technical reasons why MTBs haven't moved to 30 spd?

[damyth]

What are the technical reasons why MTBs have not migrated to 30
speeds? I want to make clear I'm not trying to "advocate" MTBs move
to 30 speeds, just seeking to understand the technical reasons. That
said however, given the greater variation of terrain while riding a
MTB, I'd imagine that 30 speeds on a MTB would be "more useful/
necessary" than 30 speeds on a road bike.

Wikipedia seems to suggest that there is no 10s chain strong enough to
withstand the rigors of MTB use (search for "30 speed" in following
link).
http://en.wikipedia.org/wiki/Mountain_bike

I was under the assumption that 10spd chains are no weaker than 9spd.
Is this assumption incorrect?

 

[jim beam]

damyth wrote:
> What are the technical reasons why MTBs have not migrated to 30
> speeds? I want to make clear I'm not trying to "advocate" MTBs move
> to 30 speeds, just seeking to understand the technical reasons. That
> said however, given the greater variation of terrain while riding a
> MTB, I'd imagine that 30 speeds on a MTB would be "more useful/
> necessary" than 30 speeds on a road bike.
>
> Wikipedia seems to suggest that there is no 10s chain strong enough to
> withstand the rigors of MTB use (search for "30 speed" in following
> link).
> http://en.wikipedia.org/wiki/Mountain_bike
>
> I was under the assumption that 10spd chains are no weaker than 9spd.
> Is this assumption incorrect?
>
the assumption is correct, the chains are no weaker, but overall, a
finer mechanism is more susceptible to dirt abrasion & clogging, hence
10 may be a little more problematic.

 

[Ron Hardin]

Gary Young wrote:
> * For standing pedaling, the farther out the pedals are from the
> centerline, the harder you have to pull on the handlbar to counterbalance
> the tendency of the pedaling force to tip the bike sideways.ite).

No, counter-tipping the bike puts the force in line with the tires, but the
tip is larger. The force accordingly is reduced by the cosine of the off-vertical
angle, but also then doesn't result in work being done, and doesn't represent
much more than an impedance change, ie. just makes the cranks act like shorter ones.

The counter-tipping is necessary just as part of balancing, but this reorienting the
bike isn't work.

It's not a pull up in any case, until the bike is tipped as necessary to balance.

--
Ron Hardin
[email protected]

On the internet, nobody knows you're a jerk.

 

[Michael Warner]

On Wed, 21 Mar 2007 05:37:09 -0500, Gary Young wrote:

> Personally, I've never seen any solid evidence that a narrow q-factor is
> actually more efficient.

FWIW, Armstrong tried it and found it less efficient in practice.

--
Home page: http://members.westnet.com.au/mvw

 

[Gary Young]

On Wed, 21 Mar 2007 05:37:09 -0500, I wrote:

<snip>
>> What's a Q-factor?
>
> From Sheldon Brown's site:
>
> "Tread ("Q Factor")
>
> The tread, or "Q factor" of a crank set is the horizontal width of
> the cranks, measured from where the pedals screw in. The wider the
> tread, the farther apart your feet will be. It is generally considered a
> good idea to keep the tread fairly narrow. There are three main reasons
> for this:
>
> * The hip joint is optimized for walking, and in normal walking
> the footsteps are pretty much in line, with little or no "tread."
>
The more I think about this, the less convincing it becomes. Efficient
walking may have been the overriding consideration in the evolution of
the hip joint, but it also easily adapts itself to a variety of other
activities.

Right now I'm sitting, and keeping my feet together is downright
uncomfortable. The usual explanation I see for in-line footsteps when
walking is the need to keep the feet below the center of gravity. That
makes sense for a weight-bearing activity like walking. But in cycling,
one takes a good bit of weight off one's feet by sitting. Arguably,
pedaling is more akin to sitting than walking.

No offense to Sheldon or others who tout a low q-factor, but I'd like to
see what medical experts would say about this.

 

[- Bob -]

On Wed, 21 Mar 2007 09:02:11 -0500, John Forrest Tomlinson
<[email protected]> wrote:

>>FWIW, Armstrong tried it and found it less efficient in practice.
>
>Surely if Q factor matters it will vary depending on the size of the
>person and their various body parts.

