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Roof-mounted bike rack: fork mount or whole bike?



 
 
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  #1  
Old July 2nd 07, 11:54 PM posted to rec.bicycles.misc
Bob Weissman
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Posts: 9
Default Roof-mounted bike rack: fork mount or whole bike?

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.)

Thanks,
- Bob
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  #2  
Old July 3rd 07, 05:33 AM posted to rec.bicycles.misc
Doug Smith W9WI
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Posts: 43
Default Roof-mounted bike rack: fork mount or whole bike?

On Mon, 02 Jul 2007 22:54:45 +0000, 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.


Largely off-topic, but my bike has survived two Nashville=Milwaukee
round trips (plenty of freeway speeds, and two drives through Chicago) on
a trunk-mounted strap-on rack.

But I'm going to be watching the replies to your post...


  #3  
Old July 3rd 07, 11:48 AM posted to rec.bicycles.misc
SMS
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Posts: 7,983
Default Roof-mounted bike rack: fork mount or whole bike?

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.
  #4  
Old July 3rd 07, 03:27 PM posted to rec.bicycles.misc
Bob Weissman
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Posts: 9
Default Roof-mounted bike rack: fork mount or whole bike?

In article ,
Doug Smith W9WI wrote:
On Mon, 02 Jul 2007 22:54:45 +0000, 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.


Largely off-topic, but my bike has survived two Nashville=Milwaukee
round trips (plenty of freeway speeds, and two drives through Chicago) on
a trunk-mounted strap-on rack.


Well, there are a few things happening with my trunk rack which
inspired me to start shopping.

1. The straps twang like guitar strings at freeway speeds, causing a lot
of noise and vibration. The vibration is starting to chip away at the
paint on my trunk lid. Plus it seems to make the bike move around on the
rack's support arms, which makes me nervous.

2. The rubber bolsters which support the bottom of the rack are
disintegrating. I didn't notice this until recently, because the broken
sides are on the inside, hidden against the license plate.

3. There's no way to lock the bike onto the trunk rack, so I'm
uncomfortable leaving it unattended.

- Bob
  #5  
Old July 3rd 07, 03:32 PM posted to rec.bicycles.misc
David L. Johnson
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Posts: 1,048
Default Roof-mounted bike rack: fork mount or whole bike?

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
  #6  
Old July 4th 07, 12:11 AM posted to rec.bicycles.misc
SMS
external usenet poster
 
Posts: 7,983
Default Roof-mounted bike rack: fork mount or whole bike?

Bob Weissman wrote:
In article ,
Doug Smith W9WI wrote:
On Mon, 02 Jul 2007 22:54:45 +0000, 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.

Largely off-topic, but my bike has survived two Nashville=Milwaukee
round trips (plenty of freeway speeds, and two drives through Chicago) on
a trunk-mounted strap-on rack.


Well, there are a few things happening with my trunk rack which
inspired me to start shopping.

1. The straps twang like guitar strings at freeway speeds, causing a lot
of noise and vibration.


I was just talking to someone today about kayak carrying. She said if
the straps twang, put in a couple of twists and it stops it.
  #7  
Old July 4th 07, 12:17 AM posted to rec.bicycles.misc
SMS
external usenet poster
 
Posts: 7,983
Default Roof-mounted bike rack: fork mount or whole bike?

David L. Johnson wrote:
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.


I don't think this is the case. The bicycle is mainly sitting on the
wheels which cushion it, the upright mount is just holding it up.

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.


The forces are completely different.

When the vehicle is in motion shock from the road is transmitted up to
the roof rack. When a bicycle is clamped by the fork, into a fork mount,
the fork and headset are held rigidly in place. As the vehicle goes down
the road the headset will be constantly absorbing small shocks. This
would not be a problem if the headset were also turning, because the
lubricant inside would be distributed by the rolling of the bearings.
But the headset is not turning and therein lies the problem. From:
http://draco.acs.uci.edu/rbfaq/FAQ/128.html: "The damage occurs when
these small motions occur when there are no steering motions to
replenish lubricant while the bearing balls fret in place. Fretting
breaks down the lubricant film on which the balls normally roll and
without which they weld to the races and tear out tiny particles." This
was written by Jobst Brandt, a well known and well respected engineer
and author of The Bicycle Wheel.

