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Suspension and Balance |
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Romeo 
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Joined: 16 November 2008 Location: Canada Status: Offline Points: 3033 |
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 Posted: 13 September 2010 at 9:51pm |
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Yeah, you're spot on. If you want later, you can also send me your current ride height, tire type and roll-stiffness and I can run it through for you too.
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Never shift into reverse without a back-up plan.
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Romeo
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Joined: 16 November 2008 Location: Canada Status: Offline Points: 3033 |
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Posted: 17 September 2010 at 5:58pm |
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Some trivial and useless facts for anyone who has nothing better to read: As the Fiero is not in that racing simulator, I had to find another car with similar attributes. Some will find it comical that the closest analogue I could find was the Ferrari GTO. Same weight balance, same weight, same suspension height and a 2.9L V6 (Although given that it's a turbo six, it devellops over 300HP. Could put restrictors on it in-game, but it's just as easy to hold the gas at 70% throttle). I had to alter it's tires to match my Fiero's mind you. The suspension set up still causes drastic oversteer if the rear stiffness exceeds the front. The can be slightly corrected by matching up the sway bars, or by increasing the stiffness of the front struts. My idea of 275 back, 245 front will cause the car to have a neutral characteristics, unless the brakes are touched, in which case snap-oversteer is the result. Peak lateral G's on my current tire set-up with that alignment will cause a peak lateral G of 1.04 at 60MPH, but it causes positive camber beyond that which means by 120MPH peak lateral G has diminished to .92 |
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Patrick
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Joined: 19 April 2008 Location: Vancouver Status: Offline Points: 5 |
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Posted: 17 September 2010 at 6:53pm |
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I trekked out to Colby's place yesterday and we spent several hours setting up the alignment on my lowered '84. Gotta get ready to spank some Vettes on the 25th! We spent a heck of a lot of time setting up the rear camber... Measure camber, jack car up, remove wheel, loosen two large strut mounting bolts, tweak camber, tighten two large strut mounting bolts, replace wheels, lower car, bounce car to settle springs, measure camber, rinse and repeat and repeat and repeat until the camber is where it’s supposed to be. Next time we’ll try using these. I think it’ll make setting the rear camber a whole lot easier.
We didn't do any camber adjustment on the front because neither one of us was really sure which way the factory upper ball joints were supposed to be flipped around to tilt the tops of the wheels in a little more. Anyone know? (I believe one side on the ball joints has a "flat" edge that's either supposed to face in or out.) The front upper ball joints are probably already flipped around the "correct" way, but it would be nice to know for sure. Anyway, the car feels really good after Colby's fine job as the rear camber was way off previously and the toe-in/out front and back is set up properly now.
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Colby
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Joined: 30 March 2009 Location: Abbotsford/Sask Status: Offline Points: 665 |
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Posted: 17 September 2010 at 9:21pm |
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Yeah, those bolts would have saved us a lot of time. If we had them, instead of having to jack the car up every time to adjust we probably could have just jacked it up once to loosen the bolts then adjusted it by turning the bolt with the wheel on the ground and raising again only to torque it in place. At least it's not something that needs to be done very often.
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88 Formula 5 speed
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Colby
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Joined: 30 March 2009 Location: Abbotsford/Sask Status: Offline Points: 665 |
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Posted: 17 September 2010 at 9:35pm |
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Which racing simulator is this? How many G's do you figure you'll be able to reach at 30MPH? 30MPH is closer to the speed you'd be going in a turn for autox anyway. And what kind tire are you using for this simulator? Obviously the easiest way of increasing your max lateral acceleration is by getting soft, grippy tires. |
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88 Formula 5 speed
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Patrick
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Joined: 19 April 2008 Location: Vancouver Status: Offline Points: 5 |
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Posted: 17 September 2010 at 11:19pm |
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Colby Colby Colby... Tristan fully intends to be rocketing through the autocross course at 120MPH after his engine mods.
