Campy Chorus Compact question

[profàvélo]

I've been riding for over 5 years with a Shimano 9-speed triple, first 105, then Ultegra. On my brand-new bike I have a Campy Chorus 10-speed compact. It's my first time with 1) Campy or 2) a compact crank (or 3) a 10-speed). My DH is pretty good with bike mechanics, and he is trying to help me get everything adjusted right, but since he's never dealt with Campy or compacts before, either, I am not totally convinced he knows what he's doing. The way it's adjusted right now, I have to trim the front every time I switch to the bigger ring. He says this is normal, considering the distance between the two rings. Is he right? I just don't think I should have to trim it all the time.

[Pedal Wench]

I have compacts on two of my bikes - one is Campy Centaur, one is Campy Record, though I doubt there's any difference with Chorus. I don't have to trim all of the time, but depending where my chain is on my rear cassette, I do have to adjust. But, that's usually if I'm on one of the bigger cogs in the back. I do not trim every time.

Oh - do you have a compact-specific front derailleur? I do on my Record bike, do NOT on my Centaur bike. That being said, I don't notice that I have to trim more with one or the other.

[Kalidurga]

Trim? That's a term I haven't heard before, but I'd love to know what it means.

[alpinerabbit]

I have a Chorus set, but went with the Centaur compact crankset because the chorus was too pricey.

If trimming is a bit of adjusting, I have to do it in the small ring now and then.

I think Campy components are valuable enough to take your ride by a bike store. No offense to DH's technical skills of course.

[DebW]

I've been riding for over 5 years with a Shimano 9-speed triple, first 105, then Ultegra. On my brand-new bike I have a Campy Chorus 10-speed compact. It's my first time with 1) Campy or 2) a compact crank (or 3) a 10-speed). My DH is pretty good with bike mechanics, and he is trying to help me get everything adjusted right, but since he's never dealt with Campy or compacts before, either, I am not totally convinced he knows what he's doing. The way it's adjusted right now, I have to trim the front every time I switch to the bigger ring. He says this is normal, considering the distance between the two rings. Is he right? I just don't think I should have to trim it all the time.

Do you have the front derailleur that's meant for a compact crank? I haven't worked on modern Campy equipment or compact cranksets, but I would certainly expect that Campy has the system well tuned and overshifting isn't required. Perhaps if you're using the double or triple FD it might be. Did your DH set the vertical and horizontal position of the FD carefully? A tiny bit of horizontal swivel on a derailleur cage can make a big difference in a good shift.

[profàvélo]

Thanks for the ideas. The bike came fully set up by the bike builder, so I am 99.9% sure everything is positioned correctly. As for the front derailleur, I was supposed to get the whole gruppo, so I assume it's a compact derailleur, but I will check.

I think I'm going to have to sneak it to a mechanic. I often have to trim the left (front) twice!

BTW, trimming is when you 'click' the gear shifter and the chain does not move out of its position, but it is tweaked (I don't fully understand the mechanics of it) such that it quits making the noise that it was making. I'm sure DebW could give you a better definition.

[velogirl]

I often have to trim the left (front) twice!

I've been riding Campy record (first with a double and then with a compact double) for many years. It sounds to me that when you're on the small ring, you need to trim as you get to the smaller cogs on the cassette. The nice thing with a 10-speed double is that you can get away without doing this most of the time. However, if you don't trim on the small ring, you will indeed need to shift twice to get the chain to move to the big ring.

[mimitabby]

However, if you don't trim on the small ring, you will indeed need to shift twice to get the chain to move to the big ring.

Hey, Velogirl, what does TRIM mean?

[SadieKate]

Profavelo explains it a couple posts up. Campy has the ability to trim the front derailleur in minute amounts without moving the chain.

[DebW]

Thanks for the ideas. The bike came fully set up by the bike builder, so I am 99.9% sure everything is positioned correctly. As for the front derailleur, I was supposed to get the whole gruppo, so I assume it's a compact derailleur, but I will check.

Look at the pictures on the Campy web site. The difference is in the inside plate of the FD cage. For a double, there's not much difference in the inner and outer plate, the inner is just a little deeper. For the compact, the leading 1/3 of the inner plate is much deeper. For a triple, the whole plate is much deeper. It's the inner cage shape the helps lift the chain smoothly to the next larger cog. The bigger the difference in cogs, the more difficult it is to make that happen smoothly.

BTW, trimming is when you 'click' the gear shifter and the chain does not move out of its position, but it is tweaked (I don't fully understand the mechanics of it) such that it quits making the noise that it was making. I'm sure DebW could give you a better definition.

The noise is the chain scraping on the FD cage. Trimming shifts the cage until the chain is centered within it and not scraping it. When you shift the rear derailleur, the chain angle changes and the front derailleur cage needs to move to remain centered over the chain. There is some leeway as the cage is wider than the chain, but it can't be wide enough the accommodate the full chain motion (i.e. the chain's position on its most inside and most outside rear cog) or you'd get lousy shifts. Ideal shifting of a double front derailleur is to always throw it to it's limit, wait for the chain to shift to the new cog, and then trim or center the cage over the new chain position. Easier done with friction shifters than indexed. Indexed shifters are a compromise and entirely unnecessary (IMO) on a double.

[DebW]

It sounds to me that when you're on the small ring, you need to trim as you get to the smaller cogs on the cassette. The nice thing with a 10-speed double is that you can get away without doing this most of the time. However, if you don't trim on the small ring, you will indeed need to shift twice to get the chain to move to the big ring.

profàvélo, are you shifting through 2 clicks to get from the small to the large ring, or are you getting the shift with one click and then having to trim? If the former, you need to follow VG's advice. Assuming your rear derailleur is on a middle or outside cog before you shift the front, your front derailleur should already be trimmed out one stop to be properly centered in the small front ring. If the latter, you should not need to trim if the rear derailleur is on an outer cog. If you do, then the outer stop of the FD is set wrong.