I have a Tiagra 4600 10 speed rear mech (mid length) which is sluggish to shift into higher gears.
Shifting was all over the place, I’ve replaced the jockey wheels and checked the hanger alignment. Shifting is now indexed fine up the cassette but lags behind every click when shifting into harder gears, when the return spring is doing the work. It’s indexed ok this way too, but lags a full cog every click.
Is there any way to service a rear mech, to increase the spring tension? I could source a replacement spring or other parts off junked derailleurs at LBS if there’s a solution to be had there.