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Chainstay length with asymmetric dropouts

Using Paragon DR1102 dropouts as my selection, the chainstay view and dimensions show the chainstays as being idenical in length even though the drops are asymetric with the DS shorter than the NDS. I have slected asymetric in the chainstay options. What am I missing?



Chainstay length with asymmetric dropouts

If you select these dropouts, by default BikeCAD will suggest different values for Cx vs C2x and Cy vs C2y. These are the dimensions controlling the ends of the chainstays relative to the rear axle. Cx is the drive side and C2x is the non-drive side.

You don't actually have to select asymmetric stays. If it is only C2x and C2y that will be different when you compare the drive side chainstay and the non-drive side chainstay, you can leave the chainstays set to symmetric. In this case, technically the chainstays are asymmetric, but because that asymmetry is defined in the Rear dropouts dialog box, and all the specifications given in the chainstay dialog box are applied the same to both stays, BikeCAD is fine calling these stays symmetric in the context of the chainstays dialog box.

However, if you would also like to define some differences in curvature or tube shape between the drive side and non-drive side stays, it is also fine to click the aymmetric checkbox in the chain stays dialog box.

The only problem here is if you toggle back and forth between asymmetric and symmetric stays. When you go from asymmetric to symmetric stays, BikeCAD will set C2x equal to Cx and C2y equal to Cy. In your example, I assume that C2x was initially a different value than Cx. However, because at some point, the stays may have been toggled from asymmetric to symmetric we now see C2x equal to Cx.

To resolve this, simply select a different dropout and then go back and select the DR1102 dropout again. This will reset the values for Cx, C2x etc. Be aware that you can also modify the values for Cx and C2x to suit your own preferences. The DR1102 dropouts are a plate style dropout and you do have some flexibility in terms of how much the ends of the stays overlap the dropouts.

Let me know if this behaviour does not explain the situation you are seeing in your example.


Oh, I see. Thank you for clearing this up for me. Now when this change occurs the tire view in the chainstay view seems to display 2 tire positions at once and the shorter stay does not line up with the BB. I am unsure as to the accuracy of tire and crank clearance. Is there a way to correct this?

Asymmetric stays

The auxiliary view of the stays is projected from the line running from the back end of the chainstay to the front end of the chainstay. When you have a set of asymmetric stays, the drive side and non-drive side stays are often projected at different angles. This is why we have two sliders to separate the display of each of these stays. This is illustrated below:

Ok, got it. Thanks!

Ok, got it. Thanks!

Curved CS

So everything has been working as predicted until I introdiced curved stays into the mix. Now when the asymetric option is selected so I can adjust the viewing angle for tire clearence I get problems with the view on the NDS (shorter) stay.

Send file?

Could you send me the BCAD file for this design? I'd like to investigate.

Your BCAD file

Just in case anyone else is following along, I was sent two BCAD files. The first surprisingly opened without any issues. The only thing I was able to point out is that by using the problem curves checker, we're able to see the bends at the far end don't quite fit within the space allowed. This is shown below:

The second file did reveal the issue with the wacky chainstay curves. However, that was explained by the asymmetric chainstays. There wasn't enough length in the non-drive side chainstay to accommodate the specified curves.

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