AWD vs. RWD?

[Caspuh]

OK, seriously, what's with the all-wheel-drive crap? I understand how it could be an advantage in the rain or under 30 mph, but other than that, is it really better? It seems like it would add alot of un-balanced front-end weight and drivetrain loss.

What's the deal?

[JamesM3M5]

You can put the power down coming out of turns earlier on an AWD car. Audi's Quattros always carry the heaviest weight penalty in Touring car classes because of this. The RWD cars carry more weight (EDIT--I meant WEIGHT PENALTY) than FWD cars. FWD is probably the worst choice for a pure racecar.

[ihooklow]

Check out the latest issue of Grassroots Motorsports. They do a comparo... "Front, Rear, or All-Wheel-Drive" (RSX Type S, 330i, and WRX, respectively).

All three of these cars were put on the same tires and are close enough in the power-to-weight ratio (the BMW suffers with an extra #/hp - but hey, it probably had the nicest interior and lowest cabin noise).

The WRX wins in both wet and dry times despite the tight course which is usually not a turbo's strong suit.

[JamesM3M5]

Was this an autocross or track event?

I need to get a subscription. I would rather read stuff than read about it. Always a step behind....

[oober]

I used to drive an AWD turbo Talon.

A few things about AWD that are GREAT and that I miss.
1) Launching at 6500 RPMs, and DROPPING the clutch with out tire spin. That Is FUN.
2) Traction in Wet weather (mentioned above)
3) being able to apply power earlier in the exit of a corner, (mentioned above)
4) less tire wear, because of less spinning of the tires
5) braking. (with ABS disable, Not installed-whatever) You are not going to lock up one or more tires if the car is in gear.
6) FUN in the SNOW

Someone mentioned Drivetrain loss and additional Weight.
That is Made up for with the improved traction and ability to Power out of corners faster.

And finally - 4 Wheel Drifts!!!!! (made easy)

[saitam]

I have both a AWD Subaru Legacy and RWD BMW

AWD is no crap. It gives you a big safety advantage.

RWD is more fun only when you know how to drift/drive.

[SilverStreak]

All the best dragsters out there are RWD, not that I'd ever drive one of those in the rain... :D

[DSK M3/4]

my last vehicle was a GMC Typhoon. 4.3L turbo w/ fmic and some other goodies, AWD, 245 tires. well over 300hp at the crank. some of the Typhoon and Syclone crowd would remove the front propshaft to create a RWD truck, and they would do burnouts for days. with the AWD in place, traction was amazing. it does add extra weight, but when you can pull a 60' time in the 1.7 range with street tires, the AWD pays off.

[B.Watts]

Originally posted by oober
5) braking. (with ABS disable, Not installed-whatever) You are not going to lock up one or more tires if the car is in gear.

AWD has no effect on braking. If anything it owuld make the front tires easier to lockup due to the engine braking also being applied to them or a bad downshift entering a turn.

Depending on how my braking bias is set, I can lock up the front or REAR tires on a RWD car. Same for a FWD car. Same for an AWD car.

[ihooklow]

The tires may break traction and slide, but they should not lock up if the car is in gear (they will continue to spin under engine power) unless you try really hard.

I really don't think that this has any advantage, I am just clarifying what he was referring to.

[ihooklow]

Was this an autocross or track event?

I need to get a subscription. I would rather read stuff than read about it. Always a step behind....


The GRM article was on an autocross setup at Michelin's facility in SC.

GRM is a great magazine, and not being BMW-specific (biased), you can get some really good information there. Including suspension, braking, tires, etc. as well as good driving advice. One good suspension / braking tip is easily worth the price of the subscription.

Their subscription cost ($19.99) is about half their otc price (8 x $4.99). I highly recommend it.

[JasonJ75]

Originally posted by ihooklow
The tires may break traction and slide, but they should not lock up if the car is in gear (they will continue to spin under engine power) unless you try really hard.


Wait a sec...

AWD + Car in Gear + ABS off +standing on brake = stalled engine.

Unless you're on the gas which wouldn't make sense...

[ihooklow]

Originally posted by JasonJ75
Wait a sec...

AWD + Car in Gear + ABS off +standing on brake = stalled engine.

Unless you're on the gas which wouldn't make sense...

That's why I put the "unless you're trying really hard" statement in there. I was more referring to normal braking situations. Like I said, it also provides no advantage (esp over ABS) imho.

[B.Watts]

Originally posted by ihooklow
The tires may break traction and slide, but they should not lock up if the car is in gear (they will continue to spin under engine power) unless you try really hard.

Actually, I guarantee you that I can lockup all four wheels of an AWD car without even applying the brakes. All it takes is a downshift to 2nd gear at about 100mph.

As for not being able to lock the brakes with the throttle applied, why would you ever apply throttle while braking hard anyway (save for a few mid-corner left foot braking situations on a race track)?

And actually, the brakes on modern cars are more powerful than the engine anyway. Hence the reason a car accelerates to 100 mph from 0 much slower than it can brake from 100 to 0. You would be able to lockup the brakes regardless.

[CJ]

Anyone know how hard it is to convert say an A4 to RWD? Can it be done? Advantages, disadvantages?

[ihooklow]

Originally posted by BMWRacerITS


Actually, I guarantee you that I can lockup all four wheels of an AWD car without even applying the brakes. All it takes is a downshift to 2nd gear at about 100mph.



You had better hope that you loose traction - or you just lunched your motor and/or ate your steering wheel.

I would disagree with the lockup however. I think that although you would be sliding, the wheels would still be turning - unlike locking up the wheels with the brakes.

Either way, I think this still falls into the category of 'trying really hard'.



As for not being able to lock the brakes with the throttle applied, why would you ever apply throttle while braking hard anyway (save for a few mid-corner left foot braking situations on a race track)?


Who said ANYTHING about applying brakes while under throttle?



And actually, the brakes on modern cars are more powerful than the engine anyway. Hence the reason a car accelerates to 100 mph from 0 much slower than it can brake from 100 to 0. You would be able to lockup the brakes regardless.

You can remove the word 'modern' from the above statement. Brakes have always been more powerful than engines. (I am sure there are some genius american muscle car engineers/designers/owners to whom this does not apply...) Physics has quite a bit to do with this as well (drag, friction).