One of the more common problems that customers approach me about is poor shifting gears. Bicycle drivetrains are unique in a sense, as unlike cars and other motor vehicles the parts are mostly exposed to the elements and are often made as lightweight as possible, which can result in them being delicate and more prone to failure.
The first thing I check when assessing gear shifting issues is the gear cable (provided its not an electronic groupset). This is the most common cause for shifting problems that I find on customers bikes. If the cable is old, it can stop moving properly inside the cable outer housing. The best way to diagnose this is to see if the gears will shift up the cassette into the lowest sprockets but are reluctant to shift back down into the highest gears. Another gear cable related issue is fraying, which can often be found just inside where the cable meets the gear shifter, or where the cable is clamped to the derailleur. Internal cable routing can also be a cause for gear cable problems, as cables can become tangled or not routed correctly through the frame.
Secondly, I check the drivetrain for wear using a chain checking tool. If the chain is stretched beyond the wear marker, this indicates that the chain is worn, but perhaps also the cassette, chainrings and jockey wheels. Have a look at the teeth on the sprockets, if they are starting slope off, or "shark tooth", this will cause gear problems. Another tell tale sign for this, is if the chain skips over gears when applying higher pressure to the pedals whilst riding. The solution for this is usually to replace the chain if you've caught it in time, or if it's too far worn, the drivetrain sprockets that have been affected too.
A misaligned hanger is another common cause for poor shifting which I see often in the workshop. If the bike has been in a crash, fallen over, or even just lent against a wall in the wrong way, this can easily knock the derailleur and bend the hanger out of alignment. Derailleur hangers are designed to be made out of soft materials and can be easily bent to avoid causing more expensive damage to the bike. Have a look at the derailleur and see if the jockey wheels are in line with the cassette sprockets; if not, you may need your derailleur hanger realigning.
When initially setting up the gears on a bike, the limiter screws on the front and rear derailleurs must be set up properly to prevent the chain falling off, but also to make sure the shifting actuation starts in the right place. If the "high" limiter screw on the rear derailleur is not in the right position, it can cause all of the gears on the bike to be slightly out. I like to think of it like tuning a guitar; if the open strings are out of tune, the rest of the notes along the fretboard will also be out of tune...🎸
Another issue I sometimes see is mismatching components. One thing to check before doing any work on the bike is to make sure the components are actually compatible with each other. I have spent many an hour working on a bike's gearing only to discover that the cause of the problem is a mismatching shifter and derailleur. Different group sets nearly always have different shifting ratios, even if you're matching the same brand. For example, an 11 speed Shimano Ultegra shifter/lever, will not work with an 11 speed Shimano Deore derailleur. You can often find the manufacturers compatibility charts online, which will say what components will work with each other.
The more money you spend on a groupset does not always mean you will get better shifting, but in most cases it probably will! Budget components are often cheaper because they don't shift as well as their more expensive counterparts. They are made out of softer/more affordable materials and machined with less tolerance, which results in less precise shifting. As you go up the groupset hierarchy, you notice that different materials are being used in the manufacture of each component, as well as different processes and more refined technologies which increase shifting accuracy, speed and reduce the amount of play or "slop". Although these groupsets promise superior shifting performance, they can still be susceptible to some of the issues mentioned, whether thats, incorrect installation, wear, or gear cable related issues.
As a final note, with the relatively recent innovation of electronic shifting becoming more mainstream, this technology will mitigate a lot of the issues discussed, and although it comes with a more hefty price tag, it does seem to reduce the number of shifting related issues coming in the workshop. That being said, these group sets are still susceptible to some of the problems discussed, including hanger misalignment, worn components and even incorrectly set up limiter screws. They also present a new set of potential complications, including battery shortages, water ingress to name a few. Although there are other solutions which do mitigate some of the issues discussed, for example internal hub gears or even crankset gearboxes; none of them are perfect, so knowing how to spot these more common problems should hopefully help you understand what is causing your poor shifting and more importantly what you can do about it.
I enjoy answering questions about anything bike related, so get in touch via the contact page of the website, or feel free to pop in to the shop if you have any more queries.