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SUVs Acura RDX BMW X3 vs Acura RDX
324 messages, Last post on Sep 25, 2009 at 12:27 PM
You are in the Acura RDX Forum. Your Hosts are steve_ & tidester
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Replying to: pp2009pp (Sep 21, 2009 12:51 pm) With FWD & F/awd vehicle inadvertent/unavoidable engine compression braking, or "regenerative" braking for hybrids, even at the slightest level, can result in virtually INSTANT loss of directional control in those conditions. To that end the Ford Escape hybrid significantly reduces the level of regen braking used to simulate engine compression braking as the OAT approaches freezing. Ford also disables, regardless of road condition, regen braking the very instant there is an indication of the need to activate the anti-lock braking system to prevent interference with ABS. VW now has a technique wherein the engine of their FWD vehicles with stick shift is automatically up-revved should the driver inadvertently downshift to a level that produces so much engine braking that front wheelslip results.
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Replying to: wwest (Sep 22, 2009 9:05 am) Are you saying that loss of speed during slippage causes loss of directional control or are you saying that the mechanism that causes the engine braking also causes lack of directional control regardless of any loss of speed.
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Replying to: pp2009pp (Sep 22, 2009 9:57 am) Willard and I have had this discussion before. 
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Replying to: steve_ (Sep 22, 2009 12:21 pm)
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Replying to: pp2009pp (Sep 22, 2009 2:57 pm) Of course, I've had my FWD minivan up at the local ski hill some and never had trouble (usually I'm in my AWD wagon though). Not to mention 20 winters driving only FWD when I lived in Anchorage, but the storms there weren't like his experiences in Montana. But if FWD was inherently unsafe, where's the carnage on the highways? The AWD/FWD/4WD wars will go on and on, but ultimately it's the tires that make the real difference anyway. In my opinion anyway.
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Replying to: pp2009pp (Sep 22, 2009 9:57 am) During panic/HARD braking on a tractive surface there is a very REAL danger of losing directional control if your front wheels begin to skid/slip due to the braking friction overcoming the tire-roadbed traction coefficient. With the tires skidding across the roadbed you have NO LATERAL control with which to deviate from the path set by the vehicle's momentum/inertia, nor the ability to hold the direction if the vehicle begins to "drift" in an undesired direction. The same circumstance will exist if the roadbed happens to become an "ice rink", except now it is entirely possible that even the slightest level of engine compression braking, or "regen" braking, can result in an adverse effect. Engine braking that (today) ABS CANNOT abate/alleviate in order to allow you to maintain directional control. With RWD engine compression braking occurs at the REAR WHEELS and therefore does NOT INTERFERE with the lateral traction at the front wheels. Back in my days in NH or MT (and more rarely Anchorage/Fairbanks), BEFORE ABS, if I were driving a stick shift I would often downshift and then use the clutch to moderate the level of engine braking at the rear. With an automatic I often used a very slight application of the e-brake to add a slight "drag" anchor to both slow the car going down a SLIPPERY roadbed section and to hold the car "in line". If you should ever find yourself travelling down a fairly steep incline, SLIPPERY incline, with, as recommended, tire chains ONLY on the front wheels of a FWD or F/awd vehicle you will know, INSTANTLY, of which I speak. If you are driving a FWD or F/awd vehicle on a wintertime adverse condition, SLIPPERY, roadbed, keep this advice from the AAA in mind. Be prepared to QUICKLY shift the transaxle into neutral the INSTANT you begin to feel the onset of loss of directional control. The advice also applies to RWD and R/awd with automatics. Anyone driving a stick shift doesn't need to be, SHOULDN'T need to be, told what to do. |
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Replying to: steve_ (Sep 22, 2009 7:32 pm) No, the rear end coming around is really a result, "after effect", of having lost traction at the front tires, and therefore directional control, "control of direction". If lateral traction remained at the front, as would happen with the new VW technique, you could simply "stear into the skid" and thereby quickly recover.
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Replying to: wwest (Sep 23, 2009 8:13 am) Maybe us FWD guys just know the limits of our vehicles better. 
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Replying to: steve_ (Sep 23, 2009 11:26 am) http://www.youtube.com/watch?v=zMzeiMJQrvk&feature=related |
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| The TL with manual transmission is NOT available with FWD, only SH-AWD. | |
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