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Old 09-10-2017, 11:40 AM
dddd dddd is offline
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Cable and shifter life and proper adjustment.

On the subject from another thread/topic (of worn-out shifters, and the related premature failure of cables), I find that both of these problems relate to the habit or tendency of mechanics and (owner/mechanics) leaving the low-limit (hi limit in front) screw too tightly adjusted.

Thus, there is no overshift movement allowed at the derailers, which puts tremendously increased stress on cables and shifter mechanisms, and even forces cables/housings and shifter detents to endure cyclic overloading as the rider pedals and flexes the frame.

I would like to say that this is just an amateur's mistake, but no, I still see bikes coming from this or that shop (not all shops) with the limit screws set "on the safe side" with respect to chain control, the "better" to keep the chain out of the spokes and off of the crankarm.

So if anyone has wondered why today's shifters seem to eat cables, or why their Ergolever detent springs don't last as long as they should, this is the main reason, from what I have seen.

Also note that Shimano is addressing this with cable travel-limiting stops now incorporated in their latest STI shifters, and with their front derailers no longer even having a hi-limit screw. The hi-limit screw having been replaced by the lever's own limit stop, and the hi-limit function of cage travel limit now being adjusted via a booster screw that adjusts cage travel from the push side instead of using a screw stop, and with a separate cable-adjusting spool screw.

Leaving the derailers free to overshift slightly eases the force at the lever to the largest cog or chainring, which further helps the rider adapt to a consistently less ham-fisted use of the levers while shifting "up" to larger sprockets, so cabling (and the service interval of cable adjustments) can last a whole lot longer.

Does anyone else here find it strange that this issue seems to never get mentioned?

Last edited by dddd; 09-10-2017 at 11:46 AM.
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Old 09-10-2017, 01:34 PM
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Quote:
Originally Posted by dddd View Post
On the subject from another thread/topic (of worn-out shifters, and the related premature failure of cables), I find that both of these problems relate to the habit or tendency of mechanics and (owner/mechanics) leaving the low-limit (hi limit in front) screw too tightly adjusted.

Thus, there is no overshift movement allowed at the derailers, which puts tremendously increased stress on cables and shifter mechanisms, and even forces cables/housings and shifter detents to endure cyclic overloading as the rider pedals and flexes the frame.

I would like to say that this is just an amateur's mistake, but no, I still see bikes coming from this or that shop (not all shops) with the limit screws set "on the safe side" with respect to chain control, the "better" to keep the chain out of the spokes and off of the crankarm.

So if anyone has wondered why today's shifters seem to eat cables, or why their Ergolever detent springs don't last as long as they should, this is the main reason, from what I have seen.

Also note that Shimano is addressing this with cable travel-limiting stops now incorporated in their latest STI shifters, and with their front derailers no longer even having a hi-limit screw. The hi-limit screw having been replaced by the lever's own limit stop, and the hi-limit function of cage travel limit now being adjusted via a booster screw that adjusts cage travel from the push side instead of using a screw stop, and with a separate cable-adjusting spool screw.

Leaving the derailers free to overshift slightly eases the force at the lever to the largest cog or chainring, which further helps the rider adapt to a consistently less ham-fisted use of the levers while shifting "up" to larger sprockets, so cabling (and the service interval of cable adjustments) can last a whole lot longer.

Does anyone else here find it strange that this issue seems to never get mentioned?
I think it does get mentioned in that limit screws for low gear cogs or big ring, the limit screw should be turned in so it just gently touches the stop, along with a thumb on rear der to make sure a thumb force can't have the der even tickle the spokes. Most chain shuck off big ring is front der alignment/height, not limit screw.
I think at least as responsible is the 'busy' cable spool routing of the STI that are 'famous' for breaking/fraying cables...7800/6600/9000...

And broken spring carriers for 2008 and older ERGO...glad the 2009 US don't have these. Nothing in there to really 'break' except shift lever blades('fiber ones) or thumb buttons(rusty pivots), and those are replaceable.

