I just change my old hardtail (Marlin 5-TREK) for a full-suspension bike (Siskiu D7). The bike runs smoothly, but I notice how frequently strike my pedals with the ground and other obstacles. I already adjusted the SAG and checked the pressure of my rear shock, but still happens. I have found that some people have experienced the same problems when they change to full suspension, but I did not have found a clear explanation why is this happening. Is the technique so different? the geometry? Using the website 99spokes.com I noticed that even the full-suspension bike is higher from the floor than my previous bike. However, with the hardtail, to strike my pedals just happened occasionally. Thanks
Yes, while it is a common enough problem for people moving from hardtail to softtail, it can also happen when people change bikes of the same type but different geometries. The lowering of the BB when the front and rear suspension are compressed is more pronounced than when you are on a hardtail. The BB height becomes more dynamic, and to begin with pedal strikes occur when the suspension is compressed while cornering or going over obstacles. (Compressing though corners is a good thing - don't stop doing it to avoid pedal strike)
I had this issue when I moved to softtail. The good news is you quickly learn the characteristics of you new bike, and instinctively manage the loading of the suspension long with bike lean and terrain to avoid strikes. If you still suffer pedal strikes, its likely technique - learning correct techniques (plenty of videos online to help) will practically eliminate pedal strike.
Pay attention to when its happening, adding more damping may help, as will increasing shock pressure. While adding pressure is really only masking the problem, as a temporary measure as you transition to the ride and feel of a softtail I am not against it.
As far as shock tuning - hit a local trail you love to ride and know well, pick a short (50-100meter) sweet section, and session it, changing pressure and damping/rebound to get a feel for what works for you and not. If the book says "Set sag to 25%" and you like it at 10%, then 10% is correct. Likewise, if it says "Set pressure to 120psi" and you like 90psi with lots of damping, 90 with lots of damping it is. Main thing is as you get used to the bike you preferred settings are likely to change, shock settings are not a 'set and forget' thing.