Four wheel drive physics question

[flatbutt]

I've been driving 4X4 for years . I'm aware that the absence of a center differential is a critical factor which makes running in 4X4 on a dry road a really really bad idea .I know it can cause all kinds of damage due to lack of slippage and inability to compensate for differences in grip between the tires and I don't do it.

What I can't figure out is why running in 4X4 on a dry road can cause a flip over.

Any explanation from the brain trust?

[kaisen]

Cause it? No way

Play a factor? *Maybe*, but it would be a stretch

If there were loads of grip and no slip, the axles can wind-up (bind) with a tension that forces one wheel to suddenly "spring" that kinetic energy. If the truck were already at the limit in a curve I suppose it might be the grain of sand that makes the cart tip. But, like I said, it would be a stretch. It can cause quite a tug at the steering wheel, so perhaps that's a more likely cause of losing control.

[M.D. Holloway]

AWD v. 4x4...

I tried to explain the difference to my Son and got all twisted up in my explanation. Any help would be appreciated

[lm6y]

Easy Lubey, AWD has a differential in the transfer case that will allow the front, and rear tires to spin at different speeds, usually allowing the torque bias to go to the tires that are gripping the most. 4WD sends torque equally to both front, and back all the time.

Flatbutt, I've never heard of 4X4 CAUSING a flip over on ANY type of surface. Now can it make someone with a less than optimal grasp of physics ten feet tall and bullet proof? I've seen that many times, and it never really ends well.

[5String43]

Also, AWD doesn't have a low range, true 4WD does.

As for 4WD causing a vehicle to turn turtle, I do not believe it's a factor.

[vash]

maybe if the tires going around the outside of the turn belong on a fully locked up 4x4 (like with air lockers), and you are going into the turn all herky-jerky on a grippy surface..the extra grip on the outside will pitch you over.

i know using 4x4 on the streets is a bad idea. my truck has a rear locker..it goes around a turn..not smooth. add some speed, i guess it could happen

[M.D. Holloway]

Originally Posted by lm6y

Easy Lubey, AWD has a differential in the transfer case that will allow the front, and rear tires to spin at different speeds, usually allowing the torque bias to go to the tires that are gripping the most. 4WD sends torque equally to both front, and back all the time.

Flatbutt, I've never heard of 4X4 CAUSING a flip over on ANY type of surface. Now can it make someone with a less than optimal grasp of physics ten feet tall and bullet proof? I've seen that many times, and it never really ends well.

Yup, that help thanks! I explained that the 4X4 was fixed while AWD wasn't. He asked me to draw it out and thats when things got dicey. Prolly the site 'How it works" would be a good pictorial instead of my scratches

I did a decent job explaining torque convertors though, used the idea of two fans facing each other and instead of having air between them they have oil. One is driving the other driven and the fluid is pushing the blades. While the idea that fluid could transfer such power is difficult to understand until you start messing with hydraulics and what not.

I gotta get a good gear set up to explain it better - using a real gear box would be pretty heavy and costly. A working plastic model of different transmissions would be cool. I gotta look into that.

[intakexhaust]

Running what one would call the 'old traditional' 4wd can enhance a situation for a rollover on tarmac. Much of this is attributed to conventional differentials and one side of the vehicle unloading the inside of a radius.

This site is decent for understanding AWD Audi all wheel drive explained | awd cars, 4x4 vehicles, 4wd trucks, 4motion, quattro, xDrive, SH-AWD, Haldex, Torsen, wiki - How it works
Remarkable how its all evolved. I don't know if much of the old school awd performance driving applies anymore. The new stuff is so idiot proof, you just mash it and steer.

A good book on the subject was AWD High Performance Driving by the meister Vic Elford (I think that was the title??).

[intakexhaust]

Originally Posted by lm6y

Easy Lubey, AWD has a differential in the transfer case that will allow the front, and rear tires to spin at different speeds, usually allowing the torque bias to go to the tires that are gripping the most. 4WD sends torque equally to both front, and back all the time.

Flatbutt, I've never heard of 4X4 CAUSING a flip over on ANY type of surface. Now can it make someone with a less than optimal grasp of physics ten feet tall and bullet proof? I've seen that many times, and it never really ends well.

Not all AWD behave this way. It wasn't until the late 1980's when Gleason introduced the torque sensing differential which put power to the wheel with the most friction.

[Dottore]

I believe it's relatively intrinsic.

[vash]

Originally Posted by Dottore

I believe it's relatively intrinsic.

Ha!

[M.D. Holloway]

been on-line looking for a model of different transmissions. While I did come across info on models of transmission communication (which is interesting in its own right!) I still haven't found a kit to build different transmissions.

[Laneco]

Add alcohol or stupidity to the equation and any result is possible.

angela

[herr_oberst]

Originally Posted by Laneco

Add .... stupidity to the equation and any result is possible.

angela

Exactly what I was thinking, it's that bulletproof mentality some have when driving the 4x4 that might cause it to flip over.

[svandamme]

4x4 vs AWD only affects grip... if anything , less grip is less likely to flip and 4x4 should have less grip then AWD..

[fastfredracing]

Originally Posted by herr_oberst

Exactly what I was thinking, it's that bulletproof mentality some have when driving the 4x4 that might cause it to flip over.

Last night, was our first real snow here, no real accumulation but the roads had a light covering, and were slippery. I'm doing the speed limit, when some joker in his quad cab 8 ft bed powerstroke blows by us at I'm guessing 75 mph. I guess he wanted to be the first to the scene of the accident.

[flatbutt]

thanks guys. I've just heard some anecdotal type comments on dry surface rollovers. Like I said I couldn't figure it. Thanks for the verification.