There looks to be 2 threads on this topic (the other here: Oval Chainring on Road and MTB Bike - Pros/Cons - #19 by eerke). Perhaps they should be combined.
So here’s my experience and thinking on this.
I have 3 Absolute Black rings now.
- TT bike 36T inner, di2 6800
- Road 34T inner, Etap 11 spd
- Gravel 42T 2x front, Sram Force 1
My road bike needs a new big ring, hence revisiting this subject.
I have read from many sources (including AB staff) that Oval big rings and Sram YAW FR don’t work the best together. Hence researching the potential gains here and if it is worth it.
Experience
I was surprised how subtle the AB inner rings were. I had to look down to check I put the AB ring on rather than putting my round ring back on. As I do better on flat terrain than climbing, I think the AB inner rings do help my climbing. Obviously no shifting issues at all being just the inner ring.
Thoughts
A premise for my thoughts. The purpose of non-round rings is to make it easier to get through the “dead stop”, the part of the pedal stroke you at your weakest.
So my thinking is non-round rings only help with low inertia pedalling, ie while climbing. The reason for this is, while climbing, you need to put torque through the pedals for more of the pedal stroke, including your dead spot otherwise you lose a noticeable amount of speed, or on more steep terrain, the bike falls over. However, on high inertia pedalling, ie flats and downhill, you don’t need to put toque through the pedals through the dead spot, but rather, can put torque down at any part of the pedal stroke you please, as the bike won’t lose any noticeable speed and certainly won’t fall down. So as a result, being non-round or round would only alter the way you pedal but once accustomed to either, you could be putting torque down through a small or large part of the pedal stroke, how it suits you, regardless of the ring shape.
So with that, wouldn’t you only gain benefit from the small, inner ring being non-round and nearly no benefit from a non-round larger, outer ring? AB staff said you will see “…when you climb the oval advantage is by far the most visible.” However, I see people saying non-round rings are good for time trialling (I assume mostly flat terrain). This puts a hole in this theory, but why would TT racing suit non-round rings?
Looking forward to people’s thought. @chad?