8/6/2019 FWD vs RWD

1/21

As we see most the cars that is produced inIndia is Front-Wheel Drive(FWD) cars,

only some cars are Rear-Wheel

Drive(RWD) like Omni,Ambassador e.t.cSo my question is, why doesn't India

produce RWD?

Karthik.

its because rear wheel drive cars needmore energy to push the car. and in a rear

wheel drive car, most of the enegry getswasted more that what we loose in a frontwheel drive, and that indirectly effects

your mileage and in india, people arealways behind mileage and stuff so we

hardly find RWD cars. this question wasactually answered this way in someautomobile show. im not exactly sure in

which channel

I would say it primarily revolves aroundhigher production cost, as RWD would callin for safety devices which would increase

the cost and not all indians are autoenthusiast and they want to just move

8/6/2019 FWD vs RWD

2/21

from point A to B without much of anissue. So it would be wise for the

manufacturers to invest in producing a car

which could solve this purpose ratherthan thinking about a RWD which wouldincrease the production cost.

i was searching the internet after reading

a few post on here and stumbled acrossthis.....and it kinda put an end to some ofmy questions. hope it helps others

What Offers the Best Performance? FWD,RWD, or AWD?

Agent009 submitted on 7/9/2007 OfficialAutoSpies Timestamp: 3:13:39 PM

SOURCE: www.world-challenge.com

Front Wheel Drive, Rear Wheel, or AllWheel Drive, the age old question which is

the best way of quickly getting around atrack.

FWD fans tout predictability and overall

8/6/2019 FWD vs RWD

3/21

consistency as hallmarks of the drivetrain. Many claim that properly set up

front wheel drive vehicle is just as fast

any one else.

RWD advocates on the other hand tend tofocus on intangible balance and control

factors of the vehicle, and the ability toplace the rear drive wheels exactly at the

appropriate angle to maximize power to

the wheels upon acceleration. Soundsgood in theory at least.

AWD zealots throw all arguments out ofthe window and claim that with all 4

wheels driving, maximum power andtraction go to the ground at all times.

While parasitic drive train drag is a factor,many times it is made up be deterioratingtrack conditions.

There are countless one off tests showing

the strong points of all of these formatsbut due to rules classification they rarely

meet on the track in an all out test ofprowess. Great for the theories, but shorton factual proof. However if you look a bitcloser, the melting pot of all racing the

SCCA Speed World Challenge Touring Car

8/6/2019 FWD vs RWD

4/21

Series does just that.

With displacement limited to 2.8-liters

and power ranging from 225 to 275 bhp,the vehicles can be FWD, RWD, or AWD.But the most important part, is that all ofthe formats fall into this category under

very controlled circumstances. FWDAcuras and Mazdas, RWD BMWs and

Lexus, and even AWD Audis all tangle in a

fiercely competitive racing series.

So who comes out top in a series whereconsistency and handling are at aparamount? Oddly enough to many, the

FWD Acuras and Mazdas typicallydominate the crowd, followed very closely

by the AWD Audis and RWD BMW teamsnipping at the heels.

But surprising to me, is the drive trainsmostly associated by enthusiast

everywhere for true handling performancethe RWD and maybe even the AWD

consistently fall in the middle of the pack.Actually save one victory this season by aBMW and another by an Audi thesesupposedly superior forms of transport

are routinely regulated to being

8/6/2019 FWD vs RWD

5/21

bridesmaids, not the bride.

The morale to the story for those of you

wanting to know, is that we can all bickerback and forth about who is the best. Butevery dog has his day, and in rare classeswhere everyone meets, the outcomes are

not always as expected.

