CdCf

I'm thinking of ordering a 48/32/22 for a new bike build.
The FD will be a Deore 510, which has a recommended max capacity of 22T.
Obviously, the triple mentioned has a 26T difference, and a 16T difference between middle and large rings.

My question is, will it work? I.e., will I be able to shift into all three without problems?
And by problems, I mean, without any top/bottom scraping and without chain jamming or falling off.
Slower shifting is acceptable between middle and large, so that's not a problem, the way I see it, as long as it reliably shifts in the end.
Front shifter will be D-A barend friction shifter, if that matters.

I really would like the higher top gear. This gearing would give me one additional effective gear combo (total of 15 instead of 14) and a top gear of 107 GI, instead of the current 93 GI.
Running 26" wheels and narrow tyres (24.4" effective wheel size) means even a 42-11 gear isn't high enough going down.

sydney

Front capacity typically gets exceeded by that much in road triples using a26 granny instead of a 30. It works but may be a bit clunkier.

CdCf

Ok, so if I'm not interested in lightning-fast shifting, it should work?
That's good.

After all, Shimano makes these combinations, so I figure they know there are FDs out there to shift them...

Retro Grouch 

I don't think that you'll have any shifting troubles at all.

The issue is that you'll have to raise the derailleur a bit higher to clear the 48 tooth ring. When you do that, the chain might rub on the bottom of the cage when you're in the 22/11. So when's the last time you used the 22/11 combination?

moxfyre

You might be better off with a ROAD triple front derailer meant for a 53/39/30. The range there is 23T, and the spacing is 14-9 (compared with 16-10 for your setup, or 12-10 for a typical mountain setup of 44/32/22).

The spacing between the rings that the derailer is meant for is important: you want the top part of the cage to line up with the big ring, the middle part to line up with the small ring, and the bottom part to line up with the granny ring. If this doesn't match up well, you'll have to trim the FD a lot more because the chain won't be sitting in the wide parts of the cage where it has more room to move side to side. But it's not a dealbreaker, clearly the capacity is the most important thing because you don't want the chain bumping the bottom of the cage.

So if slow shifting and trimming is okay, then pretty much anything with sufficient capacity will work. If you have a choice though, I think you'll be happier with a road triple front derailer.

CdCf

Hmm, well I'm already used to trimming my shifts since I'm using a friction shifter. Using the middle ring on my current 42/32/22 requires some minor trimming when I go from the larger to the smaller rear cogs.

I guess I'll start out with the FD I have, and if it turns out it doesn't work well, I can always try a road FD. It's certainly more economical than buying another FD just in case...

And good point Retro Grouch!
Yeah, I'll take the FD off my current bike and mount it on the new one, so it'll be in the correct position from the start.

Michel Gagnon

Will it work ? With bar-end shifters or downtube shifters, it will definitely work. The front derailleur has more than enough capacity for what you want to do.

With STI, there's a question on whether or not the indexing will work fine. I have no experience on that issue.

moxfyre

Okay, didn't realize you were using friction mode exclusively. Go for it. I'm using old suntour bar end shifters, and I like the predictability.

CdCf

I have to say I really love friction shifting for the front.
Used to have indexed, but I never managed to get it to feel right. Some combos always had chain rub no matter how I adjusted it.
Now, I just tweak it "on the fly"!

Thanks all!

Gonzo Bob

It will work. The shifing between middle and big rings may be a bit sluggish, though.

I run 46/32/22 with a Shimano LX derailer spec'd for 44T big ring and 22T max difference. I was running 42/32/22 but I built up some road wheels and run a narrow slick on those so I wanted a taller gear.