Sunday, August 31, 2014

Basement Bike Shop: Upgrades to the Cervelo

The Cervelo P2 was dropping chains on the inside for a while, I got sick of the lame Shimano "Dura Ace" TT shifters, and the Ultegra 6600 group that came new on the original P2SL in 2008 was showing its age, so I invested in some tidbits for an upgrade:
  • Sram R2C shifters, indexed, optimized for the Yaw front derailleur.
  • Sram Red Yaw front derailleur,
  • Sram Force rear derailleur.  (Have you seen the price on the Red option?)
Sram Red Yaw FD

Sram R2C Shifters
Sram Force RD

Other projects:
  • It's not new, but I also determined to swap in a Sram Force crankset (172.5 crank arm length) that's been gathering dust in my parts bin.  As part of that task I needed to move the chainrings from the current crankset to maintain my 52-36 gearing.
  • I decided to swap in the Hed wheelset to replace the uber-bling Supra set I've been racing recently.  Somehow they look better on the Focus.
  • May as well replace a cable or two while I'm at it.  They do break with use, if thankfully infrequently.
  • Other tweaks that made sense while the bike was in pieces, including new bar tape and new brake calipers.
One challenge:  I needed to get this done in time for the Saratoga 12-hour, which I rode in mid-July.  The parts did not arrive until Monday and the race was Saturday; making matters worse, I was off on Wednesday-Thursday for a funeral.
Here is my report on the upgrade process.

A.  Installing the Sram Force rear derailleur:

No surprise, but this could not be any more straight-forward.  Here's the process:
  1. Pull the metal crimp-thingie from the end of the derailleur cable with a pliers.  Keep.  These can be re-used and I can never seem to find the jar of new ones.
  2. Using a 5mm hex wrench, release the cable from the derailleur.
  3. Using the same wrench, remove the derailleur from the hanger.
  4. Set the old derailleur aside.  It will build back on the FUBAR P2SL frameset for a wall-mount bike using old parts.
  5. If the cable is not terribly frayed, pull it through from the shifter end.  Use the pliers to reshape the crimp-thingie as needed and replace it on the end of the cable, crimping it to hold.  Coil the cable and preserve for emergency use on a tour.
New RD.  Housing is in place but cable is not yet threaded.
Old front and rear Ultegra 6600 derailleurs.  Anybody want 'em?
Old RD cable.  Keep for roadside repairs.
 B.  Installing the Sram Red Yaw front derailleur:

a.  Removing is trivial:
  1. Rinse and repeat the above instructions for the cable.  In this case mine was too frayed to be worth keeping.  Because the longer rear derailleur cable that I am keeping will work fine as a backup for either the front or the rear, I tossed this one.
  2. The attachment bolt for the Ultegra front derailleur turned out to require a 4mm hex wrench and you had to remove the bolt, then replace it in the now removed unit so as not to lose it.
b.  Installing the Sram Red Yaw FD proved to be a tad more complicated than was installing the Force RD:
  1. Use a 4mm hex wrench to get the unit started in the slot on the braze-on.  Tighten enough that it holds on its own but you can still manipulate it up and down and side-to-side with a little effort.  Don't do as I did and forget the convex washer-spacer on the opposite (front-facing) side of the braze-on.
  2. The instructions require 1-2mm spacing between the bottom edge of the derailleur and the top of the tall teeth on the large chainring.  Measuring is a minor challenge, but I found using a 1.5mm hex wrench as a spacer worked quite well.
  3. The Sram derailleur has a line imprinted on the top side that you are instructed to line up with the teeth of the large ring to get the side-to-side position correct.  This works well, but you then need to ensure it does not move when you tighten the fixing bolt.
  4. Tighten the fixing bolt to 5nm of force.  Having spent hundreds on near-top-end componentry, I gave up on the usual "until it feels snug" approach and pulled out the torque wrench.
Using a 1.5 mm hex wrench to check the derailleur-to-chainring tolerance.
A really bad picture of the Sram Red Yaw FD installed, with my foot on the right.
Torque wrench tightening the new FD.  5nm of force is prescribed.  With expensive parts, no more "tighten until it feels right"!
 c.  The chain-catcher.  The new FD came with a chain catcher, which -- having been dropping chains to the inside -- struck me as an excellent addition:
  1. This installs with a 2.5mm hex wrench, tightened to 1-2nm of force.  
  2. The key is spacing on the small chainring.  With the FD in the correct position, it is not hard to get the spacing correct -- but because the chain-catcher bolts into the if the FD is not in the correct position, you have to remove the chain catcher to reposition it.
  3. The chain catcher has a 2.5mm adjustment bolt that interacts with the convex washer-spacer (number 1 in the immediately prior set of instructions).  Loosening the bolt moves the spacer toward the center (inward) -- away from the small ring; tightening it moves it outward -- toward the small ring.  The idea, obviously, is that with the chain turning the catcher does not ever quite encounter it, and the place to test the position is in the smallest gear (small ring, large cog). 

