agermano

Picked up my brand new 2016 Synapse 105 on Saturday. On Sunday I go out on first ride. First, I apologize that I do not know all the correct terms of components so I will describe them as best I can.

1. When switching from the smaller front gear to the bigger front gear, the chain kept coming of the front.
2. When in the bigger front gear, when I would get to the top three gears in the rear, it would feel like it was skipping at times, and the chain kept coming off the front.

I brought it back to the LBS which was open yesterday (Sunday) but it looked like all kids working that day (maybe 16 to 22). One of them "adjusted the derailer", but when I took it outside and rode it down the road, the chain popped in the biggest gear.

Any thoughts? If you know and could explain it to me that would be great as I like to get educated.
Thanks
Tony

HillRider

Your front derailleur "high limit screw" need to be adjusted (tightened) properly. Your LBS certainly needs more competent mechanics.

mstateglfr 

If you are in the large ring up front, dont use the largest 3 or so cogs in the rear. Use the smaller 7-8 rear cogs when using the large front ring.
Switch to the smaller front ring to use the larger 7-8 rear cogs.

Using the large ring up front and the large couple cogs in back is called cross-chain. Same term applies for using the small ring up front and the smalled couple cogs in back. It makes the chain go across the cassette(all the cogs) at an extreme angle and causes components to wear out faster than necessary and also can lead to a skip here or there at times.

50tooth up front and 32 tooth in back(so big ring in front and large cog in back) is equal to 34tooth up front and 21tooth in back(so small ring in front and a middle cog in back). The 34T-21T combo will be easier on your drivtrain.

agermano

No its only happening when on the large ring up front and the smallest rings in the back (which I believe are the "largest" or hardest gears).

Shimagnolo

I agree with the diagnosis of FD high-limit adjustment.

BTW When it happens, there is an easy way to fix, which I learned from a former amatuer racer:
Don't stop.
Keep slowly pedaling while shifting the FD toward the smaller ring(s).
The large ring will engage the chain, and probably throw it over to the smaller ring.
This has worked for me *every* time.

rm -rf

Your LBS isn't very competent. Limit screws are critical, and should have been set correctly before they delivered the bike.

You'll want to re-do the rear derailleur also. If the limit screw that controls the largest cog isn't set correctly, the rear derailleur can be overshifted into the spokes. The derailleur arm catches a spoke, which then rips the derailleur apart, usually damaging the frame at the same time.

It's useful to know how to do these adjustments yourself. You'll want some way to hold the rear wheel off the ground, either a bike repair stand (very useful and worth the investment), a rope loop under the nose of the saddle, or a helper to lift the saddle. (Since you'll need to turn the cranks and shift gears to finish the derailleur adjustments.)

The Park Tool repair guides go step-by-step, and are easy to follow. Don't shortcut the process, start from the beginning.

Front derailleur adjustment
Rear derailleur adjustment

Terminology
Front gears are chain rings. Rear are cogs. The correct description of the rear cogs are: "low" is the biggest cog, to go slowest, and "high" is the smallest cog, to go fastest. Just like shifting low to high in a car. I usually just say "biggest cog" or "smallest cog" to eliminate any confusion.


You need to do a full front derailleur setup.
Since you can't get the big chainring and smallest few cogs to work, you'll need to adjust the limit screw and then adjust the cable tension. Just follow the repair guide, one step at a time. And don't skip the first few steps that check the position of the front derailleur's height and angle.

(It appears that the 105 front derailleur low/small chainring limit screw is the one closest to the frame. Shift to the small chainring. You can usually see the bottom of the screw where it contacts part of the derailleur to limit the movement, and identify which one is touching or almost touching--that's the low limit one.)

After you've done the adjustments a few times, and understand the concepts, it's very fast and easy to make minor adjustments if the derailleurs aren't quite centered correctly (usually due to minor wear in the shift cable housings).

It usually takes me a couple of tries to get the front derailleur cable clamp just right. I normally screw the front derailleur barrel adjuster all the way in, pull on the end of the cable with my fingers, then clamp it down. Then I can unscrew the barrel adjuster to the middle of it's range, and go from there. Everything else is pretty easy.