I have all the parts for 1992-2017 ERGO-shameless pitch...
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Old 09-10-2017, 01:55 PM
bikinchris bikinchris is online now
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Please explain too tight. As for rear derailleur, I was taught to adjust the low limit a quarter turn from the chain failing to shift to the last cog.
I would like to hear anything new and see links to proper adjustment techniques.
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Old 09-10-2017, 02:04 PM
sdrides sdrides is offline
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I would be comfortable saying this is an amateur's mistake. An observant mechanic at home or in the shop should be able to see and understand the correlation between these adjustments and transmission fatigue after the first broken shifter, cable, housing, ferrule, etc. I think it's always best to leave just a tiny bit of travel past the click, but you have to be careful not to leave too much. That's one reason why it's nerve wracking to send a ham-fisted beginner out on their new bike - the same person who reefs the derailer past the gear is also going to keep pedaling hard when the chain starts to wrap around the back of the cassette.
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Old 09-10-2017, 02:13 PM
sdrides sdrides is offline
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Originally Posted by bikinchris View Post
Please explain too tight. As for rear derailleur, I was taught to adjust the low limit a quarter turn from the chain failing to shift to the last cog.
I would like to hear anything new and see links to proper adjustment techniques.
"Too tight" is essentially setting the limit screw so that the derailer doesn't get the full swing from the shifter into the biggest cog or ring. It's a "conservative" setting that's intended to keep the chain from going over the biggest cog into the spokes, or off the outside of the ring. The problem is that it stores a lot of extra tension in the cable, ferrules, housing, and shifter, so stuff is more apt to break. These small parts, especially shifter internals, aren't designed to sustain and function with that much tension.

I have found it best to back the limit screw out a ways, shift gently into the biggest cog, then kiss the derailer with the low limit screw, then back it out a quarter/half turn. Enough that the derailer can just "flex" a little past the shift, but not anywhere near enough to put it into the spokes.
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Old 09-11-2017, 12:37 AM
dddd dddd is offline
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I think that you get it, leaving just a bit of freeplay so that flexing frame tubes don't cause the cable to pull the derailer repeatedly against the hard stop of the limit screw, which would fatigue cable strands rapidly.
I usually back off the limit screw at most a quarter of a turn from the last-gear position, and always after the cable adjustment is finalized.

One more thing is when riders swap wheels and then make a small cable adjustment to correct the indexing adjustment, but ignore that the limit screw now is not free of the derailer's movement to the last cog, or is now too far out to limit the derailer's movement past the last index position.

I mention this issue because I often work on bikes that only shops have worked on, and find limit screws set too far in, as if the trauma to the cable and it's adjustment might be expected to bring in more service work. Probably though it is just the hasty or precautionary setting of the screw, seasonal workloads being what they are(?).
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Old 09-11-2017, 03:13 AM
rustychisel rustychisel is offline
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Interesting point, fair point.

I'm going to suggest the cable flexes to soak up some tension, but the major problem with wear patterns is hamfisted shifting from idiots who have not been taught to ease up pedalling fractionally when changing gear.
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Old 09-11-2017, 07:21 AM
bikinchris bikinchris is online now
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Quote:
Originally Posted by sdrides View Post
"Too tight" is essentially setting the limit screw so that the derailer doesn't get the full swing from the shifter into the biggest cog or ring. It's a "conservative" setting that's intended to keep the chain from going over the biggest cog into the spokes, or off the outside of the ring. The problem is that it stores a lot of extra tension in the cable, ferrules, housing, and shifter, so stuff is more apt to break. These small parts, especially shifter internals, aren't designed to sustain and function with that much tension.

I have found it best to back the limit screw out a ways, shift gently into the biggest cog, then kiss the derailer with the low limit screw, then back it out a quarter/half turn. Enough that the derailer can just "flex" a little past the shift, but not anywhere near enough to put it into the spokes.
Sorry, that's a non answer as far as I'm concerned. The terms used are like the OP. Vague.
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Old 09-11-2017, 10:10 AM
dddd dddd is offline
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Quote:
Originally Posted by bikinchris View Post
Sorry, that's a non answer as far as I'm concerned. The terms used are like the OP. Vague.
How was I vague? I explained it literally almost twice, and then again.

