Join Date: May 2004
Location: Wilmington, DE
Bikes: 1984 Trek 660, 2003 Specialized Hardrock, 2004 LOOK KG386i (RIP), 2005 Iron Horse Warrior Expert, 2009 Pedal Force CX1, 2014 Islabikes CNOC 14 (son's)
Mentioned: 2 Post(s)
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Quoted: 297 Post(s)
I've used an Acera group during the past 5 northeast winters and aside from needing new cables and housing and some lube here and there, nothing has needed replacement. If you are breaking shift cables, I can almost guarantee you that you have some other problem than the front derailler. If your front derailler was that stiff, you'd have broken your shifters long ago. More likely, you have a cable/housing routing issue that is causing excess friction possibly bending the cable at too small of a radius and that is causing the breakage.
Try disconnecting the cable and see if you can move the front derailler by hand. If it moves through the full range and always springs back to the inner chainring position, it does not need to be replaced. It will feel stiff but it should not bind. If it does bind, you may just need some lube on the pivots.
Once you've verified that the derailler is operating ok, remove the cable from the shifter and try actuating it. Does it feel just as stiff without a cable in place or does it feel normal? If normal, the problem is the cable and housing between the shifter and front derailler. If your front derailler is a bottom pull, check the cable guide under the bottom bracket. If you haven't replaced the housing, definitely do that along with using new ferrules. Make sure you have enough slack in the housing that the handlebars can be turned fully without pulling the housing tight.
To answer your final question, everyone I've heard talk about their experience using a 8/9 speed chain with a 10 speed front derailler has had the same unsatisfactory result. No amount of tweaking with give you the same noise-free performance that you'll get by using a matching chain and derailler. You are welcome to try it. you won't break anything but you likely will be disappointed. You'll also be disappointed if you go installing new components without first fixing the underlying issue that is causing the excess friction and cable breakage.