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Sliding dropouts - frame not locking

I'm trying to see the effects on geometry of different positions of the sliding dropouts.

I'm using the Paragon DS0001 dropouts

I lock the frame, and adjust the slider from 0 to say 20mm and back to 0, but when shifting back the frame has changed. bb drop, hta, sta, reach, stack all change.

I've checked out the video and am following the right procedure afaik. 

Can anyone confirm they are seeing this issue also?



Sliding dropouts and locking the frame

Typically, one would set the angle of a sliding dropout to zero. If this is the case, as the dropout is slid fore and aft, all movement is horizontal. Therefore, the BB drop, seat angle, head angle etc should all be constant. The chainstay length would however change.

I just tested this on version 17.1 and as expected all the dimensions you listed remained constant as I moved the slider fore and aft. The chainstay length did change but returned to the original value when I restored the slider to the initial value of dimension Z.

As an additional test, I set the angle of the dropout to 30°. Sliding the dropout fore and aft with the frame locked did change BB drop, seat angle, head angle etc as expected, but all those numbers went back to the original values when dimension Z was also set back to the original value.

If this is not the behaviour you are observing at your end, could you please send me a copy of the BCAD file you are working on? I would like to investigate this.

Yeah that is what I'd expect

Yeah that is what I'd expect should happen but it is not. 


Where should I send the file Brent?

email file
Thanks Brent,

Thanks Brent,

I'm not sure what I've done but it's now behaving as intended. No idea what I changed.

OK scratch that. 

OK scratch that. 

The issue I'm having is on frames with mixed wheel sizes. If the rear wheel/tyre is a different diameter to the front the scenario I described persists. 

If I use the same wheel size front and rear then adjusting the dropouts behaves as it should 

Mixed wheel size and sliding dropouts with locked frame

Thanks for bringing this to my attention. You are correct. BikeCAD is good about handling locked frames and switching out different sized wheels and forks. However, there is obviously an issue with the specific scenario involvling different wheel sizes and sliding dropouts. I will have to correct that for the next update.

No worries thanks Brent. Love

No worries thanks Brent. Love the tool!!

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