kmart

Long post I know, please bear with me...

My Felt F55 is geared 50/34 up front and 11-23 in the back. More specifically, that's 11-12-13-14-15-16-17-19-21-23. The gear combinations are nice in theory (I like the idea of a straight block with no jumps) but my shift patterns can be messy and even cause chain drops sometimes. Let me explain.

When I am in the 34 sometimes I will creep up on the rear to 13, then 12. Then I realize my chainline would be straighter if I go to the 50 up front. If I want minimize the jump in gear ratio when I shift, I need to shift down 4 on the rear while simultaneously shifting up on the front. Since Shimano DA shifters can shift down 3 at a time, the entire shifting sequence becomes: upshift front while downshifting 3 rear at the same time, release shift levers, shift down one more on rear. That's some complicated shift work!

Same thing happens in the reverse direction: say I am in the 50 and start creeping down to the 19, then 21 on the rear. If I shift the front down from 50 to 34, I need to shift the rear up by 4. Since Shimano only shifts up one gear at a time, I have to rapidly click the shifter 4 times while shifting the front down. This is where the chain drop happens sometimes.

Shifting from 50 to 34 is very abrupt and kicks the chain over pretty hard. If at the same time the rear is shifting up one or two cogs, the chain tension drops for a moment and leaves enough slack for the chain to miss the inner chainring and drop onto the BB shell. I think the safe way to avoid chain drop is to shift the front, then the rear, or vie versa, but never simultaneously.

This whole procedure was a lot simpler on my 9-speed triple. 30/42/52 front, 12-25 rear. If I wanted to go from 42 to 52, I shift down 2 in the rear to minimize the gear ratio change. Two simultaneous flicks of the shifters and I'm there.

Is this a typical thing for compacts to do?

BigSean

I prefer a 12/27 with my compact. I do alot of climbing and have found the wider gear range works great for me.

cuski

Sounds to me like you should be shifting to the 50 earlier. I have no issues with multiple front and rear shifts at the same time - then again, I run a 50/36.

ggg300

you can cross chain...

FlashBazbo

My crank is a Shimano R700. My chain never jumps off and my shifts are smooth -- but nothing eliminates that shift ring+4 mess. I consider this the primary downside of a 50/34 compact. (My older 50/36 obviously didn't have the problem to the same extent.) Of course, the worst part is that the shift ring+4 happens right in the middle of the usual cruising range -- 18 to 21 mph, between 90 and 100 rpm. So, because of the gearing, in rolling hills, you have to make the five-shift shift back and forth a lot. Not fun. A double or triple (either one) is a lot more convenient at cruising speeds -- which is where just about everybody spends most of their time.

It has just about driven me to a triple crank for my next racing bike build. (The fact that I'm building for the mountains contributes to the idea, as well.)

ggg300

or you could get a 36...

Dubbayoo

I don't shift front and rear simultaneously on any system. I usually shift the rear first about halfway to where I want to be, shift the front then complete the rear. It's more work but less so than getting off and fixing a dropped chain.

adam

I shift rear and front simultaneously on this exact set up (50/34 with a 11-23) all the time. Once you get your gears dialed in perfectly - everything should be flawless. Mine took a while to do, but once it's there, it is sweeet.

I rarely (can't remember last time) have the chain go off the chain rings and cross chain a lot now. I stay in my 50 almost all the time, which is great.

Loving my new compact!!!

adam

Have also used the exact setup on a 50/36 (11-23) and recently a 50/34 with a 12-27 with no probs at all.

rm -rf

Can't avoid the shift+4. I have Campagnolo shifters, I can in one motion shift down (to larger cogs) 4 gears or up 4 (or more). This is a real advantage with the 50 / 34 gearing. I was occasionally dropping past the 34, and I adjusted the front derailleur limit screws inward a bit, which solved the problem. I can do both front and rear shifts at the same time, but I usually try to shift one, then the other.

"They" say that cross chaining isn't as big a problem with the more flexible modern chains. So I don't worry about cross chaining to the 9th gear, but still avoid the full cross chain of 10.

