So, I have run a SolarisMAX/SodaMAX at 120mm, 130mm and 140mm.
120mm is best for climbing for me (at 140mm on the steeeep stuff it feels a little light front end (nothing to bad, and more a feeling than the old Solaris wandery front end of a mk1). Unsurprisingly 140mm is best on the downs.
Most of the SodaMAX’s life has been helms at 130mm. Didn’t really notice any discernible improvement in climbing from 120mm (apart from the SolarisMAX at 120mm was also B+ so a 2.8” which has obviously more traction so a little difficult to compare directly) or conversely that an extra 10mm makes that much difference on the downs.
My Helms are in need of a service (and have been sitting off the bike for three months waiting for me to decide whether to get them increased to 140mm or keep them as is at 130mm). My heart says 140 but my head says 130mm…
I’ve until February to make my mind up. The new SolarisMAX will get the Trace36s (and will be my ‘bikepacker’) and I’ll see how that goes…
TL;DR 130mm on a SolarisMAX is a pretty safe bet.