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4WD vs. AWD. What's the Difference?

outsideonline.com

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Re: 4WD vs. AWD. What's the Difference?

#171

Post by lsllc »

mariusc23 wrote: post #165
lsllc wrote: post #163

Alright, time to bust a myth. As an AWD owner, every time I have a tire issue, they tell me I need to replace all 4 even if the others are good ... because AWD. "Won't someone think of the tires ... the tires need to to be the same size so they can rotate at the same rate." Clearly, with AWD the car is designed to allow wheels to rotate at different rates (hence the diffs). Otherwise you would't be able to make a tur…

The reasoning I've heard is that your differential will get worn out.

That makes no sense to me. Unless you are driving in straight lines, the 4 wheels will always be turning at different rates (and consequently, the front and back axles will be rotating at different rates).

Re: 4WD vs. AWD. What's the Difference?

#172

Post by TylerE »

SomeCallMeTim wrote: post #51
blackguardx wrote: post #5

Earlier quoted context omitted.

Generally a sign saying you need 4wd in the US really means you need a lot of ground clearance. Your car probably would have high-centered, that is stuck resting on the middle of the car with the tires in the air. The annoyed ranger was probably just tired of pulling stuck tourists out.

>Generally a sign saying you need 4wd in the US really means you need a lot of ground clearance The Subaru Outback (AWD) has 8.7" of ground clearance. The Ford Explorer ("Intelligent" 4WD) has a ground clearance of 7.8". If "Intelligent 4WD" means some kind of differential, then it really is just a marketing term at this point, though I learned about the distinction between 4WD and AWD when I bought a Subaru.

It's about more than just ground clearance. Approach and departure angles matter too. The Outback has long overhangs, especiially the front.

Re: 4WD vs. AWD. What's the Difference?

#173

Post by linsomniac »

I don't really buy this article. The terms AWD and 4WD don't really define a set of functions, but the article says they do then waves hands at all the exceptions.

Really, from what I've seen, current usage is AWD is a 4WD system marketed for on road use, and 4WD is an AWD system targeted to off road use. The biggest indicator seems to be if a vehicle has a low range transfer case, it will likely be marketed as 4WD. Also, if it is marketed as 4WD, HOPEFULLY it will have under body armor.

Remember, not all AWD/4WD systems are equal. Last winter our neighbor's Subaru Impreza with Symmetric AWD (which Subaru claims is super good) couldn't make it up a small incline by our houses. Both my Audi and Land Cruiser on all season tires had no problem.

Re: 4WD vs. AWD. What's the Difference?

#174

Post by TylerE »

rconti wrote: post #37
kinofcain wrote: post #18

There's a lot of blurring and different labeling of 4WD systems based on the market segment. Generally it's more helpful to think of 4WD/AWD as fitting into three categories: 1: A system with a transfer case that predominantly drives one axle (almost always the rear, and almost always labeled "4WD"). This is your typical pickup truck 4wd system. When it is engaged, the two axles are locked together and may as well be…

Right. I've got a Golf R with Haldex; it allows 30+mpg under cruising conditions but can "lock 100%" in the sense that the fronts and rears are locked together. It's created a lot of forum wars because some people read the marketing materials saying "100% of torque to the rear wheels" or "max 50/50 split" and don't understand the difference. If it's fully locked, on dry pavement, of course you're getting 50/50. If th…

Can't wait to get one of those, just waiting on my TDI buyback...

Re: 4WD vs. AWD. What's the Difference?

#175

Post by djsumdog »

linsomniac wrote: post #173

I don't really buy this article. The terms AWD and 4WD don't really define a set of functions, but the article says they do then waves hands at all the exceptions. Really, from what I've seen, current usage is AWD is a 4WD system marketed for on road use, and 4WD is an AWD system targeted to off road use. The biggest indicator seems to be if a vehicle has a low range transfer case, it will likely be marketed as 4WD.…

I owned a WRX that I never got stuck in snow. I once came up to a hill with a Sabb and Civic both spinning; and a semi-truck that couldn't really move when they were in the way. I had to wait for both of them to give up, left off my clutch, and crawled up the hill.

Re: 4WD vs. AWD. What's the Difference?

#176

Post by [deleted] »

justinph wrote: post #100

In real life, in most situations, ground clearance, good tires, traction control and ABS make more difference than driving all four wheels, most of the time. Personally, I'm more concerned with stopping than starting, and that's where ABS and good tires matter and what kind of transmission you have doesn't. This is a sales pitch video, but it is interesting to illustrate the differences in AWD approaches, with differ…

[deleted]

Re: 4WD vs. AWD. What's the Difference?

#178

Post by zensavona »

taneq wrote: post #155
sunstone wrote: post #33

Earlier quoted context omitted.

And in the next paragraph "To counteract this [sending of power to the wheel of least resistance] , the better AWD cars are fitted with a center differential that contains a clutch or viscous drive unit. This splits torque front-to-rear, directing it away from the spinning wheel. " So, a well engineered AWD system actually sends power away from the slipping wheel(s) and towards the wheels with traction, which makes m…

Everyone's focusing on the technology involved, but that's kind of pointless because AWD isn't a technical term. It's a term to distinguish an on-road car with four driven wheels from an all-terrain car, because when the first WRXes and such came out, people saw 4WD and thought that meant they could be used to go bush bashing.

Take her for a bush bash m8

Re: 4WD vs. AWD. What's the Difference?

#179

Post by rsync »

Animats wrote: post #146
mcpherrinm wrote: post #136

Earlier quoted context omitted.

One more thing to think about, on this line of questioning, is efficiency in "normal" driving situations. If you're driving in a straight line, with good traction on all wheels, will a single larger motor be more efficient than two smaller ones on each wheel? For many people, I think that's 99% of their driving, so it makes sense to optimize. Especially on electric vehicles, where increasing battery capacity is much…

One motor per wheel, in the wheel, is an old idea. It's been used most notably on LeTourneau heavy equipment. The usual problem is too much unspring weight, not a problem for giant earthmovers but bad for fast cars. Michelin was pushing it for cars, with their "Active Wheel" concept, from about 2003 to 2012.[1] That seems to have disappeared. Siemens has demoed a motor-in-wheel unit, and Volvo and Nissan have fooled…

"One motor per wheel, in the wheel, is an old idea. It's been used most notably on LeTourneau heavy equipment. The usual problem is too much unspring weight, not a problem for giant earthmovers but bad for fast cars."

hmmm ... I wasn't thinking about motors in the wheel, although I am familiar with that concept.

I was thinking about a more pedestrian motor per wheel configuration wherein the motor is just behind the spring ... and is thus, sprung weight ... is there even space for that ?

Re: 4WD vs. AWD. What's the Difference?

#180

Post by fungi »

taneq wrote: post #155
sunstone wrote: post #33

Earlier quoted context omitted.

And in the next paragraph "To counteract this [sending of power to the wheel of least resistance] , the better AWD cars are fitted with a center differential that contains a clutch or viscous drive unit. This splits torque front-to-rear, directing it away from the spinning wheel. " So, a well engineered AWD system actually sends power away from the slipping wheel(s) and towards the wheels with traction, which makes m…

Everyone's focusing on the technology involved, but that's kind of pointless because AWD isn't a technical term. It's a term to distinguish an on-road car with four driven wheels from an all-terrain car, because when the first WRXes and such came out, people saw 4WD and thought that meant they could be used to go bush bashing.

just got a 2nd hand impreza, can confirm more then a couple flogged cars in the market!
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