Old shimano altus front deraillier question...

[northwind]

Right, so, I'm about fit enough to cycle again now, I can ride 2 days in a row and still walk the day after, which is a step forward... So I've got my old carrera in rideable trim, but the gears are giving me issue. Rear just needs some light fettling but the front one's giving me gyp. It's an old shimano altus deraillier, fairly standard 2 screw adjustment- which I believe are both to limit hte range of movement, one for the top and one for the bottom. I've set it up at the cable to run right on the middle chainwheel, and the bottom one's now fine too, but it won't shift into top. The adjuster screw's all the way out but it doesn't go high enough, it needs at least another 2mm. Is there any further adjustment possible do you think? I don't know much about pushbikes...

Alternatively, will I be able to just go and get another deraillier if this one's knackered? Are they pretty universal? There's no point spending money on this bike so i'd be after teh cheap.

I know there's some proper cyclists on here, hopefully some of you will condescend to offer advice on my museum piece

Northy you need to pull in the cable as from what I can remember (without going outside) the cable gets tighter on pulling it onto the top sprocket. Just adjust that first so that you have enough pull on the cable to get it into top, then adjust the screws to shift down the other 2 sprockets

[fizzwheel]

Northy, about halfway down this page, more in front mech adjustment than I can explain and better put to...

http://www.sheldonbrown.com/derailer-adjustment.html

If its been sat about for ages, might be that the cable is stretched beyond help or that you need to adjust the cable tension, but it'll depend on your shifters as to what you need to do on that.

HTH

[northwind]

Yeah, I read that article, that's the only reason I know what the screws do Funny, I kept this bike on the road for a decade without having even the slightest idea what I was doing I can see it's going to be very helpful

Thing is, the article doesn't really seem to cover the problem- basically nothing i do shifts the plates far enough to make the jump into top. I thought about it being a stretched cable, it's an obvious suspect, but pulling the cable independantly of the lever doesn't seem to shift it out far enough. I'm wondering if it might have taken a knock in storage, or when my brother was using it.

Robchester, I'm not sure that works, the screws are to set the top and bottom limits according to that article, so since it's an index shift I need to use the cable adjustment to get the middle chainwheel right then use the adjusters for the top and bottom, if I understand rightly. Which I might not

[mattSV]

Northy - try dropping it on to the lowest chainring, and then check and see if there is any slack in the cable - if so, disconnect the cable from the derraileur end and pull it taught, and then re-tighten.

This should then allow the lever to operate through its full motion.

Another thought - is the derailleur 'band on' mounted (i.e. a clamp that goes around the seat tube) - if so, the derailleur might have been knocked up/down or twisted around the seat tube, which will affect it - does it look square? If not, adjust that before you start playing with the cable

[northwind]

Cool, I'll give that a crack. It doesn't look like it's moved around the tube (that would have disturbed the muck!)

[JamesMio]

If you manually push the front mech up towards the front cog (or if you can get the back wheen off the ground, ie on a stand, you can simply pull the gear cable until it reaches it's upper limit), does it stop before going close to the big cog?

If it doesn't then it's the mech, either it's position or the stop-screws, if not and it 'would' go far enough then it'll be the gear cable.

Fixes for each:

Top screw stop is preventing the mech from going far enough to drag the chain onto the biggest cog.

Gear cable is stretched / slack - try tightening this up as much as it'll go (make sure the chain's on the bottom front cog when you do this, as this is the gear cable at it's slackest point).

Front mech is out of wonk, but you say that doesn't look to be the case - it might just be a bit too low down, ie slipped a bit.

Is it Altus gear shifters you've got? The two-trigger types with a yellow bit on the dial?

Cycles I can do, spent a few years of my youth working in a Cycle shop!

Motorbikes/Cars etc...? Not so good!

[fizzwheel]

Northy this might help

http://bicycletutor.com/adjust-front-derailer/

[northwind]

Sorted it... And bizarrely enough, the problem wasn't the derailer at all, it was the selector. The cable end had- somehow- got out of hte receptacle on the selector lever, and was sticking out the side. It'd sliced slightly into the soft plastic so it wasn't moving about, but when I was shifting into top it was restricting the cable slightly, so it wasn't giving its full pull. I couldn't figure out how first and second were spot on but top didn't work

But, thanks all for the help, it's meant my gears are actually adjusted right for the first time in, well, ever And also, I now want a maintenance stand! I've been using the SV!