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Author Topic: Front Wheel drive ! rear Wheel drive...they're the main two eh ?  (Read 11660 times)

Offline neilep

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Dearest Nude Degree Owners And Manifest Makers of My Awe,

(yea....ewe know you're klevur don't cha ??..well that's because ewe are !!...and I am eternally grateful for it !! :))

See my Bugatti Veyrons here !



Nice eh ?...This blue one is for Monday to Thursdays and the red one:



.............is for Fridays and the weekend !


Now, I knows that cars go vroom vroom and go and stop.....which is nice !!

But..I also know that you can get cars that are front wheel driven and rear wheel driven !!..LOL...someone even told me ewe can get four wheel driven cars  !!..LOL !!..yeah right !!..I wasn't born yesterday y'know !! ::) ::)

So....what's the main differences between front and rear wheel drive cars?

What about performance ?...grip ?......economics ?......y'know....all that kind of stuff ?

What process determines which way the car is to be driven ?

Thanking ewe with les hugs et les shmisheys

neil
xxxxx

mwah mwah mmwah mwah..





 

Offline ukmicky

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Neil
Can i have my car back please.you said you only needed the keys so you could clean the inside of the windows. Next time I'm taking it to the car wash.  [:(!]

In general most expensive high performance cars have rear wheel or 4 wheel drive as it improves handling .  Front wheel drive cars are generally easier and cheaper to produce and also allow for more space inside the cabin for your feet due to there being no need to have a tunnel for the gearbox or prop shaft.
 
The main differences however are in the driving characteristics . As a car accelerates you get weight transfer to the rear of the car this causes the front of the car to lift and at the same time the rear squats down ,this reduces traction to the front wheels causing them to spin and lose traction.

Obviously a high powered high performance car would just wheel spin if it was front wheel drive due to this and therefore its advisable to have most of the power being directed to the rear wheels where the weight transfer goes .
Having a lot of power being directed out of the front wheels can also cause torque steer which occurs when one of the front wheels grips more than the other and can cause the car to jerk violently to the left or right.

Front wheel drive cars also tend to understeer around fast bends, in other word's they continue in a straight line. Whilst rear wheel drive cars tend to oversteer where the back of the car steps out and tries to over take the front of the car. Of the two oversteer is preferable as it can be easier to control and in racing situations a good driver can still accelerate whilst oversteering. If a car understeers your only option is to come off the gas.

Even though rear rear drive is usually preferred most of the problems with front wheel drive can be overcome if the car is set up right or has has limited slip diffs or traction control fitted. However these devices come at extra cost and cant eliminate the problems totally.
« Last Edit: 22/12/2007 16:19:51 by ukmicky »
 

another_someone

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Additional consequences:

Front wheel drive means the front wheels do all the work - both power and steering, so the front tyres burn out quicker, while the rear remain largely untouched.  With rear wheel drive, it is more balanced.

Four wheel drive has not even been touched above.  The steering characteristics of 4 wheel drive (whether it understeers or oversteers) depends on whether more power is sent to the front wheels or the back wheels, but in general the effect will be less pronounced than on 2 wheel drive cars.  On the other hand, some cars (Honda CR-V, and many of the more recent Audi's) are part time 4 wheel drive, where they drive 2 wheel drive (for efficiency) most of the time, but switch to 4 wheel drive when traction gets difficult - but that means you can get half way through a bend, with strong understeer, and suddenly find the understeer disappears half way through the bend - which can be disconcerting.

Since you have transmission going to all 4 wheels, you have transmission systems going both front and back, and so you have slightly greater inefficiencies due to friction effects in the extra transmission (although if a 2 wheel car loses traction, you waste even more energy, where a 4 wheel drive car would still be effectively laying its torque down on the road rather than burning rubber).

The main benefit in 4 wheel drive is because you are driving 4 wheels rather than 2, you are spreading the driving load between all 4 wheels, so each wheel is doing less work, and so is less likely to lose traction (this is also complimented by most 4 wheel drives having some sort of limited slip differential, so even if one wheel does spin, it will not drain all the power from the other 3 wheels).  This is what makes 4 wheel drive cars good in situations where there is limited grip (mud, ice, snow, etc.).  On the other hand, because of the limited slip diffs, it is imperative that all the tyres have about equal grip (otherwise you burn out the limited slip diffs), so when you change one tyre, you should change them all, so they all have about the same depth of tread, and so equal grip.

I love 4 wheel drive because of the security the extra grip on the road gives you, but otherwise, rear wheel drive is certainly the more fun to drive, as the oversteer allows you to balance the steering on the throttle, and can allow you you nicely swing the tail out to pull you around sharp bends in a way that front wheel drive just wont allow.  Ofcource, the ultimate in overstear was the old beetle (not the mockery of a beetle that VW sells at present), which was not only rear wheel drive but rear engined (thus also avoiding a tunnel through the passenger cabin) - having the weight at the back, combined with the power at the back, really did throw the back out in the bends (the Porsche 911 had the same set-up) - but with so much oversteer available, you have to be very careful lest you end up pointing in the direction you came from.
« Last Edit: 21/12/2007 04:25:18 by another_someone »
 

Offline lightarrow

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Probably one of the main reasons most present day cars are front wheel driven is for security: the engine shields the pilot in case of front collision.
 

another_someone

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Probably one of the main reasons most present day cars are front wheel driven is for security: the engine shields the pilot in case of front collision.

On the contrary, I would have thought.  What shield the driver these days is the crumple zone, and the engine will merely add a problem if it actually intrudes into the cabin area.  The best this to have in front of the driver is lots of air into which the crumple zone can fold.

In any event, are you really talking about front wheel drive there, or simply front mounted engines?  It is true that rear wheel drive cars tend to have longitudinally mounted engines, whereas most small front wheel drive cars in recent years have transverse mounted engines, but I am not sure that makes much difference in safety, but it makes a lot of difference in compactness (although that very compactness actually is detrimental to safety).  Then you have cars like the Mercedes A-class, that has the engine under the cabin area, and the smart car that is one of the few cars that have rear mounted engines.
 

Offline lightarrow

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Probably one of the main reasons most present day cars are front wheel driven is for security: the engine shields the pilot in case of front collision.

On the contrary, I would have thought.  What shield the driver these days is the crumple zone, and the engine will merely add a problem if it actually intrudes into the cabin area.  The best this to have in front of the driver is lots of air into which the crumple zone can fold.

In any event, are you really talking about front wheel drive there, or simply front mounted engines? 
The second, because usually it means that it's also front wheel drive.
 

another_someone

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The second, because usually it means that it's also front wheel drive.

But how many production cars exist on the market that do not have an engine on the front - even amongst rear wheel drive cars.

Yes, the smart car, some mid engined sports cars, the Porsche 911 and some of its variants are rear engined - and what else?

All the major rear wheel drive saloon (most Mercedes, BMW, Jaguar, larger Fords, Vauxhall Omega, and many others), and all 4 wheel drive cars of any sort, all have the engine in the front.

On the other hand, the Mercedes A and B class are front wheel drive, but don't have front engines - just to show there is no guarantee in either case.
« Last Edit: 21/12/2007 17:38:55 by another_someone »
 

Offline that mad man

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I don't own a car any more but you are making me miss my old Hillman Imp, rear engine/drive and economical.

The only other current rear engined car I can think of is A VW Beetle.

As a note, not long before I bought it petrol had almost doubled in price, going from 17p to 32p per GALLON! [:0]

 

another_someone

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I don't own a car any more but you are making me miss my old Hillman Imp, rear engine/drive and economical.

The only other current rear engined car I can think of is A VW Beetle.

You mean current at that time (although the Porsche 911 was based on the same design, and certainly there was an old Skoda 100/110 from 1969-1982).

The Beetle (the rear engined, rear wheel drive version) is no longer current, although it continued to be manufactured in Mexico until 2003 (the new Beetle is front engined, front wheel drive).
 

Offline that mad man

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The Beetle (the rear engined, rear wheel drive version) is no longer current, although it continued to be manufactured in Mexico until 2003 (the new Beetle is front engined, front wheel drive).

 [:0]

Well that has surprised me. A friend has one, rear engine type, and it seems so new!

Thanks for the info another_someone.  :)
 

lyner

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The reason for so many front engine - front wheel drive cars must be price, in the end.
I read, in Colin Chapman's book on sports cars (years ago) that a front wheel drive car is better behaved when cornering under easy to moderate conditions.  Cornering improves a bit as you continue to 'drive' round a bend because of the slip angles of front and rear wheels. There is less likelihood of oversteer, which happens with RWD cars. Oversteer is very confusing and dangerous for your average driver. FWD is not as much 'fun' to drive like a mad thing -but how many of us want to do that very often?
 

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