Karl Bloss wrote:

> ...
>One concern I would have with a rooftop bike rack is the clearance.
>I don't want to be flying down the road and smack my bikes into an
>overpass and peel back the roof like a sardine can.  Anyone have
>experience with this w.r.t. height and typical clearances?

Our typical (87 non-poptop) roof configuration is a canoe, two road bikes,
one mountain bike, and a kiddie bike with training wheels.  All this on a
75" Yakima that's probably very similar to your Thule. The total height is
about 9.5 feet.   I haven't hit anything yet, but it sure gets the heart
rate up when you see a sign saying -- Clearance 6' 9"  Yowza!!

I live in southern NY where  there's lots of Parkways (no commercial
traffic) with low clearance.  These are typically very old roads that are
narrow and have low bridges.  Modernization is slowly fixing them.  The 6'
9"  stated is the lowest I've seen and it's on one of the clover-leaf
entrances to the Southern State Parkway on Long Island.  I tried calling
around to find out, for a given route, what's the minimum clearance.  But I
couldn't find a definitive source.  One guy (forgot what dept it was) told
me "I didn't tell you this, but we get our 12' trucks through the entire
span of the Southern State Pkwy".

So here's the catch ... the low clearances almost always occur with arched
bridges and the minimum is typically at either the right edge of the right
lane, or, further to the right on the shoulder.  I'm not sure which.  As
you cruise along and approach a low clearance bridge, get to the left where
the clearance is higher.  You can also minimize risk by keeping the high
stuff (ie, bikes) on the left (driver's) side.

This all can make for some serious paranoia, but its not that bad, really.
Long Island parkways are the worst since there's overpasses every 200 yards
(or so it seems).  The Westchester, NY  Parkways are better.  I've done the
entire span of the Garden State Parkway in New Jersey, and the Taconic
State Parkway in NY.  Other than that, anywhere that commercial traffic can
go, you can go without worry (exceptions will be ominously posted).

The other case is cruising around backroads to get to trailheads,  camping
spots, and the like.  Expect to do some light tree trimming.

Tom Ervolina
Enterprise Solutions Research
IBM
Yorktown Heights, NY
ervolina@us.ibm.com