Originally Posted by
ricefarmerr
Ahh ha, Thank you SOOO much. Just the exact explanation that I was looking for. Also thank you for the warning, I am aware of the new 2015 groupo. drool ! :-)
Any how, since you brought up another topic, "return spring force". I'm quite new at this, so sorry if my questions can be quite long and frustrating to answer.
I could be totally wrong, so correct me if I'm wrong. Based on my understanding, for shifting in the rear, when I use my thumb to shift, this will shift me into a "harder" gear. In this situation, the cable is being loosen, so that the RD can spring into the "harder" gear. In order for the RD to go into the "harder" gear, this is where the "return spring force" concept comes into play, is that correct? There must be a correct return spring force for the RD to spring back into the "harder" gear. Now over time, does this force gets weaker? If this force does get weaker over time, what are some options to correct it? Can you replace the spring? Can the RD be rebuilt? Or do you just replace the entire RD? And on average, how long, millage wise do you need to replace the RD? I understand that the last questions can be difficult to answer because that depends on the rider and his/her riding style.
Thanks.
You are correct with the function of the return spring on the RD. As gfk_velo said, Athena uses PowerShift (single upshift per press) versus UltraShift for Chorus and up (multiple upshifts per press), therefore the spring doesn't need to be as strong because the RD only needs to move by one cog. IMO, if you're not fond of doing multiple upshifts in one go, you may not notice that at all. But if you do, the shifting may feel a little sluggish.
The RD is rebuildable and the spring replaceable. One cannot give a 'mileage' limit for spring replacement. A better indicator of wear on the RD spring would be number of shifts, but that would be an impossible number to ascertain due to individual riding styles and the terrain that the rider encounters.
IME, I haven't needed to replace springs on any of the RDs I have used. I have a 20+ year old Shimano RX100, and an unknown age Suntour (can't remember the model). Granted I've used friction shifting on the RDs before and then moved them over to STIs later (which is a one upshift per click as well), I haven't seen a noticeable change in shifting up to now.