awd/fwd when wanting to go cheap

[freeskier93]

with an open differential, there wouldn't be any biasing then because power always moves to the wheel with least grip. The braking force wouldn't be manipulated by the drivetrain then. If you have decent grip yeah that can have an effect but then the issue is moot unless you're like racing or something.

Again, in 4wd where the front and rear are locked together, this is not completely true. In a braking scenario only one wheel on an axle could lock up, the other cannot as long as at least one wheel on the other axle has traction. In terms of powering the wheels, as long as the wheels on one axle have traction the wheels on the other axle cannot spin, however if one wheel from each axle has no traction then they will spin.

 

[tortillasoup]

Again, in 4wd where the front and rear are locked together, this is not completely true. In a braking scenario only one wheel on an axle could lock up, the other cannot as long as at least one wheel on the other axle has traction. In terms of powering the wheels, as long as the wheels on one axle have traction the wheels on the other axle cannot spin, however if one wheel from each axle has no traction then they will spin.

I was thinking along the lines of a full time 4wd vehicle where there is a center differential. Yes, locking up the center differential helps and having locking hubs helps moreso.

 

[jlee]

I was thinking along the lines of a full time 4wd vehicle where there is a center differential. Yes, locking up the center differential helps and having locking hubs helps moreso.

How would locking hubs be relevant in this case? All they change is they allow the wheel to spin freely (independent of the front axle) when unlocked.

 

[Eug]

just got the snows on our AWD Hybrid RAV4.

Again, if you're going to get AWD, you still need snows (if you're in an area that needs them). The winter tire purchase should not factor into your AWD vs FWD decision at all.

 

[tortillasoup]

How would locking hubs be relevant in this case? All they change is they allow the wheel to spin freely (independent of the front axle) when unlocked.

Read the earlier posts in regards to the benefits 4wd for braking purposes. In simplest terms, a 4wd vehicle with fully open differentials isn't really going to have much of an effect on braking performance because the wheel with the least grip will slip first whether accelerating or decelerating with engine braking. Using the hydraulic brakes will not behave any differently because when traction is limited, the wheel with the least traction will break free first.

But when you start locking up the center differential (if there is one) and the rear/front differentials, what happens is the two wheels on each axle are tied to each other so that they cannot spin faster than the other. If there is no center differential and the front & rear differentials are locked, then all 4 wheels are locked to the same speed so 3 tires could lose grip and the 1 with grip will make sure the rest don't get out of line by spinning slower/faster than the 1 with grip. I.e. They all are required to spin at the exact same speed. So when you're using the foot brake and braking force is being applied, a single wheel is less likely to break free due to being speed limited by the other wheel which should have more grip than the one that wants to break free. Tires with more grip will assist the ones with less grip by making sure they don't get out of control.


The vehicles yuppies drive don't have these features typically (fully locked differentials) so the argument over 4wd vs FWD, a FWD with snow tires is more than sufficient for most people because most people shouldn't be on the road when it's treacherous.

 

[jlee]

Read the earlier posts in regards to the benefits 4wd for braking purposes. In simplest terms, a 4wd vehicle with fully open differentials isn't really going to have much of an effect on braking performance because the wheel with the least grip will slip first whether accelerating or decelerating with engine braking. Using the hydraulic brakes will not behave any differently because when traction is limited, the wheel with the least traction will break free first.

But when you start locking up the center differential (if there is one) and the rear/front differentials, what happens is the two wheels on each axle are tied to each other so that they cannot spin faster than the other. If there is no center differential and the front & rear differentials are locked, then all 4 wheels are locked to the same speed so 3 tires could lose grip and the 1 with grip will make sure the rest don't get out of line by spinning slower/faster than the 1 with grip. I.e. They all are required to spin at the exact same speed. So when you're using the foot brake and braking force is being applied, a single wheel is less likely to break free due to being speed limited by the other wheel which should have more grip than the one that wants to break free. Tires with more grip will assist the ones with less grip by making sure they don't get out of control.


The vehicles yuppies drive don't have these features typically (fully locked differentials) so the argument over 4wd vs FWD, a FWD with snow tires is more than sufficient for most people because most people shouldn't be on the road when it's treacherous.

Ahh, okay. You initially said locking hubs, not locking differentials.

Locking differentials would cause that behavior, but the downsides of having differentials locked on the street are extreme. With a rear diff locked, you'll be much more likely to swing the rear end out and you'll be breaking traction in turns. With a front diff locked, a vehicle becomes much more difficult to steer (since the outer wheel isn't permitted to move any faster than the inner wheel).

