Rear derailleur adjustment

DrunkenBiker

Hola,

Cannondale M400. Shimano LX rear derailleur.

I can adjust the derailleur so that it shifts fast and smooth for all cogs except for the top *or* bottom cog. On both of those, it goes to the cog but hesitates for several pedal revolutions before shifting off it. Meaning I can only really use 7 of the 8 cogs on the hub at any given time depending on my adjustment.(yes I've heard that all gears shouldn't be used due to chain angle. I don't when riding. I just want it setup correctly)

I can't finesse it to have it shift correctly for all cogs.

Just learning how to maintain my bike. I hope I explained this right

Thanks for any ideas.

John

gclark8

The Low Limit screw will effect shifting into the largest cog. Strike a balance between what you have now and overshifting. :D

DrunkenBiker

The Low Limit screw will effect shifting into the largest cog. Strike a balance between what you have now and overshifting. :D
Thanks for the reply.

I think I explained it wrong tho. :D

I can adjust the low/high limit screws so it goes into top and bottom cog perfectly......shifts *in* to those gears fine.

But I can only adjust it so it shifts *out* of one of them right(top or bottom).

I can't get it to shift out of both top and bottom cogs with same settings. It hesitates up to 5-6 pedal revs for one of them.

And 10 bucks says I explained it wrong again. lol

John

1id10t

If you've set the limit screws correctly you might want to try the cable tension adjuster barrel on the rear of the derailleur. This is the part into which the cable housing/cable is inserted. Maybe there's too much/little tension in the cable. Support the bike so the rear wheel is off the ground, turn the cranks and simultaneously turn the adjuster. Do this only in quarter turn increments. Hopefully this might yield some results.

mcrowe

I have problems with my Shimano rear derailleur. First, I can't shift to the smallest cog. Second, the gear shifter show tjat the the chain is on cog number 7 but it is actually on cog number 6.

Does anyone know what's wrong? Please help.

Thanks

1id10t

I have problems with my Shimano rear derailleur. First, I can't shift to the smallest cog. Second, the gear shifter show tjat the the chain is on cog number 7 but it is actually on cog number 6.

Does anyone know what's wrong? Please help.

Thanks

Here's a link to the Park Tools how-to on derailleur adjustment.

http://www.parktool.com/repair/readhowto.asp?id=64

Try this first. After that I would then be looking at the cable tension (see my previous post).

p38lightning

Maybe this is an angle "B-Tension" problem. See Sheldon Brown's comments on this as well as other derailer adjustment.

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

mcrowe

Thanks for reply. The website has quite good information of bike maintenance.

I have tried the basic derailleur adjustment. Perhaps I should try to look at the cable tension.

Here's a link to the Park Tools how-to on derailleur adjustment.

http://www.parktool.com/repair/readhowto.asp?id=64

Try this first. After that I would then be looking at the cable tension (see my previous post).

JungleBiker

Thanks for reply. The website has quite good information of bike maintenance.

I have tried the basic derailleur adjustment. Perhaps I should try to look at the cable tension.

It could be your derailleur hanger is not straight so that no matter how much you tweak the screws and cables it will never be working perfectly. There is a special tool which a good bike shop should have that is used to check and adjust the alignment of the hanger.

effectivepull

i have another rear derailleur issue. i run the sram rival group.

i can get the gears to shift smoothly on the bike stand using the barrel adjuster.

BUT, if the chain is on the smallest cog in the back and the big chain ring and i apply additional torque on the crank (or actually riding the bike), the chain jumps. it doesn't move up to the next cog or embed itself against the frame, it just kind of jumps (i can't see it, but can feel and hear it) and settles back in but does the same thing again if apply torque again.

it's driving me nuts!

can anyone help?

alienator

You need to twiddle with the limit screw.

kdelong

i have another rear derailleur issue. i run the sram rival group.

i can get the gears to shift smoothly on the bike stand using the barrel adjuster.

BUT, if the chain is on the smallest cog in the back and the big chain ring and i apply additional torque on the crank (or actually riding the bike), the chain jumps. it doesn't move up to the next cog or embed itself against the frame, it just kind of jumps (i can't see it, but can feel and hear it) and settles back in but does the same thing again if apply torque again.

it's driving me nuts!

can anyone help? Are ya sure this is a limit screw problem? Sounds more like worn cogs, chain, or chainring would be the culprit here. Check your chain. If it is within specs, then you may have to replace your cassette and/or large chainring. Now you're probably gonna tell me that the bike is only 2 months old. :confused: If that's the case, twiddle with the limit screw.:rolleyes:

effectivepull

You need to twiddle with the limit screw.thanks! i just got back from borders and look up the symptom in one of the bike mechanic books - it said the likely cause is a screwed up chain, or bent cog. i don't think either is the case since the bike and components are new (07 Cervelo Soloist) with less than 40 miles on it, no crashes.

i'll give the limiter a go and see what happens.