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beach and sand

Posted: Tue May 18, 2004 7:25 pm
by jpoyann
Hello!
Yesterday I went to the beach with my Legacy Turbo (sedan). My trip last 1 yard. The car atasked. And tring to take off, only rear whiles had traction. And I trought what kind of 4WD have I bought?. Can somebody explain this to me.
Thanks for your help.
Jose

Posted: Tue May 18, 2004 7:30 pm
by vrg3
It is very difficult for any car to drive through sand. The best way to drive on the beach is normally to keep the car above the sand.

If you deflate the tires, that helps to keep the car from digging into the sand.

Also, if the wheels start to spin at all, you have to immediately stop applying power. Otherwise, they will dig a hole and get stuck.

Also, if the front wheels are slipping, sometimes you have to turn the steering wheel to a different angle to find grip.

Posted: Tue May 18, 2004 9:51 pm
by BAC5.2
It's very simple. Our cars aren't 4-wheel-drive. They are All-wheel drive.

There's a very significant difference. 4WD sends power to both axles evenly. The axle determines which side has power bias, but not front to rear. It is a dead on 50/50 split.

AWD uses a vicious coupling that detects wheel slip (wheels slip, fluid heats up, power is transferred to the other wheels). Your front wheels will slip, and when that happens, the fluid heats up and sends power to the rear.

Like Vikash said, if you start to spin wheels stop applying power or you will sink. This is where traction control like that found on the VW Toureag and the manual system on the Hummer (H1, real balls Hummer). When wheelslip is detected, the brakes are applied to that wheel.

If in the sand, the right rear starts to slip, the brake is applied to that wheel and power is transferred to the other wheels. The Toureag and other SUVS of nature do this automatically. The Hummer requires you to press the brake pedal while you are on the gas to get this effect.

For weighing 10,000 pounds (not an exageration) the Hummer is one of the best vehicles you can have in the sand. Torque to move a house, ULTRA low gearing in 4-low, CTIS, and the traction control. Plus, they look cool.

Posted: Tue May 18, 2004 9:54 pm
by vrg3
BAC5.2 wrote:AWD uses a vicious coupling that detects wheel slip (wheels slip, fluid heats up, power is transferred to the other wheels). Your front wheels will slip, and when that happens, the fluid heats up and sends power to the rear.
That's not quite true... Assuming we're talking about a manual transmission (which is the one that has the viscous coupling), torque is normally sent evenly to both axles. Wheelspin causes the center differential to partially lock, to try to prevent excessive speed differences; that's all.

Posted: Wed May 19, 2004 2:30 am
by BAC5.2
Thanks for the correction, my mistake.

Posted: Wed May 19, 2004 11:34 am
by jpoyann
Yes, it has a manual transmition. So then my car has an all-wheel-drive system and it´s no possible to drive in the beach. Isn´t it?

Posted: Wed May 19, 2004 3:12 pm
by vrg3
It is possible to drive on the beach. You have to be very careful and you should follow the suggestions that both I and BAC5.2 gave.

You should also remove the mud flaps if your car has them.

Posted: Wed May 19, 2004 5:19 pm
by evolutionmovement
Keep in mind that sand (especially salty beach sand) will corrode your car quickly. I recommend at least washing the underneath and wheel wells out thoroughly afterwards. And bring an air compressor to reinflate the tires when you leave.

Steve

Posted: Wed May 19, 2004 7:48 pm
by BAC5.2
And bring a shovel and a few 2x4 planks (2x6 planks are better, 2x12 are the best).

If you've got street tires of ANY kind, stay off the sand.

Posted: Wed May 19, 2004 11:02 pm
by rsstiboy
if its anything like the aussie RS's you will also have a 1.1 centre stepper making the front diff 3.9 and the rear diff 3.545, hence why your rears were spinning more than your fronts, it also makes it impossible to get your car on a 2wd dyno simply by removing the tailshaft........
basically you will need load on the front axles and rear axles to make your car go forward/backward

Posted: Thu May 20, 2004 3:49 am
by THAWA
interesting, the only AWD car like that here is the impreza wrx i believe. same ratios too. All the others are 1:1

Posted: Thu May 20, 2004 5:52 am
by BAC5.2
Yea, the WRX has the 1.1 center diff.

Did you know.... The STi's 4th gear is the same ratio as the 5MT Turbo's 3rd gear?