Originally Posted by
noglider
FBinNY, could you clarify what you're saying about bad shifting? In the old days, it was usually impossible to shift under load. Now it's possible. In fact, it's easy. Are you saying that although it's easy, it's also risky to your chain?
Tom, thanks for being the straight man.
Before hyperglide shifting under load was virtually impossible because the moment the chain dis-engaged from one sprocket, and before it would settle into the new one it would skitter across the top and riders rapidly learned that they had to reduse the chain tension during a shift to prevent that.
The gated shifting that hyper glide allows the chain to complete a shift in a short section of arc, so the chain would engage the new sprocket while still attached to the old one, with a sharp S-bend in the transition. It's fine if there isn't too much tension, but as the transition zone comes around the cassette towards 12 o'clock chain tension in the upper loop forces it back down deeper on the old sprocket putting tremendous side pressure on the plates and forcing them out on the pins and/or twisting them, before they finally disengage as they come over the top.
You can see the potential for harm if you put a bike in the stand and do a shift in slow motion and gently hold back the wheel as the shift zone comes over the top.
So while hyperglide (or gated shifting by any name) has been a great benefit to new riders, making unskilled shifts possible, there's a cost in chain breakage.