Geralds car is now a space frame/tube chassis hybrid, as are most low budget race cars (by low budget these days we mean anything under 6 figures). Chassis rigidity is not an issue, the problem is that the original spring rates were too high for the lower weight. This brings about two problems, too much weight transfer to the outside tires, and tires which can leave the road surface when the hit small irregularities in the track surface.
Too many people still subscribe to the archaic "traditional American" method of making a car "handle" (and I use that term loosely), stiff springs and sway bars with soft shocks (oversprung and underdamped). GM is particularly guilty by using shocks with almost no jounce resistance, and then fairly stiff in rebound. Try it sometime, take a brand new GM original shock for a Fiero and try to push the piston in, there is almost no resistance, now try to pull it apart, very stiff. Shady mechanics would use this demo to show unwitting customers that their shocks were worn out just to bilk them out of the repair cost. Anyway, cars like that feel stiff and light on there feet, but only if you do all of your driving doing circles on billiard tables. In the real world they bounce slip and slide. Many early muscle car "tuners" would actually just install better shocks and change the alignment to get more caster and suddenly these cars were transformed (some even installed softer springs and smaller front sway bars).
Well, its late, I am not an engineer, or even a mechanic, I am just a teacher, so who listens to me anyway The last car I modified was a 1976 Monza, but boy did I drive the Trans Am guys nuts when they tried to keep up on a winding road. Times have changed and cars have become more sophisticated, but Newton's Laws of Motion still hold in the macro world of our automotive pursuits. Philosphising??? I must be tired.
Good night
Ira "Page 2 is mine!!!", did I actually type that, God I really am tired!!
[This message has been edited by Monza76 (edited 08-06-2003).]
in addition to reading his post I looked at his site and the pic's there and still think his car needs the roof steel replaced by a full cage to tie the front and rear together you can't be tooo stiff but you sure can flex tooo much esp if you cut out major parts like a roof
------------------ Question wonder and be wierd are you kind?
In some cases, yes you can throw out the math (physics, laws, etc) Otherwise how can you explain why 2 cars, identical in every way, same exact engine/trans/rear end, will totally run completely different. Dont math say same exact car, same engine and everything else, even with same driver should run exactly the same? I can almost guarantee than you can take any 2 random (same models, same equipment) cars off the dealer lot and find differences from subtle to extreme between how they both run.
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07:26 AM
Pyrthian Member
Posts: 29569 From: Detroit, MI Registered: Jul 2002
well, I'll take it by observation. the best handling cars, cart/F1, are light. the worst handling cars, or should I say trucks, are heavy. but also, where the wegiht is matters. cart is low & light. truck is heavy & high. then theres the oddballs - heavy & handles. but, these are low also. so, I'd say weight is importnant, but not as important as Where You Put The Weight. 2 cars - identical. add 200 pound pole going 10 feet straight up off the roof. this car will not handle at all. same car, add the 200 pounds as a undercarriage plate down the center of the car. it MAY handle better - i dunno the answer here. I suppose at this point it depends on what you started with.
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10:02 AM
Will Member
Posts: 14226 From: Where you least expect me Registered: Jun 2000
In some cases, yes you can throw out the math (physics, laws, etc) Otherwise how can you explain why 2 cars, identical in every way, same exact engine/trans/rear end, will totally run completely different. Dont math say same exact car, same engine and everything else, even with same driver should run exactly the same? I can almost guarantee than you can take any 2 random (same models, same equipment) cars off the dealer lot and find differences from subtle to extreme between how they both run.
Originally posted by rogergarrison:I can almost guarantee than you can take any 2 random (same models, same equipment) cars off the dealer lot ....
isnt that what the IROC race was? everyone gets an identical camero?
they have the same idea in catamaran sailboat racing (olympics) - everyone gets an identical boat, 30 minutes to adjust it the way they want, and first boat across the finish line wins.
There are many variables in a race car, and few can be changed without affecting others. Like rayB said, taking the sheet metal out of the roof seems innocent, but it removes the trianglation that gives the frame stiffness.
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07:43 PM
Razor_Wing Member
Posts: 1753 From: Blowing Rock, NC, USA Registered: Apr 2003
weight effects handeling, handeling does NOT effect wheight
When a car goes into a turn, the weight of the car leans away from the turn, which hurts handeling, by minimizing weight, you minimize this effect, there fore greatly improving handeling. Also, wight effects acceleration and braking by having more mass to get moving on take off and greater velocity at lower speeds to stop. Hope this helps man! .
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07:48 PM
Aug 8th, 2003
joeformula88 Member
Posts: 114 From: arnhem, the Netherlands Registered: Mar 2000
Only thing in this discussion I cannot understand is how large body roll can have a positive effect on cornering, especially saying it will distribute weight more evenly over the tires (left/right). The way I see it is that body roll raises the center point of gravity, therefore inevitably putting MORE pressure on the outside tires. Am I missing something??
The larger amount of body roll that results from a softer suspension does not change weight transfer. When the body gets fully leaned over, the weight transfer is the same regardless whether the suspension is stiff or soft. (It does take longer for the body to lean over on a soft suspension though, and this "can" cause other problems with handling if not properly addressed with better shocks, etc.)
