Google was my friend.
per WorldClassCycles.com
REYNOLDS 853 / 853OS info
Reynolds 853 is a high strength, 210,00 psi, heat treated, air hardened steel alloy. Careful control of the alloying elements combine to give these tubes enhanced mechanical properties surpassing other materials currently available.
The main advantage of Reynolds 853 is its ability to air harden after joining, a characteristic not shown by other chrome molybdenum / manganese molybdenum materials presently on the market. When building frames using either TIG welding or high temperature brazing, above 1600 degrees, the joints increase in strength as the frame cools to room temperature.
LUG CONSTRUCTION IS THE PREFERRED METHOD OF JOINING 853. It allows a much larger area to be heated than tig welding which concentrates the heat to a very small area at the weld. This completely goes against the “AIR HARDENING” building philosophy of the material and adds nothing to the strength of the joint. It is however a much cheaper joining method, requiring less time and skill to perform.
Due to the superior mechanical properties of 853 tubing, there are several benefits which will translate directly to the cyclist. The wall thickness of 853 has been reduced to 0.4 mm, a full 0.1 mm thinner than Reynolds other top of the line 753 tubing. This translates into a frame weight of under 3 pounds 5 ounces for a 56 cm frame (less fork). Because of the added hardness of this alloy the chances of denting the tubing are no greater than that of present materials being employed. The final significant advantage is the increased stiffness of the frame and its ability to transmit all of the cyclist power into forward motion. The oversized 853 tube set, with its oval chainstays represents the ultimate in power transmission. Aside from the 853 OS tubeset, conventional diameter sets are available which will allow for a more comfortable ride, while still retaining most of the benefits associated with 853 oversize.
853 is currently produced in 8 tube tubesets. There are no fork blades drawn from this alloy. Bob Jackson will supply 853 frames with your choice of fork material., and configuration.
via the "info" link above:
Reynolds 853 - heat treated
UTS: 81 - 91 Tsi, 180 - 210 Ksi,
1250 - 1450 MPa
STEEL IS REAL !
This seamless air-hardening steel tube sets new standards for professional cycle frames and proves that steel still has a future at the highest levels. It is suitable for TIG welding and brazing, using lugged or lugless construction. The production process ensures tight tolerance, gauge tubes. The strength to weight ratio of 853 is close to that of quality titanium frames. A normal chrome molybdenum steel will lose strength in the joints after the heat has been applied.
This material (853) INCREASES in strength as the frame cools to strengths well in excess of the delivered values shown above. This unique air hardening property of Reynolds 853 provides additional stiffness through reduced microyielding at the joints, allowing stiffer frames with excellent fatigue strength (when compared to standard chrome molybdenum) and a superior ride quality from the finished frame. On road and touring frames we recommend the use of 631 or 725 fork blades with 853 frames.
We offer this tube set in many sizes for custom framebuilders, and is suitable for lightweight frames, strong/tall riders and has also been specified for free-ride and BMX frames due to its' high impact strength.
Last edited by Mike Mills; 08-17-11 at 03:18 PM.