but there are not lengths or angles to simulate the movement of the suspension.
  3. Yeah, it would be nice with lengths etc, but if they had lengths they would have to be very comprehensive to be useful, and I don't think anyone doing even a fairly serious review like these would go that far :D

    Only uber geeks like us would go that far, purely so we could simulate with it :D

    I think they are very valuable for the descriptions and information they have in them as they are though. There is lots of knowledge in there and the author clearly knows a thing or two about suspension. I can now look at suspension and better visualise how it will react simply from where parts are relative to each other.
    Ie, toe in or out under extension at different ends of the car and so on. They are great guides on general tendancies for when setting up a car in Racer :D

  4. I don't really know much about suspensions (yet another thing to learn), but I did manage to find a picture of the Aronde's front suspension (the 1.25 degree positive camber's consistent with other info, so I believe this is with no passengers)
    Is this sort of thing enough info to do a good job with the simulation in Racer? The bump/rebound stops are pretty obvious, though I'm not sure how to estimate their lengths for Racer (since they're going to have some amount of mechanical advantage)

    And it's obviously lacking a scale, though the wheel is 14" so that should be a decent way to approximate it.
  5. That diagram gives you quite a lot of information. If you start drawing construction lines on it.

    Top bump stop is ~3.75cm total length
    Bottom bump stop is ~ 7.15cm total length (to bolt head at base of bump stop where it would undoubtedly stop)

    Travel to top bump stop from that static diagram is ~ 4.36cm
    Travel to bottom bump stop from static is ~ 1.75cm


    It looks like a double wishbone suspension. The KPI angle is clearly seen here, and a fairly large scrub radius (offset from where tyre hits floor and the wheel steering axis hits the floor)

    The wishbones look fairly flat here, so not sure where that puts the effective roll-centre as a number you would use for Racer... ummmm, probably very low, almost on the floor.

    The bottom wishbone is very long vs the bottom one. Quickly doing a bone-simulation in 3DS Max, you can see it goes negative in camber under bump or rebound. I've not done it to scale, but I'd say about 1deg under 2.5" travel each way.
    Not sure if Racer can do this though, you can only define camber change with deflection, so it's always + one way and - the other, or vice versa...

    If you know the spring rate, you could get a pretty good idea of wheel rate. You can see when the spring will bind fairly easily. Lots of information there you can extrapolate from and put useful numbers into Racer from. Just as said, a shame that our camber/toe changes are so limited. Curves would be better, but then you are just adding more bodges to what is actually a fairly simple system to just simulate.

    In theory this is why Racer would be lots better with a real kinematic system. Define these points in space, what are joints, arms, ball joints, fixed axis joints etc... All the things we are worrying about are done automatically. You could in theory sim the Simca's suspension twice as good as Racer can right now, even with that one diagram. You'd just need to take a good guess at what it's like from the side (a few pictures would be a good enough guide!)

    Toe change with bumper, camber changes, kpi, castor influence, migration of the scrub radius etc... all done automagically :D

    Of course, we can still keep the old suspension in a way, maybe just have a switch in the car.ini!? Because it is useful if you have no data or can't be bothered being too detailed.

    Just had a cool idea about how to get loads of suspension data now, mmmmmm... will do a full model in 3DS Max then I can plot out my curves for everything and best-fit them to what we can do in Racer right now :D

  6. Thanks for the advice, KPI is 8.5 degrees, also from the manual. Thinking about buying a copy, that diagram's on one of the free sample pages, so there are probably other ones (have one for the leaf rear suspension too, not as useful 'cause Racer's all independent). Also got exact gear ratios + differential from it, so the .ini is much more reality-based now.

    Side pictures, this is the best I can do.
    This is a photograph of the back; front of the car is into the picture, tie rod is in front of the wheels when mounted. The upper wishbone has an obvious inward angle, so caster increases on deflection.
    And a picture of the front, anti-roll bar and tie rods in place. Not sure if it's good enough to get an angle on the lower wishbone's mounting axis. Kinda looks like it's higher and maybe farther out at the front.

    Manual lists recommended settings (loaded like 1st diagram):
    Caster: 1.5 to 2.5 degrees
    Camber: 1 to 1.5 degrees
    KPI: 8 to 9 degrees
    Toe-in: -0.20 degrees

    The caster is most useful in setting up things that aren't visible from the photos, probably.
  7. Yeah, caster will help you get an idea of the static kinematics for steering... ie, pneumatic trail amount, and the camber with steer amount...

    For those right now, I set up a wheel (right size), and strut in 3ds max, then rotate it, and measure the deg change in camber with deg of steer... then trail is just the intersect line of the caster line with the ground, to the contact patch...

    I've just got good data for Cam's F458 and having these fundamental values set down makes determining/tuning the unknown values lots easier!