What can't you understand at this point?
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Old 09-11-2017, 02:16 PM
djdj djdj is offline
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Call me conservative, but I'd rather take the chance of greater wear on a small, relatively inexpensive part like a cable, g spring or carrier than risk clipping the r der with the spokes, which could cause much more damage. I set my limit screw so the der climbs quietly onto the largest sprocket and stops right there.
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Old 09-11-2017, 04:20 PM
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Originally Posted by djdj View Post
Call me conservative, but I'd rather take the chance of greater wear on a small, relatively inexpensive part like a cable, g spring or carrier than risk clipping the r der with the spokes, which could cause much more damage. I set my limit screw so the der climbs quietly onto the largest sprocket and stops right there.
Nope, smart. Regardless of limit screw, if you can push rear der with thumb and it tickles the spokes, turn the limit screw further in till it doesn't. Assuming straight der hanger, of course.
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Old 09-11-2017, 08:07 PM
bikinchris bikinchris is online now
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Originally Posted by dddd View Post
How was I vague? I explained it literally almost twice, and then again.

What can't you understand at this point?
Lets look at your description:
"I have found it best to back the limit screw out a ways, shift gently into the biggest cog, then kiss the derailer with the low limit screw, then back it out a quarter/half turn. Enough that the derailer can just "flex" a little past the shift, but not anywhere near enough to put it into the spokes."

A ways? Kiss the derailleur? Back out a quarter/half turn? All of those terms are very vague. Also, if a quarter turn is good, a half turn is way too much.

I'm not trying to be hard here, I want to hear if I am doing something wrong, So far, I have heard no solid instructions on what the problem really is and how to make sure not to repeat it.

I understand that setting the stops on derailleurs is important. I don't think I am setting them too tight. Setting them too loose can also cause lots of damage.

I set both the low and high stops on the rear derailleur to 1/4 turn from the point that it shifts. I shift by pulling the cable (or letting it go on the high stop) and tighten the stop until it doesn't shift anymore, then loosen 1/4 turn at a time until it JUST shifts, plus a 1/4 turn.
On the front derailleur, a 1/4 turn can be a too much adjustment. So I look at the travel of the front derailleur and adjust to that it is impossible to overshift past the big ring and not drop off the inside. Usually 2mm of extra room on the outside and a little less (roughly 1.5mm) in the inside of the little ring, as long as shifts are smooth.
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Old 09-11-2017, 11:09 PM
sdrides sdrides is offline
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Quote:
Originally Posted by bikinchris View Post
Sorry, that's a non answer as far as I'm concerned. The terms used are like the OP. Vague.
Let me try again:
Back out the low limit screw so that it is a non factor.
Shift into the biggest cog.
Tighten the low limit screw so that it touches the stop on the derailleur - there should be no visible flex or movement from the derailleur if you push on the shifter at this point.
Now back it out 1/4 to 1/2 turn - enough that there is some flex in the derailleur when you push the shifter, but not so much that it even hints at derailing into the spokes.

The derailer should never touch the spokes. If it does, it's likely the hanger is bent to the inside (assuming you've done your limit screws correctly).

There are no hard and fast numbers in bike repair. In this case it depends on the shifter, derailer, bracing angle of the spokes, hanger alignment, cable and housing selection, front or rear, etc. You have to watch the screws go in and out, and tune the system specifically to its own capabilities so that it looks and works right.
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Old 09-13-2017, 01:49 AM
dddd dddd is offline
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Good point about having to deal with the particular system.

While I was using a Shimano system as an example of what I was saying, I find that Campagnolo gruppos/wheels tend to cause spoke contact more easily.
I think that Campagnolo has addressed this somewhat with their more recent wheels and grouppos, but with the 8 and 9s systems I find the correct limit screw adjustment to be a sensitive issue, even settling for occasional spoke contact, which has yet to cause a catastrophic problem on any of the Campag-equipped bikes I've owned.
For this reason, a lot of the Campag-equipped bikes from the 90's got set up with a limit screw so tight that under hard pedaling the shifter could get nudged to the next-smaller cog under hard pedaling, just the sort of setup that would accelerate wear/fatigue of the shifter detenting springs.
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