Top Ten Drivers

1. Randy Pobst - TriPoint Motorsports

Mazda62. Jeff Altenburg - TriPoint Motorsports Mazda6

3. Pierre Kleinubing - RealTime Racing Acura TSX

4. James Sofronas - GMG/Greek Bros.Racing BMW 325i5. Peter Cunningham - RealTime Racing

Acura TSX6. Kuno Wittmer RealTime Racing Acura

RSX7. Chip Herr - STaSIS Engineering Audi

A48. Charles Espenlaub - Tindol Motorsports-Mazda69. Michael Galati - Tindol Motorsports-

Mazda6

8/6/2019 FWD vs RWD

6/21

10. Brandon Davis - RealTime Racing Acura TSX

* 25. Andrew Wojteczko(R)- AutoAnalyzer Racing- Lexus IS (only two racesthis season)

Manufacturer Points

Mazda 47 PointsAcura 32 Points

Audi 19 PointsBMW 17 Points

*Lexus 0 Points (only two races thisseason)

Prior to the fuel crises in the 1970's, rearwheel drive was king. Just about everyvehicle, from economy to luxury, came

with rear wheel drive. The shift from rearwheel drive to front took about a decade.

Since the mid eighties, just about everyeconomy car, family sedan, minivan andeven many sport coupes came with front

wheel drive. Luxury marks such as BMWand Mercedes-Benz continued on with

8/6/2019 FWD vs RWD

7/21

rear wheel drive but Cadillac eventuallymoved every vehicle to front wheel drive.

Once again, times have changed. Over the

last few years we've seen more and morevehicles (re) introduce rear wheel drive.Why? Well, it simple.

As cars become more powerful it isdifficult to have one set of wheels doing

the steering and the accelerating. By

having the front wheels do the steering,and the rear wheels driving the car, you

get a better-balanced vehicle. Thiseliminates torque steer and improvesacceleration. Rear wheel drive offers

better weight distribution (much closer to50/50 than fwd), which in turn offers

more predictable handling. Finally, withthe advent of traction control and stabilitymanagement systems, the front wheel

drive advantage in slippery conditions hasbeen significantly reduced. More and more

rwd vehicles have the option of AWD aswell. If nothing else, this is a great way

for automakers to hedge their bets. Still,some consumers are skeptical of rearwheel drive. Perhaps they are the victimsof clever marketing by Madison Ave. that

tried to get people to accept fwd and

8/6/2019 FWD vs RWD

8/21

forget all about the virtues rear wheeldrive. They did a great job. Perhaps too

good.

Today cars are more powerful yet yieldbetter fuel economy. As such, we can lookat fwd and rwd more objectively. Is one

better than the other? Fwd still holds anadvantage in terms of packaging

efficiency, offering greater interior room

in a smaller package. Rear wheel driveprovides better handling and acceleration

and with the addition of traction control,virtually eliminates the fwd advantage inthe snow.

In the end, it depends on what you want

from your car. If it's performance, you'relooking at rwd. If you're indifferent,perhaps looking for a small car with

greater interior volume, it's front wheeldrive for you. Over the last 20 years,

technology has improved both layouts,reducing the advantages of fwd to a point

where rwd is a viable option for mostpeople. Ultimately, you've got morechoice, and when more choice is offeredwe all win.

8/6/2019 FWD vs RWD

9/21

Front or Rear Wheel Drive?

One of the many issues to consider when

designing a recumbent, is whether tomake it front or rear wheel drive (FWD orRWD). The choice is not clear cut. Eachapproach has its strengths and

weeknesses, and like all good design, youhave to find the best solution fit for your

specific requirements.

FWDMoving BB

FWDTwist

Chain

RWD

Limitationssteepgrades

steepgrades

-

PSI manageable

minimal -

Chainline simple complex complex

Adjustability

easier harder harder

SteeringBehavior

oversteer oversteer

understeer

The above table attempts to compare the

relative advantages and disadvantages of

8/6/2019 FWD vs RWD

10/21

each approach, however these aregeneralizations, and the devil, as always,

is in the details.

LimitationsFirst and foremost the significant

limitation of FWD designs is theirpotential to loose traction on steep grades(hills).

Minimum 60:40 weight distribution

On level ground, the FWD recumbentshould have more weight distributed tothe front wheel than the rear. Ratios of

60:40 or higher are reccomended.

