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Tech News – April 29, 2003
Edited by Paul Mirtschin
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Shimano unveils 2004 Dura-Ace brakes and derailleurs
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Shimano has released another set of CAD drawings showing off the 2004 Dura-Ace group. Also, with Lance Armstrong racing the group at both the Amstel Gold Race and Liège-Bastogne-Liège, we have had a chance to see just how it looks in the flesh.
The latest release of CAD images are of the new Dura-Ace BR-7800 dual pivot caliper brakes and the FD and RD-7800 derailleurs. Both have been completely redesigned to reduce weight and improve performance, in fact Shimano claims to have increased the stopping power of the new front brake by a whopping 25 percent, something that normally comes with an increase in weight, not a decrease.
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The brake pads are made from a new compound, claimed to offer 100 percent improved wear, while a convex washer system on the anchor bolt makes it easier to get the toe-in right. Shimano tells us that the rear caliper was as powerful as it needed to be, so all changes to the design of the rear brake were for weight reduction.
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The RD-7800 derailleur is 15 grams lighter than current model RD-7700, and the outer link has been redesigned to make it more rigid. And of course it'll move across ten sprockets instead of nine. Shimano says the new rear derailleur will work with nine speed systems (and presumably vice versa).
To assist with front shifting, Shimano has increased front derailleur rigidity when shifting from low to high gears by 30 percent by moving the main pivot location. The chain cage has also been narrowed to accommodate the new ten-speed Dura-Ace chain.
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Another small but important change to the Dura-Ace group has been in the cable outers. Shimano has changed the grease in the SIS-SP41 cables to a silicon-based grease, claiming a reduction in friction of ten percent.
Although Lance Armstrong's USPS bike is the only one currently fitted with the 2004 Dura-Ace group, the list of teams awaiting the release for racing is quite impressive. Rabobank, Kelme, Lampre, Gerolsteiner and Credit Agricole are all preparing for their groups to arrive.
We have received a number of emails asking for more information on the 2004 Dura-Ace group, so we will summarise them here, hopefully answering all your questions.
How does the crank attach? Will a worn bottom bracket mean the crank needs replacing?
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As with this year's XTR group, Shimano has decided that the use of larger, oversized axles and a two piece bottom bracket and cranks is the way of the future. The right hand crank and the bottom bracket are one piece, while the left crank is splined. As in a threadless headset, a threaded cap draws the crank onto the splined bottom bracket, where a pinch bolt is tightened to hold the crank arm onto the bottom bracket axle.
The bottom bracket axle has been increased in diameter as much as is possible; any bigger and it wouldn't fit inside the frame. The bearings have been moved to the outside of the bottom bracket shell. The effective bottom bracket width is therefore wider, which should make for a stiffer bottom bracket.
The axle is a sliding fit into the bearings in the bottom bracket. If the bearings are worn or damaged, it is almost painless; the cranks and axle can be re-used.
How compatible with the nine-speed Dura-Ace will the group be?
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Not very. As with the jump from eight-speed to nine-speed, you'll be looking at some extensive replacement. At the minimum it looks like you'll need new shifters, sprockets, chain, front derailleur and chainset. The top to bottom distance on the cluster hasn't changed, so a 2003 rear derailleur should work, but while you're spending all that money, what's a new rear mech?
The chain is thinner, so the chainrings will be slightly thinner and spaced more closely, which in theory means they should all be replaced too. However, we've seen and heard of plenty of examples of n-speed parts being mixed with n+1-speed chains and shifters, so there might be a dodge there for those prepared to accept a non-Shimano-approved set-up.
So far, Lance Armstrong's 2004 Dura-Ace bikes have been using what appear to be current production wheels, so it looks as if Shimano has crammed ten sprockets into the space previously occupied by nine, If that's the case, it means you won't need new wheels, so the CFO of the family can breathe a little easier.
When can we buy it?
Not for at least six months, unless you have good connections inside a TT1 trade team.
Hollow axles, ten speed, two-piece cranks? Whatever next? Tell us what you think.
Photos
Images by Shimano
- Side view of the 2004 rear derailleur
- Side-front; no, it doesn't come in these colours
- Side-rear view, showing all the adjustables
- Front view of the 2004 dual-pivot brakes
- It might not look like it,but a lot has changed
- It does look nice in red, blue and green doesn't it
- 2004 Dura-Ace front derailleur
- a slight change in the pivot makes for a much stiffer derailleur
Dura-Ace in action at the 89th Liège - Bastogne - Liège
Images by Jeff Tse/www.jefftse.com/cycling
- Lance Armstrong (US Postal) arrives in Liège on a new Trek frame, equipped with Dura-Ace 10 speed
- The new Shimano Dura-Ace 10 speed crankset, pictured on a US Postal spare bike
- The new Shimano Dura-Ace 10 speed brake lever/shifter
Images by Luc Claeseen/www.actiefotos.be
- Armstrong on his 2004 Dura-Ace equipped bike
Dura-Ace in action at the 38th Amstel Gold Race
Images by Jeff Tse/www.jefftse.com/cycling
- Lance on his Trek 5900 with 2004 Dura-Ace
- A closer look at the cranks and bottom bracket bearings
- Count the sprockets if you can
- Lance's hand on the 2004 levers
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