Got lubricant on limit screws,

[jhkuo]

I stupidly applied some lubricant on the limit screws of my front derailleur (before I learned how they work), I am not sure if this is the cause, but I've seem to having to adjust the limit screws to ensure the smooth gear change quite often.

Do I need to think about getting rid of the lub and maybe apply some thread seal to make these screws a bit more "sticky"?

 

[Davidc]

Lube on them sounds like a none too good idea.

You could try taking them out carefully (count the turns to speed up replacement) and degrease them and, very carefully, the threads (white spirit should work).

When they're clean and dry again put them back, but be wary of thread locking compound. Those adjusters need to be used every so often. If there aren't any there try to get hold of some of the small springs designed to hold adjusting screws in place (by increasing the force between the fixed and moving threads, hence the friction force)

The limit screws should only affect whether the chain comes off the chainrings or not. Smoothness and accuracy (on an indexed shifter) should be determined by the position of the cable adjuster.

 

[jhkuo]

Thanks for this, it sounds like I was beating the wrong bush, I will check my cable shifter.

Would applying some WD-40 on the limit screws an advisable way to clean up the lube?

 

[Smokin Joe]

Lubing the threads won't make the screws loosen, mine get a spray of GT85 every now and then when I'm cleaning the bike. The limit screws are only to stop the chain derailling and will not effect how smooth the gear changes are, as DC says that is down to cable tension.

 

[jhkuo]

Thanks for clearing this up, this is a new (2 week old) bike so maybe the gear cable just got stretched. :-)

 

[2Loose]

Thanks for clearing this up, this is a new (2 week old) bike so maybe the gear cable just got stretched. :-)

That'll be it.

 

[Davidc]

If you're not sure how to set gears up say so on here, and I'm sure you'll be told several ways of doing it!

 

[jhkuo]

Thanks :-)

I think I got how the front derailleur works now (after checking various videos), the low limit screw controls the angle of the arm and hence how far the chain gets pushed down to the small cog, and high limit screw determines the push up action to the large cog. The shifter cable controls how much/far the derailleur moves.

My problem was when I thought I got everything adjusted correctly when my bike was on the tripod (I used a camera tripod to lift the rear wheel off the ground), when I actually sit on the bike, the front derailleur doesn't seem to move quite the same way...

I think I will live with it for a while until the cable fully stretched out.

If you're not sure how to set gears up say so on here, and I'm sure you'll be told several ways of doing it!

 

[Davidc]

I always find that however well I set things up on the workstand there's fine adjustment needed when I go back on the road. On the bike which has lifetime LBS servicing the same applies - they set it up but there's always a differrence on the road.

 

[Globalti]

Thanks :-)

I think I got how the front derailleur works now (after checking various videos), the low limit screw controls the angle of the arm and hence how far the chain gets pushed down to the small cog, and high limit screw determines the push up action to the large cog. The shifter cable controls how much/far the derailleur moves.

Doesn't sound quite right. The cable moves the paralellogram between the limits allowed by the two limit screws. If you look carefully behind the derailleur you should be able to see the ends of the screws and how they bear on two lobes that move as the derailleur moves. Your rear derailleur has the same limit screws and once these are set you might never need to touch them again. What will change is the length of the cable as it stretches and this can be accommodated by tightening the cable at the derailleur or with the adjusters at the head tube where the cable outers end or possibly with adjusters incorporated in the outer cables just inboard of the brakes.