8/6/2019 FWD vs RWD

11/21

Loss of traction of steep grades

The problem is that as the grade becomessteeper, the weight distribution changesto favor the rear wheel. The illustration

above is extreme, and most riders even on

hilly terrain don't consider FWD traction asignificant issue. If however you are

planning to ride off road, the frictioncoefficient of gravel, mud and dry grass is

much less than tarmac, so traction willbecome a limiting factor. You can reducethe impact of grade on weight distribution

by keeping the seat height low andincreasing the wheelbase.

Pedal Induced Steering

8/6/2019 FWD vs RWD

12/21

Effect of Trail on FWD

One significant issue for FWD designs is

the effect of trail on dynamic stability andpedal induced steering (PSI). To illustrate

this, the diagram above represents theview looking down on a 20" front wheel

that is moving forward down the page. Ithas a 75 pivot angle, 20mm of fork offsetand is leaning 30 to the left. As the frontwheel leans, the contact patch moves to

the inside of the pivot axis. This isbecause the contact patch is moving

around the outside wall of the tire. This

causes the driving force (Red) to generatea turning force (Blue) around the pivot

axis, but because the application ofhuman power using pedals is not

constant, the turning force oscillates.

8/6/2019 FWD vs RWD

13/21

These oscillations will generatesympathetic harmonics at certain cadence

frequencies due to the shifting weight of

the legs while peddling, and theirinteraction with the dynamic trackingbehavior of caster.

On FWD twist chain designs, having a

shallow pivot axis, short trail and longtiller minimizes the impact. On FWDmoving BB designs however, the turning

force will interact with the pedal force,alternating between cooperation and

opposition. At some cadence frequenciesthis actually eliminates PSI effects andworks well, at others, particularly high

cadence it causes stability problems.

Chainline

In my experience chainline management

is the single biggest issue in recumbentdesign. You can come up with a beautifulbike or trike, but if you can't transfer

power efficiently form you feet to thedrive wheel(s), then you will have to

revise your design.

8/6/2019 FWD vs RWD

14/21

FWD moving BB chainline

The FWD moving BB design is used bythe TT, Cruzbike, Speculoos,Python

lowracer and Flevobike, as well asthe Hipperion trike. When properlydesigned, pedal induced steering can be

kept to a minimum. This is a challenging

configuration, but in the case of thePython lowracer, it can produce a verylight bike. The direct, unencumberedchainline is also the most efficient, the

chain routing used in the other designshas been reported to consume over 5

watts.

http://traylorfwd.home.mindspring.com/http://www.cruzbike.com/http://les-velos-de-laurent.skynetblogs.be/http://www.python-lowracer.de/http://www.python-lowracer.de/http://www.flevobikeusa.com/http://personal.eunet.fi/pp/davinci/fill.htmlhttp://www.cruzbike.com/http://les-velos-de-laurent.skynetblogs.be/http://www.python-lowracer.de/http://www.python-lowracer.de/http://www.flevobikeusa.com/http://personal.eunet.fi/pp/davinci/fill.htmlhttp://traylorfwd.home.mindspring.com/

8/6/2019 FWD vs RWD

15/21

FWD twist chain chainline

The FWD twist chain design has becomeextremely popular of late, particularly in

the HPV racing scene. This design isfavored by fully fared streamliners used inHPV speed trials because it helps to keep

the frontal profile of the faring to a

minimum.

RWD chainline

8/6/2019 FWD vs RWD

16/21

RWD is by far the oldest and most widelyused chainline design. It is constrained by

the seat height -- make the seat high and

you can have an unencumbered chainlinelike the Cycloratio -- make the seat lowand you have to route the chain over thefront wheel and under the seat. For a

tadpole trike this is less of an issue thanfor a bike, in that you only have to route

the chain under the seat, but the front

cross member and steering tie rods canalso get in the way.

