Front Derailleur Trouble

Max Phillips said:

Alright so this evening I took my new bike out for a ride... when I took it for a test ride from the shop everything was smooth, but by today, just a day after I bought it, there seems to be some stretch in the front derailleur cable. it's a 52/39 config, and getting from the 39 up onto the big chain ring was a major pain. that being said, even when i did get up onto that ring, i had to be on the 12 cog on the cassette, otherwise it would slip back onto the 39.

when I came home i noticed there was a considerable amount of slack in the cable, and was wondering what all there was to tightening it up. how tight should it be is the only real question i can think of, but any answers to questions I don't have would be appreciated also

Thanks

bring it back to the shop and have them fix it for you rather than you bunging-up the bike.

if you're a little more adventurous, ParkTool has the drill on the adjustments

Max Phillips said:

Alright so this evening I took my new bike out for a ride... when I took it for a test ride from the shop everything was smooth, but by today, just a day after I bought it, there seems to be some stretch in the front derailleur cable. it's a 52/39 config, and getting from the 39 up onto the big chain ring was a major pain. that being said, even when i did get up onto that ring, i had to be on the 12 cog on the cassette, otherwise it would slip back onto the 39.

when I came home i noticed there was a considerable amount of slack in the cable, and was wondering what all there was to tightening it up. how tight should it be is the only real question i can think of, but any answers to questions I don't have would be appreciated also

Thanks

I agree w/ guevarra to bring it back to you LBS to get it sorted.
That said I just want to say that brake cables/housings are different from shift cables/ housings. Contrary to what is generally perceived, brake and shift cables do not stretch. It is the housings that compress thereby creating the slack. Brake cable housings are constructed differently that shift cable housings and are not interchangable. Brake cable housings feature a spiralled material inside the outer covering. The downside of this is that it is prone to compressive forces that slacken a cable. On the other hand, shift cable housings have metal strands running length-wise the entire cable. This way the cable withstand compressive forces better than brake cables and therefore they are ideal for shifting purposes to always maintain shifting accuracy. So one might say why cant we just use shift cables as brake cables - the answer is you cant because a shift cable will explode when used for braking purposes due to higher stresses required for braking and therefore the spiral core is the ideal constuction for brake cable housings.

hd reynolds said:

.... shift cables do not stretch.

I agree with your statement that housings compress. However, cables to stretch. I installed hundreds of front derailleur cables on downtube shifter equipped bikes which had no shifter housing to compress, and I can say that the cables do stretch initially and require readjustment after initial stretching.

Sounds good, and John, please make another post, I don't like seeing your post count at 666

Max Phillips said:

Alright so this evening I took my new bike out for a ride... when I took it for a test ride from the shop everything was smooth, but by today, just a day after I bought it, there seems to be some stretch in the front derailleur cable. it's a 52/39 config, and getting from the 39 up onto the big chain ring was a major pain. that being said, even when i did get up onto that ring, i had to be on the 12 cog on the cassette, otherwise it would slip back onto the 39.

when I came home i noticed there was a considerable amount of slack in the cable, and was wondering what all there was to tightening it up. how tight should it be is the only real question i can think of, but any answers to questions I don't have would be appreciated also

Thanks

It's a pretty easy adjustment. I would shift to the inner most ring, loosen the pinch bolt and pull out the slack. It will take all of about 2 minutes and it will help you become familiar with your bike. As long as the limit screws are set properly, it shoud work fine. I must say, I had a similar issue once, and it wasn't the cable. The bottom bracket had worked loose and the crankset had moved a 1/4 inch or so away from the frame. This prevented shifting into the big chain ring. It's a strange occurance, but just make sure that the lockring of the bb is snug against the frame. That was the last time a shop touched my bike. Now I do all of my own repairs and maintenance.

John M said:

I agree with your statement that housings compress. However, cables to stretch. I installed hundreds of front derailleur cables on downtube shifter equipped bikes which had no shifter housing to compress, and I can say that the cables do stretch initially and require readjustment after initial stretching.

That is not due to cable stretch. When installing cables to der. be it front or rear, one requires readjustment because the housings bed into the the lever bossess, cables bed into the cable guides under the BB, housings compress and lastly but not least, you cannot apply enuf force to pull the cable prior to tightening the retaining bolt that holds down the cable to the der. Hence, you need to adjust the barrels or a/b screws so on and so forth....

PeterF said:

It's a pretty easy adjustment. I would shift to the inner most ring, loosen the pinch bolt and pull out the slack. It will take all of about 2 minutes and it will help you become familiar with your bike. As long as the limit screws are set properly, it shoud work fine. I must say, I had a similar issue once, and it wasn't the cable. The bottom bracket had worked loose and the crankset had moved a 1/4 inch or so away from the frame. This prevented shifting into the big chain ring. It's a strange occurance, but just make sure that the lockring of the bb is snug against the frame. That was the last time a shop touched my bike. Now I do all of my own repairs and maintenance.