Few vehicles have locking rear differentials (from the factory, anyway). Very, very few have locking front differentials. Other than getting un-stuck, I can't think of any situations where I would recommend locking front/rear differentials on a road.

*edit* Actually, I lied. During a snowstorm, I learned that one of my rear drum brakes was a bit sticky. It never stuck on dry pavement, but when the roads were covered in snow (up near the Grand Canyon) it would lock (and then drag) one rear wheel. I "fixed" (cough) it by locking my rear diff. It became un-stuck. :whiste:

 

[tortillasoup]

Ahh, okay. You initially said locking hubs, not locking differentials.

Locking differentials would cause that behavior, but the downsides of having differentials locked on the street are extreme. With a rear diff locked, you'll be much more likely to swing the rear end out and you'll be breaking traction in turns. With a front diff locked, a vehicle becomes much more difficult to steer (since the outer wheel isn't permitted to move any faster than the inner wheel).

Few vehicles have locking rear differentials (from the factory, anyway). Very, very few have locking front differentials. Other than getting un-stuck, I can't think of any situations where I would recommend locking front/rear differentials on a road.

*edit* Actually, I lied. During a snowstorm, I learned that one of my rear drum brakes was a bit sticky. It never stuck on dry pavement, but when the roads were covered in snow (up near the Grand Canyon) it would lock (and then drag) one rear wheel. I "fixed" (cough) it by locking my rear diff. It became un-stuck. :whiste:

All true. The people who have vehicles with locking front and rear differentials are those who do rock crawling and other extreme 4x4 activities.

 

[NutBucket]

The only vehicle I know of with 3 lockers from the factory is the G-wagon. I think some trucks offer rear lockers though.

 

[jlee]

The only vehicle I know of with 3 lockers from the factory is the G-wagon. I think some trucks offer rear lockers though.

Wrangler Rubicon?

The 80 series Landcruiser (and LX450) had front/rear lockers as an option (I had one), but the new ones don't.

 

[monkeydelmagico]

Locking differentials would cause that behavior, but the downsides of having differentials locked on the street are extreme. With a rear diff locked, you'll be much more likely to swing the rear end out and you'll be breaking traction in turns. With a front diff locked, a vehicle becomes much more difficult to steer (since the outer wheel isn't permitted to move any faster than the inner wheel).

It would have to break traction in order to turn regardless of if it was front or rear locked. Any time a diff is locked you better either be going straight (drag car) or have slippery surface.

I find some of the best AWD systems to be more of a hindrance than a help. False sense of security and getting stuck worse. We used to always go off roading without turning on 4wd. If you got stuck then you had the fall back ability to activate the 4wd and probably get un-stuck. With AWD systems you are already sliding off the road and stuck in the ditch before you realize it's too slippery.

With a FWD open diff car and some decent snow tires you will know before you are out of your driveway if you should stay home or not.

 

[jlee]

It would have to break traction in order to turn regardless of if it was front or rear locked. Any time a diff is locked you better either be going straight (drag car) or have slippery surface.

I find some of the best AWD systems to be more of a hindrance than a help. False sense of security and getting stuck worse. We used to always go off roading without turning on 4wd. If you got stuck then you had the fall back ability to activate the 4wd and probably get un-stuck. With AWD systems you are already sliding off the road and stuck in the ditch before you realize it's too slippery.

With a FWD open diff car and some decent snow tires you will know before you are out of your driveway if you should stay home or not.

Correct - but it's a hell of a lot harder to turn with a front diff locked than with a rear diff locked.

 

[freeskier93]

It would have to break traction in order to turn regardless of if it was front or rear locked. Any time a diff is locked you better either be going straight (drag car) or have slippery surface.

I find some of the best AWD systems to be more of a hindrance than a help. False sense of security and getting stuck worse. We used to always go off roading without turning on 4wd. If you got stuck then you had the fall back ability to activate the 4wd and probably get un-stuck. With AWD systems you are already sliding off the road and stuck in the ditch before you realize it's too slippery.

With a FWD open diff car and some decent snow tires you will know before you are out of your driveway if you should stay home or not.

That's not AWD being a hindrance, that's being a moron who doesn't drive appropriately for the conditions.

 

[Eug]

That's not AWD being a hindrance, that's being a moron who doesn't drive appropriately for the conditions.

Sounds about right.