Cracked Bike Frame: Is It Repairable? How To Fix?

Many people are worried about their cracked bike frame while cycling, resulting in serious accidents and injuries. So how to avert this problem?   

The following section will provide comprehensive insights into the bicycle’s frame crack and propose feasible remedies to the issue that are worth your consideration. Keep scrolling down for further information!

Why Does A Bike Frame Crack?

Bike Frame Crack

The scenario of a bike frame crack is not uncommon, and you must watch out to see whether something goes wrong with your bike. Its materials and structure can be damaged over time, snapping into pieces and falling apart. 

To dive into details, a bicycle’s frame consists of many tubes with their various width, length, shape and thickness. It is responsible for holding all parts of your bike together and supporting its weight. 

Suppose you don’t take much care of the frame, or your bike is not frequently maintained; cracks will appear due to stress rendered by the shocks and vibrations when you ride your bicycle. 

If prolonged, there are more cracks on your bike, or the gap enlarges, affecting the frame’s structure and hampering its capacity for serving the bicycle’s purpose.  

How To Fix A Cracked Bike Frame?

Here is all-inclusive guidance on fixing your cracked bike frame that you should know. 

Step 1: Take The Bike Apart

Take all your bike’s components off so you can know what part is susceptible to wear and make a prompt replacement. 

Some parts, like the bottom bracket and crank arms, are hard to remove manually, so it would be best to use specific tools, such as a plier or a wrench socket, to pull them out. 

Step 2: Tape Off The Area

You prepare some tape and wrap it around your bicycle’s tubes. Putting a few layers of blue painter tape is highly recommended, which helps protect your bike well before the sandblasting step. 

However, a powerful sandblaster could penetrate through two or three layers of tape, so wrapping the frame with black plastic bags is advisable. This method helps minimize the possible damage to your bike frame when sandblasted. 

You don’t need to tape all of your bicycle; just pay attention to some core parts, like the cardboard or threads inside the bottom bracket.  

Step 3: Sandblast

Before welding, you must strip the paint off your bike’s surface. The reason is that the leftover paint will burn and trigger toxic grasses during the procedure. That’s why sandblasting is necessary because the firing sands could remove the paint completely. 

After being wrapped with tape and plastic, please put your bike frames into a machine and wait a few minutes before taking it out. 

Then, check the inner part of your bicycle’s bottom bracket to see if any paint is left, and use a sanding attachment or flap wheel to remove it. 

Step 4: Make The Bandaid

First, you must repair a steel tube with a thickness level of .058 inches before cutting a slit down its center with the help of a hack saw. Next, continue to cut it into pieces; you will likely need these pieces at the end of the process. 

If your tube is not in a suitable shape for the frame, bend it before putting the tube on your bike frame. Ensure that the two cut edges are pointed to the front and back of your bicycle’s frame. 

Now, you will move on to shape the patch by using your already-made tubes. At this stage, you must adjust the patch’s bottom edge to match the tube’s contours. Once they fit together, you will notice a curve on the top of your tube. 

Please don’t disregard this curve because it is functional at generating localized pressure on the frame. And now you have formed the final patch that should reach the height of 2 inches and resemble a section taken from a lugged bicycle. 

Step 5: Weld

This step is most important in fixing your cracked bike frame. One note for you before starting the step is that you must drill a small hole at each crack’s end to prevent it from propagating. 

Welding is simply a process of making several metal pieces together by heating their edges and pressing them. When you weld your bicycle, remember to weld the bottom of your patch, as welding its top edge could weaken the frame.

However, this practice requires much knowledge, so it would be best to call a qualified mechanic if you lack experience in this field. 

Step 6: Seal

It’s time you fill the gap between different parts of your bike after welding. You are advised to use only a small amount of epoxy resins or bondo to cover this gap. 

This act doesn’t make your patch become stronger, yet it is good at preventing water leaks and avoiding your frame’s corrosion problem. 

Step 7: Paint

how to fix a cracked bike frame

As mentioned earlier, you must remove all the paints to prepare for the welding step. After completing it, paint your bike frame again to offer the best protection from rust and other wear. 

Attach the tape to it very closely and apply at least two coats of primer paint on the metal frame. This coating layer is very important by providing a stronger seal and smoother finish for your bicycle.   

Step 8: Put Your Bike’s Parts Back Together

Although it sounds easy, the practice of putting all your bike’s components together causes more trouble. You must follow the manufacturer’s manual carefully so you don’t mistake this part for another. 

Call a professional bike mechanic for prompt help if you find it too difficult. Good luck!

Can A Cracked Aluminum Bike Frame Be Welded?  

A crack in aluminum bike frame could be welded, yet the process is complicated and time-consuming. It can take about 2 weeks to finish, and the cost is not very cheap either. 

There are some points you should acknowledge before welding.

  • It is inadvisable to weld on top of another weld because this risky act could affect the surrounding materials that are intact. 
  • Suppose the crack is near the wheel drop-out; you should stop repairing it because the area is very thin while the loads are great. 
  • If the gap is on the head tube, quit the process as well. The potential wear is induced to the two bearing sets, which take charge of holding the forks in place. 
  • As presented above, the patch material or filler should be added before welding. 
  • Suppose the crack appears in the bottom of your bike’s pedal cranks (this area is particularly vulnerable to failure that stops your bike from pedaling forward); stop welding it since 5 adjacent tubes are located in this place. 
crack in aluminum bike frame

The Bottom Line

This article has equipped you with comprehensive knowledge about the cracked bike frame and thorough guidance comprising full eight steps.     

Always wear protective garments when performing this procedure to ensure your safety, and call a licensed mechanic if everything is out of control. Align with my instructions, and wish you good luck! 

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