By now the new SRAM Red group has been available for about a year (if you recall it was introduced last year and ridden to great success by Tom Boonen in the spring classics.) I've been using the shifters for a year now, and the front derailleur for only a few months less. However, there is still some confusion about how to install the front derailleur properly.
Installing the Yaw derailleur isn't vastly different than installing your garden variety front derailleur (which is really every other one on the market) but there are some subtle differences that vastly change the unit's function. Without taking these special steps into account, users may be significantly frustrated by the poor shifting performance and constant chain rub.
After the jump, we'll go step by step through the installation process.
Before installing the Yaw derailleur, you'll need to ensure that you've removed the chain and you have the following tools:
- 5mm allen key
- 4mm allen key
- 2.5mm allen key
- Small screwdriver (preferably bladed, but narrow phillips will do)
- Pliers or channel locks
- Torque wrench (if working on a carbon frame)
- Carbon assembly paste (if working on a carbon frame)
Installation will vary a little bit depending upon if you're using a clamp style derailleur, a braze on with a separate band or a braze on with a frame mounted tab. If you're using a braze on unit with a separate band, I HIGHLY suggest one of the new style Red bands that have the “chain spotter” tab on them. This will make setting the chain spotter a much simpler affair and it will be a much stouter setup in the long run.
Install The Clamp and Derailleur
The first order of business is to screw the derailleur into the band (if using one). Smear a fine layer of carbon assembly paste onto the band and clamp it around the seat tube/ Use the 4mm allen key to snug up the clamp bolt just enough so that it won't slide around without a little effort; you'll need to move the derailleur up and down the tube as well as twist it around to find the yaw angle, so don't clamp it down tight.
Setting The Height And Yaw Angle
The first order of business is to set the proper derailleur height. To do this, we'll slide the derailleur down so that the front of the cage is touching the teeth of the large chainring, then we'll simply raise it up about 2mm off the teeth. Alignment at this stage is not really important, only the clearance from the big ring is.
[pullquote]Missing this step results in poor shifting performance and neverending chain rub. [/pullquote]To set the yaw angle, use your fingers to actively pull the cage over the big ring and begin tightening the low limit screw. The ultimate goal is to center the cage over the big ring so we can set the yaw angle. Once the low limit screw has the cage centered over the big ring, you need to align the cage properly. You need to twist the derailleur around the seat tube in order to align the front and rear alignment marks (etched into the top of the cage in front and the top of the plastic part of the cage in the rear) so that they line up directly with the big chainring.
This small step is the one that many people miss, since it's different from installing a normal front derailleur. Missing this step results in poor shifting performance and neverending chain rub. Once the angle is set, double check the cage height over the big chainring and snug down the band bolt (or fixing bolt) with a 4mm allen key or torque wrench.
With the yaw angle set and the derailleur still hovering over the big ring, install the chain and grab your screwdriver to set the low limit. With the chain installed, unscrew the low limit screw a few turns and spin the cranks. Repeat this process until the chain drops to the small chainring, then shift into the largest rear cog. At this point, the chain will probably be rubbing the inner plate of the cage, which we don't want.
According to SRAM, the low limit screw should be adjusted so that the chain just barely rubs when in the small chainring and largest cog. They suggest that under pedaling tension, the rub will be eliminated. In my own experience, this is NOT the case. Leaving the chain to rub on the cage while in the stand will end up with it rubbing the cage while riding, particularly in the case of today's ultra stiff carbon frames that have almost no bottom bracket flex at all. I recommend leaving about 1mm of space between the inner derailleur cage plate and the chain plates. This will ensure rub free operation and will not affect shifting performance.
Attach The Cable, Set High Limit
Pull the cable tight into the groove of the derailleur fixing bolt and snug the bolt down with a 5mm allen key. Once attached, shift from small ring to large, taking note of how far the cage travels. You'll want to set the high limit screw such that the yaw alignment marks are moved no further than centered over the large chainring. If the chain drops off the outside of the large chainring, continue to screw in the high limit screw until it does not.
Adjust the cable tension as you normally would. Shifts should be quick and smooth, with no rubbing in the small ring/large cog and minimal rub in the big ring/large cog. There should be no rubbing on the front derailleur inner plate while in the big/big combo. When shifting down, the chain should drop readily and not skate over the top of the chainring teeth.
To install the chain spotter, slide it over the head of the fixing bolt and thread the small bolt into the head of the fixing bolt. Using a 2.5mm allen key, tighten the chain spotter just enough that moving it with your fingers requires some effort. Using the same 2.5mm allen key, adjust the “bump stop” screw so that the chain spotter is about 1-2mm from the chain as it sits on the inner chainring, then tighten down the chain spotter mounting bolt completely.
If you're not using a band that has a chain spotter stop, or you're using the braze on mount on the frame itself, the “bump stop” screw has no use. (There is some hope though, in the curved washer that comes with the derailleur: this curved “washer” has a chain spotter stop integrated into it. I've not had the pleasure of trying this approach, so I can't comment upon it, but it appears to work just fine from the design of it.) Set the chain spotter's distance from the chain to 1 or 2mm, then use the blade of a screwdriver or something similar sized in order to hold the gap while you tighten the bolt.
For those of you who prefer an audio visual element, check out my video tutorial on installing the Yaw derailleur: