Bike hubs are under constant stress, especially in the case of mountain bikes and gravel bikes for road bikes cracked hubs are not very common but in mountain biking, this can happen and it happens quite often as well due to enormous stress on the wheels and improper tensioning of the spokes
The right and left flanges of the rear hub where spokes are mounted within the holes are known as the hub and contain the axle interiorly. sometimes flanges on a single side become cracked near the spoke holes, these flanges break because of the high tension and pressure of the tire which reduces the lifespan of the hub and limits your ride.
All the tension produced from the spokes aligns on the flanges and hub and it supports and lifts all the weight of the bike. the wheel does not run smoothly if the hub has cracked and also you could not install a new wheel with a broken and cracked hub. sometimes the central portion of the hub cracks and or gets twisted and changes its shape from normal, it is also dangerous because it completely stops the function of the axle within the hub or it breaks the axle.
There are different sizes and lengths of hubs from 120mm to 140mm, you can change a cracked or broken hub with a new one but it needs time and skill level, you have to build your wheel from scratch, remove all the spokes from both flanges, uninstall the hub and axle, change the hub with a new one of any size related to the size of the wheel axle, install all the spokes on both sides of the hub flanges and mount the wheel with the hub.
The cracked hub can not be welded or recovered always go for a new hub especially if you are riding your bike on aggressive and rough terrains. thru axle within the hub gives enough support to the hub if it suddenly cracks on the trails.
Spokes holes of flanges sometimes crack due to the higher tension and stretching from the tire and the more weight you are putting on your bike. hubs have more than 1 year of warranty, if it cracks in its warranty then you can replace it with a new one, and remember that it will only be possible if you dont make any changes to it like try to weld it or something else that will nullify the warranty.
Causes Of Crack Hub?
hubs usually last their warranty duration if you are constantly aggressively riding your bike but normally they can even last 5-10 years ofcourse it never happens with one on a mountain bike.
there is also the high or low tension between the spokes which does not maintain the stretching and tensioning and some spokes are stretching the flanges of the hub more tightly while some spokes are loose with lower tension. as a result pressure difference occurs within the flanges and more pressure points of the hub become cracked.
Sometimes there is a difference in the length of the spokes mounted on the flanges of the hub on both sides, which causes a hub crack.
Sometimes the spokes are not better designed and there is a difference in their widths and mounting points some are thin while others are thick within the same wheel, chances of hub cracking are possible in this condition.
Following more aggressive and rough terrains which do not support a moderate-level hub cause a hub crack, bike hubs are different in their quality, characteristics, properties, and price ranges, which differ them to ride on their own level trails.
Riding a bike for a longer time heat up the hub and flanges of the hub, and you will hear a sudden crack sound coming from the rear hub because of heating due to the rotation of the wheel for many hours.
Hubs cracks are very hard to visible, and every rider ever ignores to inspect the hub completely, during washing and servicing of the bike wheel you will suddenly see a hub crack, so always inspect every small part of your bike keenly and thoroughly before going on a ride.
If your bike is not in use it is standing for months then there are chances of taking rust in the spokes holes of both flanges of the hub which will weaken them for riding, after riding on bumps and drops wheel hub cracks.
Sometimes the axle bends and deforms within the hub which affects negatively the performance of the hub works double the weight of the bike the rider depends on the hub because the axle is broken, in such cases mostly the hub cracks.
Sometimes the wheels, spokes, rim, and axle stops working, all of these parts are connected to the hub, and as a result, hub breaks and cracking occurs.
Cracking of hub dysfunctions the inner bearings and barrels of the hub, almost the wheel totally does not perform smoothly.
There is also a size difference between hubs and bike frames, but it could not matter, you can install a longer or shorter hub in a bike wheel with any frame size your bike will run smoothly and perform well and well.
Rear Hub Crack:
When you push the pedals of your bike, you will hear a bad irritating voice coming from the rear hub, it’s a sign of cracking of the rear hub. you can check the rear hub there are many things that would happen with the rear hub which confuse a rider about indicating a problem.
the balls within the bearings are not maintained in the correct way and causing a disturbance with the rear hub.
There is also different size of cassettes of mountain bike gears, if the rear hub is small in size and it is not matchable with the cassette of your bike then it will constantly cause forceful pull-in the horizontal hub line direction, which will affect the hub.
Most of the time the width of the tire, weight, and the size of the rim and its weight does not maintain a better relationship with the center line of the hub, because the size of the hub would be small, or the hub quality matters, due to which a large force comes from the tire and rim in both sides of the flanges and the center line of the hub, as a result, the hub fatigue increases and it does not control over weight and wrong partnership which causes hub crack.
The other major reason is that the world is changing and becoming modern day by day and the riders are discovering more ways and trails for mountain biking even more aggressive and hard terrains also the riding style of the riders and the bike speed have changed everything as compared to the past, for this modern world hub needs to be more powerful and responsive, but if the hubs are still coming weak with fatigue then obviously these would crack for the same situation.
When installing a new hub if you never know the best skill of a hub and you will hesitate in doing hub building then you will confuse about maintaining the cone bearings of the hub if it slightly differs from its normal place hub will not work for a long time.
Loose tensioning in spoke nipples affects negatively the wheel hub.
If threads are wobbling then it would not cause tension as a result of the misguidance of the force of the wheel and tire cracks in the hub.
The dirt and muddy water of the trails will go deep within the hub which becomes dry and the rotation wheel cause rubbing with the hub, axle also causes rubbing with the hub, and this drying of the hub cracks the hub. you need to give oil and lube to the hub on regular basis to avoid drying.
Cheap hubs are not made of aggressive uphills and descendings pro riders have installed expensive and good-quality brands of hubs for their bikes.
Hub dimensions also matter a lot for mountain biking it’s not located in its recommended place it will misbehave on every rotation of the wheel.
If you have installed a bike hub from a non-experienced wheel builder, he will not exactly know the skill and work of the hub, surely hub will not stay long.
The weight of the rider also matters a lot for the hub, if you have more than 100kg weight use an expensive and new hub for your bike wheel the hub is not installed accurately it will distract you after some rides and starts slipping from its actual place which is risky regarding hub crack.
Conclusion:
Although cracked hubs are not quite common but it does happen and the main causes of it are spokes, they are either too tightened or too loose which puts more pressure on the hub flanges and twists them and even breaks them spokes even tension also causes the wheel to go untrue so make sure that you keep a check on your wheels if they are true or not with which you can avoid hub cracking incidents as well.