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Colby
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Joined: 30 March 2009 Location: Abbotsford/Sask Status: Offline Points: 665 |
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Posted: 17 September 2010 at 11:54pm |
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To go 120MPH at .92g he'd need to have at least a 640m wide (in
diameter) turn. Maybe he wants to pave some more of the field for us.
 But the largest turn I've seen has only used maybe 3/4 of the 250' width, and when you consider that and assume a peak lateral acceleration of 1.04g, you'll only be going at most 38MPH around a corner. Of course some of the straights are just wide circles/arcs too. |
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88 Formula 5 speed
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Romeo
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Joined: 16 November 2008 Location: Canada Status: Offline Points: 3033 |
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Posted: 18 September 2010 at 2:22am |
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Forza is the simulator. I can check that tomorrow night, didn't really grab that. 60MPH was the highest I managed to get last time, so I set that as my "worry up to this level" point. I'm only using my street tires. I could put in really nice, grippy semi-slicks, but that's beyond my budget. Far, far beyond it.
And you know it will Patty. |
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Colby
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Joined: 30 March 2009 Location: Abbotsford/Sask Status: Offline Points: 665 |
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Posted: 18 September 2010 at 11:07am |
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If you could do 1.04g with street tires, imagine what you'd be able to do with a dedicated autox tire. Are you getting there with just a better alignment, wider tires, and balancing the stiffness between the front and rear? I hope that the simulator is correct.
With my car, because of how slowly it accelerates, maximizing the speed I can go around corners is very important. I don't think I even reached 50MPH last time, but if I could carry that much speed through the largest turns I'd be much better off. But until I learn to take full advantage of the grip I have available to me now, increasing it won't do as much for me, just hide my mistakes. |
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88 Formula 5 speed
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Romeo
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Joined: 16 November 2008 Location: Canada Status: Offline Points: 3033 |
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Posted: 18 September 2010 at 9:31pm |
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You might be even better off than I am, as the duke surely weighs less than the six. But the next level of tire I can input is a street-legal slick, not unlike what Brian utilizes. However, I simply don't have the fiscal ability to afford changing tires more frequently.
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Romeo
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Posted: 18 September 2010 at 9:59pm |
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Well, I've noticed that Koni Reds are only adjustable on the rear... This is problematic, as the only place with the now discontinued Koni yellows are Westcoastfiero, who want $499 for the front axle alone. Oh well, still planning on picking them up, need to try and balance out finances and figure something out... Don't want anything less. |
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Colby
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Posted: 19 September 2010 at 12:48am |
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You sure about that? The Koni website shows that the red shocks for 84-87's are adjustable. You can even buy a pair of them there for $258. Hopefully you can find some adjustable shocks for less than $499 since I was planning on getting some myself too in the future, just not if they're that pricey. |
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88 Formula 5 speed
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Patrick
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Joined: 19 April 2008 Location: Vancouver Status: Offline Points: 5 |
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Posted: 19 September 2010 at 9:35am |
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And a quick google search shows them to be had for $105 apiece, probably less elsewhere.
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Romeo
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Posted: 19 September 2010 at 12:08pm |
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From what every site I've read says, the fronts can be adjusted outside of the vehicle, but that doesn't much help me. The rears are still externally adjustable, meaning that you can reach in the tire well and stiffen/softer bounce jounce and rebound settings without taking anything out. The Koni yellows, which are both stiffer and adjustable at all four corners, are worth about half of what I paid for the car. The reds are a little softer (But still plenty stiff), but can only be adjusted (Normally) on the rear, and still arn't what you'd call "cheap". Also, the fronts are usually $110-130 per shock, and the backs about $200-240 each (For the reds).
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Colby
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Joined: 30 March 2009 Location: Abbotsford/Sask Status: Offline Points: 665 |
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Posted: 19 September 2010 at 1:11pm |
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OK... but you seem to be forgetting something. In general, for maximum cornering traction, you want the least amount of vertical force/weight at each wheel. Of course other factors come in like body roll and alignment.
