Exhaust Pipe Measurement Tips For Harley Davidson

When installing a custom exhaust system to your Harley Davidson motorbike, you should consider the exhaust pipe sizing or measurement well. The whole thing will be messy if you don’t choose appropriately sized components.

As a result, more gases will flow through the pipe, or excessive noise will be produced. Plus, an appropriate exhaust pipe size is crucial to remove the engine waste and residues properly to keep it in good condition.  Therefore you must understand how is exhaust pipe measured for Harley Davidson motorcycles. Once you know the measuring tip for the Harley motorcycle’s exhaust pipe and muffler, you can customize it quickly. 

Thankfully, the measurement technique of exhaust pipes for motorcycles is easier than you anticipate. You have to know about the different components of the exhaust system. Then you may quickly calculate their diameter and length. It helps you understand what size exhaust pipe you need for your Harley Davidson motorbikes for quick customization. 

So, without wasting much time, let’s jump into the size measurement tip of the exhaust pipe. 

Exhaust Pipe Measurement

Benefits Of Using The Right Exhaust System For Motorcycles 

Benefits Of Using The Right Exhaust System For Motorcycles

The exhaust pipe is an integral part of any automobile, including motorcycles. It helps maintain the engine in good condition. Also, motorcycle riders appreciate the deep rumbling sound of the muffler and exhaust pipe. It brings a sense of style to them as they ride their motorcycle. 

However, the main benefit of a proper exhaust system is its cleaning capacity. The engine develops different residues and wastages when you ride the bike for miles. These wastages and residues will escape the motorcycle engine through the exhaust system. That’s why the exhaust pipe must be of the correct size. If it is too small, engine wastes won’t pass through it.

As a result, the manure will block inside the exhaust pipe. It forces engine failure, which is the last thing you want. Another critical importance of an exhaust system is its ability to increase engine efficiency. As the exhaust system removes engine waste, the engine remains more efficient.

So, it uses less fuel and improves the riding experience. When the exhaust pipe becomes dirty, the engine loses its efficiency. So, it will consume more than the required fuel. A wrong-sized exhaust pipe is one of the main culprits for unnecessary fuel consumption. 

Maintaining the exhaust system properly and getting the correct replacement size are the following advantages. 

  • It helps you in controlling the harmful gases. The poisonous gasses for the engine will emit through the exhaust pipe. It will extend the lifespan of your motorcycle engine. This emission includes lead, sulfur dioxide, carbon dioxide, and hydrocarbons. 
  • When you have the right sized and adequately maintained exhaust pipe, it lowers the engine temperature. So you won’t face engine overheating problems. It becomes beneficial during long rides. 
  • Many people complain about excessive noise from their motorcycles while driving. It happens when you have the wrong exhaust system. With the right exhaust pipe, you will enjoy the quieter functioning of your motorcycle. 
  • The exhaust pipe works properly and keeps your motorbike engine and other parts in good condition. So, your motorcycle maintenance and repairing costs will reduce considerably. 

How Is Exhaust Pipe Measured?

We have described the importance of a suitably sized exhaust pipe for motorcycles. Thus, you must find a way to measure your exhaust pipe length and diameter. Then, you can quickly get the replacement for the older exhaust pipe and install it. 

Usually, an exhaust system can be built with four components as the industry also uses them. These are:

  • Piping
  • Mufflers
  • Reducers 
  • Tips

These parts are sized differently from each other. This way, you can ensure the exhaust pipe’s compatibility and fitment. So, it will be conducive for fitting exhaust pipes together effectively and properly. 

OD And ID Measurements:

OD And ID Measurements

Most piping is measured in OD dimensions. OD is the short form of “outside diameter .”For example, you have bought a 3” exhaust pipe. It means if you use a tape measure across the pipe opening, it measures 3” across the pipe. 

Generally, the pipe is designed so that you can flip it inside another component known as a muffler. You can measure mufflers and exhaust tips in ID dimensions. Likewise, ID refers to the “inner diameter.”

Some exhaust pipes will use the OD, and others will use the ID measurement. So, be aware of these two exhaust pipe diameter measurement techniques. Also, ensure that it matches the diameter of your existing muffler model. 

Lap And Buck Joint:

Both components are designed to create a lap joint, a point where the pipe is slid inside the muffler. Consider a 3” muffler and 3” exhaust pipe for a precise concept. You can consider that the pipe will easily slide into the muffler openings and create the lap joint. However, you can secure the joint using a saddle clamp or band clap. Also, you can use a welding machine to seal the joint. 

Sometimes, you may find a situation when two pipes with similar OD need to be connected. In such a condition, you cannot slide one pipe inside another, and no lap joint will be created. This situation is known as the buck joint. Hence, a buck joint is the butt of two components against each other. You can weld the buck joint or use a band clamp like a lap joint. 

Dealing A Butt Joint

A band clamp is a comparatively more upfront choice to secure the butt joint. But you may find a unique welding clamp to weld the pipes properly. This welding clamp comes with windows to place tack well. Later, you can remove the attached clamp and the rest. 

Another way to deal with the butt joint is turning the butt joint into a lap joint using a tubing expander. It enlarges the pipe opening. It helps another pipe or reducer to fit inside it. 

What Size Exhaust Pipe Do I Need?

What Size Exhaust Pipe Do I Need

Knowing the measuring technique for the exhaust pipe isn’t sufficient. You must also know the exact exhaust pipe size you need for your Harley Davidson motorcycles. Of course, the best way is to look at the user manual of the motorcycles to know the exhaust pipe size requirement. However, many bike owners will still find it difficult. 

So, here we put the shortest and easiest way to know what exhaust pipe size you need. 

  • As a rule of thumb, for each 100HP (Horsepower) of your engine capacity, the exhaust pipe diameter should be 1″. For instance, if your Harley motorcycle has 450HP power for the engine, the exhaust pipe diameter should be 4.5 inches. 
  • You have to split the diameter into two equal halves for a dual exhaust pipe system. So, each exhaust pipe will need to increase its diameter by ½ inch for every 100HP engine capacity. Thus, an engine with 500HP and dual exhaust pipe will need 2.5 inches of exhaust pipe for each one. 

You may quickly follow this technique to find the right-sized exhaust pipe diameter. However, it is a presumed measurement system. We suggest you consult a mechanic and know from him about the exhaust pipe size measurement. It will help you quickly choose the right size for the exhaust system. It would help if you also focused on the exhaust pipe’s efficiency, appearance, and sound. It is vital because many people will customize their bikes to get the loudest and most resonant sound from them. 

Diameter of the Pipe ( In inches) 

Pipe Area (In square inches) 

Estimated CFM rating 

Max HP for pipe 

Max HP (Dual Pipe System) 




































As you see in the table, the diameter of the pipe will increase with the horsepower enhancement of the engine. For the best result, you can look for an exhaust pipe size calculator on the internet. It will help you calculate the precise size of the pipe. 

Exhaust Pipe Size For Torque

As the torque increases, the capacity of the engine increases as well. As a result, you need to find an exemplary relation between the torque and exhaust pipe size. Sadly, there’s no strict rule on it. So, you should follow the user manual for the torque of your motorcycle and the exhaust pipe accordingly. Or else you may contact your motorcycle mechanic. 

Nonetheless, there’s a thumb rule for the torque and exhaust pipe relation. Typically, you will get better torque at low-to-mid RPM with a smaller exhaust pipe diameter. 

Final Words 

You should now have a clear concept of how is exhaust pipe measured. This measuring technique for the exhaust pipe isn’t tricky at all. It would help if you simply had its inner and outer diameter. Also, it would help if you looked at the user manual for the correct exhaust pipe measurement

Once you have picked the right exhaust pipe size, you can follow the installation techniques. It isn’t complex either. 

Frequently Asked Questions 

1.What is the outside diameter of a 2.5-inch exhaust pipe?

Ans: The outside diameter, aka OD, of an exhaust pipe with 2.5 inches inner diameter will be roughly 4 inches. So, you must carefully look for both the internal and outer diameter of the pipe to choose it rightly. 

2.Are exhaust pipes measured ID or OD?

Ans: Most exhaust pipe manufacturers will express the measurement in Outside Diameter or OD. Only a few manufacturers will showcase the exhaust pipe measurement in Inner Diameter or ID. 

3.How do you know if a muffler will fit?

Ans: You will need to consider a few fitment measurements to know whether or not the muffler will fit. It includes the position of the outlet and inlet ports, inner and outer diameter, and finally, the actual size of the muffler. 

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