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?
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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.
Technique, body weight, and the suspension adjustment are your options. Otherwise like you indicated you may need a shock with greater travel or aggressive compression curve options to send the features you’re bottoming out on. If you have people sending the same features and not bottoming out you can compare your differences in setup.
Might just be landing a bit rear heavy, though if you’ve got 130mm up front you’ll need to find a good balance.
When was the last time the shock was serviced?
Has it always bottomed out?
You say the sag is 20% but who set it? Are you confident that is the correct sag settings?
When was the last time the shock was serviced?
I did 200h service couple months ago, but I’m not sure of the services done before that. Bought the bike last summer
Has it always bottomed out?
Eh, yeah I’ve been progressively been hitting bigger jumps past year back on the bike, and gone from 190 -> 250psi on the shock to compensate
You say the sag is 20% but who set it? Are you confident that is the correct sag settings?
Set by me with riding gear on. I’ve been messing a bit with the shock testing different sag last year and also with air volume reducers (tokens) and running the maximum tokens at the moment (3.5 if I recall correctly)
Honestly it sounds like the shock is toast. I’d take it to your LBS and see if they have a shock guy who can rectify it. That will be cheaper than buying a new one. If you’re mechanically inclined you could do it too but you’d need a bunch of specialized tools. They might open it up and find something easy to fix is broken, like an o-ring. Or they might tell you it’s toast but at least you’ll know for certain.
