Yes, my math skiills suck

So, how do you determine, at a given gear combo, what speed will pedaling
have no affect.


I'm trying to figure out if I want to run a double or triple upfront.
--
Slack

"Slack" wrote in message
news
So, how do you determine, at a given gear combo, what speed will pedaling
have no affect.


How fast can you spin?

http://sheldonbrown.com/gain.html


I'm trying to figure out if I want to run a double or triple upfront.

Triple.

Greg

Slack wrote:

So, how do you determine, at a given gear combo, what speed will pedaling
have no affect.

I'm trying to figure out if I want to run a double or triple upfront.

You're worrying about the wrong end of the speed range (if I'm reading
your question correctly). Pedaling only loses its influence over the
speed of the bike when you're going down a STEEP hill. The difference
between the biggest and smallest big rings up front isn't likely to
make any difference in velocity down a hill that's steep enough to
spin out a 48-whatever combination.

That said, there's very little reason NOT to go with a triple. The
weight you add to the crank can be offset by the much smaller, lighter
cassette you can run (and still get the same gearing as a double crank
with a wide-range cassette). In addition, you end up having smaller
gaps between gears, which is a nice bonus.

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $795 ti frame

On Mar 21, 9:33 pm, Slack wrote:
So, how do you determine, at a given gear combo, what speed will pedaling
have no affect.

I'm trying to figure out if I want to run a double or triple upfront.
--
Slack

Is this for a CX bike? These comments are based on something I think
you mentioned last week about considering going from 2 to 3
chainrings.

1. I think you'll need a new, long rear derr too if you go from double
to triple, no?
2. I'm even less sure of this, but can you use the same Shimano
brifter with both 2 and 3 chainrings? I think if you were going from 3
to 2, you could manage it with the limit shops. I _think_ I've read
that a 9sp Ultegra shifter will work with 2 AND 3, but I could be
wrong.
3. The longer rear derr might lead to more chain slapping around.

/s

On Mar 21, 5:33 pm, Slack wrote:
I'm trying to figure out if I want to run a double or triple upfront.


You? A triple.

JD

On Thu, 22 Mar 2007 05:50:56 -0700, Mark Hickey wrote:

Slack wrote:

So, how do you determine, at a given gear combo, what speed will
pedaling
have no affect.

I'm trying to figure out if I want to run a double or triple upfront.

You're worrying about the wrong end of the speed range (if I'm reading
your question correctly). Pedaling only loses its influence over the
speed of the bike when you're going down a STEEP hill. The difference
between the biggest and smallest big rings up front isn't likely to
make any difference in velocity down a hill that's steep enough to
spin out a 48-whatever combination.

That said, there's very little reason NOT to go with a triple. The
weight you add to the crank can be offset by the much smaller, lighter
cassette you can run (and still get the same gearing as a double crank
with a wide-range cassette). In addition, you end up having smaller
gaps between gears, which is a nice bonus.

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $795 ti frame


I have a bad habit of not fully explaining my intensions, so let me
elaborate.

The new, and better, xc bike I'm currently building is going to have
6"+ front and 6" in the back.
Now running it downhill on rocky/washboard terrain (doesn't have to be
steep) at speed is going to make
my chain bounce like crazy. So many bikes in this travel range are coming
with a chain-guide
like http://www.e13components.com/product_drs.html And it has the added
benefit of providing
a little protection for BB/lower shock mount on my frame since mine didn't
come with a lower
shock mount protector as shown here
http://www.mcconveycycles.com/smsimg...rame-reign.jpg
Although, I'm trying to locate one now.

But, and it's a big but, if removing the large ring upfront means I'm
almost never going to be able to pedal dh,
that is going to truly suck! I'm not sure it's worth the sacrifice..
--
Slack

On Thu, 22 Mar 2007 15:21:27 -0700, JD wrote:

On Mar 21, 5:33 pm, Slack wrote:
I'm trying to figure out if I want to run a double or triple upfront.


You? A triple.

JD


Yes, get it straight; triple chain-ring; double chin.
--
Slack - sponsored by In-&-Out

Slack wrote:

The new, and better, xc bike I'm currently building is going to have
6"+ front and 6" in the back.
Now running it downhill on rocky/washboard terrain (doesn't have to be
steep) at speed is going to make
my chain bounce like crazy. So many bikes in this travel range are coming
with a chain-guide
like http://www.e13components.com/product_drs.html And it has the added
benefit of providing
a little protection for BB/lower shock mount on my frame since mine didn't
come with a lower
shock mount protector as shown here
http://www.mcconveycycles.com/smsimg...rame-reign.jpg
Although, I'm trying to locate one now.

But, and it's a big but, if removing the large ring upfront means I'm
almost never going to be able to pedal dh,
that is going to truly suck! I'm not sure it's worth the sacrifice..

I think this is a good example of something (potentially) evolving
into something less viable... The big ring would seem to provide as
much protection as that plastic ring could (lots of riders out here in
AZ have some pretty rough-looking big rings as a result, due to all
the predatory boulders on the trails). ;-)

A DH bike that can't go fast down hills seems like a waste of
components. There are other ways to keep the chain on the bike
without having to give up the top half of your gearing!

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $795 ti frame

On Thu, 22 Mar 2007 18:36:02 -0700, Mark Hickey wrote:

Slack wrote:

The new, and better, xc bike I'm currently building is going to have
6"+ front and 6" in the back.
Now running it downhill on rocky/washboard terrain (doesn't have to be
steep) at speed is going to make
my chain bounce like crazy. So many bikes in this travel range are
coming
with a chain-guide
like http://www.e13components.com/product_drs.html And it has the added
benefit of providing
a little protection for BB/lower shock mount on my frame since mine
didn't
come with a lower
shock mount protector as shown here
http://www.mcconveycycles.com/smsimg...rame-reign.jpg
Although, I'm trying to locate one now.

But, and it's a big but, if removing the large ring upfront means I'm
almost never going to be able to pedal dh,
that is going to truly suck! I'm not sure it's worth the sacrifice..

I think this is a good example of something (potentially) evolving
into something less viable... The big ring would seem to provide as
much protection as that plastic ring could (lots of riders out here in
AZ have some pretty rough-looking big rings as a result, due to all
the predatory boulders on the trails). ;-)

A DH bike that can't go fast down hills seems like a waste of
components. There are other ways to keep the chain on the bike
without having to give up the top half of your gearing!

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $795 ti frame


Good points. Ok, I'm convinced.

Thanks.
--
Slack

On Mar 22, 9:34 pm, Slack wrote:
On Thu, 22 Mar 2007 15:21:27 -0700, JD wrote:
On Mar 21, 5:33 pm, Slack wrote:
I'm trying to figure out if I want to run a double or triple upfront.

You? A triple.

JD

Yes, get it straight; triple chain-ring; double chin.
--
Slack - sponsored by In-&-Out

I was LOL, until I started to cry.

Excellent rule of thumb, anyway.

/s