Long cage designs are trying to make initial contact with the chain by the side plates at a place where the most effective use of lateral movement is. FD design to accommodate more gears on triples and integrated brake/shifters has to deal with both trim and rapid contact with the chain at a point that is most likely to initiate the chain being dropped to a smaller or letting go of a ring's teeth and climbing onto a bigger.
Ramps and pins handle the work once the chain contacts a bigger ring. Abrupt movement initiates shifts to smaller rings. I think in some of the designs the longer tail of the FDs came from the contouring of the side plates reducing trim needs as you shift across the cassette while on a specific ring. When in larger rings the chainline is proximate to the front or middle of the cage but plate shaping to reduce trim requirements in that area of the FD might create some long movement before contacting the chain for an up shift from the smallest ring. I suspect that the answer was harmonics and the abruptness of the trigger release nature of most integrated shifter actions, that the long tail placed the initial contact at a place (when using the brand's specified chain) creates a wave complimentary to the pretty specific chainring reccos (limitations) of the package inserts. That's a brittle system if it's true but after looking at how deep Shimano goes in this sort of secondary or tertiary physical function in other cycling and fishing gear, I think it's for real. Not interested in click shifting? FD cages don't have to be such elaborate origami or '60s Cadillac long. Look at this one. <https://www.renehersecycles.com/my-pbp-bike-derailleurs/> Not only friction but no cable either. Again why I ended up with what seem like obscure antiques to move my chain between the rings...because I am doing it, not the snap of a spring loaded device on my handlebar. Modern cycling is trying so hard to remove cycling as a barrier to cycling that it gets tangled up in its own line like a fly fisher trying to cast too far. Sometimes a learned skill will be required. Andy Cheatham Pittsburgh On Wednesday, May 26, 2021 at 11:18:06 PM UTC-4 Joe Bernard wrote: > Andy, I think you're onto something with the long tail of that particular > mech. It appears to be a clone of the "9-speed" Shimano 105 that Riv used > to spec on their triples 15-20 years ago, and they had a problem with them > landing on the chainstay because of a combination of low BB (creating a > steaper stay angle) and 46t big rings (instead of 52). Which is to say I'll > bet most mountain triples would work better on that frame. > > Joe Bernard > > On Wednesday, May 26, 2021 at 5:39:41 PM UTC-7 ascpgh wrote: > >> Real world gearing has lower tooth count/smaller circumference than big >> brand OEM spec. The profile of front derailleurs caters to precisely what >> they choose as your gearing, even MicroShift: >> [image: Screen Shot 2021-05-26 at 8.10.13 PM.png] >> That derailleur expects to be at a 52t chainring's radius (plus 1/8"for >> tooth clearance) above the BB. Don't have to see it with those specs to >> know there's a lot of cage tail to cope with possibly meeting the chainstay >> when lowering it on your seat tube. >> >> >> When you choose smaller chainring combos it requires moving the FD down >> the seat tube to the right proximity of your big ring and if you've gone >> below manufacturer's recommendations (or have a low BB) the tail of a >> triple may hit the chainstay. >> >> As viewed from above, larger rings intersect the out angling stays if not >> on longer spindles. Reduce those rings' toothcount and you just bought >> clearance from the stay and you can lower your Q with a shorter spindle. >> Max outward reach issue negated. >> >> This is how i've come to use old road double FDs on my compact >> drivetrains. >> >> Andy Cheatham >> Pittsburgh >> On Wednesday, May 26, 2021 at 3:48:55 PM UTC-4 Tom Wyland wrote: >> >>> Um, it seemed like the cage wouldn't clear the stay? Also it didn't >>> appear to move far enough for the "low" gear when I pushed it all the way >>> in. Maybe it could be modified. I could re-purchase it (LBS) and try >>> again, I supposed. Seems like you're all saying that most of them should >>> work. So user error on my part, maybe? >>> Here's the model: Microshift 539 Triple 9-speed: >>> https://www.jensonusa.com/Microshift-R539-Triple-Front-Derailleur >>> >>> Tom >>> >>> On Wednesday, May 26, 2021 at 2:43:23 PM UTC-4 Joe Bernard wrote: >>> >>>> Tom, what exactly is/was the problem with the Microshift you tried? >>>> >>>> Joe Bernard >>>> >>>> On Tuesday, May 25, 2021 at 6:27:10 AM UTC-7 Tom Wyland wrote: >>>> >>>>> OK, I'm still struggling to find a FD. I tried a Microsoft R9 and >>>>> that didn't seem to work. The local bike shop said 10 speed won't work >>>>> with 9 speed (which is all they had). I'm running friction. >>>>> >>>>> Leah was nice enough to show how her older Deore (9 speed triple >>>>> mountain?) was set up. Has anyone purchased a FD that works for them? >>>>> I'm >>>>> having a hard time with all of the different variations (on ebay) or the >>>>> myriad of 10-speed triples new. >>>>> >>>>> Thanks! >>>>> Tom >>>>> >>>>> >>>>> -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bunch+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/rbw-owners-bunch/cde07540-728c-4654-97bd-9cc4445c4fd6n%40googlegroups.com.
