Tech News August 4, 2006
Edited by John Stevenson, James Huang and John Kenny
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Rotor's Ágilis arms
It looks like a standard
Rotor's new complete crankset.
Rotor's elliptical Q-Rings now available as a complete crankset
By James Huang
The company that brought you the unique Rotor crankset and the elliptical
Q-Rings now brings a conventional crankset to the table. The new Rotor
Ágilis incorporates some unique features, and for the first time, allows
consumers to purchase the company's Q-Rings as part of a complete package.
As such, Q-Ring purchasers will not have to resort to retrofitting another
manufacturer's crankset which often results in the removal of a perfectly
good set of round rings right from the get-go.
The Ágilis crankarms start out as extruded aluminum bars which
are then lathe-turned, CNC-machined, and centre-bored in a process dubbed
'Hollowminium'. This effectively yields hollow arms that retain the stiffness
of the outer shape, but removes the extra material from the center that
would otherwise just add mostly useless mass. Not surprisingly, most high-end
crankarms are now filled with nothing but air for exactly that reason.
The Ágilis crankset will be a 'semi-integrated' crankset, with
a pseudo-permanently fixed aluminum spindle attached to the non-drive
side with a double-threaded bolt. This unique style of attachment will
allow for slight adjustments in spindle length to accommodate variations
in bottom bracket shell width. The driveside arm will attach via a seven-sided
In keeping with current industry trends, an external-style bottom bracket
will be used, but with a novel twist. The cartridge bearings in Rotor's
Self Aligning Bottom Bracket (SABB) are housed in spherical supports that
automatically keep the bearings parallel to each other, resulting in reduced
friction and increased bearing life. This shouldn't be a replacement for
proper facing and thread-cutting, but improved bearing alignment can hardly
Distinct road and mountain bike versions will be available, either with
or without Q-Rings. Road chainring spiders will be offered in both 130mm
and 135mm BCD standards, and all mountain cranksets will bear the current
104/64mm 4-arm pattern. Target weights for the complete Ágilis,
including Q-Rings, are 720g and 780g for the road and mountain versions,
respectively. Rotor's new crankset has yet to hit production and suggested
retail pricing is yet to be announced, but production is slated for later
For more information see www.rotorbike.com
SRAM urges rethinking of proper chain sizing
By James Huang
Sizing a chain used to be a rather straightforward affair, with any one
of the several accepted techniques yielding chain lengths that are typically
within a link of each other. In general, if the chain could accommodate
the large chainring-large cog combination without sagging in the other
extreme, you were good to go.
The prevalence of full-suspension mountain bikes, however, has complicated
the matter as the effective chainstay length can change dramatically as
the suspension moves through its travel. Usually, this length increases
during compression, and the change can be particularly pronounced on certain
suspension designs and/or longer travel rigs. Therefore, if chains are
sized using the old standard methods and the suspension is compressed
when in the big-big combo, the results can be rather "unpleasant", and
In response to what has clearly been a marked increase in "JRA rear derailleur
explosion" (industry jargon for 'Just Riding Along' ) complaints, SRAM
has released the following "Chain Sizing Made Easy" guidelines, which
are applicable regardless of chain make or model:
1. Wrap a full-length chain around the largest chain ring and largest
cog combination, bypassing the derailleurs.
2. If applicable, chain sizing should be performed when the rear suspension
produces the maximum effective chainstay length. This usually, but not
always, occurs at full compression. Deflating the rear shock, removing
the coil spring, or unbolting one end of the shock may make it easier
to determine this point.
3. Add one inch of chain to the minimum length required to accommodate
this gear combination.
4. Remove excess links as necessary.
5. Route the sized chain through the drive system and connect as directed
by chain manufacturer.
Keep in mind that this method may result in insufficient chain tension
in some cogs while in the inner chainring, but you probably already know
better than to run in those cross-gear combinations anyway. Besides, the
elimination of a few mostly-unusable gears is a much more appealing alternative
to having your entire rear end shatter in spectacular fashion.
