Many moons ago I worked in the tread design office at BFG. The phenomena
you are describing was referred to in house as rain groove squiggle - I
know, a highy technical term - but we had several computer simulations that
were used to evaluate a new tread design for things like dry traction, wet
traction, snow traction, tire noise on various aggregates, etc. and rain
groove squiggle was another.
The rain grooves in the roadway, which were either cut into existing
pavement, or formed when a new slab was being floated, are intended to
channel away water in heavy rain areas to prevent hydroplaning. The cause
of squiggle it is the relationship of the tread pattern edges to the
grooves - the edges of the tread blocks deflecting and "falling off" the
raised ribs between the grooves. Different tread patterns react differently
to these grooves. Tires that have distinct circumferential grooves are more
prone to squiggle, and those with more random, multiangled main grooves (
like most general purpose all -season tires) are less suseptible.
Worst personal experience was on an old Triumph Daytona, with those old bias
ply front tires with the narrow circumferential grooves....
first time I encountered one of the "new" grooved freeways back in the late
70's, the bike started swaying like a drunken sailor. Had to send my jeans
to the cleaners...........
Mark Sedlack
OROC
Cuyahoga Falls OH
66 1600 http://home.neo.rr.com/mark2000/images/datsun1600/
77 280Z http://home.neo.rr.com/mark2000/images/datsun1600/Z/Z.htm
----- Original Message -----
From: "Ryan Bird" <birdman@myrealbox.com>
To: <datsun-roadsters@autox.team.net>
Sent: Thursday, April 04, 2002 3:53 PM
Subject: Driving Question
> Hey guys and gals,
>
> I have noticed that at certain times when I drive my car on the
> freeway, it gets real sloppy, particularly the rear end. It is a very
> uncomfortable feeling, almost as if the car is unstable beneath you.
> I first noticed this on the 91 heading out of Orange County to
> Riverside County. I've also felt it on I-60 here in AZ. I at first
> blamed it on back-draft/wind, as going up the 91 there was a good
> amount of back draft as well as the 60 could have some "tunnel" effect
> due to how it is dug down low, but upon further experience, I have
> narrowed the problem down: When driving on what seems to be concrete
> freeway with small, narrow groves, perhaps an inch or two apart, going
> in the same direction I am, my car gets very sloppy. I don't know how
> to describe this type of road any better. The groves are placed in
> the road over all lanes, I have never felt this way with any other
> vehicle when driving on these sections of freeway.
>
> Anyway... Anyone who can decipher what I am trying to say, feel free
> to explain why my car does this, and if I should be concerned.
>
> Thanks,
>
> Ryan Bird
> 67 1600
> Tempe, AZ
> www.azroc.org/ryan
>
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