Jim’s Tech Talk
By Jim Langley
My son-in-law Frankie has really taken to cycling. I introduced him to you a year ago when he asked for tips on shifting double-chainring road bikes to share with his riding group. Here’s that story in case you’re learning to shift or know someone who needs a quick primer: Beginners’ Guide to 2X Shifting.
Since last time, Frankie has added a mountain bike to his stable. Now that he’s got two rigs to keep running, he reached out to me for a lesson on derailleur adjustment. He only lives an hour away, so he came down to my house where we could put both bikes in a repair stand. With them off the ground, it’s both easy to pedal and to see how things are functioning because the bike is up high, close to you.
We worked on Frankie’s Felt first and that’s the one we’re concerned with for this article and contest. It’s a 2017 55x “gravel bike.”
This is the first time for a contest in Tech Talk. Like a city limits sprint, the idea is to add a little fun. And the prize is a nice tool that is sure to see plenty of use in your home bike shop. Or, if you win it and already have one, you’ll now have one for your traveling toolbox and bench.
How this contest works is that I’m going to describe Frankie’s shifting problem and the steps we took to try to fix it. Keep in mind that this was a lesson on adjusting derailleurs for Frankie. Hopefully, if you’re learning, too, you’ll pick up some helpful tips.
To enter the contest, simply follow along reading everything we tried. At the end, there’s a cliffhanger of sorts because I don’t reveal what the problem was or how we fixed it. The first reader who posts a comment identifying the exact problem causing Frankie’s shifting issue will be the winner. We’re looking for a very specific problem and the fix for it.
The photos show the bike as it was when we worked on it. To give you a hint, the thing causing the issue is shown in the photos but that probably won’t help you come up with the prize-winning answer.
I will reveal the problem in next week’s Tech Talk. I will also tell who won the contest and prize unless that individual specifically requests anonymity (and reach out to learn where to ship the tool).
Frankie’s Shifting Problem
Ideally, to teach someone rear derailleur adjustment (the Felt is a single-chainring bike), the drivetrain actually needs something adjusted. So, I asked Frankie if he was having any shifting problems.
He said that he had recently changed to an 11-42 cassette for easier climbing. And now when he shifts, there is sometimes hesitation. And, also that the bike doesn’t always stay in gear. Instead it occasionally auto shifts into a harder gear.
“Perfect!” I told him, explaining that hesitation and shifting out of gear are often related, common problems and relatively easy to fix.
I wasn’t certain that the SRAM Rival derailleur could handle such an oversize cassette (Frankie had bought it online). If not, that could cause the shifting glitches. But, a quick check of the derailleur specs online said it could.
Since it was a new cassette, I next checked to make sure it was properly installed and fully tightened. Because loose cassette cogs will move around, which can cause shifting issues like Frankie’s. The cassette was nice and tight.
Bikes can fall over and when it happens the rear derailleur often takes the hit and gets bent, messing up the shifting. I showed Frankie how to check for this by standing behind the bike and sighting to see if an imaginary vertical line would bisect the cassette sprocket the chain is on and both derailleur pulleys. It would.
Another quick check, I showed Frankie was to make sure his derailleur and its hanger on the frame were tight by checking with the right wrenches. Again, everything was fine.
Wanting to check the shifting, I quickly operated the lever to see if the bike would shift up and down the cassette and hit the gears with each click. It worked fairly well in the repair stand but did exhibit some slight hesitation shifting into the larger cogs.
Since this was a shifting lesson, I ran through basic system checks so Frankie could see how it’s done. I told him to always check the shift cable and shifter since cables can rust or fray and the housing they’re inside can get damaged over time. These things can cause shifting hesitation and worse, a broken cable.
I showed him how to pedal and push on the rear derailleur with his hand to shift up onto the largest cog. Then, by stopping pedaling and letting go of the derailleur, I showed him how slack is created in the shift cable and how you can free the housing from the frame shops. Once you’ve done that, you can slide the housing out of the way and visually check the cable for signs of rust or fraying. Also you can spot housing issues.
And, with the housing out of the way you can lube the cable. Frankie’s cable and housing sections were in near perfect shape and we just put a little grease on everything.
Next, since the cable was slack, I showed Frankie how you can test the shifter function by pulling on the cable with your left hand (holding onto it right next to the frame) and operating the lever through its entire range of clicks. That way, you feel the shifter itself through the cable because there’s no derailleur spring pulling on it.
Frankie’s shifter operated perfectly. No issues.
Rear Derailleur Adjustment Checks
Moving on to the rear derailleur, I went over the functions of the 3 adjusting screws so that Frankie would understand. First, I showed him the top screw for getting the clearance between the top derailleur pulley and the largest cog just right. Too close and the derailleur can jam instead of make the shift onto the big cog.
After that, I showed him the low and high gear limit screws that define how far the derailleur moves in and out when shifting. I explained that once correctly set, those screws usually stay in place and don’t need adjusting. But, so that he could learn how they’re used, I changed the screws and let him put them back in the right place.
I also taught him how to operate the derailleur by hand, pushing to shift onto the larger cogs and letting go to shift back down. Testing shifting like this is the best way to tell if the limit screws are functioning correctly because you can feel the stops. NOTE: this is for cable systems only, not electronic shifting.
Finally, the Cable Tension Adjustment
Yes, I could have started with this adjustment, however remember that this was a lesson to teach adjusting shifting. So, I took the long way to get here in order to teach Frankie other important checks first.
To do this final tuning, I had Frankie connect the shift cable again as it was before we started. I told him to make sure all the housing sections that we’d pulled out of the frame stops were fully seated again. I also reviewed with him that we had verified that the shifter, cable and housing were A-OK. That the rear derailleur was adjusted correctly and that there was no issue with the cassette.
At this point, I jinxed myself by telling Frankie we only had one easy last adjustment to make to get his bike shifting perfectly again. I then proceeded to show him the cable tension adjustment barrel on the rear derailleur and told him how it works. That counterclockwise turns make the cable tighter. And that shifting hesitation like his and a bike coming out of gear after a shift are frequently the result of a slightly loose cable.
But, when we made this “easy last adjustment,” it did not fix the shifting hesitation.
Can you identify the issue and win our contest?
Those are all the clues in Frankie’s lesson – that turned into a mechanical mystery. Now it’s your turn to try to solve it. Again, we’re looking for a specific answer in order to win the contest and prize. If no one comes up with the exact answer we have in mind, the winner will be the roadie who comes closest. Good luck!
Ride total: 9,772
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.