How to drive down a steep gradient with auto rwd?

chris snell

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Staff member
Aug 15, 2005
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I have a set of Nokian Hakkapeliitta tires from my wife's old 2009 Lexus IS250. We kept the tires when she traded the car in. They have two winters on them, maybe 6 months usage. I will make you a good deal on them. Not sure what your Lexus runs with regards to tire size but it may be the same.
 

p m

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Apr 19, 2004
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Have a half-glass of whisky in your hand, and watch someone going from 0.1 mph to half the speed of sound going downhill - priceless.
 

kennith

Well-known member
Apr 22, 2004
10,891
172
North Carolina
Go faster?

Correct. There's a little more to it than that, though.

You must allow the vehicle to accelerate until the driven wheels rotate freely; directly between slippage and overrun. Once that speed has been reached, it is imperative to remain in the gear in which you mean to pass beyond the descent onto a level surface.

Some distance will be required to reach the appropriate descent speed. Even more distance will be required to slow the vehicle to a stop. This is why you can't do it in a populated area. You may have the room to accomplish the action, but any unexpected interference may place others or their property at risk.

Snow tires, and/or studs are the answer. I personally have never used chains, but I suspect the result would be similar. Once physical traction aids are employed, the vehicle can be slowed earlier, without further increases in speed.

You can freely manipulate a car on an empty stage, as you've got the whole road to use, and no bystanders. Even racing cars are equipped with studded tires when conditions warrant them.

If these tires weren't fitted, winter rally stages would be very short, slow events.:rofl:

Skill only takes you so far. Beyond a certain point, one must bribe the laws of physics.

Cheers,

Kennith
 

Blueboy

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Apr 20, 2004
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Back in the USA; Rockwood, PA
@Garrett-while I totally agree with you for the majority of the time to be in gear, on a cold day with the engine not up to temp the idle is slightly higher. You can feel the push when in gear. And as a rock wall sits across the curve coming down the bitch of a hill, I don't need to fight it. 0.1 mph might be slightly off however it is a creep going down in neutral.

@Dean-yes in my Saab which although frt wheel drive it doesn't really matter going down.

although said before it is worth repeating, snow tires and or chains are your best friends.

and if the hill is solid ice and you don't feel like chaining up, fuck it - wait till the salt truck comes.
 
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garrett

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Jun 18, 2004
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www.blackdogmobility.com
Nope sorry wrong - you don't get engine braking at 0.1 mph. Can it truly be so hard to read the actual question?:banghead:

My response wasn't directed to you, but rather stating to NEVER use neutral in an off-road situation - which is correct. Neutral is never going to the correct option. Add momentum in gear sure, but never place a vehicle in neutral. And yes you get engine braking and gear reduction at .1, .01, etc mph. Just not in your automatic RWD Lexus or whatever. Having the vehicle in gear is your back up plan so to speak. Creeping down in neutral and finding out it's not working and then having to put back in gear, stay on brakes, etc - let me know how that works out on a snowy, steep hill. I'm sure it would be fine....really.
 

K-rover

Well-known member
Jan 15, 2010
2,179
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Raleigh, NC
I personally wouldnt drive any RWD car on snow.. period! FWD is only sightly better. Although I had a 96 chevy cavalier V6 that would plow a road like nobody's business!

Snow tires make a huge difference as everyone has said, and I agree with Garrett to never use neutral.
 

Racer X

Well-known member
Jul 26, 2012
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NYC
I think its 225 50 R17 stock, but I will buy a set of wheels. I'll probably go with my old favs Michellins
Dedicated winter tires definitely, but I would choose Nokian over Michelin for winter tires any day. The Nokian Hakkapeliitta's are a pretty unbeatable winter tire, and would be my first choice over any of Michelin's offerings.
 

emmodg

Well-known member
Apr 17, 2006
4,273
1
Ooooooooh boy...

A RWD car is wholly different than a 4WD/AWD vehicle concerning engine braking. There is not enough gear reduction in a RWD vehicle to reap much benefit from engine braking going down hill. Your rear isn't "pushing" your front is. Vehicle weight is now biased towards the front and quickly surpasses your front tire's ability to support traction(the combination of grip and surface), steering input, and in your case braking. Your front begins tom"push". Snow tires give your wheels a "leg up" in conditions like the one you describe. Snow and gravel make it hard for your abs to function so you then need to rely on your ability to threshold brake. Cut braking and steering inputs to a minimum - don't make your front tires do more than they have to in sketchy conditions. (Search Kieth Code's $20-Rule as it concerns tires. He is an amazing motorcycle racing instructor and many race car instructors use this analogy as we'll.) When all else fails? Get her straight and keep it pointed downhill!

It's X-mas - treat you and you wife to a class at Skip Barbour or Team O'neal.
 

emmodg

Well-known member
Apr 17, 2006
4,273
1
To the original poster - hit up forums like Rally Anarchy and SCCA forums. Good stuff there. There's a few of us here that instruct off road driving at stupid slow speeds but translation to on-road vehicle dynamics is seldom found. Even whether or not be in in neutral or clutch lifted while going down hill is quite different between the two disciplines. Many a professional driver lifts the clutch occasionally on downhills and turn-ins and mid turns, etc... In wet, snow, pavement and gravel. I think you have a good question and the consequences to the wrong decision can be much more "costly" when driving on public roads at speeds way beyond what most of us here do when we "play" off road.
 

Tugela

Well-known member
May 21, 2007
4,764
564
Seattle
Matching the rotating speed of the wheels to the road speed of the vehicle is paramount in this situation. I learned this lesson the hard way in my foolish youth. First car was a 1994 Ford Exploder. I was returning from an ice climbing trip in the Cascades, descending Icicle Creek Canyon Road, which was covered in snow and ice. Having engaged 4wd, I decided to use engine braking on the descent and downshifted too far, too fast. The truck was moving faster than the wheels were rotating, so I lost traction, went into a skid, did a 360-degree spin with a terrifying view down the wall of the canyon at the class 5 rapids below me, bounced off a snowdrift, and somehow ended up going in the original direction of travel. Nearly soiled my trousers.

Moral of the story: engine braking is good, but make sure your road/wheel speeds match before trying it on a slippery surface.
 

Blueboy

Well-known member
Apr 20, 2004
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469
Back in the USA; Rockwood, PA
I drove RWD cars on snow for many years without any issues. I'd have no problems doing it again.

Exactly! Driving my mother's 1965 Riviera in W Pa was a learning experience. And we made it around without too many problems with just studded snows on only the rear.
 

kennith

Well-known member
Apr 22, 2004
10,891
172
North Carolina
I drove RWD cars on snow for many years without any issues. I'd have no problems doing it again.

I never really understood the problem.

RWD is not worse than FWD in snow, it's simply different. Each technology has it's benefits and drawbacks.

I've always liked RWD in snow.

Cheers,


Kennith