PVD, or Physical Vapor Deposition, is a surface treatment technology that, in a vacuum environment, uses physical methods to evaporate target materials into vapor or gaseous atoms and molecules, which then condense on the substrate surface to form a thin film with a specific color.

Principle: The process mainly involves two methods: evaporation and sputtering. Evaporation utilizes a heating source to raise the target material to a sufficiently high temperature, allowing its atoms or molecules to gain enough energy to escape into a gaseous state and then deposit onto the substrate surface. Sputtering, on the other hand, involves bombarding the target material with ions from a plasma in a vacuum environment, causing the target atoms or molecules to be ejected and deposited onto the substrate to form a thin film.

The PVD process is applicable to a wide range of materials: it can be used to deposit coatings on almost all types of materials, including metals, alloys, ceramics, and plastics, making its applications very broad. In sports bicycles, the PVD process is widely used on frames, handlebars, hubs, chains, drivetrain components, seatposts, and pedals.

Using PVD coloring provides these components with excellent wear resistance and corrosion resistance. For example, when cycling outdoors, the frame is frequently exposed to rain and mud, and the PVD coating effectively prevents the frame from rusting and corroding. Furthermore, the variety of colors makes the vehicle more aesthetically pleasing and personalized.

If it's a newly purchased flywheel, the problem is most likely with the derailleur adjustment. You can try the following methods to adjust the rear derailleur (Note: Beginners are advised to go to a bike shop and have a professional technician adjust it).

The rear derailleur has two limit screws. One of these screws adjusts the limit of the derailleur pulley relative to the smallest cog on the cassette. This screw is usually marked with the letter "H," representing "High" speed. Turning the screw counterclockwise moves the pulley closer to the outside; turning it clockwise moves the pulley closer to the inside. The ideal position is when the pulley is perpendicular to the outermost edge of the smallest cog. This prevents the chain from falling into the gap between the frame and the cassette due to excessive shifting range.

Another screw is the limit screw that adjusts the position of the rear derailleur guide pulley relative to the largest sprocket on the freewheel. This screw is usually marked with the letter "L," representing "LOW" speed. Turning the screw counterclockwise moves the guide pulley closer to the outside; turning it clockwise moves the guide pulley closer to the inside. The ideal position for the guide pulley is perpendicular to the largest sprocket, which prevents the chain from falling into the gap between the spokes and the freewheel due to excessive shifting range.

The third screw is the limit screw that adjusts the distance between the rear derailleur guide pulley and the flywheel. It is usually a single screw located near the derailleur hanger. Because the tension of the rear derailleur during shifting affects the shifting speed, theoretically, the closer the rear derailleur guide pulley is to the flywheel, the better. However, if it's too close, the guide pulley and the flywheel's gear teeth will collide, producing a "clicking" sound. The ideal adjustment gap is when the guide pulley and the largest flywheel gear are parallel to each other with a distance of 5-6mm.

First, let's shift the chain to the smallest sprocket, and while we're at it, flip down the rear derailleur's damping switch. We'll flip it back up later after the shifting is properly adjusted.

Method 1: Check the small exposed section of the gear cable on the rear derailleur to see if it is bent or broken. If so, replace it with a new one.

Method Two: Replace the derailleur hanger. If your shifting system was previously smooth, but then you notice scratches on the rear derailleur, it's very likely that the derailleur hanger is bent. A bent derailleur hanger can also cause chain skipping. Furthermore, it's usually impossible to fix this problem using other methods. The derailleur hanger connects the frame to the rear derailleur, and it's easily bent when the rear derailleur is hit or compressed. The solution is to buy a new derailleur hanger and replace the old one.。

Method 3: Adjusting the rear derailleur limit screws. Most rear derailleurs have only three limit screws. The H/L screws are responsible for preventing the chain from falling off the sprocket to the left or right. If your chain won't shift to the smallest sprocket, loosen the upper screw counterclockwise, but be careful not to loosen it too much, otherwise the chain will get stuck between the sprocket and the frame. If your chain won't shift to the largest sprocket, loosen the lower screw counterclockwise, but again, don't loosen it too much, otherwise the chain will fall off to the left. The last screw adjusts the distance between the rear derailleur guide pulley and the sprocket; we generally don't need to adjust this screw.

Method four: Use the adjustment knob on the shifter to improve chain shifting problems. Most shifters have this adjustment knob, which is used to adjust the tension of the shift cable. If the chain won't shift up, turn the knob counterclockwise to tighten the cable. If the chain won't shift down, turn it clockwise to loosen the cable. Before adjusting this knob, remember to shift the chain to the smallest sprocket. You don't need to turn it too much at once; half a turn will have a noticeable effect.

