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I am installing a new XT top pull band on front derailleur. The placement of the cable connection will require me to replace the shift cable too.
I am wondering when installing the derailleur what should be in the initial cable tension? Should I just have it 'taught' as much by my hand strength while I tighten the derailleur screw?
In most cases the order of operations should be orient the front derailer at your best attempt at a final clamp position, then set the low limit screw so that it's about 0.5-1mm away from contacting the chain but doesn't rub as you turn the cranks, then pull the cable taut with a plier or 4th hand tool as you anchor it.
New cables tend to settle in by about 1-2 barrel adjuster turns worth of slack, or sometimes more if the housing is also new, so you can pull it pretty taut while anchoring it and you'll still likely need to use the barrel adjuster before you're done anyway.
Sometimes one encounters shifter/FD/crank combinations where the low-position tension needs to be pretty slack for the indexing to work well without rub. Re-anchoring the cable in a looser position can be necessary then. These situations are fairly uncommon though, so you don't want to preempt them because you do want only a minimal amount of the barrel adjuster used up front as a general practice.
For initial setup, you’ll want the cable to have just a touch of slack, not overly taught. Shift into the big ring, then anchor the cable with just enough tension to lift the derailleur into place, aligning the outer plate about 1-3mm above the big chainring. Too much tension will prevent smooth shifting.
Secure the cable anchor bolt snug but not overly tight. Now you can make micro adjustments to the cable tension using the adjustment barrel. Shift through the gears and tweak until the transitions are crisp but not sluggish. Keep your high limit screw handy for fine tuning the range.
It’s a process of gradual refinements - tweak, test, repeat. Don’t rush it! Ride through all your gears methodically to ensure precision engagement on both up and downshifts. Get that sweet spot dialed in where the shifts glide effortlessly.
Installing a fresh cable and housing is also a great opportunity to check your housing length and use some quality cable lube. Those small details make a big difference for slick and reliable shifting performance.
