ABS and winter driving, and New Zealand eh?

[C M Smith <cmsmith@xxxxxxxxxxxxxxx>]

You have to be careful when generalizing about ABS weakness in loose snow 
or on glare ice. It is truly rare to actually encounter these road 
conditions in the real world of winter driving. When you do, stopping 
distances aren't much on your mind as opposed to actually getting going or 
stopping at all, or even staying on the road. Plus, there are enough non 
ABS cars and trucks out there that minimum stopping distances just get you 
rear ended. It is rare that you can brake to the max with a all disc 
European car without carefully checking your rear view mirror first, wet, 
dry or snowy.

Road & Track has done a couple of very good articles about this ABS 
performance issue. Their field results suggest that ABS can get fooled by 
consistent very low friction surfaces such as glare ice, or by granular 
surfaces that tend to mimic the lubricating effect of glare ice such as 
sandy road surfaces or loose gravel or unpacked snow. Apparently, the 
wedging action of a locked wheel on snow or gravel has no effect whatsoever.

I interpret these results as an indication that under certain low friction 
conditions the ABS computer is tricked into thinking a wheel is about to 
lock substantially before it actually would lock. I believe I have had some 
success counter-tricking the ABS by, in effect, pumping the brake pedal on 
low friction surfaces. By pumping I do not mean the old press and release 
used before ABS did this for you, but a variation of threshold and cadence 
braking. You press hard then lift  a little then press hard again 
repetitively. My idea is that by varying the brake line pressure out of 
sync with the ABS attempting to do the same you can restore wheel rotation 
behaviour back to what ABS is programmed to deal with and delay the release 
of line pressure by the ABS computer enough to shorten braking distances. 
Also, I have noticed that ABS is superb on any inconsistent surface such as 
bumpy ice, packed snow, rutted gravel or roads with a bit of sand but 
mainly bare. It really comes into its own when each wheel is on a different 
surface. In general, only the super talented among us ( I am not one) can 
beat ABS in the vast majority of driving situations, and in the exceptional 
circumstances where ABS may be said to be inferior, minimum stopping 
distance is not an important consideration compared to say steering control.

I am unable to conduct empirical testing of my instinctive tests so who 
knows. I do know that it is imperative on any good friction surface to 
hammer the brakes if equipped with ABS and keep standing on them regardless 
of the ABS activity if minimum stopping distance is important (driver error 
causing a failure to properly anticipate conditions, in other words!). 
There is an almost irresistible tendency to back off when the ABS kicks in, 
the natural assumption being that once the ABS is working maximum braking 
has been achieved. This is completely wrong as the ABS kicks in on a wheel 
by wheel basis (accepting that many systems are only three channel and the 
rears operate together) so continuing to apply maximum pedal pressure is 
essential to ensure that ALL wheels are braking to the max, even if the ABS 
is only releasing one or two. There is nothing like extensive winter 
driving to drive this message home as the four wheels frequently have 
totally different traction available in winter, maximum braking may be 
achieved with only one wheel actually able to brake the car for example.

And, finally, the 164 could never compete with the Milano based cars if 
only because it is so darned heavy. Without wishing to resurrect the old 
fwd/rwd debate I suggest that on the street fwd is every bit as quick as 
rwd, assuming similar torque to weight ratios!

On a final, final note, I have been enjoying driving in New Zealand this 
past three weeks so you have all been temporarily unburdened by my 
egotistical view of the world. One thing struck me while casually strolling 
up a main street in Wellington in pouring rain, man those New Zealanders 
can buy anything car wise. (Assuming they can scrape up the ready, 
expensive!!) On this one street you could buy Renault, SAAB, Alfa Romeo, 
Porsche, Audi, Jaguar, Rolls Royce ( I think) and etc etc. I saw all manner 
of late model Alfas that are just too gorgeous for words when seen actually 
in the flesh or being driven with that casual flair Kiwis have made their own.

Driving on the left is a piece of cake after a couple of harrowing days of 
looking the wrong way all the time. Solution? Start looking BOTH ways for a 
while and you soon get used to it. Also, most Kiwi drivers will cut you a 
bunch of slack unless you really mess up big time. Kiwi's have a strange 
attitude to driving: they share the road (sometimes both sides of it!!!) 
and drive in the expectation that you will too. If the oncoming is using a 
bit of your road you are expected to move over a bit to accommodate him 
rather than insist you need all of your side of the road. If there's room 
for two then two will be using the road even if it is clearly marked for 
one vehicle. To surprise a Kiwi when driving you need to be aggressively 
rude eh? So cutting off is exceptionally rare, merging is almost always 
stress free, and if the Kiwi senses you might be a tourist (there are a lot 
of tourists on the road all of the time over there) then you will have 
absolutely no difficulty even if you mess up a bit.

Great beaches too BTW...

Cheers




Michael Smith
White 1991 164L
Original owner
--
to be removed from alfa, see /bin/digest-subs.cgi
or email "unsubscribe alfa" to majordomo@domain.elided