C.  Installing the Sram R2C indexed shifters:

This turned out to be the greatest challenge in this upgrade process.  Suffice it to say that internal cable routing is nice for the person riding the bike and a real pain for the person wrenching on the bike.

a.  Removal:
  1. The Dura-Ace bar-end shifters come apart with a flat-head screwdriver.  That part is easy.  Screw them back together at the end to keep for a different project.
  2. Having separated the body from the mount, use a 5mm hex wrench to loosen the insert and remove it from the bar ends.
Remove the lever.

5 mm. hex wrench to loosen the compression plug.

The shifter once removed.  Put it back together or the parts will get lost!

b.  Installing the new levers:
  1. Insert the shift levers into the ends of the aero-bars.  Using a torque wrench with a 5mm hex attachment, tighten the compression plugs to 8nm.
  2. Loosen the hex bolts on the inside (red-colored side) of the levers.
  3. Position the levers in an "aerodynamic angle."  (Seriously.  In my case that meant pointing them basically straight ahead, which I assume to be aero, and trying to match the angles between left and right.  The matching process is not trivial, and I did not accomplish the goal in several tries -- but it's pretty close.)
  4. Tighten the hex bolts to 9nm.
  5. On each side, feed the cables into the housing.  Install the dial tension adjuster in the front derailleur housing somewhere before it meets the frame by (1) cutting the housing; (2) trimming off ~1/2 inch; and (3) bringing the two ends of the separated housing together on either side of the tension adjuster.  The cable then runs through the entire rejoined length as if it were a single piece of cable housing.  (There is no tension adjuster to install for the rear derailleur because the barrel adjuster is built into the derailleur.)
Tighten compression plug to 8 nm.

Good thing I have a basement wind-tunnel.

Oh yeah, that feels way aero!

9nm.  Good luck hitting that tightness without disturbing your aerodynamic angle.
c.  Running the cable:

The next bit is frame and cockpit dependent.  I have a Cervelo P2 (carbon) with Profile Design T2+ aerobar extensions.  Different bikes and bars will require different steps.  I hope they are easier:
  1. Where the cable housing runs depends on your bars -- with my Profile Design T2+ alloy bars, it enters into the bars through slots on the underside about 3" back of the ends and exits the back end through holes in the specially-made end caps.  The housing then runs to the down tube on the frame, with the right shifter entering the right-side port and the left entering the left-side port.  The front derailleur tension adjuster should be somewhere between the exit from the aero-bars and the frame entry point.
    Tension adjuster for front derailleur, just back of the aero-bar extensions.
  2. Feed the naked cables into the frame at the ports.
  3. Wiggle, twist, pull and push, and generally move the cables for however long it takes to get them to emerge from the frame just below the bottom bracket.  This process took me ~20 minutes.  (It turns out the inside of the tubes on a carbon frame is not nearly as smooth as is the outside!  Past experience with two different aluminum-framed bikes was much, much easier.)
  4. Run the cables through the plastic cable guide screwed to the frame at the underside of the bottom bracket housing.
  5. Bend the front derailleur cable upward and insert it back into the frame at the entry point in the seat-tube behind the crankset.  Wiggle, twist, pull and push, and generally move the cable for however long it takes to get it to emerge from the seat-tube below the front derailleur.  This process took me another ~20 minutes.  Take whatever steps necessary to be sure it does not slip back out!
  6. Run the rear derailleur cable along the drive-side chain-stay to re-enter the housing for the final loop to the new rear derailleur.
D.  Attaching the cables and tuning:

