My wife’s bike uses a bottom pull front mech with the cable running on the guide under the BB but it’s running stiff despite all of my best efforts, so has anyone got any tips for reducing friction? Are there specific cables to use rather than standard 1.2mm steel ones?

Thanks.

Genuine SRAM pit stop cable is 1.1 mm

new outers and inners?
run those rubber boots where teh inner exits the outer presumably under your downtube near the headset

open ended cables collect grime like no-ones business

Put a new cable guide on.

Have you routed the cable into the front mech properly?

BB cable guides usually work very well.

Problem likely to be elsewhere.

I’m with al on this. unless the guide has become damaged, it’s usually the slickest form of cable routing and can be serviced with a garden hose.

as above, unless the plastic bit under the BB is damaged it won’t be the cable routing that’s the issue unless the bit of outer by the shifter is borked.

Try the black PTFE coated stainless XTR or Dura Ace cables as well as new SP41 outer and sealed ferrules from shifter to downtube.
Check the mech is free to swing….there are 4 pins in the parallelogram as well as the lever pivot.

PaulD

I never have had issues with a front mech not working. It has a much stronger spring than a rear mech, so rarely loses the ability to index and until it get VERY loose and rattly will work fine.
Does the mech move freely if the cable is disconnected?

As mentioned above – the problem is likely to be elsewhere, eg. corrosion of the cable on entry and exit from the outer cable run between shifter and frame stop.

I have cheap-skate 99p ebay gear cables on a couple of under-bb routed bikes and don’t have any issues – nice slick shifting. I do make suer i inject some gt85 down the outer housing each time the bike gets wet/cleaned though – seems to help prevent corrosion in there, which IME is by far the main culprit in sticky cables/shifting issues.