I had a stock 12 13 14 15 16 17 19 21 23 25 cassette, and got a 13 14 15 16 17 18 19 21 23 26 now. I use the 17 18 19 range a lot, so the small jump at 18 is nice. (50-18 at 90 rpm is 20 mph.) I spin out the 50-13 at about 33 mph, but I usually coast downhill at faster speeds than that, anyway.

Retro Grouch 

Living in Houston I'm surprised that you can find places to use either a triple or a compact crankset.

kmart

This is exactly what I mean! I am considering the switch to the 36, but it will not eliminate the problem, just reduce it slightly. And believe it or not there are times when I need that 34/23 really bad (not anywhere near Houston, but when I take my bike to Austin it really saves my butt).

kmart

I have learned this to be another safe solution, but still messy. And actually, sometimes it seems more like I have to shift 5 in the rear rather than 4.

The triple came on my old bike, I didn't choose it. Never did use that granny ring. And the compact, well that came with the Felt. I tend to cruise between 18-21mph between 90 and 100 cadence, and I do the front-rear "exchange" I described in the OP to keep cross-chaining to a minimum (although I realize that it's going to be inevitable with a compact)

I don't get it, are you suggesting a double would be a better choice? If I went, say, to a double 42/52 and 12-25 on the back (essentially my old triple minus the granny) do you think that would suit flat riding better?

kmart

I wish I could say the same, but it's flat as a pancake down here.

kmart

Yea, staying in the 50 is pretty cool, but that 34 feels kinda lonely ya know? Actually, there are a few combos with the 34 that are in between combos with the 50 and sometimes I just can't make up my mind which I like and messy shifting ensues.

zacster

I have a 50/36 and a 13/26 Campy setup with an FSA crank. The thing I really hate about it is that I never ride the small ring except on hills, and since there are no hills in the immediate vicinity on my quick daily rides it almost never gets used. It really has limited my gearing. I can climb the little hill in Prospect Park on my 50/18 or 50/20 combo now. It takes a triple or quadruple shift with ease when I need to do it though.

DasProfezzional

I have an identical setup, id est, an FSA 50/34 compact and an 11-23 cassette, and have no such problems. I've also got Campy stuff, which is very trim-able up front. At the moment I forget if you can trim front derailleurs with Shimano shifters. If you can't, then it's a tricky fix. Not being able to trim means your drivetrain's capacity and quietness are dependent upon how perfectly you set up your front derailleur, which means, depending on the bike, a whole bunch of rotating, raising, lowering, and general fidgeting on your part. As far as I can see.

Alternatively, you might just need to get into better shifting habits. I used to stay in the 50 ring and cross the whole cog range just to not feel wimpish, but it's much better to anticipate a change in terrain and shift your front derailleur accordingly when you're in the middle of the cogset.

80vette

Then why do you need the 34?

80vette

Change to the 50/36 and when you goto Austin put a 12/27 cassette on and be done with it!

srsly

i have a felt f65 with the same setup. i got rid of the FSA and put on a R700 and my chain dropping problems went away; no derailleur adjustments needed. shifting from the small to large ring also improved dramatically.

i do agree that it is kinda messy to deal with dropping that many cogs in the back when approaching a hill and that could probably be fixed with a different cassette setup.

SteveE

Campagnolo, baby!

urbanknight

+1 You shouldn't be creeping to the 12 unless you know you're not going to need the big ring.

kmart

Because I don't like the idea of a bike that costs me over a thousand dollars not being able to handle anything I throw at it.

Swapping the 34 for a 36 should be easy. I like the idea of having a spare cassette for the hills (I don't change terrain too often so this has not been a necessity so far). If I still have horrible chain drop problems after I do that I will look at the Shimano R700, but the FSA Carbon Pro is pretty sweet so I think it will stay for now.

rm -rf

I wondered how a 36 would compare to a 34. It doesn't seem to make enough difference to bother with.
Use Sheldon's gear calculator Put in your tire size, calculate mph @90 rpm, select your cassette from the list. Then put in 50 36 34 as the three chainrings and see the differences between 34 and 36.

55-11

+2... although with practice you can effectively shift front/back simultaneously, you shouldn't be waiting so long to shift up ( or down for that matter).