That's what I would think. Depending on the width of your pelvis, the
hip joints are located differently. What's a narrow Q for one person
is wide for another.

It might be interesting too see a study of both components - natural
hip line vs. Q - but then there would be yet another item to spin into
the scientific bike fitment models

 

[John Forrest Tomlinson]

On Wed, 21 Mar 2007 22:13:17 +1030, Michael Warner <[email protected]>
wrote:

>On Wed, 21 Mar 2007 05:37:09 -0500, Gary Young wrote:
>
>> Personally, I've never seen any solid evidence that a narrow q-factor is
>> actually more efficient.
>
>FWIW, Armstrong tried it and found it less efficient in practice.

Surely if Q factor matters it will vary depending on the size of the
person and their various body parts.
--
JT
****************************
Remove "remove" to reply
Visit http://www.jt10000.com
****************************

 

[John Forrest Tomlinson]

On Wed, 21 Mar 2007 13:32:57 GMT, - Bob - <[email protected]>
wrote:

>On Wed, 21 Mar 2007 09:02:11 -0500, John Forrest Tomlinson
><[email protected]> wrote:
>
>>>FWIW, Armstrong tried it and found it less efficient in practice.
>>
>>Surely if Q factor matters it will vary depending on the size of the
>>person and their various body parts.
>
>That's what I would think. Depending on the width of your pelvis, the
>hip joints are located differently.

Not just width of pelvis but also the length of the legs. And other
details of the hip, knee and anke joints.

>What's a narrow Q for one person
>is wide for another.

For sure.

--
JT
****************************
Remove "remove" to reply
Visit http://www.jt10000.com
****************************

 

[Matt O'Toole]

On Tue, 20 Mar 2007 20:06:50 -0700, damyth wrote:

> What are the technical reasons why MTBs have not migrated to 30
> speeds? I want to make clear I'm not trying to "advocate" MTBs move
> to 30 speeds, just seeking to understand the technical reasons.

There's no technical reason. It's all marketing. Give 'em a year or two.

> Wikipedia seems to suggest that there is no 10s chain strong enough to
> withstand the rigors of MTB use (search for "30 speed" in following
> link).
> http://en.wikipedia.org/wiki/Mountain_bike

Anyone can edit Wikipedia, and anyone does.

Matt O.

 

[Mike Jacoubowsky]

>> I was under the assumption that 10spd chains are no weaker than 9spd.
>> Is this assumption incorrect?
>>
> the assumption is correct, the chains are no weaker, but overall, a finer
> mechanism is more susceptible to dirt abrasion & clogging, hence 10 may be
> a little more problematic.

The chain itself may not be weaker, in terms of resistance to wear, but in
terms of failure due to pins not holding, there is a dramatic, not subtle,
loss of durability when moving from 9 to 10-speed. Anyone believing
differently hasn't worked in a shop. In fact, the 10-speed chain pin
installation is so much more critical than with 9 that some bike companies
are installing quick links instead of the supplied Shimano pin when
installing the chains.

Campy has also had some infamous 10-speed chain failures (during the Tour de
France).

10-speed chains are *not* ready for mountain bike use. Making the chain
narrow enough for the space between the cogs, and yet wide enough internally
to fit over the teeth, has resulted in pushing the limits of design &
construction.

--Mike-- Chain Reaction Bicycles
www.ChainReactionBicycles.com

 

[Sheldon Brown]

A shy person asked:
> What are the technical reasons why MTBs have not migrated to 30
> speeds? I want to make clear I'm not trying to "advocate" MTBs move
> to 30 speeds, just seeking to understand the technical reasons. That
> said however, given the greater variation of terrain while riding a
> MTB, I'd imagine that 30 speeds on a MTB would be "more useful/
> necessary" than 30 speeds on a road bike.

This is a repeating pattern: It happened with the transition from 6-
speed to 7-speed, then again with the transition from 7-speed to 8-
speed, and yet again from 8-speed to 9-speed.

