Shifting problems w/new compact crankset

[jenxxs]

I just had a compact double crankset installed on my bike, and while my mechanic did his best to set it up, I'm having some stress-inducing front shifting problems with it. I'm hoping those of you with experience riding compact cranks can help steer me toward possible solutions.

First, here are the basic facts. My original crankset was a standard Ultegra double, 53/39, in a full Ultegra 9-speed setup. I just put on a Sugino XD-500 crankset with 48/34 Stronglight rings. I picked the Sugino because it seemed to be my best affordable option for getting really short crankarms (152.5). The new crank length and gearing seem to be working very well for me, so I would like to make this set work!

OK, here are the problems - both with the front shifting:
A) I'm dropping the chain A LOT (more than half the time) when shifting from big ring to small. I understand this is a pretty common problem when converting to compact. By practicing on a trainer, I now know which rear cog will minimize this problem, but I'm still dropping the chain so often that I'm nervous to use the small ring at all on the road.

B) The shift from small to big now takes a very hard push of the shifter. And frequently it "groans" during this shift.

Here are some specific solutions I've heard about - would appreciate feedback on any of them!

1) A chain deflector (Third Eye Watch, Deda Dog Fang). Do these things really prevent the chain from overshifting past the small ring? Because they're so cheap, I think I'm going to try the Dog Fang.

2) Adding spacers between the crank spider and small ring? If the chain is frequently shifting too far, does it make sense to move the small ring slightly further inward toward my frame? My mechanic says this can increase the risk of getting the chain stuck in between the rings.

3) Decreasing the tooth gap between the rings? If this would help, I think I'd be fine with either 46/34 or 48/36. I thought I was playing it safe enough by staying with the same tooth difference as I originally had. My guess is that this will probably help my shift from small to large, but I'm not so sure about large to small.

4) Get a compact-specific derailleur? I know that my Ultegra doesn't have the right curve for the new, smaller big ring. Would a compact derailleur help solve the problem of overshifting to the small ring?

Any advice in this area would be much appreciated!

[velogirl]

The best tip I've got is shift with front and rear at the same time. So, let's say you're shifting from your big ring in the front to the small. At the same time, press the small lever on both left and right sides. This will all but eliminate dropped chains.

I've got a third eye on my cross bike. We use them in cross because it's so bumpy it's easy to drop a chain -- I never do (but now that I've said that I'll probably drop it 20 times in tomorrow's race).

You know that if you drop your chain you can pop it right back on by back-shifting, right? Say you drop it to the inside, with your front shifter, shift to the larger ring. You have to keep pedalling, and it'll feel strange because there's no torque on the chain, but it really works about 99.9% of the time.

Not sure about your other ideas. The differential between the two rings shouldn't be a problem. A standard compact is 50-34 (16t) and you'e got a 48-34 (14t).

A compact front derailleur might help. I've been riding compact cranks since they first came onto the market and I've never used a compact derailleur.

[Triskeliongirl]

I know this sounds really basic but could it simply be out of adjustment. You need to adjust the screw that tells the derailleur where to stop properly or it overshifts and drops the chain. This is how I stop the problem. I bought a compact derailleur, but then it wasn't good for my eliiptical chain rings so I took it off and got another one that worked better for my crank system. If you are interested in buying it, its an IRD compact double derailleur. Its for a braze on but I also have it attached to a 28.6 problem solvers clamp. PM me if you are interested, it looks brand new as it has ~50 miles on it.

[jenxxs]

Thanks for the tip about shifting both front and rear at the same time - I will try this out on my trainer first. I also didn't know about backshifting to get the chain back on - I've actually never experienced any chain dropping before this, so I had no idea what to do other than stop and put it on by hand.

And I guess I'm hoping that the chain watcher thing will also eliminate most of the chain dropping.

[Triskeliongirl]

A few more thoughts:


OK, here are the problems - both with the front shifting:
A) I'm dropping the chain A LOT (more than half the time) when shifting from big ring to small. I understand this is a pretty common problem when converting to compact. ...

B) The shift from small to big now takes a very hard push of the shifter. And frequently it "groans" during this shift.

I have been using compact cranks (50/34 elliptical) for a few years, and disagree that this is a common problem with compacts. As I said above, it happens only when the lower limit screw is set too far. Likewise, in point B you mention having trouble shifting back, this suggests the uppper limit screw is set too far. Before I did anything else I would adjust my limit screws. If that isn't enough, I would look into a compact derailleur.

