silly question - what are those short barrel adjusters on Shimano gearshift cables
 

Warning - dumb question to follow:

What are those short stubby barrel things found on Shimano gearshift cables and what is it that they adjust?

Should I ignorantly tamper with them and see what happens or are they set for best performance?

Also, my front deraileur has started rubbing on the chain when the gearing is set to the largest cog / smallest chainwheel ... I havent attempted to fix this one yet ... should I simply adjust the H or L screws on the deraileur or can i fix it by twiddling one of those barrels?

god i am so mechanically inept...

thanks all

simple rule of thumb:

if you don't know what it is/does, don't touch it.

the chain should (well, in a perfect world it wouldn't, but it's excusable) rub in the large/small and small/large combinations. you aren't supposed to be in those combinations anyway.

I assume you are referring to the cable adjusters where the cable housings attach to the down tube. Those allow you to adjust derailleur cable tension on the fly. In real life, if your bike is maintained properly, you will never or only very rarely find the need to fool with them.

Fooling around with the high and low limit screws on your derailleur is a sure sign of somebody who has no concept of what they are doing. I actually had a customer bring a bike back to me who had tightened those screws until the bike souldn't shift at all! Then they asked me if the bike was a lemon. If they bike shifted right when it was new, there is rarely any need to make further adjustments of the high and low limit screws.

[QUOTE]Originally posted by dazknee _66
Warning - dumb question to follow:

What are those short stubby barrel things found on Shimano gearshift cables and what is it that they adjust?

Should I ignorantly tamper with them and see what happens or are they set for best performance?

Use them to adjust cable tension if your bike doesn't shift or shifts aren't executed crisply. Turn the top of the adjuster 1/4 turn at a time in the direction your shifts aren't happening i.e. if your having trouble moving to the larger cogs in back, turn the adjuster so the top moves toward the bike. Trouble going to the smaller cogs in back? Rotate the top of the adjuster 1/4 turn away from the bike. There, now you can tamper with then in a non-ignorant fashion.

Warning: If your bike is jumping two gears instead of one at a time or you have to contunually rotate the adjusters one way and then the other, this isn't the problem.


Also, my front deraileur has started rubbing on the chain when the gearing is set to the largest cog / smallest chainwheel ... I havent attempted to fix this one yet ... should I simply adjust the H or L screws on the deraileur or can i fix it by twiddling one of those barrels?

You shouldn't ride in the large / small or small / large combination, it causes excessive wear on drive train components. However, there are times this is going to happen and a little deraileur / chain rub, although annoying, isn't a terrible thing. You can try to use the barrel adjusters to alleviate the rub, but it may cause shifting problems addressed earlier. Depending on your components, you may have a "trim" adjustment built into your shifter for making less then full shift deraileur position adjustments. Ask the LBS.

Stay away from the "H" & "L" screws, these are "stops" designed only to allow or limit the deraileur's range of motion.

god i am so mechanically inept...

Most of us start that way, it's not fatal, but can be costly in some instances ;)

Please don't feel so self-effacing. The only dumb question is the one you want to ask but feel too shy to. Ask away: that's what forums like this are for.:)

h:)

:)

:) Hey guy,if I read your post correctly,and its rubbing on big cog -small chainring than its the cable not being adjusted properly.Try moving black barrel adjuster in or out about 1/4 to 1/2 turn on the left lever cable. don't mess with the H/L screws unless chain is over shooting or under shooting the front chainrings. Hope this helps.:beer:

:)

Dang, RD Warrior, easy on the reply button.

:) Sorry about all the replies,the sumit reply was telling me the system was too busy.I didn't mean to duplicate:confused:

Not a problem, thought it might be to much coffee or maybe newb jitters.

Now I'm confused...........what's wrong with the big/small or small/big combo? Cross-chaining would be the small/small and big/big combos, right?

that's what i meant. i wasn't fully awake when i replied. i'm sure that's what the others meant as well.

Yeah, cross chaining is big/big...etc.

If you're in Big (F) and Small (R) and getting some rub, turn the front derailleur cable stop out in 1/4 increments. If by 1 full turn it still rubs, you can loosen the "High" stop out in similar 1/4 turn increments.

