Better way to do fork sag?

BikeCAD Official
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How are people handling sag in BikeCAD? I feel like this is a pain point for me in my design process.

I typically design the bike unsagged and check fit and geo with the fork sagged. My current workflow involves several steps and room for mistakes.

  1. Lock the frame geometry
  2. Change switch to “custom fork”
  3. Adjust the sag
  4. Look at the geo
  5. undo the sag
  6. unlock the frame geometry

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Is there an easier way of doing this?

I wish you could toggle the sag amount without having to have a “custom fork” and without having to toggle the “frame lock”.

Is there possible to code the sag variable such that it is not a “permanent” geometry change or a fork parameter? It would be great if it would just toggle the geometry change.

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Why do you feel the need to design the bike unsagged?

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To clarify, I’m not suggesting that hardtail designs shouldn’t consider sag, I just think it would be nice to easily toggle and adjust the sag without accidentally changing the frame or fork geometry.

I know my thinking goes against the established framebuilder wisdom, but these are the reasons why I design without sag:

  1. Sag is subjective to the user: 20, 25, 30%? I have no idea what the sag is on my fork. I would argue that most mountain bikers do not look at the sag when they set up their fork. They adjust the spring rate, damping, and air volume to get the proper grip and feeling of support.
  2. All full suspensions and all major frame manufacturers list their geometries unsagged. I feel like this is the industry convention, and it leads to customer confusion when I show sagged geo.
  3. I feel that designing around sag puts too much confidence in a parameter that is subjective, fork-dependent, and terrain-dependent.

In light of all those reasons, I prefer to design based on a nominal static parameter (unsagged), knowing that the bike will sag.

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In addition to what Daniel said, here’s another reason why:

If you spend any non-negligible amount of time climbing a hardtail on a relatively smooth (paved or otherwise) surface, you will do yourself a service by locking out your fork. In my experience, through motion of the rider the fork creeps upwards over time (because the lockout prevents it from returning to the sag point) until it is essentially topped out. In this configuration (because the rider is on a hardtail), the head tube angle is at its slackest possible configuration. This corresponds to the longest trail and flop height. If you’re at all like me, you find that climbing (at low speeds in particular) is where any unwanted effects of long trail and flop height are the most salient. As such, I want to design around these factors where they are the most important, i.e. when the fork is unsagged. Hope my wording makes sense.

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It sounds like things would be easier if I made it so that when you select a standard fork, the input field for sag would be left enabled. I’ll plan to implement this change in the next update.

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Yes! That is a great compromise. You wouldn’t have to mess with your standard fork parameters to adjust sag.

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Not 100% BikeCAD specific but this site is handy if you’re comparing geo between sagged and unsagged bikes. Defo helps if you’re buying off the shelf or trying to wrap ya head around industry geo trends since most manufactures seem to list unsagged geo for hardails.

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