A Sports Car For a First Car?

[Bo]

All of the big brands do, but Renault has a TV channel so that's even better.

 

[kikie]

I understand that there's a language barrier, so I'll try my best to correct misconceptions where there may be any. You may already know some of what I said in Dutch, but just not expressed correctly in English; in which case, I apologize. Note that I am (and has been) very specifically speaking about oversteering not due to increasing engine output (putting your foot to the accelerator pedal).

You know Dutch?

With that last caveat, I guess that's a fair generalization. I think something like "engine forces" will be a better term because just "forces" is too general. Technically gravity is exerting a downward force and the road is exerting a normal force that is equal and opposite of gravity (assuming the road is flat). Just because the two forces don't cancel each other out does not mean that they don't exist. There are more forces acting upon a tire than just forces due to engine output.

I know that. I only used the forces applied to the tires by the engine because in a 4WD, the engine forces are applied to all 4 tires and with a 2WD, the forces are applied to only 2 tires. The more forces applied to one tire, the faster this tire will reach it's threshold and starts losing grip.

Why? (Let me give you a hint, if two cars are identical in every way other than one is 2WD and the other is 4WD, then the maximum force that a tire can handle without sliding is the same)

I don't agree. You can definitely carry more speed through a corner with a permanent 4WD than with a 2WD. As I said, all the engine forces are applied to the 2 wheels of the 2WD car, which means more forces are applied to each wheel, which mean the forces a tire can handle is reach earlier than when all force are applied to 4 wheels (tires). With a FWD, the car will understeer much earlier than with a 4WD. With a RWD, the car will start to oversteer faster than with a 4WD, making a 4WD to have more grip and can carry more speed through corners.

It's really not the speed that is higher that's causing the forces to be higher. It's that a higher speed (vector-less, direction-less) causes a higher acceleration in order to maintain that speed, thus the higher acceleration that is causing a higher force.

Yup, it's acceleration, not a constant speed.

Only one net force. There are multiple forces acting on the tire, which aren't too important when traveling at a constant velocity, but they do get very important very quickly as soon as you accelerate.

There are more forces active on a tire but I wasn't trying to explain that. I was only explaining the fact that the engine force are distributed over 4 tires with a 4WD instead of onto 2 tires with a 2WD. If the engine forces are distributed onto 4 tires, the combined forces on this tire will exceed the forces a tire can handle much later than when all the engine forces are applied to only 2 tires. In this case, the two tires will exceed their grip limit faster, losing grip earlier than with a 4WD.

I'm not 100% sure if you are saying what you said up there, but ummm...

So if you turn, a "sideway force" is indeed added, but it's the sum of the "sideway" and "straight forward" force that matters. If the sum of the two forces exceed the tire's maximum static friction (the tire's grip capabilities), then the tire will start to slip.

That's what I basically said but in other words. I said "a secondary sideway force is applied to the tire", which is basically saying that there are two force (probably more but that's not the point in this post) active.

If you turn a secondary sideway force is applied to the tire. If the sideway force exceeds the straight forward force and the tire isn't designed to cope with this sideway force, this tire will lose grip and you have understeer.

It's not that a 4WD car is "grippier" than a 2WD car. The two have the same amount of grip at the tires. The maximum amount of static friction a tire has does not change whether it is 2WD or 4WD. It is that a 4WD car can put a greater amount of power to the ground when accelerating out of the corner without slipping than a 2WD car because as you said, the forces are distributed to four wheels instead of two.

But then this is untrue during lift off oversteer as there's no engine power at that time (technically there's engine braking, but let's ignore its effects for now).

That's what I wanted to say with grippier. Don't forget, my first language is Dutch, not English.
I wasn't talking about lift off oversteer in this example.

Those don't matter. It only matters that we assume two cars are exactly identical except one is 2WD and the other is 4WD. This doesn't happen in the real world, so the practical effects may be slightly different, but as a thought process, one must assume that the only difference is the number of drive wheels, otherwise, one would be unable to attribute what caused the difference in vehicle behavior.

It does matter.
When I was controlling (oversteer) a car with a limited slip differential, it was very difficult to keep the car under control. A fraction of second too late when counter steering and you will lose the car.
A standard road car with a standard diff on the other hand, is much easier to control.

As far as I know, a differential divides the forces of the engine, and other forces as well when you push the clutch, over the engine powered wheels. So it does matter. Even the shockabsorbers are an important in the "grip of a tire" thing.



