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Discussion Starter · #1 ·
What is the service life of a front derailleur return spring?

My XT front der seems less willing to shift from middle to small ring under load. I know about easing up when shifting, but I have to be very gentle now to avoid the no shift/clacking sound situation. Or is the problem elsewhere? Problem continues after replacing rings with Race Face and new SRAM chain (to fix chain suck). Stumpy hardtail with about 2,400 xc trail miles. Thanks for your help!
 

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Mmm... Tasty
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BerryBoy said:
What is the service life of a front derailleur return spring?

My XT front der seems less willing to shift from middle to small ring under load. I know about easing up when shifting, but I have to be very gentle now to avoid the no shift/clacking sound situation. Or is the problem elsewhere? Problem continues after replacing rings with Race Face and new SRAM chain (to fix chain suck). Stumpy hardtail with about 2,400 xc trail miles. Thanks for your help!
Front derailleurs are one of the most durable, problem-free components on a bike. Only the cheapest ones have less than an "i'm simply getting bored with this" lifespan. My cross bike has a 14 year old XT front derailleur that still works perfectly.

Now, having said that, check your derailleur adjustments (maybe you should dial out the inner derailleur stop a touch?), make sure your cables are clean and lubed, check to make sure the der. cage is also aligned with the chainrings... this can get whacked, or tweaked somehow so that it points slightly outboard (but this is rare).

Lots of things to check before you toss anything out.
 

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two things

thing #1: if you add a JumpStop or Cateye Chain Watcher to your seat tube, you can adjust the low limit screw further in, to the point that the chain would shoot on past the granny ring and derail were it not for the presence of one or the other of the aforementioned devices. With one of those in place, the derailleur forcefully slams the chain inward, the chain hits the device and falls unfailingly onto the granny ring, every time with no hesitation. I use them on all my bikes. Some teams in Le Tour also run them on their bikes to guarantee flawless downshifting with zero chance of dropping the chain off the inside ring.
thing #2: SunTour had the problem solved a decade-plus ago, with a front derailleur that worked opposite all existing ones. Instead of relying spring tension to initiate downshifts to the smaller rings, it worked in reverse and used the cable pull to downshift, and spring tension to upshift to the big ring. That way by pushing on the thumbshifter you could always get the thing to downshift even if it was coated in mud or ice. Real good idea. Now we have a similar idea for Rapidrise rear derailleur from shitmano, only that's a real bad idea for the same reason SunTour's was a good idea. With rapidrise, the critical downshift to a larger easier gear, a critical make or break shift on the steeps, is no longer controled by pulling the cable. Instead it relies on a spring, and a wimpy one at that, so when you need to shift to an easier gear RIGHT NOW lest you wobble to a halt on a steep climb, you better hope there's no mud or ice on the derailleur to interfere with the wimpy spring doing its job.
Point of this rant is, you can still occasionally find the old reverse action SunTour front derailleurs at places that deal in older stuff like that. One of them would solve you problem without the need for a jumpstop type device. I got some myself and ain't gonna part with them. try www.bikeman.com, or of course ebay.
 

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Discussion Starter · #4 ·
interesting rant

Thanks for the responses. Gives me a much better idea of what is going on with this component.

I wonder why a reverse rise front derailleur (downshift via cable rather than spring) hasn't gained favor. Seems it would be a technical and marketing opportunity for SRAM to further differentiate from Shimano.
 

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BerryBoy said:
Thanks for the responses. Gives me a much better idea of what is going on with this component.

I wonder why a reverse rise front derailleur (downshift via cable rather than spring) hasn't gained favor. Seems it would be a technical and marketing opportunity for SRAM to further differentiate from Shimano.
While i agree with a lot of what BulC said, and i like the theory behind a reverse-action front derailleur, the problem lies with gravity. A chain *wants* to fall to a smaller ring. You let the less definitive direction of the derailleur (the spring controlled one) do the little nudge to drop the chain down. The benefit of your thumb is that it is relatively strong, so it can really jam that chain over (and up) on to that bigger chainring.

A *real* solution would be to eliminate the spring all together and have a cable loop that positively pulls the derailleur in both directions. This was tried earlier by White Industries, but i think failed do to cost, weirdness, and possibly poor execution.

Anyway, poorly shifting front mechs can be a real mystery simply because they are so simple. An insidious little problem can hide surprisingly well in this simplicity.

-Damon
 
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