Thanks Peter...I've already done some tinkering with it, more than likely I'll do all you said, but then right before I take it back to the shop for a 90 day tune up (they said the cables would stretch and you have free service for a year...most people opt to bring their bikes in around 2 or 3 months) i'll switch everything back to the way it was (15* up stem, loosen the front derailleur cable, etc.).

Max Phillips said:

Thanks Peter...I've already done some tinkering with it, more than likely I'll do all you said, but then right before I take it back to the shop for a 90 day tune up (they said the cables would stretch and you have free service for a year...most people opt to bring their bikes in around 2 or 3 months) i'll switch everything back to the way it was (15* up stem, loosen the front derailleur cable, etc.).

I don't understand why you would de-tune a bike before having it looked at...

If you leave it as you set it, they could confirm that you have done it right because no adjustment will be needed... If you set it back to where you thought it was, you have now adjusted your cable at least twice, the second time to a known problematic state.

If you fear that the LBS won't honor their commitment because you adjusted the cables, adjusting them a second time won't eliminate that issue.

Frankly, if an LBS had a problem with the owner adjusting cable tension, stem height or any other simple adjustment, I would look elsewhere the next time I buy.

gregory...you too have a valid point, and i'm 99% likely to be following your advice

Max Phillips said:

gregory...you too have a valid point, and i'm 99% likely to be following your advice

I don't know what kind of bike you have but new Cannondales (for example) have cables that stretch like crazy, when brand new. When you build them up they need a lot of attention to get the cables stretched properly. This is not a knock, or negative comment, about Cannondales - it is just something that needs a little extra attention with a new build. All new cables will stretch to some extent and the housings getting seated in add to the problem. I'm sure that Cannondales are not the only bikes like this, but I have noticed that they are significantly worse than other makes. The point is that if it's a new bike with very stretchy cables and the shop was not vigilent in pre-stretching them, then you may require more tension and there may not be enough adjustment in your barrel adjuster to get it. The point where the cable is locked down at the FD is for the coarse adjustment of cable tension and the barrel adjuster/s are for the fine adjustments.

If you decide you want to DIY, it's no big deal for a front derailleur. I'm only going to describe adjusting cable tension - nothing else. You should assume that the shop did the FD alignment correctly. Limit screws, FD height and rotation should not change over time. Cable stretch is a completely different issue, so leave those other adjustments alone. If you start messing with the limit screws or change the derailleur height or rotation, then you must do a complete FD alignment and unless you are very confident about what you are doing, then you are best to leave that to the shop. Barnett's rates a full FD alignment as a job of "moderately high difficulty". If you become determined to do the complete alignment then go to the Park Tool site and follow the directions there to the letter. You absolutely must do those in the correct order or you will be chasing your tail for many hours.

Back to the cable tensioning. Just put the rear derailleur in the lowest gear (largest cog) and the front derailleur in the lowest gear (smallest chainring). Since you say there is already slack in the FD cable, you should see it in this configuration. Loosen the cable locking bolt (usually a 5mm hex head) enough so the cable can slide under the locking bolt. Now, turn any barrel adjusters CW as you look at the end that moves in and out. I turn them all the way in. Next, grab the cable end with a pair of pliers (don't crush the cable - just grab tight enough to keep it from slipping). Pull the cable tight - not deathly tight, but just so there is no significant slack - and while holding the cable tight, tighten down the locking bolt. You'll get any additional tension needed with the barrel adjusters.

Now test the FD shift/s and fine adjust the cable tension ....

For a double: It should shift up smoothly to the big chainring. If it does not, add some tension by turning the barrel adjuster 1/2 turn at a time until it shift smoothly. If it seems good, test RD shifting and keep in mind that you're likely to get some cross chaining in the (small cogs & small chainring) and (large cogs & large chainring). The (large chainring & small cog) and (small chainrign & large cog) combinations should work perfectly with no rubbing on the derailleur cage.

For a triple: This is pretty easy. Keep the chain on the large cog and shift the FD to the middle chainring. The inboard side of the chain should be just barely clearing the inboard side of the FD cage. If it's rubbing, you need some added cable tension to make it stop. Crank the barrel adjuster CCW until the rubbing just barely stops, but no more. That's it.

Once you get the correct cable tension dialed in, it should only take an occasional 1/4 turn or so (on the barrel adjuster) to make it perfect again.

As was already pointed out, since your bike is new, then you are perfectly within your rights to go back to the shop and get it fixed. While you are there, get them to show you how the barrel adjusters work and what the telltales are that indicate you need a little more tension as the cable ages. Any decent shop should be happy to help you out with this type of problem. If you go in and tell them that you only have a cable tension issue then there should be a good chance they'll fix it on the spot. Best luck with your fix.