Pfff, I think I'm going to stop discussing this. My brain wants to stop. It's too much trying to explain everything in English what I'm actually thinking.

 

[Azuremen]

I don't agree. You can definitely carry more speed through a corner with a permanent 4WD than with a 2WD. As I said, all the engine forces are applied to the 2 wheels of the 2WD car, which means more forces are applied to each wheel, which mean the forces a tire can handle is reach earlier than when all force are applied to 4 wheels (tires). With a FWD, the car will understeer much earlier than with a 4WD. With a RWD, the car will start to oversteer faster than with a 4WD, making a 4WD to have more grip and can carry more speed through corners.

You've missed the part where drive train doesn't magically give tires more traction.

It does matter.
When I was controlling (oversteer) a car with a limited slip differential, it was very difficult to keep the car under control. A fraction of second too late when counter steering and you will lose the car.
A standard road car with a standard diff on the other hand, is much easier to control.

Umm, how much have driven cars with LSDs, because what you are saying is the exact opposite of what most drivers would claim to experience.

 

[Crash]

You know Dutch?

Oops, I mean English. Brain fart there, my bad.

I know that. I only used the forces applied to the tires by the engine because in a 4WD, the engine forces are applied to all 4 tires and with a 2WD, the forces are applied to only 2 tires. The more forces applied to one tire, the faster this tire will reach it's threshold and starts losing grip.

But oversteering is not only achieved by adding engine force; it can be achieved via other means.

I don't agree. You can definitely carry more speed through a corner with a permanent 4WD than with a 2WD. As I said, all the engine forces are applied to the 2 wheels of the 2WD car, which means more forces are applied to each wheel, which mean the forces a tire can handle is reach earlier than when all force are applied to 4 wheels (tires). With a FWD, the car will understeer much earlier than with a 4WD. With a RWD, the car will start to oversteer faster than with a 4WD, making a 4WD to have more grip and can carry more speed through corners.

No it doesn't. The maximum speed that a vehicle can carry through a corner is determined by the maximum static friction available to the tires.

So how does 4WD vs 2WD change the tires' maximum static friction?

Hint: static friction = coefficient of friction * normal force exerted on the object.

It does matter.

When I was controlling (oversteer) a car with a limited slip differential, it was very difficult to keep the car under control. A fraction of second too late when counter steering and you will lose the car.
A standard road car with a standard diff on the other hand, is much easier to control.

That's opposite of what is commonly said about limited slip vs normal differentials.

That aside, how does the differential impact that maximum static friction that a tire can hold?

 

[ZHPbimmer]

I could get an MK1 Miata, those are awesome, not practical at all though, lol. Never know that about GSRs! Would have never guessed that they are high theft.

EX-R, hmmmm, not my thing, I can be very picky.

What about this? http://vancouver.en.craigslist.ca/rch/cto/4265556667.html

Please, no. You do not need or should ever have an M3 as your first car. Dont even give me "it's not that fast, only an e36" BS.

You'll crash it and probably hurt yourself.

 

[SVX]

Can I put my question in here? I'm 14,

Yay, another 14 year old.

 

[Bo]

Yay, another 14 year old.

I thought I was alone in my age when I first joined the site.

 

[Brend]

One of the reasons I want a Renault is so I can walk around with all this stuff:

You need a car to buy over-priced tat?

 

[Bo]

You need a car to buy over-priced tat?

Yes, precisely .
It would be pointless wearing a Renault shirt and watch, whilst carrying a Renault umbrella and writing in my Renault notebook with my carbon fibre Renault pen if I didn't actually have a Renault, wouldn't it?

 

[Brend]

Yes, precisely .
It would be pointless wearing a Renault shirt and watch, whilst carrying a Renault umbrella and writing in my Renault notebook with my carbon fibre Renault pen if I didn't actually have a Renault, wouldn't it?

Suppose I see your point, but still...being an ehtusiast would be enough merit to buy it surely?

 

[Bo]

Suppose I see your point, but still...being an ehtusiast would be enough merit to buy it surely?

I like Honda, therefore I own a Honda pen (X2), Honda plastic bags, Honda Racing sunglasses, Honda keyring and I keep all the brochures and flyers that are Honda related. I've got this obsession with buying everything brand related.

 

[SVX]

I thought I was alone in my age when I first joined the site.

I was alone for awhile.

 

[Zenith]

Human beings, who are almost unique in having the ability to learn from the experience of others, are also remarkable for their apparent disinclination to do so.

-Douglas Adams