With any number of gears, shifting will be better with a close range
cluster than with a wide range cluster. Since MTBs use wide range
gearing, the manufacturers wait to get the system debugged and fine
tuned with close-ratio road-racing gearing first before they apply it
to wider range MTB/touring gearing.

See also: http://sheldonbrown.com/carapace.html#thin

Sheldon "Seen It All Before" Brown
+----------------------------------+
| What sane person could live in |
| this world and not be crazy? |
| --Ursula K. LeGuin |
+----------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

 

[Rick]

On Mar 20, 8:06 pm, "damyth" <[email protected]> wrote:
> What are the technical reasons why MTBs have not migrated to 30
> speeds? I want to make clear I'm not trying to "advocate" MTBs move
> to 30 speeds, just seeking to understand the technical reasons. That
> said however, given the greater variation of terrain while riding a
> MTB, I'd imagine that 30 speeds on a MTB would be "more useful/
> necessary" than 30 speeds on a road bike.

It is neither more useful nor necessary. The move from 5 to 6 to 7 to
8 to 9 to 10 speed clusters have all been to add increments within the
same range. That is, arguably, a good thing for road racers, and of
no particular use to any other road rider, and no use to MTB riders.

- rick

 

[Lou Holtman]

Rick wrote:
> On Mar 20, 8:06 pm, "damyth" <[email protected]> wrote:
>> What are the technical reasons why MTBs have not migrated to 30
>> speeds? I want to make clear I'm not trying to "advocate" MTBs move
>> to 30 speeds, just seeking to understand the technical reasons. That
>> said however, given the greater variation of terrain while riding a
>> MTB, I'd imagine that 30 speeds on a MTB would be "more useful/
>> necessary" than 30 speeds on a road bike.
>
> It is neither more useful nor necessary. The move from 5 to 6 to 7 to
> 8 to 9 to 10 speed clusters have all been to add increments within the
> same range. That is, arguably, a good thing for road racers, and of
> no particular use to any other road rider, and no use to MTB riders.

Why is it of no use to a MTB rider. What makes him so different?

Lou
--
Posted by news://news.nb.nu (http://www.nb.nu)

 

[Mike Jacoubowsky]

>> What are the technical reasons why MTBs have not migrated to 30
>> speeds? I want to make clear I'm not trying to "advocate" MTBs move
>> to 30 speeds, just seeking to understand the technical reasons.
>
> There's no technical reason. It's all marketing. Give 'em a year or two.


Matt: As I detailed in my prior post, I have to disagree. We're pushing the
edge as we make ever-narrower chains. And perhaps you recall Shimano's first
year with 9-speeds on MTBs... we saw quite a number of bent/folded-over
larger-sized cassette cogs. Just because something works in a relatively
clean & predictable road environment doesn't mean you can expect the same
off-road.

--Mike Jacoubowsky
Chain Reaction Bicycles
www.ChainReaction.com
Redwood City & Los Altos, CA USA

 

[James Thomson]

"Rick" <[email protected]> a écrit:

> The move from 5 to 6 to 7 to 8 to 9 to 10 speed clusters have all
> been to add increments within the same range.

That isn't actually true for mountain bikes.

A typical 21-speed mountain bike transmission had a 12-28 cassette with
24,36,46t chainrings, giving a high-gear:low-gear ratio of 4.47:1or gear
inch range of 22"-100"

A typical 24-speed mountain bike transmission was 11-28 with 22,32,42t, for
a ratio of 4.86:1 or 20"-99"

A typical 27-speed mountain bike transmission is 11-32 with 22,32,44t, for a
ratio of 5.82:1 or 18"-104"

The sprockets of the seven speed cassette (12,14,16,18,21,24,28) are common
to all three transmissions. The 8-speed gets an 11 one end, and the 9-speed
gets a 32 on the other.

Of more practical benefit than the wider total range is that a greater
variety of terrain can be ridden in the middle ring, reducing the need to
drop to the granny gear.

James Thomson

 

[Ron Hardin]

Rick wrote:
> It is neither more useful nor necessary. The move from 5 to 6 to 7 to
> 8 to 9 to 10 speed clusters have all been to add increments within the
> same range. That is, arguably, a good thing for road racers, and of
> no particular use to any other road rider, and no use to MTB riders.

