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Praxis Works upcoming Dura-Ace 7900 replacement ring kit (Praxis Works)

A single Dura-Ace 7900 outer chainring costs around US$200. Praxis Works doesn’t dispute that it’s an amazing
example of forged and mated materials, however, they do believe that many folks
might rather pay US$200 for a set of
chainrings built to fit the 7900 crankset.

Praxis Works showed their latest project during March’s
Taipei Cycle Show, which is a kit comprised of two, single material forged
rings, bolts, and outer chainring nuts made to meld with the industrial design
of the Shimano Dura-Ace 7900 crank.

“Every other email we get from dealers and
customers asks if our rings work on the 7900 and 7950 cranks,” Adam Haverstock,
marketing director at Praxis Works told BikeRadar. “The short answer is yes,
of course, they’re a standard 130 and 110 [BCD], and they work great, but the
second part of that question is: do they look good?”

The forged 7075-T6 alloy rings will be available in a
specific kit to fit the Shimano 7950 (compact) crank first, which fulfills two
needs according to Praxis, it gives compact users access to 50-/36-tooth
replacement rings, and will serve to usher in two Praxis’ cyclo-cross chainring
kits, featuring either 46-/36-tooth or 48-/36-tooth ring sizes. 130 BCD kits
will follow shortly thereafter, and also include a 46-/39-tooth ‘Pro’
cyclo-cross chainring kit.

The key to making the Dura-Ace 7900 kits work, and look
good, are the chainring nuts, which are engineered to match the industrial
design (ID) of the contemporary Dura-Ace crank, and because of the crank’s
design it forced Praxis to design three different nuts to best match it. While
the chainrings will be anodized black, Praxis are in the process of working to
best match the anthracite finish of the crank, which is no small feat.

“We’ve
got it pretty darn good, but the tonality is off by a shade or two,” said
Haverstock. “It’s not an exact science — it’s an acid bath.”

Praxis have no plans to sell the bolt kits alone, as they’re
hoping to use the Dura-Ace kits to introduce riders to their forged chainrings.
Aside from Shimano, most manufacturers use machined chainrings, and with such
rings their complexity — in terms of timing and shift ramps — is directly
related to machine time, and as in any business time equals money.

Praxis forge their rings, which, they say, allows them to
offer more heavily engineered ring designs — i.e. better shifting — without the
costs associated with more machining. The downside, each ring forging ‘tool’ is
a considerable investment, thus the small 12-person firm (split between Santa
Cruz, CA and Taiwan) moves relatively slowly, which is illustrated by the
August release target for the Dura-Ace 7900 products.

Sensible manufacturing: stamped and machined single rings   

Praxis Works’ single, guide-rings, will be available in one-tooth increments between 32- and 38-teeth

Praxis Works’ newest product, their single, or guide rings
(available in April) are machined from 4mm 7075-T6 blanks. They use stamping
and machining as the manufacturing method, here, because their designs are
relatively simple, when compared to those engineered to shift.

The focus of Praxis’ single-ring construction is on
stiffness, wear resistance, and a wide range of options — they make their
single rings available in seven sizes, from 32- to 38-teeth, and the rings are
rated for both nine, and 10-speed use with a 104 BCD.

While the final price has yet to be set, Praxis Works
estimate between US$45 to $50 per ring, and claim weights for the rings between
36g to 70g.

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