Bob Weissman wrote:
I've been using a trunk-mounted strap-on bike rack on my car, but
it doesn't exactly inspire confidence that my beloved bike won't
fall off at freeway speeds.

I'm starting to look at roof-mounted racks and see there are basically
two kinds: the kind that hold onto the fork and require you to
remove the front wheel, and the kind that allow you to leave the
front wheel on.

Which is better? Obviously the fork mounts require more work, so
they must have some other advantage? Is there a problem with the
whole-bike mount which would cause me to regret choosing it?

(The bike is a 2007 Trek Pilot 5.0 and the car is a 2000 BMW 528i
sedan, if that makes any difference.)

The newer mounts that let you leave the wheel on will work with that
bicycle, i.e.
"http://www.thuleracks.com/thule/product.asp?dept_id=8&sku=594". I have
upright mounts that cannot be used with a carbon frame as they grip the
down tube, and would deform it.

The advantage of the fork mounts is that they are cheaper to manufacture
and cheaper to purchase.

There are four main advantages to the "leave the wheel on" mounts:

First and foremost, it holds the bicycle in place by he strongest part,
the frame, while all of the weight of the bike is on the wheels (just
like when you are riding). Second, it prevents the problem of bearing
wear (fretting) in the headset, which is a potential problem with fork
mounts. Third, in gusty winds the whole bike sways, rather than the
frame exerting forces on the headset and dropouts as occurs with a fork
mount. Fourth, you don't have to remove the front wheel and store it
somewhere

There are two disadvantages of the upright mount. First, it costs more
than the fork mount. Second, it is harder to place the bicycle in the
rack if you are short, or if you have a tall vehicle.

With a bicycle that expensive, don't skimp on the fork mount, especially
with a carbon fork.