Re: Roof-mounted bike rack: fork mount or whole bike?
- From: "David L. Johnson" <david.johnson@xxxxxxxxxx>
- Date: Tue, 03 Jul 2007 10:32:23 -0400
SMS wrote:
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 managed to damage an aluminum frame on a trunk mount, because of how the hooks grabbed the frame. I would think a carbon bike would be even more subject to such damage.
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.
I would distrust the mounts that clamp the middle of the downtube. But the one you point out would place just as much force on the fork and headset as a fork mount.
The advantage of the fork mounts is that they are cheaper to manufacture and cheaper to purchase.
I think you are understating the advantages of a fork mount. The fork ends are _designed_ to be clamped. Any fork strong enough to safely support you while riding over a rough road are certainly strong enough to hold just the bike on top of the car.
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,
You seem now to be talking about a mount that grabs the downtube. The center section of the downtube is by far not the strongest part, especially under clamping force. But the link you provide is to a clamp that grabs the top of the fork, and the front wheel, not the frame.
while all of the weight of the bike is on the wheels (just
like when you are riding).
The "weight of the bike" is 20 pounds. That is all that is being supported on the rack. While riding, some of us provide considerably more weight.
Second, it prevents the problem of bearing
wear (fretting) in the headset, which is a potential problem with fork mounts.
Nonsense. The fork is still up there with either rack, and the steerer is, yes, slightly moving as you go along. This also happens while riding, and then there is considerably more force. Bearing fretting is much less of a problem now than it was with older headset designs, and you really can't blame roof racks for that.
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.
The bike then exerts pressure on that downtube clamp.
Fourth, you don't have to remove the front wheel and store it
somewhere
Don't most cars have a trunk?
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.
These rooftop racks that do not require all the "work" of removing the front wheel have gone through quite a bit of re-design in recent years. Those re-designs are probably a result of damage claims. I would not use any rack that grabbed the downtube. Even steel bikes these days have such thin tubing, especially in that area, that clamp damage will be likely. For a while they heavily marketed racks that grabbed the crank arm. While that would seem to be a strong point, these racks have fallen out of favor, maybe with reason. I like the idea of securing the bike where it is designed to be supported. Your fork supports you and the bike just fine while riding. If it didn't, then the roof rack would be the least of your worries.
Better yet, ride to the ride. Oh, and if you do use a roof rack, hide the garage door opener.
--
David L. Johnson
When you are up to your ass in alligators, it's hard to remember that
your initial objective was to drain the swamp.
-- LBJ
.
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