3x9 front shifters on a 3x7 system
 

Hi.

I have bike with pretty low end shimano 3x7 components.
now, my front shifter passed away and I bought new Shimano LX front shifters pretty cheap.

thing is that I only now have noticed from description that it is designed for 3x9 systems.

can I still use these shifters or do I need to change something else?

The 7 in the back means that is how many gears you can run back there.
you need another 9 speed indexed lever to shift, the right distance.
[unless you go to a friction shift scheme.]

Your bike frame at 126mm width may not accept any new wheel
to get in #9, it has to be wider. frame spreading ..

NB: Gear Ratios are different than 'speeds' ..

For the front derailleur, (left-side shifter), it should be just fine. Just make sure the top and bottom stops on the derailleur are adjusted correctly, and then use the barrel nut on the shifter to fine-tune the position of the derailleur for the middle chain ring.

Obviously, if we're talking about putting a 9-speed rear (right) shifter, to control a 7-speed rear derailleur & cassette, that won't work.

Also, if you're mechanically-inclined and like to tinker - try taking apart your 'broken' shifter. Degrease it, clean it up, make sure all parts move freely, and re-grease it. You may get some more life out of it afterall. I just did this for a friends shifter that wouldn't allow him to utilize the large chain ring. The pawl's pivot point was gummed up. I cleaned it up, and it worked like new.

The center-to-center spacing of a 7-speed cassette/freewheel and 9-speed cassette are different, so the indents of a 9-speed shifter won't line up with the cog positions of a 7-speed cassette/freewheel. See: http://sheldonbrown.com/cribsheet-spacing.shtml

Do you have a 7-speed freewheel or cassette? See: http://sheldonbrown.com/free-k7.html

If it's a freewheel, there's not much you can do except get yourself a 7-speed shifter.

If it's a cassette, then you probably have a 7peed-only freehub. In this case, you can try the "8 of 9 on 7" trick by getting a cheap 9-speed cassette and using the 8 smallest cogs on your freehub. You'd also need a 9-speed chain. Your shifter will only use 8 of the gears, but the indents will line up. More info: http://sheldonbrown.com/k7.html#up7

I believe he's talking about the shifter that controls the front derailleur, not the rear.

.. read all the 'my chain drags on my front derailleur cage' posts,
Friction shifters work better on the front, than STI big ka-thunk throw,
1 per chainring, shift levers , IMHO.
:50:

Oops, missed that.

Shimano(-compatible) 3-speed front is 3-speed front. OP: Can you just replace the left shifter?

Also, if you haven't uninstalled it yet, you can try flushing the internals of the shifter with WD-40, work the shift levers, and repeat. No disassembly needed, you should be able to spray in through some openings. The grease can harden over time, making the internal pawls of the gears not engage.

+1 For this reason, I prefer the Tourney trigger shifters: indexed rear, friction front. A 7 speed set up costs about $15, including cables and housings.
Putting a Tourney friction front on a bike this afternoon.

Thanx for the replies.

I want to make it clear that i want to change JUST the front shifter and not to convert bike to the 3x9 system.
I noticed that shifter was for 3x9 system after I received it.

is the distance between front cogs on the crankset same for 3x7 and 3x9 systems?

about the repair: yes, I'm mechanically inclined but I'd prefer to install what I've already bought, than to use old broken one. plus the new one is decent one :)

All of Shimano's front, 3-speed, indexed, flat-bar shifters are compatible. You're good to go.