GT3

^I said some relative ease, implying, yes, there is some strain but not enough to crazily distort the chassis to the point where the suspension works improperly with changing geometry.

I think of it this way. Evos are still Lancers with hopped up powertrains. People love to stiffen the suspension, which may increase structural loads to the chassis rather than the suspension absorbing the shock. Those cars are still continually bumped from 400hp-700hp. I don't really recall being much done to the chassis except what, a couple of tower braces and a roll cage?

Bravodor

No Id still say ease.The chassis is steel, it is not going flex because of rubber on road.Youd need a hell of a footprint to ever get the force to do that.HP isnt really important because your tires would never stay planted to use that HP, especially in FWD.a cheap steel rod about one inch in diameter or less with easily support 500 pounds, you dont think the reinforced, braced, and metallurgically superior thick car frame cant handle a few pound foot of torque limited entirely by friction of relativly thin rubber on realativly smooth concrete.Mabey if you had 2k plus HP and sticky dualies on a civic you might manage to go back quickly.

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"The Greatest Sophistication is Simplicity."

GT3

A chassis isn't always 100% steel.

A rubber tire doesn't fully compress before the suspension takes action. There's still 30-40psi worth of air pressure that transmits shock through the suspension system, connected to chassis.

Now in a FWD car with massive horsepower, the tires don't stay completely on the road with full contact patch, and that's true. But, the tires do expand internally because of heat (from friction of the tire) expanding the air within the tire, and tires are not perfectly round under hard acceleration under heavy power. The effect is a vibration or oscillation effect, little amplitude, but high frequency. Obviously that energy transmits through the driveaxles and into the powertrain, but at the same time, the suspension arms and chassis are sharing the abuse as well. Average road cars aren't meant for that kind of high frequency. I think F1 cars are.

Flex may be minimal and hardly felt, but it's still present. Otherwise things like strut tower braces and elaborate roll cages wouldn't really be necessary. When those items are on a car, it's easy to tell how much the car handles the road and heavier lateral loads. Why? Minimal to no chassis flex while the suspension geometry remains consistent during cornering forces and absorbing shock as well. Steering always seems to feel more direct and responsive.

That being said, if factory chassis's were that strong, factories wouldn't need to add so much torsional rigidity with cars over 300hp. It's just additional cost.

Now, it takes a boatload of HP and torque to really get noticable chassis twist to comprimise torsional rigidity under acceleration and other driving conditions, but hypothetically, it's quite possible.

allone

So, is it possible to twist the chassis on a FWD car bad enough to cause it to shoot into a curb causing damage? The car in question is a beast...an 06 honda civic with 140hp stock, with an ebay fart can muffler.

ps. no I don't really believe it, I just know a guy who made this claim. Blames the damage he did by being an idiot on twisting his chassis while drag racing his awesome (automatic) JDM civic, yo.

Bravodor

Usually the base chassis is some for of steel or steel alloy, just for the cost to strength ratio and the ease of availability, but yes some are alluminum and other metals. But still, average car, still has a mostly steel frame.


The oscillation will not bother the chassis much because it is free to vibrate at will, it would have disasterous consequences if it ever reached the natural frequency of the steel frame...

But that would be almost impossible to attain, even in a lab, the frequency would never be high enough.

Now going around a corner in a high HP car, or a FWD car, you could easily flex the chassis, probably not to the point of permenant deformation, but in a really weak car it wouldent be that unlikely if the tires had good grip.

That would be less about the engine's power and more about the weight of the car and grip of the tires.

But were talking about from a standstill right ?, theres no cornering or momentum forces invovled.


The thing is, cars are mabey what 6-7 feet across, less for a smaller car, think about how the force is being applied, its running parrallel to the chassis, and its reinforced by a complicated truss system.


Even if the chassis were just a steel box, it would handle a 3000 HP take off with little difficulty, because you could never get enough of that 3000 on the ground to exert anywhere near the pounds per inch needed to deform steel, with only a minor perpendicular force, past its point of deformation. With enourmous tires it might flex a little, but would go right back.

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"The Greatest Sophistication is Simplicity."

GT3

Excellent point. I think I am thinking of cornering forces and just initial load under acceleration.

But from what I know, it's never good to even get close to the chassis limit with the effect of raw horsepower on a car. Leeway is necessary for horizontal and cornering loads under stress, unless the car is going to the Salt Flats all the time.

Bravodor

Well yes, the chassis would need much more strength if conering hard, but thats not as much a factor of its power as it is the grip of the tires, the suspension set up, and the weight of the car.

My only real point being, you cant really bend a chassis with excessive HP because the tires cant put it on the ground. I wasnt really arguing that chassis' didnt need to be strong, just that they didnt need to be strong to prevent the engine from bending them.

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"The Greatest Sophistication is Simplicity."

VTEC_Dreams

Really, he wasn't talking about the engine, guys. It was a CHASSIS question, as in suspension/tires/wheels/body. So, Lambospeed, now that the guys before me have muddled the question to no end and with no point other than to denounce FWD in every essence of the word, I'm going to awnser your question simply.

Yes.

If you exceed the limits of the chassis with aggressive tuning or by driving it wrecklessly it can be dangerous to drive a FWD car. There really is an extremely fine line between scary snap oversteer and steady, helpful oversteer with every drivetrain layout. In FWD cars, it's easy to overtune the suspension into oversteering and therefore getting yourself a car that tries to turn around backwards at every corner. Too much stiffness in the rear end will get you just that, as will overtly aggressive tire pressures. Even an unmodified car can be dangerous, and though everyone on here seems to think that FWD cars just understeer to oblivion, it's not hard to flick out the rear end if you know what you are doing. The problem is, most folks don't know what they are doing and they end up basically drifting into the median/guardrails/off a cliff. Name of the game? It's all in how you drive.

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Anyhow...

Godzilla:PetroLHeaD

i don't know if you meant me but i already know that and that's not what i meant. but thanks.


^^ yes, this is what i meant. but not only FWD.



thanks guys. I'm going to have to do more research on this topic though.

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Rest in Peace Randy.