You seem now to be talking about a mount that grabs the downtube.


Yes, my mistake. The new Thule mount is holding the wheel.

Anyway, I should have prefaced my comments with a statement that users
of fork mount racks will disagree with just about everything I wrote.
  #8  
Old July 4th 07, 02:21 AM posted to rec.bicycles.misc
mark
external usenet poster
 
Posts: 223
Default Roof-mounted bike rack: fork mount or whole bike?

I won't get involved in "which is better for the bike", except to say
that I use a fork mount for my fenderless road bike, and a "whole bike"
mount for my fender-equipped touring bike. The "whole bike" mount is
bulkier and cost more, although I did get it on sale. In all honesty, I
don't see a significant difference in total effort required to get the
bike onto either rack and secured, but I've spent enough time tinkering
with my bikes that popping a front wheel off is no big deal.

Just to add to the confusion, there is a third option. There are a
variety of carriers that attach to a receiver hitch installed on your
car, that appear to me to be much more secure than the trunk-mounted
strap-on rack you are currently using. Advantages I perceive are that
fuel economy and vehicle aerodynamics are not as adversely affected, you
don't have to worry about low garage entrances (but do be careful
backing up), and the risk of damaging your car's body work is much less
than with roof top or trunk mounted racks. Trunk access is easier than
with the trunk-mounted racks, but how much so will vary from car to car.
Some of these racks pivot out of the way to make trunk access easier.

Simplest of all, of course, is to pull the wheels off the bike and put
it in the trunk, or fold the rear seats flat and put the whole bike in
the trunk.

mark
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.)

Thanks,
- Bob

  #9  
Old July 4th 07, 06:33 AM posted to rec.bicycles.misc
SMS
external usenet poster
 
Posts: 7,983
Default Roof-mounted bike rack: fork mount or whole bike?

mark wrote:
I won't get involved in "which is better for the bike", except to say
that I use a fork mount for my fenderless road bike, and a "whole bike"
mount for my fender-equipped touring bike. The "whole bike" mount is
bulkier and cost more, although I did get it on sale. In all honesty, I
don't see a significant difference in total effort required to get the
bike onto either rack and secured, but I've spent enough time tinkering
with my bikes that popping a front wheel off is no big deal.

Just to add to the confusion, there is a third option. There are a
variety of carriers that attach to a receiver hitch installed on your
car, that appear to me to be much more secure than the trunk-mounted
strap-on rack you are currently using. Advantages I perceive are that
fuel economy and vehicle aerodynamics are not as adversely affected, you
don't have to worry about low garage entrances (but do be careful
backing up), and the risk of damaging your car's body work is much less
than with roof top or trunk mounted racks.


On a unibody vehicle (nearly every car and car like SUV) even a small
impact on the rear rack will cause many thousands of dollars worth of
damage. The bumper is out of the equation, and the impact goes to the
floor pan where the hitch will be mounted.

I know this from experience unfortunately.

If you use a hitch rack remove it completely unless you have a bicycle
on it.
  #10  
Old July 4th 07, 02:45 PM posted to rec.bicycles.misc
mark
external usenet poster
 
Posts: 223
Default Roof-mounted bike rack: fork mount or whole bike?

Actually I'm still shopping for the bike rack, but that's a very good
point to remember. I would probably remove the bike rack anyway, just to
make trunk access easier (I don't want the extra weight and expense of
the fancier racks that swing out of the way).

What effect, if any, does just the receiver hitch have on the car in a
rear impact?

SMS wrote:
On a unibody vehicle (nearly every car and car like SUV) even a small
impact on the rear rack will cause many thousands of dollars worth of
damage. The bumper is out of the equation, and the impact goes to the
floor pan where the hitch will be mounted.

I know this from experience unfortunately.

If you use a hitch rack remove it completely unless you have a bicycle
on it.

 




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