What you think is the change from rim brake to disc brake is nothing more than changing the rim brake caliper to disc brake caliper, which will kill the gap of dozens of grams, but in fact, this is only the most superficial.
In fact, there are many more places where this change has gained weight:
The most basic is the aforementioned weight difference between the disc brake system and the rim brake system
Circle brake C clip into a disc brake folder, weight gain
The hand change head is stuffed with an extra cylinder to increase weight. The situation has improved after the development of oil discs over the past few years, and you can take a look at Shimano's original oil discs
At that time, this thing was nicknamed the "big-headed doll", and you can imagine how much weight it has gained in terms of volume
The tubing will also be thicker than the rim brake line. I have cut a section of oil pipe before loading the car, and it is obviously difficult to cut a lot.
Continue to gain weight
The big head is coming from behind:
Where is the rim brake caliper installed?
On the fork shoulders and on the rear triangle of the frame. Some special windbreaker frames will attach the rear clip to the bottom bracket, but the feel is very poor.
Obviously, the strength of these places is not low, and installing a clamp is nothing more than adding a few mounting holes in that place.
Disc brakes are not so simple,
Look at where the disc brake caliper fits: fork fork legs, rear fork ends
These areas are not as strong as the two mounting points of the ring brake, and more importantly, you can also think of these two disc brake mounting positions as a lever
It can be seen that the force of the disc brake will be much harsher than that of the ring brake
But it's not over yet: the place where the brake caliper clamp is the brake side, and the disc brake caliper clamp is a brake disc with a diameter of 160mm, the size of the two is very different, this is another lever, that is, in the same situation, the disc brake has to bear more force than the rim brake when braking
This means that the frame must be reinforced to prevent accidents during violent braking
Weight gain
Don't worry, and:
There is also a need to work the wheels. Due to the different braking positions, the forces on the disc brake wheels and rim brake wheels are also different, which is a little complicated to explain and does not expand.
You just need to know that because of this change, some rim brake wheels can't be copied to disc wheels, and the hubs of disc wheels also need to be reinforced.
Keep gaining weight!
However, now the weight of the disc brake has slowly been able to break the wrist with the ring brake. The reason for this is that the appearance of ultra-light frames, carbon fiber parts and TPU inner tubes has made disc brakes see the dawn of weight reduction.
If these technologies can be put on the ring brake, the circle brake can undoubtedly be lighter than the disc brake, but now the big manufacturers are not working in the direction of the ring brake.
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Corrected in the comment area
However, in terms of the fact that disc brake frames are generally heavier than ring brake racks, do you really need to be reinforced?
（非業內人士，待大佬解答)