For more information see www.sram.com
Jagwire goes pink for breast cancer
Cable maker Jagwire is introducing versions of its Ripcord brake and
gear cable kits with pink housing to raise money for breast cancer research.
The housing will be available in September and for each kit sold, Jagwire
and its distributors will contribute a portion of the proceeds to benefit
breast cancer research.
"Jagwire has a tradition of supporting charity and advocacy efforts,"
said Jason Grantz, director of aftermarket products for Jagwire. "The
pink housing promotion is an opportunity to help advance research that
can save lives."
Jagwire will also make a limited number of kits available to dealers
during the Interbike and Eurobike trade shows. At the shows, dealers will
be able to obtain one kit per $25.00 contribution; Jagwire will donate
all the money to various breast cancer research organizations.
For more information see www.PinkCables.com.
By John Stevenson
There's been a bit of hoo-ha in various bike forums around the net in
the last few days about a case in Portland, Oregon where a rider was fined
for not having a separate brake on her fixed-gear bike. According to bikeportland.org,
bike messenger Ayla Holland was ticketed on June 1 and charged with violating
Oregon Revised Statute (ORS) 815.280(2)(a) which states:
A bicycle must be equipped with a brake that enables the operator
to make the braked wheels skid on dry, level, clean pavement. strong enough
to skid tire.
Ms Holland's lawyer Mark Ginsberg attempted to argue that a fixie's transmission
constituted a brake. The judge was having none of it, and in his decision
"The brake must be a device separate from the musculature of the rider.
Take me for instance. I don't have leg muscles as strong as a messenger…
how would I stop safely?"
This has led to some rather alarmist talk about the future of fixies.
"Will the cops now feel emboldened to go out and ticket everyone on a
fixed-gear? Are fixed-gears now essentially illegal? Are fixed-gears truly
a public safety hazard?" asks Jonathan Maus in bikeportland.org.
Well, no. The issue here is a badly-written piece of legislation being
interpreted by a judge so that it achieves its aims, rather than what
the absolute letter of the law says.
A fixed-gear bike with no brakes cannot stop in as short a space as one
with a front brake, because only the rear wheel is providing the braking
force. As a vehicle on the road, it's therefore clearly less safe.
This is a matter of simple physics. In the third edition of Bicycling
Science, David Gordon Wilson demonstrates that the maximum deceleration
of a crouched rider on a standard bike (that is, not a recumbent) on a
dry road is 0.56g. Try to brake any harder than that and you go over the
handlebars, which is the limit condition, as the limit from tyre adhesion
of vehicles that don't pitch over (tandems, recumbents and cars) is about
If you brake with only the rear wheel, according to Wilson, the limit
is 0.256g, because braking effectively shifts your weight forward, reducing
the load on the rear wheel to the point that it skids at that deceleration.
Once a tyre is skidding, its braking effectiveness is reduced because
you no longer have sticky solid rubber in contact with the road, but a
lubricating layer of molten rubber. (Which incidentally demonstrates that
the Oregon legislation was written by someone with no clue at all about
Therefore, however good a fixie rider is, stopping distance is roughly
doubled without a front brake. In practice, it's probably more than that.
In some jurisdictions, better-written laws make this issue moot. In the
UK, for example, the law requires a bike to have two independent braking
systems. I used to ride a fixie in the winter in the UK, and I knew quite
a few fixie riders who dispensed with a rear brake on the grounds that
the transmission was a braking system, but I never met anyone daft enough
to have just a rear brake.
This judge has clearly decided to ignore the letter of the law in favour
of enforcing its obvious intent, that bikes have at least one maximally
effective brake. That's the sort of thing judges are handy for: turning
idiotically badly-written legislation into rules that make sense in the real world.
All that fixie riders have to do to conform is slap on a front brake;
hardly rocket surgery, and a long way from fixies being suddenly illegal.
And to fixie riders who are about to reach for the email to defend riding
brakeless fixies, I refer you to Cmdr Montgomery Scott: "You canna change
the laws of physics!"