Chain rub on big sprocket help
 

Ok I can't figure this out. Am I using the wrong chains? I don't know. Got this 2011 Masi Partenza. Came with the typical FSA Tempo cranks but with steel rings. Found some aluminums of the same tooth count and bolted them up. A tiny bit of rub at one portion of the rings (they're still really straight though) so I threw in a set of .6 spacers to see how that would work. Works perfect but now when downshifting the chain gets stuck in between because of the bigger space now. (obviously) Now I know this all easy obvious stuff but what confuses me is that what was the old steel rings doing that these arent? How did the steel rings find a way to not rub and still have the correct space to not suck the chain into? How did that happen?

My Schwinn Tempo's doing the same thing. Never had this problem on all my other bikes before. This is why I'm confused.

The description is not enough to provide much advice. The drive train components are not really classic or vintage.
most often chain "rub" has more to do with the limits of derailleur travel. Anything in between is rider controlled.
the stamped steel rings may not be of the same displacement from centerline.
check the chain line after you remove those spacers.

A 2011 Masi Partenza is a vintage bike?

The chain is rubbing on what? The ring itself or the derailleur cage? Have you measured the thickness of the rings? It may be that the aluminum ones are a bit thicker than the steel ones.

^^^This, I think.

Steel rings have always given me top shifting performance, even as I have had shifting issues with OEM FSA cranksets on one or two occasions.

Assume nothing when it comes to the chainring's tooth-center offset from it's mounting surface.

You're right, I forgot, this wouldn't be the correct forum, I apologize as this is my first road bike newer than 1987. I by habit just come directly here because I don't really own or ride modern bikes. The chain rub is between the front two chainrings.

The combination of short chain stays, a wide cassette on a 130mm axle, and a wide size difference between chain rings, like 50-34 or 53-39, will often cause the chain to rub on the inside of the big ring when using the small-small combination. This is quite normal. My Felt F5 did it. My Giant TCR did it. My Trek Madone does it. My 42 year-old Masi Gran Criterium doesn't do it, because it has a 7-speed cluster on a 126 mm axle and longer chain stays. It didn't happen with your steel rings because the teeth were probably a little bit narrower. When you fudged with the inter-ring spacing it stopped shifting properly because the derailleur is designed to work with a center-to-center chainring spacing that is proprietary to Shimano (and copied by FSA, SRAM, and others).

Small-small is your sacrificial gear combination. Just don't use it. For me it results in too much chain slap against the stay anyway, and with a 10-speed cluster I know there's a combination on the big ring that's close enough. I know some guys compensate by inserting a 1mm shim behind the drive side bearing or cup to shift the whole crank to the outside a bit. If you're really hung up on this you might give it a try, but it might result in too much cross-chaining the other way on big-big. And some guys say big-big is against their religion, so they don't mind.

And I apologize to the topic border patrol, but I thought I could just put this to bed. I promise not to do it again.

I see. It must be the odd spacing that the aluminums have over the steels, PLUS, I just figured out that someone may have changed the chain on this. The factory specs say this was supposed to come with a shimano hg40 chain, but that's the chain I just threw on there that caused all this ruckus. The chain that was on there was an odd KMC Z chain, with slightly buldged side plates. By throwing that shimano hg40 on there plus adding the aluminum rings (the exact same company and shape) it caused all sorts of crap. So I put the original steels on there and it was a tad better but still rubbed. So I took the shimano chain off and put the kmc back on there and it's ok now. The chain BARELY touches the inside of the big ring but she's really nice now. Then, for science, I threw the aluminums back on and she's like 99% now. Overall it was the hg40 that was the main culprit. Though it sucked; how could the factory use it?

It must be a combination of the short stays because I have/had a TON of road bikes, and NOT A SINGLE one of them ever had this problem. Ever. And not any of countless road bikes I built when I worked at a shop. JUST this one lol. (this new stuff will be the death of me. C'mon powder coaters, hurry up with my old bianchi frame so I can ride some old school stuff again) I know it's 'cross chaining' but besides hills, I've always rode the smallest cog and the next 3 or 4 cogs up and never rode the big ring except in some situations where I was racing my brother. Not my first Schwinn Varsity in 1984 nor any other bike has the small/small combo been trouble for me. Weird.

I was thinking about the rear spacer option but it has sealed hubs with these odd aluminum collars and set screws (kind of like crupi bmx race hubs) so the distance the cassette has to the drop outs is kind of stuck, unless I want to grind some off of there. Then the dish will be a tad off. I'm going to get a 4mm wider BB and see what pushing the drive side out 2mm's does to the final alignment. Maybe that will allow me to use the shimano chain, which I feel downshifts a tad better than this one.

Your chain line is now off add a spacer to the inside of the rear cassette or BB to level the chain.

This moves the cassette in the wrong direction.