is there something wrong with my pedaling technique?
 

To preface, my Bike Friday just came back from an overhaul and has new cassette, chainring, chain (as well as other parts). There is nothing mechanically wrong with it. Before I sent it off for service, I had changed out the cassette and chain (they put a brand new chain on during service anyway).

Here's the question: sometimes, but not always, when I either stop pedaling to slow at a street ending, or when I am starting up from braking, the chain will skip one link or tooth. This does NOT happen when I stand and climb a hill. It only happens when I go from a very slack position to a slightly tensioned position. I am not mashing down hard when I resume pedaling, I mostly spin in easy gears.

I'm wondering if it is somehow technique related and has to do with how I relax and resume pedaling? It happens maybe once or twice a ride at most and it's not particularly jarring because I am not pressing hard, but it would be if I was mashing down.

Any ideas on what is causing this?

Do you pedal backwards in the process?

The pawls inside the freehub are not fully engaged after freewheeling and they skip a tooth when you start pedaling again. It may be that the grease inside the freehub is too thick or has become sticky and is not allowing the pawls to move as freely as they should.

Sounds like you need a new bike.

I don't intentionally pedal backwards but I usually stop with one crank at the very top of the rotation and my forward motion might carry it a bit back. Would that affect it?

The hubs were serviced as part of the recent overhaul. If this is the case would it disappear after I get more miles on it?

What kind of rear hub does your Bike Friday have?

It says SunRace, it is a 7 speed, bike built in 2003. Shimano compatible.

no, the OP doesnt.

Sure you do, we all want a new bike?��

If no one mentioned it yet, a problem similar to yours can happen if the freehub isn't a bit sticky. As you coast to a stop, or back pedal a quarter turn the freehub causes slack in the upper loop, which you may feel as a skip when you start out.

Similar, but not quite the same thing, is auto shift one position when you backpedal to get ready to start. Now the chain is wrapped half on one sprocket and half on the other as if you were mid shift. When you start back out that section in transition comes to 12:00 and you feel the skip as the chain takes up that bit of slack.

Not everyone does. Some are content with theirs.

I love my bike and definitely don't want a new one. I could have bought a new one but chose instead to send it to the mothership in Oregon and get it overhauled and repainted.

So I'm not really sure I've gotten an answer here...it's the hub, it's not the hub, it's slack.

It literally feels like the chain is hitting just under the edge of a tooth on the chainring and jumping up and over onto the next tooth. Just a one tooth skip. It's interesting in that this is the first time I have used a chain with a master link (PC SRAM 870) and now I am wondering if it is possible that sometimes that link is catching? That would explain the inconsistent intermittent nature. I checked for stiff links and they all seem okay. The master link is fully expanded.

I'll keep riding it and see if the problem goes away...which would indicate something wearing in. If you guys have any other thoughts, let me know and thanks.

Before crashing my bike, I had an issue with the chain and the big chainring. Every revolution, in a 53/13ish gear, the chain would ride up the chainring on the verge of falling out. I decided not to use the big chainring for most purposes.

Once I crashed, I ended up getting a new chainring... that fixed the skipping issue. A new chain quickly followed for good measure.

Perhaps the same issue for you... except with a cassette. Not saying you need a new cassette, but not saying you don't either. That's a matter of preferred strategy.

Do you have a record of your most recent drivetrain changes/mods? Perhaps a certain component has run its course.

OP. you say you have a 7-speed SunRace. That sounds to me like a freewheel, not a cassette. (A freewheel is a self contained unit that houses the freewheel system in a steel cage that screws onto threads on the hub shell. A special tool fits onto the outside face of the freewheel (FW). A large crescent wrench is used on the tool to unscrew the FW. (You pedal it tight. It takes real torque to remove.) The cogs slide onto or screw onto the FW body. Last one or two always screw on and lock the rest in place.

A cassette on the other hand is just a carrier that accommodates cogs that slide on. They are locked on with a cap that screws on with a splined took that fits onto the end. (Same place a FW remover would fit a FW.) Since the cap does little more than keep the cogs secure, loosening it is not hard. The freewheeling mechanism of a cassette hub is on the hub itself, inside the cassette carrier over it. The shop should have gotten you cassette right if that is what you have.