Adjustability

FWD moving BB adjustablity

One of the challenges all recumbentdesigns face, is making the distance fromthe seat the bottom bracket (BB-BOS)adjustable. It is often undesirable to make

this adjustment by moving the seat

http://www.jetrike.com/cycloratio-brochure.htmlhttp://www.jetrike.com/ergonomics.html#BB-BOShttp://www.jetrike.com/cycloratio-brochure.htmlhttp://www.jetrike.com/ergonomics.html#BB-BOS

8/6/2019 FWD vs RWD

17/21

backwards and forwards, because thismay upset the ride quality and handling

characteristics. Most designs incorporate

some variant of a telescopic boom.However with most chainlines, thisrequires adding or removing chain links tomake the adjustment, on the theory that

once fitted to the rider, the BB-BOSdistance never needs to change. If

however you are planning to race in a 24

hour HPV event with a team of riders,quick changeovers are a requirement. The

FWD moving BB design is rather unique inthis regard, the bottom bracket can bedesign for adjustment without any need

to modify the chain. The alternative forrouted chain lines is to have a longer

chain and use an adjustable chaintensioner on the return run.

Steering Behavior

The angle between the direction a wheel

is pointing and the path along which itactually moves is called the slip angle.

Slip occurs under power when a trike isturning. It also occurs under breaking asthe tire approaches its traction limit.

Under power the weight distributionusually moves to the rear of a vehicle, but

human power being as limited as it is,

8/6/2019 FWD vs RWD

18/21

acceleration forces are rarely an issue,unless you ride a unicycle. Under breaking

the weight distribution moves to the front

outside wheel.How the steering behaves under power is

dependent on the weight distribution andthe friction coefficient of the tire and road

surface. Steering behavior becomes morepronounced when the friction coefficientis low i.e. a verge with loose gravel while

cornering. Too much weight at the rearcauses the rear to spin out (oversteer).

Too much weight at the front causes thefront wheels to plough (understeer).Neutral handling is when the weight is

evenly distributed between the front andrear, but generally slight understeer is

considered safest.

RWD understeer behavior

RWD trikes have a tendency toundersteer. This is because the drive force

is pushing the trike forward in a straight

8/6/2019 FWD vs RWD

19/21

line, and the front wheels slip forward asthey turn. It is only the friction of the

front wheels on the pavement, not the

driving force that turns the trike. Thelocation of the optimal CoG also creates aweight distribution that favorsundersteer.

Under the decelerating forces of brakingthe steering behavior may be completelydifferent. It is dependent on the dynamic

weight distribution, which is directlyinfluenced by the location of the rider CoG

in relation to the front contact patches,the seat height, the brake forcedistribution, and the amount of brake

force applied.

FWD oversteer behavior

FWD trikes have a tendency to oversteer.The drivetrain pulls the front of the trikearound the corner. It is only the friction ofthe rear wheels on the pavement that

prevents the rear of the trike from

8/6/2019 FWD vs RWD

20/21

spinning out. However because the weightdistribution is already biased towards the

front wheel to improve traction, these

forces tend to cancel one another out. Incompetitive racing, particularly on shorttracks with lots of cornering, riders mayprefur the responsive feel of slight

oversteer, but it carries the added riskthat the rider may loose control. Too

much oversteer will make a trike unstable

and dangerous.I have confirmed this behavior with

Jetrike. When turning sharply enough ongravel so all three wheels drift, the trikeis generally well balanced, if however

traction is completely lost, oversteercombined and an abrupt loss of

momentum is the frequent result, butbeing a trike, easy to recover from.

Soloviov S-4 all wheel drive trike

http://www.trike.ru/http://www.trike.ru/

8/6/2019 FWD vs RWD

21/21

The S-4 trike pictured above, features allwheel drive (3 x 3), which would actually

come in handy on icy winter roads. It all

comes down to what your requirementsare. For most trikes the critical safetyissue is how well it handles underextreme breaking and cornering

conditions, and that is all about thelocation of the rider CoG and weight

distribution.