Method five: Shorten the chain. If the previous four methods don't work, it means your chain is too long. With the chain on the largest chainring and largest cog of the freewheel, and without going through the rear derailleur, the ideal chain length is when there are two extra links remaining after connecting the ends. Cut off the excess links.

If the gear shifting feels stiff, or you experience a "can shift up but not down" situation (i.e., shifting to larger sprockets feels stiff, but the shifting itself is not problematic, while downshifting results in a sluggish response from the rear derailleur), this usually indicates that the gear cable housing is aging, contaminated, or lacking lubrication.

If the above problems don't occur, then the remaining issue is simply adjusting the rear derailleur.。

The possible reason is that the chain guide pulley is too close to the freewheel at this point. Because the 32T freewheel has a larger diameter than the 30T freewheel, it causes the freewheel to almost touch the guide pulley.

The adjustment method is as follows: There is a small Allen screw on the back of the rear derailleur; rotate it counterclockwise, and the guide pulley will gradually move away from the flywheel. Rotating the chain will then eliminate the abnormal noise.

First, adjust the derailleur to the smallest cog position. Also, loosen the fine-tuning screw on the shifter to its loosest setting. Then, loosen the cable fixing screw on the rear derailleur. Pull the shift cable firmly; the guide pulley will move to the left. Then, release the tension slightly to allow the pulley to return to its position, but don't completely loosen the cable. With your other hand, tighten the cable fixing screw. This completes the adjustment.

Next, test whether the gear shifting is precise. Listen for any sounds of the chain or sprocket rubbing against each other. If either of these issues occurs, adjust the fine-tuning screw. Alternatively, loosen the gear cable and try again.

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Disc brake noise: If the noise is regular and matches the rotation frequency of the corresponding wheel, it is likely due to disc rubbing. You will need to adjust the position of the disc brake caliper using an Allen wrench. If the disc is warped, it needs to be replaced. If there is a screeching sound when braking, the disc may be contaminated with oil. Front derailleur noise: One possibility is that the chain is lacking lubrication; check if the chainrings, freewheel, and chain are rusty. Applying lubricant should solve this. If the noise is regular and matches the pedaling frequency, it may be due to the chain hitting the derailleur cage; the cage needs to be straightened to a completely vertical position.

Wheelset noise: This could be due to issues such as the bearings in the wheelset needing lubrication, loose or unbalanced rims, or slippage of the thru-axle. Besides the hub area, another possibility is insufficient spoke tension. If you hear this noise, you should check the spoke tension.

Rear derailleur noise: Rear derailleur noise is relatively easy to identify. It usually occurs when shifting gears, either up or down, and the derailleur doesn't move to the correct position. This is because the cable is too loose and needs to be tightened using the adjustment screw. Electronic derailleurs may make strange noises during initial setup or when changing batteries. This is due to an incorrect setting sequence for the wireless derailleur; simply reinstalling the battery should fix it (this applies only to SRAM versions).

Bottom bracket noise: If the noise is regular and consistent with the pedaling frequency, producing a "clunking" sound, it could be due to a problem with the bottom bracket bearings or slippage of the pedals (they can move vertically up and down when not being pedaled). It could also be caused by a loose but undamaged bottom bracket. In any case, it's recommended to replace the bottom bracket rather than trying to fix it.

Seatpost noise: This may be caused by a loose seatpost or saddle. The seatpost bolt may not be tightened to the specified torque. If it's loose, dust and debris can easily accumulate inside the seat tube, which is more common in aerodynamic frames. After removing the seatpost and cleaning it thoroughly, it is recommended to use an anti-slip agent, and then tighten the seatpost bolt to the specified torque.

Generally, you cannot simply replace the flywheel alone. The gear capacity of both the front and rear derailleurs must also be considered. The rear derailleur usually has the standard maximum gear capacity marked on its cage. Exceeding this capacity will prevent some gears from shifting smoothly. For example, if the rear derailleur is rated for 32T, installing a sprocket larger than 32T will prevent proper shifting. Generally, upgrading from 11-speed to 12-speed requires replacing the derailleur, chain, and other components as a complete set.

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The Sram HG series freewheels offer excellent compatibility with Shimano derailleurs. Regardless of the specific model of the Sram HG series freewheel, it seamlessly integrates with Shimano derailleurs, enabling smooth gear shifting. This is due to the high degree of design compatibility between the Sram HG series freewheels and Shimano derailleurs, as well as strict quality control during the manufacturing process. Using a combination of Sram HG series freewheels and Shimano derailleurs, riders can enjoy precise shifting and stable transmission performance, resulting in a better riding experience. This compatibility advantage not only improves riding efficiency but also significantly enhances riding safety. Therefore, the combination of Sram HG series freewheels and Shimano derailleurs is an ideal choice for many cycling enthusiasts.