I use all the gears on a 21 speed MTB (7x3), and could use more in the
gaps. The longer you ride, the more sensitive you are to exactly
the right gear. It's not even a close call.

All I do is commuting.
--
Ron Hardin
[email protected]

On the internet, nobody knows you're a jerk.

 

[John Forrest Tomlinson]

On 21 Mar 2007 13:00:08 -0700, "Rick" <[email protected]> wrote:

>That is, arguably, a good thing for road racers, and of
>no particular use to any other road rider, and no use to MTB riders.

No use? That's too definite.

--
JT
****************************
Remove "remove" to reply
Visit http://www.jt10000.com
****************************

 

[Rick]

On Mar 21, 2:28 pm, "James Thomson" <[email protected]> wrote:
> "Rick" <[email protected]> a écrit:
>
> > The move from 5 to 6 to 7 to 8 to 9 to 10 speed clusters have all
> > been to add increments within the same range.
>
> That isn't actually true for mountain bikes.
>
> A typical 21-speed mountain bike transmission had a 12-28 cassette with
> 24,36,46t chainrings, giving a high-gear:low-gear ratio of 4.47:1or gear
> inch range of 22"-100"
>
> A typical 24-speed mountain bike transmission was 11-28 with 22,32,42t, for
> a ratio of 4.86:1 or 20"-99"
>
> A typical 27-speed mountain bike transmission is 11-32 with 22,32,44t, for a
> ratio of 5.82:1 or 18"-104"
>
> The sprockets of the seven speed cassette (12,14,16,18,21,24,28) are common
> to all three transmissions. The 8-speed gets an 11 one end, and the 9-speed
> gets a 32 on the other.
>
> Of more practical benefit than the wider total range is that a greater
> variety of terrain can be ridden in the middle ring, reducing the need to
> drop to the granny gear.
>
> James Thomson

Poppycock. I can put a 32T or even 32T cog on any of them, and I can
do a slight mod to get an 11T on a 7. I can get the range 11-34 on
any cassettes from 7sp up so my statement stands. There is a
difference between what is commonly sold on bikes and what is
possible; I speak of what is possible, and has been done numerous
times.

- rick

 

[Rick]

On Mar 21, 1:24 pm, Lou Holtman <[email protected]> wrote:
> Rick wrote:
> > On Mar 20, 8:06 pm, "damyth" <[email protected]> wrote:
> >> What are the technical reasons why MTBs have not migrated to 30
> >> speeds? I want to make clear I'm not trying to "advocate" MTBs move
> >> to 30 speeds, just seeking to understand the technical reasons. That
> >> said however, given the greater variation of terrain while riding a
> >> MTB, I'd imagine that 30 speeds on a MTB would be "more useful/
> >> necessary" than 30 speeds on a road bike.
>
> > It is neither more useful nor necessary. The move from 5 to 6 to 7 to
> > 8 to 9 to 10 speed clusters have all been to add increments within the
> > same range. That is, arguably, a good thing for road racers, and of
> > no particular use to any other road rider, and no use to MTB riders.
>
> Why is it of no use to a MTB rider. What makes him so different?

Riddle me this: what use is to any rider to have 1 or 2T differences
between adjacent cogs? It really is useful only for minor adjustments
to speed at a given cadence as conditions change, something that is
unnecessary to anyone not riding in a peleton. Last I checked,
MTB'ers do not ride in peletons and usually are not into maintaining a
steady cadence. Going up and down hills is more a matter of range; I
can see adding cogs if range changes, but it is a bit of marketing
fluff to pretend that anyone other than a road racer needs closely
spaced increments within a range.

- rick

 

[Rick]

On Mar 21, 2:48 pm, John Forrest Tomlinson <[email protected]>
wrote:
> On 21 Mar 2007 13:00:08 -0700, "Rick" <[email protected]> wrote:
>
> >That is, arguably, a good thing for road racers, and of
> >no particular use to any other road rider, and no use to MTB riders.
>
> No use? That's too definite.
>

OK, let say it is has the use of 'bragging rights', the use of showing
that someone has bought into a inane marketing pitch, .... but no real
mechanical or operational use.

- rick