Quote:
Originally Posted by ckorbey
Harsh in that the 2014 frame's bottom bracket, chain stays and seat stays were massive and incredibly stiff. The rear tire sat in the curve of the seat tube and only allowed for a 23mm tire. The combination of the beefy rear end and 23mm tire made the ride harsh on imperfect surfaces and was a general beating over a long day on the bike.
From what I understand, Cervelo was clear that they intentionally compromised comfort for aerodynamics on my version of the S5. And that the two most recent S5s have thinner seat stays and more tire clearance (I've run a 25mm with no issue).
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Counterpoint:
Despite common wisdom, there isn't much comfort to be derived from the back end of any rigid bike frame - even if it does have thin seat stays. The exceptions are frames whose seat stays have exaggerated bends and pivots (such as the Serotta DKS). Typical straight seat stay frames, the frame is the wrong place to look for compliance in the back end.
Cervelo published a chart showing measurements of the
contribution to vertical compliance of different bike components, in both the front and rear of the bike. As one might expect, the biggest contributor to ride compliance in the back is the tire, supplying about 50% of the compliance. Of all the components in the load path between the ground and the rider's butt, the frame provided the least amount of compliance, only about 3% of the total. The rider's shorts provided 3 times more compliance than the frame did, and the seatpost provided about 4 times more compliance than the frame did.
I have a Cervelo S5 (2015 model), and I don't find it particularly harsh riding. Of course, I've got the fattest tires that will fit in the frame (26mm) and also a comfortable saddle. If the S5 is harsher than other bikes, it is most likely because it has tight tire clearance (precluding wide low pressure tires) and a stiff aero seatpost.
By the way, for 2018 Cervelo has redesigned the aero seatpost, adding a cantilevered clamp to improve seatpost compliance:
