Originally Posted by
EPOisDope
I have aero frameset that I bought because the vast majority of my rides are solo at a good pace (minimum of 20 MPH / 32 KPH), but the bike is WAY too vertically stiff for someone who has had quite a few serious injuries. The frameset is able to handle at most a 30mm measured width tire. I foolishly bought into the hype that GP5000s were more compliant than GP4000S IIs, so I bought 23mms (I was a bit too obsessed with aero savings!) which have a measured width of 26mm on my Hed Jet 6+ wheels (Internal width 20.7mm), but I'm still getting beaten up out there - worse so than the 25mm GP4000S IIs that I was running previously. ... I really should just sell the thing to be honest, but it is the superbike I thought I always wanted being as obsessed with the tech side of things as I am, and I can't seem to accept the idea of selling a Ferrari because, deep down, I like my Toyota Camry more!
It seems to be common knowledge that the GP5000 is narrower than the GP4000SII at the same nominal width, so your tire switch has significantly reduced tire volume; a GP5000 in 28 mm would have a comparable width to a GP4000SII in 25 mm. If that does not work, replacing your aero frameset with a more compliant one is probably cheaper in the long run because you would no longer have to switch saddles and other components periodically in search for additional comfort.