[jenxxs]

OK, thanks for these suggestions about the limit screws. I think I am going to get a second opinion about the current derailleur setup. From what I've read so far, I should be able to get my standard Ultegra derailleur to work if set up carefully.

[Triskeliongirl]

My advice is to learn how to make these simple adjustments yourself. I got so sick of bringing my bike somewhere, waiting for them to work on it, picking it up, and paying good money only to have these kinds of problems. Just pick up a good book (like Zinn's road bike maintenance) and use web resources like the park tool website and sheldon brown website. I will tell you that in my hands the compact derailleurs worked better than the ultegra since the ultegra is designed to go from a 52 to 42 or 39 not a 48 to 34. For me, an old mountain derailleur also designed for smaller rings worked better, but I also had to deal with the elliptical shape.

[mimitabby]

our tandem (which needs a new bottom bracket) also drops its chain far too often. We bought this little hook-looking thing which is supposed to catch the chain and bounce it back to where it belongs. It doesn't really work very good, and sometimes the chain gets stuck underneath it or behind it or whatever.

the reverse shifting does work unlesss you have slowed down too far and have lost momentum. But when it happens, it always feels magical to me.

[Kalidurga]

We bought this little hook-looking thing which is supposed to catch the chain and bounce it back to where it belongs. It doesn't really work very good, and sometimes the chain gets stuck underneath it or behind it or whatever.

My bike came with a chain catcher (the little hook-looking thing), but it wasn't installed correctly in relation to the small ring. I complained about chain droppage and the LBS tech realized that the Dog Fang wasn't low enough or close enough to the ring to actually keep the chain in place. It needs to be right at the level of the chain on the small ring, and only a couple of milimeters from the chain. Try moving it so that you can just slip a penny or nickel in between the chain catcher and the chain on the ring.

My bike also came with a 48/34 and I've had major issues with shifting up to the big ring. The inside of my ring is all scraped up from the number of times the chain has rubbed against the ring as I've pushed the shifter and cussed at it to go. After having three different LBS tech's play with it, I finally had to give it a try myself. Once I realized how the limit screws work, it really was easy. You just need to make sure that you check any adjustments on both rings, which is a mistake one of the LBS guys made. He adjusted it to make shifting onto the big ring easier, but then the chain rubbed against the derailleur when on the small ring. On my ride that afternoon, I was forced to sit on the side of the trail and put to use what little I had read about derailleur adjustment. I've had no problems with it since (*fingers crossed*.

[7rider]

I have an FSA compact crank on my bike (a 50-34).
When I had it installed, I had the shop put on the chain-keeper (is it a.k.a. "Anti-chain suck thang"? I seem to recall having that name in my head when I asked the shop for it. They knew what I was talking about at any rate.) I have no problem whatsoever with the chain dropping when going from the big to small ring (FWIW, it's a FSA SLK crank with a Dura Ace derailleur). Don't know if the keeper saves me, or if my bike is just adjusted okay. Maybe a bit of both?
Where I DO have problems is throwing the chain clear OFF the big ring of the crank and onto the crank arms when shifting up. That, however is "user error." I've learned to (1) be mindful of where my chain is on the cassette in back, as that has a bearing - centered is better), and (2) use a light touch. The DA shifters require a subtle touch, not the mashing I am used to giving.

[DebW]

OK, here are the problems - both with the front shifting:
A) I'm dropping the chain A LOT (more than half the time) when shifting from big ring to small. I understand this is a pretty common problem when converting to compact. By practicing on a trainer, I now know which rear cog will minimize this problem, but I'm still dropping the chain so often that I'm nervous to use the small ring at all on the road.

B) The shift from small to big now takes a very hard push of the shifter. And frequently it "groans" during this shift.

Here are some specific solutions I've heard about - would appreciate feedback on any of them!

2) Adding spacers between the crank spider and small ring? If the chain is frequently shifting too far, does it make sense to move the small ring slightly further inward toward my frame? My mechanic says this can increase the risk of getting the chain stuck in between the rings.

3) Decreasing the tooth gap between the rings? If this would help, I think I'd be fine with either 46/34 or 48/36. I thought I was playing it safe enough by staying with the same tooth difference as I originally had. My guess is that this will probably help my shift from small to large, but I'm not so sure about large to small.


I can't add much here as I've never ridden on or worked on a compact. But I'd think that your small-to-large shift would definitely be improved by decreasing the tooth gap between the rings. The smaller the gap, the easier the shift. Not that this is necessarily the best solution for you. If you like the ring sizes you have, keep playing with the adjustment to improve the shift or try a different derailleur.

