bobotech

I am nearly done building up a bike for me that was a trade, my buddy and I traded frames and he kept the 10 speed Ultegra drive train. I am putting an older mish-mash of spare parts on it to get it up and running. it is a Motobecane Ti cross bike. He had a 10 speed compact double but I'm going to a standard road triple 9 speed setup.

I first tried the bike with a non-ramped and pinned crankset that I had laying around but it shifted poorly even not under load. I had to overshift so much that it would jump from the small to the large.

My buddy then gave me an Ultegra octalink crankset minus the chainrings. I dug around our co-op and found 3 decent chainrings, the small 30 which I understand doesn't have to be pinned or ramped. The middle ring is a modern FSA 42t pinned and ramped chainrings. The big ring is an older Shimano 52t chainring that looks like it was from the early-mid '90s, its profiles and ramping is not as prominent as the FSA chainring.

What I'm really wondering is does the ramps/pins of the FSA chainring need to line up with the big ring so that it shifts well or will the different brands and different styles of pins/ramps cause problem shifting?

I tried the chainrings last night with a different set of spiders and shifting was rather poor but I also realize that the square taper bb I had with the spiders was too far out from the frame which is why I am moving to the Ultegra which has a 113mm bb.

FBinNY 

There are two drawbacks to mixed sets of rings.

1- all chainrings don't have identical offset between the center of the tooth profile, and the mounting face. Sloppy mixing can make the effective spacing different, either allowing the chain to jam between rings, or limiting your options using inner rings with the outer half of the cassette.

2- matched sets of chainrings are phased so that as the chain comes off a larger one it meets the teeth lined up to mesh perfectly. That's the glide in hyperglide, and why it's important to line up the timing marks. You lose the phasing when you mix rings, and this can result in sloppier shifting, or momentary slippage on downshifts before the chain can engage properly.

If you're careful about the offset issus, and can live with pre hyperglide shift quality, then go ahead mix chainrings.

bobotech

That is exactly what i was wondering about, the phasing of the ramps and pins in relation to the different chainrings.

So it would be probably be best if I could somehow source a 50t-52t FSA front chainring which would then probably line up nicely with the middle FSA ring.

Is it true that the small ring doesn't need anything special though?

FBinNY 

In an original set sold with the cranks, all three chainrings are phased. It's not always possible with after market rings, because makers often don't (or can't) phase all rings to work with all others. For instance, Campagnolo used to (maybe still does) have 2 versions of the 53t ring. One phased for the 39t, and one phased for the 42t.

As for the importance of phasing the granny, it matters equally, but since the shift is done less often, it's easier to live with.

dsbrantjr

There are 5 possible mounting positions for the middle ring and they will each phase differently with the outer ring. You may be able to find a sweet spot where the rings align such that the chain shifts well between rings.

HillRider

You could experiment by rotating one of the rings to various alignments with the other and see what works best, if anything. Otherwise you will do a lot better with a matched set of rings from one maker. Frankly, I'd try to find a middle Shimano chairing to match your outer. Shimano has index marks on their chainrings that show haw they should be installed relative to each other.

Yes, the granny ring is "flat" and has no ramps, pins or shaped teeth so any make with the correct bolt circle will work.

FBinNY 

Yes, you can rotate the ring trial and error looking for the sweet spot with best phasing. We used to do that for race bikes before hyperglide. I still do that because I use chainring combinations not available as a set.

Note, phasing can only be fine tuned if the chainrings tooth count doesn't divide by the number of mounting bolts.

HillRider

Not the granny ring. I have a handful of OEM take off 30T granny rings including 8 and 9-speed Shimano and 10-speed Campy rings and all of them are flat as a table. No shaped teeth, ramps, pins or any other shifting enhancements. There is also a complete absence of phasing index marks.

FBinNY 

I haven't looked in years, but some years back Campy triple granny rings did have a phase mark, but obviously no pins or ramps, since the chain will always come from the top.

RubeRad

Related question; are there "8sp", "9sp", "10sp", "11sp" chainrings with different widths to work with the different width chains, or does that not matter? Maybe the same question, does a 3x8 drivetrain have the same front-chainring spacing (same FD, same shifter pulls) as a 3x10? (assuming, say, all Shimano)

FBinNY 

With the possible exception of 11s (and maybe Shimano 10s) all teeth are the same width. But there is usually a difference in offset, or other factors which affect chainring separation.