Give it a try! Let us know if you fix it.

~~~~~
Cross chaining
I never worry about cross chaining. I'll use the large chainring-large cog or the small chainring-small cog occasionally. If I notice I'm cross chained like that, I'll shift the front as soon as it's convenient. Newer 9,10,11 speed bikes can handle cross chaining without any problems, other than a little noise.

79pmooney

Is our chain falling of to the outside or crank side? If this is the case, you need to tighten down the limit screw for your high gear. There are two small screws at the top of your front derailleur. Usually, one is marked "H" (high) and the other "L" (low). Whether or not they are marked, it is the screw that affects the high gear, ie your bigger chainring, that you need to tighten down. This you have to do by trial. Tighten say a 1/4 turn. Observe if you can still shift to the big chainring from all your cogs. (If it can do it from both the biggest and smallest, it will have no trouble with the cogs in between.) Does the chain still fall off? Go 1/4 turn more. Too much and the chain may rub in the big chainring/small cog combo. (I've had setups where I had to accept a little chain rub to keep the chain on.)

Front derailleurs are very crude devices. There is often a considerable difference between how they perform on a stand and what happens out on the road. Carry the screwdriver to make adjustments on rides.

If you cannot get the limit screw to get the chain to behave, you may need to rotate the derailleur body to change the angle of the cage. This is considerably more involved, requiring (usually) un-clamping the derailleur cable, rotating the derailleur (and often having to raise or lower it to maintain proper clearance), resting both limit screws and reconnecting the cable. In other words, every adjustment there is.

Try the limit screw and report back.

Ben

mstateglfr 

Gotcha. Well what I posted is still good info if you werent aware.
But as for the actual issue- Its just an adjustment to the limit screws as many have said. That should have been set before/when you bought it, but little things need adjusting periodically so it isnt a huge issue. Itll take a few minutes at the shop. This is one of those things that the shop should teach you about if you are interested as it isnt beneficial for you to come to them over and over with this issue.

headasunder

take it back to the shop and don’t leave with it until you are happy with the set up.

KonaRider125

The "mechanic" who put your bike together deserves a drop kick to the nuts.

Do yourself a favor and watch youtube videos, read Park Tools website and learn how to adjust the front/rear derailleurs. I would also check all your bolts, paying special attention to your brakes and make sure they are nice and snug. If you have the means, buy a bicycle specific torque wrench for the task.

HillRider

Owning a torque wrench (or wrenches of appropriate torque range) is a good idea but a "bicycle specific" one is not needed and really doesn't exist except as a marketing concept.

trailangel

I don't know about the torque wrench idea. BITD if we would've seen one of our friends using a torque wrench on a bike, they would've been laughed at endlessly. And don't tell me some parts are critical with this new plastic stuff... you either got it or you don't.

caloso

Note that all that's needed to adjust a limit screw is a screwdriver, not a torque wrench.

agermano

So I got it back yesterday. Did 15 miles this morning. Chain no longer popping off, but on the large chain ring, on the second smallest cog, there is still a skipping/crunching, which feels like it was just shifted onto that cog. It happens between the 11th and the 12th revolution consistently (it seems odd that I counted, but counting it for a good mile was actually helping me keep a good cadence). Im bringing it back again today, as it is not acceptable.

What say everyone about this issue?

dwmckee

It is critical when someone crushes a tube and you want to file a warranty claim with the manufacturer.

jyl

Derailleur cable tension incorrect which is throwing off the indexing. Back to the LBS. Insist on speaking with the owner.

ThermionicScott 

Yep, keep occupying the LBS until it hits home that they need to fix it right.

agermano

Think we found it and I don't think it is LBS fault. When I explained what it was doing he brought it out and rode it on that cog and felt it immediately. Came back and saw bent chain link. Replaced chain. As he was spinning it on the rack he noticed one of the teeth on that cog was slightly larger than the others, and triangular as opposed to squared on the end. So....think that it was it causing the jump and what bent the chain. I think, hope that is the problem and it is fixed tomorrow when I pick it up.

jyl

Modern cogs have a pattern of irregularly shaped teeth to aid in shifting. Wonder if that's what he saw.

dwmckee

Oh boy. You will have everyone curious on this one now. You'll be asked to post a few pictures. Hard to see how an irregular cog tooth could bend a chain...

ThermionicScott 

Perhaps the OP needs to invite the pimply-faced LBS wrench to join BF so we can straighten him out.

agermano

It was actually one of the owners who noticed the irregular sized tooth. He kept showing the younger kid working there and telling him it is is much bigger than it should be. I think they are putting a new cassette (I believe that is the right term) on along with the new chain.

At least they are working to take car e of the issue.