Dietmar Putzas is an enthusiastic racing cyclist - but there was one thing about the current mountain bikes that left him no peace: "I want those great disc brakes like on a mountain bike," said Putzas, "I want them on a racing bike too." And on a contemporary, lightweight carbon racer with lightweight carbon wheels. The Swabian by birth and Swiss by choice thought that a total weight of seven kilos should be possible to undercut for more braking fun.
With his idea of a lightweight carbon racer with disc brakes, Putzas is entering a market niche - at least for the time being. Component giants such as SRAM and Shimano only offer hydraulic disc brakes for mountain bikes. Hardtail carbon frames such as Merida's "O.Nine" or Scott's "Scale", which weigh less than 1,000 grams including the mounting base for the brakes, show that the technology works on lightweight carbon frames. So far, however, no mass-produced manufacturer offers road bike frames with this technology - and therefore the component manufacturers are not really pushing ahead with the development of suitable brake and shift levers. The fact that the UCI recently allowed disc brakes in cross sport may finally bring movement to the market - but certainly not overnight.
Dietmar Putzas was not deterred by such adversities. At Eurobike 2009, the doctor of chemistry and newcomer to the bike business was looking for a carbon frame builder to produce a lightweight frame and fork with disc brake mounts exclusively for him. Rejected by the big players in the industry, he finally found what he was looking for at the company Conbow, at a mini stand in a corner of the hall, between suppliers of candy-coloured bells and sprockets. The Taiwanese company actually manufactures tennis rackets. The conversation was friendly and the Taiwanese were prepared to build less than 50 frames and deliver them to Zofingen in Switzerland, along with carbon rims for wheels.
The "Disc Race" project, as the finished racing bike is now called, could therefore begin. Putzas chose the "R1" from Formula as the basis for his hydraulic brake system, a lightweight brake with disc diameters of 140 and 160 millimetres, which are rather small for mountain bikes. Putzas invented a simple converter solution for actuating the brakes with mechanical brake levers, in which the usual shift brake levers are supplemented by additional hydraulic brake levers on the upper handlebars. These are actuated either directly or by the cable of the shift brake levers. The advantage of this principle is that it works with all brake levers on the market.
The lightweight carbon wheels are also built by Putzas. The hubs are from Tune and are called "King Kong". On our test bike, 28 spokes transfer the braking forces from the hub to the 50 millimetre high "Conbow" tubular tyre rims. The Disc Race is completed with a colourful but exquisite mix of components from Fulcrum, SRAM and Shimano. The saddle, seat post and stem are from Procraft, the handlebars from Ritchey. The complete bike weighs exactly 6.95 kilos - and Putzas has made his dream of a very light racing bike including disc brakes come true.
On our standard test track, peppered with steep descents and tight bends, the Disc Race performs excellently. Riding in the rain in particular is a real eye-opener: the brake pads engage powerfully after one wheel rotation and decelerate predictably. The modulation is good and sudden locking of the wheels, which can easily happen with rim brakes on carbon, is not an issue. On dry surfaces, the advantage is no longer quite so clear; only very experienced riders can achieve more than 6 m/s2 braking power due to the unfavourable centre of gravity on a road bike - this is also possible with a good rim brake on a dry aluminium rim that matches the brake pad. Nevertheless, the operating forces are somewhat lower and the modulation is impressive - an advantage not only on long descents.
The riding safety of the frameset is high, especially the fork is extremely stiff laterally and above all in the braking direction. However, a slight tendency to brake stutter under hard braking remains noticeable. On the other hand, the fork is noticeably uncomfortable. More annoying than that, however, are the jingling spokes of the laterally soft wheels and dragging brake pads when pedalling out of the saddle. The effect is intensified by the filigree Heylight titanium quick-releases, whose contact pressure is not sufficient to fix the wheels absolutely firmly in the dropouts. As a result, the wheels move by a few tenths of a millimetre - enough for the brake pads to rub against the discs. We were able to minimise the problem with a quick release with a steel axle, but the future certainly belongs to a system with a thru axle, similar to mountain bikes.
ConclusionDietmar Putzas' courage was to be rewarded. With the Disc Race, he proves that disc brakes do not stand in the way of lightweight road bike construction and brake significantly better than rim brakes - a safety advantage on fast downhill rides and on wet roads; and with disc brakes, carbon rims finally have their unrestricted raison d'être. If the teething troubles can be eliminated and the brake discs integrated into stiffer wheels, you could say without reservation like Putzas: "Sometimes I just brake because it's fun!"
Price frame set/complete bike: 1,499/5,999 Euro
Reference/Info: DBikes, tel. 0041/62/7515408, www.dbikes.ch
Frame sizes*: 50 to 58 cm, 2 cm each; 56
Seat/steering angle: 73.5/73.5 °
Seat/top/head tube: 525/560/149 mm plus 8 mm headset cap
Wheelbase/caster: 980/54 mm
Stack/Reach/STR **: 560 mm/390 mm/1.44
EQUIPMENT
Fork: Conbow RFR 15-B
Steering bearing: FSA ZS 3
Brakes: Formula R1
Gearing: SRAM-Campagnolo-Shimano mix
Bottom bracket: Fulcrum Racing RRS
Wheels/tyres: Conbow- Tune/Continental GP 4000 Tubular
Handlebar/stem: Ritchey/ Procraft
Saddle/post: Procraft PRC/Procraft
MEASURED VALUES & INDIVIDUAL NOTES
Weight of complete bike: 6.9 kilos (without pedals)
Frame/fork/headset bearing weight: 1,098/478/71 g
Standardised weight frame set***: 1,675 g - 2.7 Steering head stiffness: 100 Nm/° - 1.0
Lateral stiffness fork: 60 N/mm - 1.0
Bottom bracket stiffness: 61 N/mm - 1.0
Comfort frame: 276 N/mm - 2.3
Comfort fork: 115 N/mm - 5.0
Manufacturer's specification; tested frame size greased; **Stack/Reach: projected vertical/horizontal measurement from the centre of the bottom bracket to the top of the headset; STR (Stack to Reach); values between 1.45 and 1.55 indicate a sporty riding position, values below are race-like, above are comfortable; ***adjusted weight for frame size 57 and fork steerer length 225 mm; ****The grade includes further individual grades, which we cannot print for reasons of space. In the case of complete bikes, 60 per cent of the final score is based on the equipment.