If this doesn't make sense to you, consider what happens when you add a large rear anti sway bar to a stock Fiero. A stock Fiero understeers a lot (ie. the front wheels lose traction). Adding a large rear sway bar, in addition to taking away body roll, effectively increases the amount of downward force on the rear wheels and results in a car that will more readily oversteer. Since it hasn't really given the front wheels any more traction while corning, it must have taken away traction from the rear of the car. So with this in mind, you can just take the front shocks and set them to the softest setting then just tune the rear struts for balanced handling. Edit: Now that I think about it, using the sway bar as the example probably wasn't the best choice since the fact that it increases the weight at the wheels isn't so obvious. But it seems like you already get that to make an understeering car more neutral you want to stiffen the rear. I'm just suggesting you consider why that is and why a totally stiff suspension isn't necessarily ideal if you want to maximize cornering traction (for example, instead of stiffening the rear to eliminate understeer, make the front softer). |
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88 Formula 5 speed
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Romeo
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Joined: 16 November 2008 Location: Canada Status: Offline Points: 3033 |
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Posted: 20 September 2010 at 9:30am |
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Bare in mind that friction is dominated by normal force, which itself is generated by how much the car is "pushing" on a tire. While it's true over-stiffening can aversely affect a car's handling, a softer suspension is bad in three ways: Driver confidence will naturally go down as body lean is increased. This unto itself is probably a soft shocks single greatest sin. The second reason is transverse balance. In a car that's leaning, there's too much weight to handle on the outside tire, and not enough weight to get friction on the inside tire. Third reason being momentum. As the car leans over, it wants to continue moving to the outside. Off-setting this is key to cornering quicker.
Remember, the fastest cornering vehicles on the planet - Formula One vehicles - Are also one of the stiffest, with a suspension capable of deflecting only 1/2" at 5 g's. |
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Colby
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Joined: 30 March 2009 Location: Abbotsford/Sask Status: Offline Points: 665 |
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Posted: 20 September 2010 at 11:49am |
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Believe me, I'm very aware of this and the fact that it seems wrong when dealing with a vehicle's corning ability bugs me. Remember though that Newton's laws aren't always correct so I can only conclude this is one of those cases where they don't apply very well, at least until I learn more.
I completely agree with this.
I'm not suggesting you build a car with excessive lean, just that saving yourself a bunch of money by going with the Koni reds may not be such a bad thing. If I had them, I would just set the shocks to their softest setting then adjust the rear struts until the car had more or less neutral steering. If I found there was too much roll or understeering still, then I would change the sway bars. I don't have enough experience to tell you for certain that doing it like that would be the best way, but it seems like it should at least be a fairly good way. Ultimately it's your car and your decision and I'm just telling you what I'd do if I had enough extra money to afford it. At least with the adjustable shocks and struts you can play with the overall stiffness a bit and decide what you like more. |
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88 Formula 5 speed
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Romeo
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Joined: 16 November 2008 Location: Canada Status: Offline Points: 3033 |
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Posted: 20 September 2010 at 12:09pm |
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That's more or less what I'm going for. I've been back on the simulator, and at the moment I'm trying to tune the shocks to find the behavior I want, as well as keeping an eye on the lateral g rating.
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Never shift into reverse without a back-up plan.
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Colby
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Posted: 21 September 2010 at 12:01am |
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Some good reading relating to this topic here (specifically, shark93726 and Monza76's posts have good info). And finally I find some kind of explanation as to why softer suspensions can improve grip:
The more I learn the more I appreciate how complicated of a subject this is. |
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88 Formula 5 speed
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Patrick
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Joined: 19 April 2008 Location: Vancouver Status: Offline Points: 5 |
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Posted: 21 September 2010 at 11:47am |
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That is a very informative thread. After reading it I suspect the lowered (and very stiff) suspension on my '84 now actually contributes to perhaps worse handling than stock, but you know what Johnny Boy says... "It doesn't have to perform, it just has to look good."
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Romeo wrote:
