Sourcing my downpipe and other tubing and am a bit confused about bend radius, Looking at a 3" stainless 180 and instead of radius it lists the pipe as 4.5" Centerline. Would that be center to center from the middle of the open ends? So far no response to me email to the vendor. After rereading this I need to clarify, is the centerline measurement taken from the outside of the tubing or center? Example, a tubing with a 3" centerline would have an overall outside measurement of 6", is this correct?

 

Centerline radius is the measurement from the center of the die to the center of the tube. So a 3" CLR die will produce a 180 that is 9" wide on the outside. Remember its radius rather than diameter, so in the case of a 180° bend its 2* die radius + 2* tube radius or 3"*2+1.5*2.

Also it wont be this exactly, there is always a little bit of deformation, even in mandrel bends, but it will be close.

 

To get outside to outside, double the bend radius, then add the diameter of the pipe.

4.5x2 + 3 = 12"

 

No, centerline radius refers to the center line of the tube. read this to better understand CLR. https://pro-tools.com/blogs/protoolsusa/18621927-tube-and-pipe-bending-basics

The reason for this is simple, the blanks bending dies are cut from are uniform. All 6" CLR dies are cut from a 12" wide billet, the billet has the tube radius cut into it to preserve the shape of the tube as it is bent (mandrel or not). So CLR holds true across any tube size, its industry standard. I bet if you measure any U bend you have at the centerline it will be a standard nominal size, usually 7", 9" or 12".

 

I stopped reading at "no". My formula works no matter the pipe or CLR of the shoe. I've been using that for 25 years and it's never been wrong. Try it for yourself. Any bend radius (180* U-bend), any pipe diameter. Double the bend radius, add the pipe diameter.

The bend radius is the distance from the center of the shoe to the center of the pipe. So If I make a 180* bend on a 4" CLR die, then I know i'll have 8" from the center of one leg to the center of the other. Then by adding back in the diameter of the pipe, you are accounting for twice the pipe radius. That will give you the outside to outside of a 180 U bend.

Run through some examples and hopefully you'll see it. I did some Bob Ross level of art on that link you showed. #ad

 

We're saying the same thing, if you'd bother to read my post you'd notice i fucked up and used a 3" clr value.

 

Thanks fpr all the input, you guys are great. What I've learned is that the 3" stainless pipe is limited in bend radius and is generally a 4.5" cl on a 180 degree. This will equate to about a 12" overall width which is just on the edge of being too wide and I would need to run an offset to clear the frame. The folks at Stainless headers suggested I use their 90 degree bend that has a 3" radius, by welding them together I should get the clearance i need to run straight through to the fender without any issues. I still plan to run a 3" round from the turbo then transition to a 3" oval to clear the frame and exit the fender.