What is going on, the stop prevents the derailleur (and chain) from moving too far to the outside and off the chainring. If you bike is new, or cables are new, they have an initial break-in period. Chances are you just need to turn the barrel adjusters and leave the set screw alone.

A great website that has a lot of instruction and decent pictures is www.parktool.com

Also, at the top of this section there is a thread titled "Barnett's ...etc." there are some great downloads that should steer you in the right direction.

Tinkering is the only way you'll learn how to make minor adjustments. Heck, you really can't screw it up too badly. If you do, your LBS will fix it for relatively cheap, or just keep asking here and I'm sure someone here will walk you though the adjustment.

Also, don't forget the "SEARCH" button, this ? has been asked before. Numerous times I'll bet!

L8R

dazknee_66 don't feel ashamed to ask anything to do with your bike. Generall speaking, when any major change is made to the front and rear mechs, those barrel adjusters on the shifters will invariably be required to fine tune the shifting. Over time, cables will stretch so again, you'll need to retention them. Fine tweaks to the adjusters are unlikely once you've got clean crisp gear changes but over time and regular use you will need to finger those little beauties.

If your front mech rubs the chain in the very highest gear (large chainwheel, small cog), then it seems to me that your front mech cannot travel enough. You need to adjust the H limit screw, backing it off a small amount (maybe 1/4 turn).
If you go too far, the chain may thrown off the big ring, in which case, you screw the H-limit screw back down a tad.

Other reasons for chain rub in the highest gear are that your frame is flexing if you pedal hard. The solution is to gear down a bit and pedal faster with less force. On a standard road bike, the times you really need to be in top gear are quite rare.

Yep, did the same thing, just went with the usual assumption and didn't read what was really written.

My bad, or for old times sake "Really bad applesauce"

What is utterly amazing is that sometimes I can type faster than I can read :o

(bump 'cuz I searched ;) )

Okay, so...

"Out" on the barrel adjuster means turning the top towards the front of the bike? Or is it like I'm looking at the brifter from the cable side, then turing the barrel left to "unscrew it" out of the brifter housing?

And "out" on the high stop screw is left (lefty-loosey again)?

Is the 105 FD high stop screw the outboard one? I can't find any markings, and Shimano's exploded view PDF doesn't label them, either.

[QUOTE=BarracksSi;5495258"Out" on the barrel adjuster means turning the top towards the front of the bike? Or is it like I'm looking at the brifter from the cable side, then turing the barrel left to "unscrew it" out of the brifter housing?

And "out" on the high stop screw is left (lefty-loosey again)?

Is the 105 FD high stop screw the outboard one? I can't find any markings, and Shimano's exploded view PDF doesn't label them, either.[/QUOTE]

When you turn the barrel adjuster counter-clockwise it makes the cable housing longer and tightens the shift cable. If it ever shifted right about 1/4 to 1/2 turn CCW will usually fix it.

If it was ever right, limit screws seldom need readjustment. I'm going to say that, as a general rule, the outer FD limit screw is for the high gear and the inner one is for the low gear. I'm also thinking that might not be true for every single front derailleur.

That's counter-clockwise if I'm standing in the middle, or on the right side, of the bike and turning the lefthand barrel adjuster while the cable is pointing from the brifter towards my body... correct?

I really, really need to get a folding workstand. I'm tired of picking up the bike, twirling the cranks, putting it down, shifting the levers, picking it up, twirling the cranks... oi... ;)

1. Imagine you were unscrewing the barrel adjuster from whatever it's attached to.

2. Make a noose in a piece of rope and hang it from something. Hang your saddle from the noose.

1. Gotcha; then "out" will be counterclockwise for both cables; the left one will turn "back", and the right one will turn "forwards".

In both cases, will "out" move the derailleurs outboard?

2. For a split second, I thought you were recommending the noose for me.. :o ;)

My wife's bike has this problem - what is the common issue here?

Cable tension is too high. Redo the rear derailleur adjustment procedure. Assuming nothing is actually bent/broken/incompatible.