I know running Big-Big (chainring/cog) combos isn't recommended because you have duplicate gears on the small ring. But sometimes you have to do it or want to do it.
What length chainstays should I be using if I wanted to use all the cogs on the Big Ring. I'm assuming 410mm won't cut it? (I should probably measure the stays I have to compare)
Are there any tricks should my stays not be long enough to make it work?
Also will using a cassette with small cogs on the back help with rub. If It matters I'm considering 11-23 vs 11-21.
I know running Big-Big (chainring/cog) combos isn't recommended because you have duplicate gears on the small ring. But sometimes you have to do it or want to do it.
What length chainstays should I be using if I wanted to use all the cogs on the Big Ring. I'm assuming 410mm won't cut it? (I should probably measure the stays I have to compare)
Are there any tricks should my stays not be long enough to make it work?
Also will using a cassette with small cogs on the back help with rub. If It matters I'm considering 11-23 vs 11-21.
This won't be a climbing bike🙂
There are a few too many variables to answer your questions. Bottom bracket drop, specific contour of your front derailer, setting of the FD stop, what chain, etc. However, if you look at most FD contours, you will likely see that Big-Big will more likely cause rubbing on 11-21 than combinations with larger cogs... plus you might not go there as often.
There are a few too many variables to answer your questions. Bottom bracket drop, specific contour of your front derailer, setting of the FD stop, what chain, etc. However, if you look at most FD contours, you will likely see that Big-Big will more likely cause rubbing on 11-21 than combinations with larger cogs... plus you might not go there as often.
How does BB drop Affect it? Will a higher BB make the problem worse?
The more I think about this question I realize there are a few more things to consider in addition to what you mentioned above.
1. Big rings chainline 2. Width of the cassette (shimano might be better than Campy in this regard)
However, if you look at most FD contours, you will likely see that Big-Big will more likely cause rubbing on 11-21 than combinations with larger cogs... plus you might not go there as often.
See that's the only reason I'd take a 11-21 over an 11-23. I don't care about the small 1 tooth gaps in the small ring, but it would be nice to have it in big ring.
If I'm out at the edge of the cassette in 53T ring I'd rather shift 53-21, 19,18,17 as opposed to 53-23,21,19, 17 (all 2 tooth jumps)
I would think bottom bracket width and crank profile as they relate to chainline would be the most important. I have a compact pro carbon FSA and a 108.5 bb. My big ring (50 I don't know if you call that a BIG ring) is more in the middle of my cassette than when my bike was a triple, I have and 12-25 (not the 11-21 you are wanting) and it runs the whole spread in the bake with no noise or rubbing that can't be trimmed out at the front derailleur, and the chain doesn't rub the sides of the cogs either, no excessive noise back there and smooth. I jumped on the compact bandwagon a while ago, and in my area which has rolling hills, no major long climbs, I have yet to use the 34 and don't think I will unless I travel so I have kind of forgot about the front derailleur and only shift at the back ala Motobecane Le Champione 10 ( only mine is nine), any one ride one of those 10 spd Motos? Real light and no front derailleur, they give you two cassettes and to front rings with the bike. Looks clean, probably not enough gears for you hilly types.
What length chainstays should I be using if I wanted to use all the cogs on the Big Ring. I'm assuming 410mm won't cut it? (I should probably measure the stays I have to compare)
Am I missing something? Are you suggesting that you should buy a bike with longer chainstays so you can cross thread your gearing better? Buy a bike with a frame bigger than what fits you because of its longer chain stay? Buy a Lemond over an Orbea because it has a longer chainstay?
Most bikes with double chainrings when set up right, can use all the gears, (Unless you ride a 48cm frame I guess.) but the further you cross the gears, the more wear you will get. I am sure you knew that though. I cross too much myself, but with the new Campy stuff, (the front shifts much more smoothly than the Shimano did) I am getting much better about it.
