A few newsletters back, RBR author and contributor Coach Rick Schultz offered tips on expanding your gearing with WolfTooth’s Road Link (his article is in the form of a downloadable PDF, in case you missed it).
This week, we’re very pleased to add a related gearing tip from RBR founder Ed Pavelka. While he was recovering from hip replacement surgery, Ed recently purchased a custom Independent Fabrications randonneuring bike equipped with SRAM’s eTap wireless electric shifting components. He loves his IF and wrote to share how easy it was to go super low with his eTap gearing. Here's what Ed wrote:
In hopes of taking strain off my new hip and my soon-to-be 72-year-old pistons, I thought it would be wise to lower the gearing on my randonnee-style bike.
The original build was with a SRAM 22-speed drivetrain – 46/36 chainrings and an 11-32 cassette. 32 is the max cog that the eTap "medium cage" rear derailleur can accept. Or so SRAM says.
I bought the WolfTooth Road Link derailleur hanger extender after reading Rick’s RBR article a few weeks ago. The plan was to us the Road Link to lower the mech so it could handle an 11-36 cassette and give me a tree-climbing 36x36 low gear. Not that that's even remotely necessary in Florida, where I live most of the year. But, the lower the better for my annual visits to Pennsylvania and upstate New York.
Before going to work, I watched several YouTube videos about eTap installation, tips and tricks. I learned that the 32T max could be successfully exceeded even without a Road Link.
Sure enough! By turning the derailleur's B-tension screw way in (SRAM provides a real long B screw), I got the recommended 6-mm of clearance between the top jockey wheel and the 36T. A longer chain was required, but nothing else. Shifting was spot-on in the work stand and on a test ride.
Every gear combo from small/small to big/big (in my case 36x11 to 46x36) is scrape- and rattle-free, with no need to trim the front derailleur. In fact, the eTap "yaw" movement is self-trimming, and it works.
The B screw was the key to the whole thing. SRAM makes 2 eTap rear derailleurs, a short-cage that it claims can take a max 28T cog and a "medium" cage that can take a 32T. Simply by running the B screw way in, on the medium-cage a 36T is easily accommodated, and it looks like a 40T might work, too, even without the Road Link. It probably won't be too many more years before I'll need to try that.
I guess the lesson here is not to take manufacturer limits as gospel.
However, in my case, I'm using 46/36 chainrings instead of the traditional compact 50/34. To get the chain length right I wrapped it directly around the 36T cog and the 46T ring (bypassing the rear derailleur), pulled the ends tight together and added 2 links. This meant cutting only 2 links from the new chain.
It makes me wonder what would happen if I did have a 50T big ring. Would a standard road chain be long enough to accommodate accidental shifts into the 50x36 cross-chain gear without jamming the rear derailleur? Would the chain be so long that it would overlap at the jockey wheels in the 34x11 opposite cross-chain? In other words, would rear derailleur capacity come into play?
It's an art, not a science!
Thanks for sharing, Ed!
Jim Langley is RBR's Technical Editor. He has been a pro mechanic and cycling writer for more than 40 years. He's the author of Your Home Bicycle Workshop in the RBR eBookstore. Check out his "cycling aficionado" website at http://www.jimlangley.net, his Q&A blog and updates at Twitter. Jim's streak of consecutive cycling days has reached more than 8,000. Click to read Jim's full bio.