MTB rear suspension fundamentals

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MTB rear suspension fundamentals
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flag andrextr
Posted: Apr 26, 2016 at 7:55 Quote
New video, about the importance of instant center (virtual pivot) in suspension behavior.
It's a bit long, but it's a topic that deserves attention into it.




Bye Smile
flag andrextr
Posted: May 6, 2016 at 8:34 Quote
Quick and simple demo of the Brake-squat principle. Smile

flag andrextr
Posted: May 13, 2016 at 8:26 Quote
Easy and intuitive explanation of Anti-squat.


Hope you like it Smile Bye
flag Lukastrekslash8
Posted: May 16, 2016 at 7:21 Quote
Hi Andrextr,

I have set my shock dampening as per your video showing the curb test and have been running this for a while now on my 2014 slash 8.
I demo a specialized Enduro other day and the rear felt like a pogo stick! I asked about putting more dampening into it but it was at max, they said that's how specialized tune it and say it's best for trail???
I asked some riders how they have their shocks setup and all seemed springy compared to mine?
Your thoughts? Cheers
flag andrextr
Posted: May 16, 2016 at 7:58 Quote
Most people out there tend to use a very fast rebound, because many believe that the faster you are, the faster the rebound should be, and some of them use a very fast rebound because it feels good on bumpy / rocky tracts (which is somehow true). However, when you use a fast rebound, during jump take-off, landings, or technical sections with successive jumps, or drops, things can get sketchy pretty fast as you start going uncontrolled (pogo-stick). Moreover, fast rebounds amplify the pedal bob oscillations which is pretty annoying.

By doing the curb method (and with +1 or 2 clicks towards a faster rebound, until you get a tiny oscillation) provides you the best balance between plushness and control.

Although the rebound adjustment window in shocks is pretty wide, there are some shocks where you cannot get the perfect rebound with the usable range of adjustment, in that case the shock is over-damped or under-damped for your weight. In your case it was under-damped. This is why some shocks offer different rebound tunes (L M H). Usually heavy guys (not sure if is your case) need more rebound damping because they use stiffer springs.


By the way, I would like to remember and quote this previous article on pinkbike:
bigquotesSo remember, we design a very wide rebound range to deal with the large weight differences between our customers. No single person should think that they can use the entire range. The useful range for a given person is only about 3 clicks.
https://www.pinkbike.com/news/To-The-Point-Rebound-Damping-2013.html


That was my thoughts. Bye Smile
flag Lukastrekslash8
Posted: May 16, 2016 at 18:20 Quote
thanks for your reply Andrextr!

im about a 98-100kg rider on my crappy drcv shock i have plenty room for dampening adjustment.
one of the guys reasoning for faster rebound was because if i leave mine like your recommendation the shock will packup over constant rough sections?

either way i like mine (your way) over the pogo stick feeling i got from the specialized !
flag andrextr
Posted: May 17, 2016 at 2:36 Quote
Lukastrekslash8 wrote:
im about a 98-100kg rider on my crappy drcv shock i have plenty room for dampening adjustment.
one of the guys reasoning for faster rebound was because if i leave mine like your recommendation the shock will packup over constant rough sections?

either way i like mine (your way) over the pogo stick feeling i got from the specialized !

Yah, with 100kg you might experience that under-damping issue on some shocks (not able to get no oscillation).

Yes, I forgot that one. Many people are afraid that the shock packs down so they use a pogo-stick rebound... With the curb method +1/2 clicks (until you get a tiny oscillation), the shock is recovering the fast as possible without trowing your weight into the air. So, you get a pretty fast rebound speed.

In my previous experiments I found that in, my bike, the shock takes about 0.2 - 0.3 seconds to extend after a bottom-out using this curb method + 2 clicks (yellow line). The recovery time was not much different comparing to the fastest pogo-stick rebound.

Unsecure image, only https images allowed: http://oi66.tinypic.com/nmgfna.jpg

This matches with the theoretical equations from damping systems (credits: http://www.shimrestackor.com/ )
Unsecure image, only https images allowed: http://www.shimrestackor.com/Physics/Spring_Mass_Damper/Figs/1-response.png
The curb method with a tiny oscillation corresponds to Zeta between 0.5 and 0.7 in the previous graph.

To conclude, the recovery time of a pogo-stick shock is not much faster than a "curb method +tiny oscillation" shock. The difference of times (0.1sec at max) is not worth the instability that it creates. Moreover, all modern shocks (even a fox float for instance) have a high-speed rebound circuit that kicks-in during high-speed bumps, such riding fast over roots, rocks and potholes, or recovering from deep in the travel. This circuit allows for even faster rebound speed at those type of high-speed events, creating an even plusher suspension without the need to have a pogo-stick "feeling" shock. Thus, IMO packing is only an issue if you use a very slow rebound speed (like slower than the no-oscillation point in the curb method, where Zeta >1.0).

Bye
flag Lukastrekslash8
Posted: May 17, 2016 at 4:38 Quote
Thank you for taking the time to explain!!!
It makes sense to me and it's helped me with jumps a lot!

Cheers
Lukas
flag andrextr
Posted: Jun 9, 2016 at 12:48 Quote
New vid .... About progressivity Smile


Bye
flag Xorrox
O+
Posted: Dec 17, 2016 at 13:23 Quote
I just found this thread. What an awesome resource and a new spin on a lot of information that is also available elsewhere.
flag andrextr
Posted: Dec 17, 2016 at 15:48 Quote
Thanks Smile

BTW, new video about spacers and secondary negative chamber
flag andrextr
Posted: Dec 29, 2016 at 7:58 Quote
FREE Simulator!


Download link: https://goo.gl/2kQOCv

 


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