Hey all, do we have any suspension nerds here?

I have some annoying troubles with the rear suspension on my 2017 Focus Vice trail bike. The shock is Rockshox deluxe select R with max tokens inside and 250psi air pressure (~20% sag)

Long story short, I keep bottoming out the rear suspension regularly on jumps and drops way easier than I’m comfortable with, but with the amount of pressure in the shock the ride starts feeling pretty harsh as well

So what I’ve thought as options, but might need some more validation:

  • bigger bike and/or bike with more progressive suspension curve

Eh, don’t really want to replace bike I otherwise love

  • different shock?

Not sure what I would look there tbh, also gets pricy but not as bad as a whole new bike

  • messing with the shock tune

The shock doesn’t have externally adjustable high/low speed compression, but perhaps could adjust the shim stack? This is completely alien stuff for me so some ideas/advice would be appreciated

  • there’s a megneg air can upgrade kit available for the shock

This increases the negative volume giving more mid-strike support, plushier initial feeling and more bottom out force using less tokens as claimed by rockshox. This upgrade kit is not terribly expensive, but is it worth if I’d better be going with a new shock anyways?

  • fake_meows@lemm.eeEnglish
    2·
    3 days ago

    It’s the bike (frame) not your shock.

    https://linkagedesign.blogspot.com/2016/09/focus-vice-275-2017.html

    That frame is basically a linear progression curve. (See “leverage ratio” graph.

    This means that there isnt much of a “ramp up” in the resistance as you hit big stuff. That’s what you’re feeling. Second point: you can’t do much to fix this from the shock perspective.

    Adding tokens and adjusting the shock tune could improve bottom out resistance at the trade off of stiffer suspension

    The megneg won’t help for this issue (it modifies only the first 1/3 of the travel).

    Different frame with much higher progression will help.

    Theory time:

    A progressive frame let’s you run suspension that is both soft at the start and very firm at the end.

    A linear frame like yours has nearly the same bump response at the start and end.

    Let’s say you hit TWO bumps. The progressive suspension has a different respond depending where the shock is within the stroke. It can move easily when extended (start), but a similar bump when the shock is partway through the travel will not move the suspension as much.

    A linear bike hitting two bumps will move a more similar amount for each.

    The above thought is why you might like the feel of one design over the other…it depends on your style and terrain.

    Theory time 2:

    On the graph “Forces”, you can see this frame bottoms out with 1600 Newtons and sits at sag (30%) with 500 newtons.

    So 500N is gravity, and 3G’s of down force is the maximum force to bottom.

    For a bike to handle extreme trails (big drops and jumps) you will find you need around 5-6G bottom out resistance in the frame. If you dont have this level of leverage / profession you’ll end up breaking the frame.

    (If memory serves, a ~6 foot drop to flat is around 5Gs of down force in the landing.)

    Link: https://vorsprungsuspension.com/blogs/learn/understanding-leverage-curves

    Says the same thing in a different way, but useful round up of the concepts.