jnobles

I am constantly having to adjust the barrel adjustment for the FD to account for chainrub. I usually only make the adjustments when in the middle ring. Once i switch to the small or large ring and then back to the middle ring without changing the gear on the rear derailleur, I have to make the adjustments again. What could be the culprit. Below are the listed components.

Front Derailleur: Shimano Sora
Shimano Tiagra ST-4500 4503 Shifter 3 X 9 SPEED
Crankset: FSA Tempo 170mm 52/42/30T
Cassette: Shimano Tiagra 9 Speed 12-25T

cny-bikeman

The components have nothing to do with your problem. If shifting back and forth change the adjustment then logically something that occurs during shifting is the cause. The levers move a set amount for each click - that cannot vary. The barrel aduster is not going to move in any reasonable amount of time, and the limit screws on the derailleur of course don't come into play in the middle ring. That leaves the cable. The cable moves through housing on nothing but spring pressure when moving from the large chainwheel inward. If there is too much friction then the derailleur will not move as far in as it's supposed to. Further, if you readjust in the middle ring when the cable has not fully released, when you shift to the small ring and back up the cage may again be off - this time too far inward. The other symptom of cable friction would be that the shifts inward (outward on the rear) tend to be slow. (reversed on Rapid Rise system)

So you need to pull the shift cable out of the housing and check for corrosion, kinks, broken strands or lack of lubrication (very light lube - no grease). Also make sure the housing ends/ferrules are in good shape, seating well into the stops with no housing wire protruding.

One other thing to check is the height and rotation of the derailleur If those are not proper it will be more difficult to achieve good shifting and avoid rubbing. Google front derailleur adjustment - the sheldonbrown and parktool sites are generally considered the best, but the first youtube video is very good on covering alignment of the derailleur.

DougG

FWIW, triples can be pretty finicky in general to get them shifting well for all combos. I also had similar issues with my Sora components that went away when I upgraded to 105. The 105 derailleur has a "trim" adjustment when on the middle ring -- sort of a half-click of the shifter that moves it slightly in or out. Otherwise, if you are trying to use the entire range of your cassette it's likely to rub either on the smaller cogs or the larger ones.

This may be part of the reason that triples seem to be disappearing in favor of compact double cranks with wide-ratio cassettes.

ultraman6970

Don't know this complain does not surprise me a bit

cny-bikeman

Again, the specific components do not explain a problem with the derailleur not being in the same position when shifting from the outer vs. inner ring to the middle, and that is the OP's specific complaint. If you had a similar problem that went away when you upgraded then it's most likely you eliminated a source of friction.

HillRider

The derailleur itself doe not have any sort of "trim" or other adjustment. It's location is controlled only by the shifter (and the cable which can hinder that movement). Using the proper shifter and front derailleur, triples are not particularly difficult to set up.

DougG

I wasn't contradicting you; just commenting that it's sometimes difficult to get all the hysteresis out of the system without a trim function. Friction in the system is of course a big contributor to hysteresis.

I just meant that the 105 triple component group has that feature. My bike's triple shifts flawlessly vs. its former 2005-vintage Sora self (I think Sora has been greatly upgraded since then).

Cyclelogikal

Could it possibly be a shift cable that is worn out and in need of replacement. How long have you been running this shift cable? Plus I agree with Doug a bit on this that some systems just start to fail if old enough. You may need to replace the FD and when you do so go up a bit in the pecking order.

cny-bikeman

Take care of the cable first, worry about the derailleur if the problem is still present with a smoothly running cable/housing system.

gregjones

Oops, I might better redo mine before colder weather finally sets in here. Although it really only gets chilly.

I have a light coat of grease on it now, what do you recommend, or mean by "light lube"?

jnobles

The cable and housing is brand new

Wilfred Laurier

the only two possibilities i can think of
are

the cable is loose or slipping or the housing is somehow compromised
or
the derailleur is not securely fastened in place

Cyclelogikal

Is it a braze on FD or clamp on? If braze on the l bracket could have gotten bent slightly. Also suggested to me due to using coated cables is to scratch the coating off where it is clamped to the FD screw down bolt otherwise it could slide slightly under pressure. Just a thought.

jnobles

it is a clamp on

fietsbob

Why I never adopted indexed derailleurs , for my own stuff ..

I could help you sort it out in the bike shop but not over the internet.

so Ill send you to your LBS.

cny-bikeman

Would have been very helpful to know that up front, but it's still possible to have a problem with a new cable housing. One thing you did not tell us and I always ask is when did the problem start? Did you replace the cable/housing in an attempt to fix it or did it start afterward. One always goes with the most likely cause first, which is why I focused on the cable. However it is possible for something to be catching when the derailleur pivots that occurs more in one direction than in the other. It may also be helpful to know whether the derailleur is farther out when shifting from the large or small ring, and of any other changes made just before the problem started.

Al1943

Most Shimano triple capable road shifters have 4 main positions for the the 3 chainrings plus a soft click trim position for the smallest ring. The second and third positions are for the middle ring. The second position is to be used when the chain is on the left side and middle part of the cassette. The third position is to be used when the chain is on the right side and middle part of the cassette. The fourth position is for the big ring. Shifting from the third position to the big ring or from the big ring to the third position takes only a single click. Shifting from the second position to the smallest ring takes only a single click. BUT shifting from the small chaining (first position) to the middle ring requires a good shove over to the third position to make the chain climb up onto the middle ring. At this point if the chain is on the largest or next to largest cog you will need to shift back to the second position to avoid chain rub.
I don't know how much experience you've had with Shimano triple shifters or if this may help you with your problem. But I have seen several riders have trouble getting use to the way these shifters work.

reptilezs

i had this problem on my commuter. the fd was physically moving on the braze on tab. some friction paste solved that problem

jnobles

I took it to my local LBS and they replaced the spring. It had cracked and was not maintaining tension.

cny-bikeman

Most of the time in-person is the best option. This example is exactly why one can't just match up a symptom to a cause - there are too many possibilities. In 20 years as a mechanic I don't think I had more than a couple of front derailleurs with a broken spring. One has to use both logic and observation in addition to experience, with the former two actually being more important in most cases.

jnobles

I do appreciate all the replies. I was hoping it would be an easy fix that I could find and do.