And, larger amounts of body lean do NOT raise the center point of gravity. The inside of the car does go up, but the outside of the car goes down, net effect, zero.
The improvement in traction is obtained because with softer suspension rate, the tires are better able to follow little bumps and jiggles in the road without losing traction. (If the surface of the road were absolutely smooth, then there would be no need to soften suspensions, and a go-cart with no suspension would stick as well as suspened cars)
A softer suspension also requires that the car have a more sophisticated way of keeping tires vertical with body roll, as well as stiffer shocks, properly proportioned, to control the suspension.
Keep in mind, that neither extreme is the best solution, there is a best comprimise somewhere between the two extremes, and finding that best comprimise is the goal of nearly all forms of racing or performance driving.
All we advocate is that you should not think that stiffer is always better. Quite often, I have found that the oem springs and sway bars are very close to ideal for maximum handling without problems on a street car, requiring little more than addition of the correct size rear bar, and much better shocks, to balance the car. (along with some alignment and bushing improvements)
Basically, the rougher the road you have to drive on, the softer the suspension should be to maintain best traction. Ask a dirt track driver, they will tell you they run much softer spring rates than asphalt track drivers, to get better traction.
joeformula88 I never meant to imply that body roll helps cornering, all I meant was that a car can have so much roll stiffness that the outside tires are overworked. Cars with good shock control can have a lot of body roll and still handle well while a stiffly sprung, monster barred car with soft shocks may be flat but has little grip since the tires are either overloaded or bouncing off the road surface much of the time.
Provided the suspension design has no major flaws, then Stiff shocks, low unsprung weight, adequate spring rates (not too stiff) and sway bars sized to balance the weight distribution will give a neutral handling car with lots of grip. The Fiero 84/87 has only two bad habits to deal with, rear bump steer (feels worse than it is) and trailing throttle oversteer (a trait common with a lot of cars with a rear weight bias, and even some without). Very stiff rear control arm bushings and solid cradle mounts will reduce those problems to manageable levels. The unsprung weight with the stock brakes is already very low, stick with smaller diameter wheels (16" or less) since they are generally lighter and do not carry the bulk of the weight (the rim) so far from the centre. Don't get carried away lowering the car, a little is for handling, a lot is cosmetic and will probably compromise handling. Spring rates are not too bad stock so leave those (unless you are using coilovers to adjust your suspension). Use the larger rear tires and use the best shocks you can afford, set them up fairly stiff, but not too stiff, the suspension still has to move . Set the alignment for a little more caster and a little negative camber, remember, no toe out at the rear and then play around with sway bars to get the balance (that is really what the bars do best). Because of the large steering axis of the front suspension, it is difficult to get that great steering feel that some cars are famous for, the kickback and the use of a steering damper numb that a little (but I do not recommend removing the damper, the steering can get a little spooky at high speeds and will try to wrench the wheel from your hands over curbs and bumps).
Oops, rambling again. My ideas are based on my experiences with other cars, my extensive reading on handling dynamics and a fair bit of input from Gerald Storvik, Will, Doug Chase and a few others on the forum. Be warned, for every person who knows what he is talking about there are at least two who sound like they know better (but don't). Get some good books on handling and read them, and take advice from people who have real experience in racing (not street racers, some are knowledgeable but most just cross the line between brave an foolhardy).
Ken, that is exactly the point, if it is a very tall vehicle with a high CG it may overturn, but more likely it will slide or break away.
Earlier someone mentioned four wheel drift, this is a condition where tire slip angles are very high but the car maintains grip. Do not confuse this with breakaway, because that now means that the tires have lost their grip.
The situation you describe in your last post has the entire mass of the car, plus the additional forces produced by the lateral acceleration, on the two outside tires. This will provoke a slide. If the suspension were a little softer some of the load may still be carried by the inside tires, however all cars, regardless of how good they handle, will reach the point where the tires let go, it is how the car makes the transition that is important. Does it warn you that it is about to go or does it just slide out from in under you? That is often far more important than cornering power.
Basically, the rougher the road you have to drive on, the softer the suspension should be to maintain best traction. Ask a dirt track driver, they will tell you they run much softer spring rates than asphalt track drivers, to get better traction.
Yep. The spring rates on my rally car are about half of what the road racers use. I'm 200 rear and 450 front with no sway bars. Those of you who saw the car on Waterford can attest to that.
In honesty, I think I'm a little low on spring rates even for my purposes, but even if I go up 50% I'll be less than the pavement racers.
quote
Originally posted by Monza76:
Be warned, for every person who knows what he is talking about there are at least two who sound like they know better (but don't).
Ain't that the truth. In anything.
------------------ Doug Chase '88 Fiero Formula 5-spd (autocrosser) '88 Fiero GT 5-spd (daily driver) '85 Fiero GT 5-spd (rally car) '87 Fiero SE V6 5-spd (for sale $2200) '88 Fiero Formula 5-spd (parts car / future rally car #2) Custom roll cage fabrication available Custom exhaust fabrication available
The last car I modified was a 1976 Monza, but boy did I drive the Trans Am guys nuts when they tried to keep up on a winding road. Times have changed and cars have become more sophisticated, but Newton's Laws of Motion still hold in the macro world of our automotive pursuits. Philosphising??? I must be tired.
.
