2x9 ala PVD
The concept for this project was driven by my upcoming races at the 2007 Sea Otter Classic. I plan on competeing in Super D, Hardtail Downhill, and Cross Country on the same bike.
I have been riding my Six-Speed on trail with great results, but I will need more range for the Sea Otter races.
Narrow Range Front Gearing
Finding a crank that will run adequate gearing for a 2x trail bike is a bit difficult. One crank that is almost perfect from the box in terms of gearing is the Ultegra 10 Speed road triple crank. The smaller gears of the crank are 39 and 30. A very good spread.
The Cassette
The Front Derailure
Chainline
The Ultegra 10 speed Triple cranks configured as a twin gear as I have done produces a chainline of 43.5mm. This is pretty bad. It brings the front derailure very close to the rear tire. Adding an additional 2.5mm spacer brings the line out to 46mm. Any more than this is very difficult to acheive.
The Shimano Road and Mountain bottom brackets and their shell and overall installed dimentions.