A couple tips on derailleur adjustment. The vertical position of the derailleur should be as low as possible, so the outer cage plate just misses hitting the teeth of the large sprocket as you shift. If it's too high, you get crummy shifts. The inner stop screw should be set so that, in your lowest gear (large rear, small front), the cage is as close as possible to the chain without scraping. If it's too far inside, you are more likely to drop the chain. The left-right swivvel of the derailleur cage also makes a difference, so you can play with that. And lastly, the shape of the cage makes a difference, so it's quite possible that you'll get a better shift with a different derailleur, though this might be a trial and error thing.

[jenxxs]

Thanks for all of this input - you've encouraged me to try to tinker with the limit screws myself. I was going to go on a 3-hr group ride today, but since it's really gusty out, I think I'll use the time to patiently teach myself about derailleur adjustment.

[jobob]

LeeBob and I really like these.

http://www.gvtc.com/~ngear/

[jenxxs]

Hi everyone,
Well, after almost 4 hours of derailleur fiddling, I'm proud to report that I have figured some things out! I found a key piece of advice from the FSA website - they suggested raising the front derailleur 1-2 mm higher than the normal recommendation, to solve the chain drop problem. This seems to work for me - the derailleur now sits 2 dime-widths above the big ring teeth, versus 1. It does slow down the shifting, but the shift is much cleaner (chain not bouncing around like crazy), so I think I can live with the slower downshifting.

In the process of undoing and reattaching the cable many times (where I had zero prior experience), I seem to have created another shifting problem having to do with the indexing. Both my downshifting and upshifting now take 2 pushes. From big to small, the first push moves the chain, but then after the shift I have to push the lever again (same direction) to trim it. From small to big, the first push moves the derailleur closer to the big ring, and then it takes a second push to get the chain up to the big ring.

Could I somehow have messed up the indexing of my STI levers while undoing and reattaching the FD cable?

Well, at least this new problem is less annoying to me than the chain dropping all the time!

[DebW]

That's probably the way it's supposed to be. The trim shifts account for the fact that you need different FD positions for different RD positions. For the small-to-large FD shift, you should already be on the 1st trim click if you are on an outer rear cog with the inner chainring. Then it would be only one click to upshift the FD. Likewise moving the other way. For a large-to-small FD shift, if you were on an outer rear cog, you'd stop with one click of the FD, but if you were on an inner rear cog, you'd need 2 (or would be at the intermediate trim to start with.

[roadfix]

My guess is also a simple adjustment problem. There is really no reason why your set up can't be almost perfect.

[jenxxs]

Well, 9 hours of off-and-on fiddling later, I think I have it set up reasonably well. Turns out my indexing problem was caused by not tightening the cable enough - I also didn't realize the cable would have a larger effect on the cage shifts than the limit screws.

Thanks to all of you for encouraging me to try this myself - I learned a lot this afternoon by trial and error! Lots of error :rolleyes:

[roadfix]

Well, 9 hours of off-and-on fiddling later, I think I have it set up reasonably well. Turns out my indexing problem was caused by not tightening the cable enough - I also didn't realize the cable would have a larger effect on the cage shifts than the limit screws.

Thanks to all of you for encouraging me to try this myself - I learned a lot this afternoon by trial and error! Lots of error :rolleyes:

Glad you got this up and running. You can practically throw away the limit screws but if you don't have proper cable tension, nothing will work right.:)

[Rai Sue]

glad you found the easy fix of adjusting cable tension. Folks having chronic problems switching from the smaller chainring up to the larger chainring in the front may also want to look into seeing if their larger chainrings have pins and ramps.

Pins are little steel bumps on the back of your chainring (facing the smaller ring) which give a little boost to the chain. Shimano makes them, so you can change out the chainring to one with pins. It totally solved my problem of the chain not switching up, even when the derailleur and cable were adjusted.

Ramps i think are little divots in the back of the chainring itself which help facilitate lifting the chain up.

You can read more about it (and see a picture!) at http://www.sheldonbrown.com/gloss_ra-e.html

[jenxxs]

While I made sure to get new rings with pins and ramps (Stronglight), I have to say that the ramps aren't nearly as effective as those on the Ultegra ones I took off. Those ramps are huge, and they worked flawlessly. I'm sure Shimano also optimized their pins/ramps to work on their matched ring sizes.

Do other manufacturers of compact-sized rings (like FSA) have matched sets with really good pin/ramp systems? Since I was going with 48/34, which is not the most popular combination, I didn't try to look for a matched set.