How to tell what you have: almost all FWs have black or grey or dark gold steel where the tool fits. Almost all cassettes have chromed or silver locking caps. Look at your FW or cassette and see what you have. (Report back if you cannot tell and quote me so I see the E-mail that you have a question. Tell us what tool appears t be needed to remove the FW or cassette. Splined or two or three rectangular holes are the most common.)

If you have a FW, what the pawls and springs need is oil. Light, clean quality oil. Doesn't have to be fancy. 3-in-1 works as well as any. Get a good sized bottle. Lay the wheel on the ground, FW up. Pour oil into the groove between the stationary inner of the FW and the rotating outer body. Spin the body and watch for the oil draining into the body. Keep adding oil until you can see oil coming out the back, ie between the FW and the hub flange. Pull a rag between the flange and FW to clean things up as best you can (it hardly matters unless it bothers you to see it) and go ride. My money's on it working perfectly. Repeat as needed, every six months if not. Using this much oil both guarantees everything is well lubed and it flushes any dirt that might have gotten in.

You will find this in any repair manual dated 40 years or more ago.

I went back and reread your post. You are quite clear you have a cassette. You can skip this, other than the advice of good clean light oil on the pawls and springs still applies. I am not a cassette guru so I will let others with more knowledge than I help you. I'll leave this for anyone stumbling on to the thread with a freewheel.

Ben

Second possibility - a tight link in the new chain, perhaps where it was joined. (A 7-speed chain can be joined with a chain riveter, a no-no with the fancier newer chains. If the mechanic didn't loosen the freshly driven pin, that link will be tight. Perhaps it doesn't straighten fully until you apply real pressure to the pedals and the kinked links jump under very light pressure.

If you have a FW, do the oiling of my last post. (Always good practice even if you see no need.) In either case, run the chain with the bike on a stand or hung by the seat and watch for a kinked pair of links going through the derailleur cage then over the cassette. (This will probably show up best on the smallest cog.)

Ben

I'm no expert, but I can't imagine how your pedalling or shifting could cause this. It is mechanical, whether it's the chain, the gear or the derailier. It is possible the problem didn't present itself at the factory because they didn't evaluate the bike off the stand under actual riding conditions with the forces that entails. Or it could be something was knocked out of alignment or damaged in shipping. Whatever the reason I would contact Bike Friday and explain the issue. They should have an afilliated bike shop or repair center in your area (the San Francisco bay area) and they should foot the bill to have the bike evaluated and adjusted and repaired if it is something caused by the overhaul.

Ah, well, that's what I needed to hear I think, that it has to be mechanical. Of course, immediately after a major overhaul I started looking for other explanations. And I do know that sometimes you can get a knock when pedaling if your stroke is weird. I had my cranks changed to shorter ones (which are so much better on my knees) and I was thinking maybe my stroke was causing it. Because it is so infrequent, I just cannot pinpoint it. A stiff link would be more consistent (not that I can find one). Every drivetrain part is brand new.
I'm going to call BF and I can Bart over to Warm Planet Bikes in the City (one of their dealers) to let them have a look. The bike wasn't shipped back, I got lucky and a friend picked it up and drove it back and BF packed it and put it in her car so if anything got messed up, it would be on them (everything looks aligned fine, though). Interestingly, yesterday it did NOT skip once but I only had time for 8 miles. Will see what happens today. Thanks everyone for all the suggestions!

Two. In case the first new one isn't quite right.

Definitely look at the chain where it was joined. My wife's bike started exhibiting exactly the same thing you are seeing. It would skip a gear here and there. After a a few more rides it would barely stay in any gear for any amount of time. She was not happy, it was taken into the shop twice. She finally made the shop owner/mechanic go for a ride with her. He immediately recognized the stiff link and repaired it quickly. She hasn't had an issue since. Oh, and that chain didn't start doing this until she had about 700 miles on it (was new this past spring).

It is not likely to be the connecting link if your new chain uses a removable master link. It's possible to find chains that don't use a master link like some of the Shimano chains but the most common, SRAM and KMC come with a master link. The easiest way to spot a stiff link is to turn the cranks backwards while watching the chain go over the rear cassette. It will go smoothly until it hits the stiff link. If you have a master link in the new chain that eliminates one likely place, where the chain was rejoined.