In a message dated 97-07-16 22:54:26 EDT, gofastmg@juno.com (Rick Morrison)
writes:
> If you think about it, given that one axle will lock up quicker than
> the other, it is much better to have the rear lock first. The reason
> being, with the rear locked, you have some directional control with the
> front wheels which are still turning.
Rick:
I think I would disagree with you on that. I'm no expert, and I may be full
of dog doo, but let me give you my rationale, and see what you think.
True, if the front wheels lock up, you have no steering control, but at least
the car is sliding in the general direction you are wanting to go. Usually,
in a panic stop, you are not trying to turn anyway. If the front wheels lock
up, you can release the brakes momentarily and regain control, and then
reapply them. I have experienced this myself. By modulating the brakes, I was
able to make the stop safely, although just barely due to the increased
stopping distance.
On the other hand, when the rear wheels lock up, the rear end of the car
comes around to the front, and you are facing backwards. It doesn't matter
how much traction the front wheels have, you are not able to control the car
in this situation. Usually, the rear end comes about so fast that you haven't
time to modulate the brakes, at least till the car is half-way 'round. I have
also had this happen to me. Luckily, the car managed to stay on the road, and
didn't hit anyone. I wound up in the opposite lane, heading back the way I
came.
In the first instance, presence of mind and a modicum of driving skill (and I
am certainly not a skilled driver) saved the day. In the second instance, it
was pure, blind, dumb luck that saved me. Luck is fickle - I don't want to
rely on it more than I have to!
No question, I think, that having all four tires just at, but not over, the
limit of adhesion is the prefered condition for a panic stop, but given the
choice, I think I would prefer the rears to lock up first.
FWIW, one way to test your brake bias is to make wide chalk marks on the
front and rear tires. Have a friend video-tape you while you make a few panic
stops. When you play back the tape, the chalk mark on the wheels that are
still turning will be a blur, while mark on the wheels that have locked up
will be crisp and sharp. This way, it will be readily apparent which wheels
locked up first.
Dan Masters,
Alcoa, TN
'71 TR6---------3000mile/year driver, fully restored
'71 TR6---------undergoing full restoration and Ford 5.0 V8 insertion - see:
http://www.sky.net/~boballen/mg/Masters/
'74 MGBGT---3000mile/year driver, original condition
'68 MGBGT---organ donor for the '74
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