The basics of this process are pretty simple.  Getting it right is art, not science, and you may conclude (as I usually do, and ultimately did here) that taking the bike to the LBS for a final tune is wise.  In short, you now need to attach both front and rear derailleur cables; adjust the limit screws; and dial in the tension to get the indexed shifts right on target.

The below assumes you have installed the chain.  In my case I replaced the crankset as well.

New Sram PC-1091 chain.  Picture is of the quick-link used to attach the chain.  I measured the chain to match the length of the one I removed and used a chain tool to remove the excess links before installing.

a.  Attaching the cable on the front derailleur:
  1. Trigger the left (front) shifter to the loosest point. On these shifters that means moving it upward one click.
  2. Tighten the inline barrel adjuster to the maximum by turning it to the right.
  3. Pull the cable through the attachment bolt on the front derailleur.  Pull it hand-tight.  Tighten the cable attachment bolt. I never waste my time with a torque wrench here.  I just yard on it.
  4. The front derailleur sits naturally at the small chainring location.  Once the rear derailleur is attached you can adjust the limit screws and cable tension.
b.  Attaching the cable on the rear derailleur:
  1. Trigger the right (rear) shifter to the loosest point.  That means moving it downward as many clicks as is required.
  2. Tighten the barrel adjuster on the rear derailleur all the way.
  3. Pull the cable through the rear derailleur attachment bolt hand tight and tighten the cable attachment bolt.
  4. The rear derailleur sits naturally at the small cog location. 
c.  Adjusting the derailleurs:
  1. Spin the pedals and operate the rear shifter (upward clicks) to move the chain to the largest cog.  With the chain on the small ring it is now in the lowest gear.
  2. Getting the chain to move will require tightening the cable with the barrel adjuster.  Tighten the cable by loosening the adjuster.  This is counterintuitive:  what you actually are doing by loosening the adjuster is lengthening the housing, which has the effect of shortening the cable that runs through it.  If you find yourself opening the barrel adjuster too far, screw it back down tight, loosen the cable attachment bolt, pull the cable tighter (perhaps using a pliers), and re-tighten the bolt.  Then try again with the barrel adjuster.
  3. Pull the lever beyond the final click to see how far you can move the rear derailleur.  If it moves toward the center from the largest cog, you want to tighten the limit screw so the unit cannot move so far inward.  (The danger, of course, is a chain dropped in your spokes.)
    Limit screws.  Much more accessible on this Sram RD than on the Ultegra 6600 I removed.
  4. Move the derailleur to the smallest cog and repeat the limit screw exercise.  When moving the derailleur, use the barrel adjuster to get the shifts crisp.  If a particular shift is not immediate, turn the barrel adjuster 1/4 turn in the direction you are trying to move the chain and try again.
  5.  Repeat the exercise for the front derailleur.  The adjustment process up front never seems to be as smooth.  You want to check the limit screws for the front derailleur with the chain in the cog most likely to cause a dropped chain -- the large cog for the inside ring; the small cog for the outside ring.  You are likely to have to tighten the cable using a pliers before it is taut enough to effect the first shifts.
  6. Once the front derailleur is shifting, the inline barrel adjuster can fine-tune the shifts.

I got this done in time for the Saratoga 12-hour and the bike worked fine for that event.  The indexed shifting on the front derailleur was a nice change from the shift-by-feel of the old Shimano levers.  The R2C shifters look cool if nothing else.  I then dropped the bike at the LBS for a $25 tune.

A worthwhile change?  I don't know.  Dolling up the Cervelo a tad will hopefully keep me from buying a new tri bike anytime soon.

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