Quoted post said:Originally Posted by 10kman
Looking to see if this can (reliably) be done -
I have a bike I use for only climbing events. I run a Sram XX1 crankset (156 Q factor) up front with a 28 or 30t ring, and in the rear I run a 10 speed cassette in 11-28 flavor.
On the worst climbing events I do, I'm in the 28t, trying to spin more than mash. I never need lower than a 1:1 gear, so I'm good with the actual gearing.
What I've noticed is the drag caused from being in those largest 2 cogs in the rear. I can hear it, and I got a little crazy Saturday and threw the bike up in a workstand and did some tests to see how much it was actually dragging, and I'd say it's significant based on sounds and the feel of things while pedaling by hand. I can't actually back spin the crank and not have it stop almost instantly, but yet in my middle/smaller cogs, I can give the pedals a push backwards and they go around nice and easy.
This is interesting. We're talking about hubbubbing Campy shifters without even looking at the chain line or the chain, or the rear derailleur that you're actually using. With one cog up front and ten out back, this shouldn't be too difficult. But you're doing something that's very non-standard so a little faking it is necessary. I assume you're using a SRAM shifter with your Red derailleur.
First, some questions. Your XX1 crankset is most likely made for a 73mm (or wider) BB shell, and the shell on your Scott is 68mm. How are you making up the 5mm difference in shell width?
Now that you're thinking about this, let's look at the chain line. Since you're favoring the low end, shift onto the fourth cassette cog (from the inside) and eyeball the chain line. It should be a straight, or pretty darned straight, line from th cassette to the chain ring. If it veers out to the chain ring, you need to figure out how to get it closer to the frame. If it veers in, you need to figure out how to get it farther out. If the chain line is no good, refer to my first question for clues on how to fix this. If you don't get it, tell me what the chain line looks like and if there are any shims between the cranks and the bearings.
If the chain line is good, let's look at the chain and rear derailleur. SRAM road rear derailleurs have a little pivoting plate that's positioned between the B-screw and the flat on the frame's derailleur hanger. Make sure you have that right. If the B-screw is hitting the plate, it is. If it's hitting the flat on the hanger, it's not. It will be easier to fix this if the B-screw is mostly retracted. It will also be easier if the shift cable is disconnected.
Messing with the limit screws was a big mistake. Now that the cable is disconnected and the derailleur is ostensibly properly mounted, test your limit screws. Turning the cranks with your right hand, push the derailleur onto the big cog with your left hand. If it hits the spokes or the chain goes over the top, tighten the "L" limit screw until it lets you hand-shift onto the big cog without going into the spokes. Next, let the derailleur drop to the smallest cog. If it doesn't reach, loosen the "H" limit screw until it does. If it tries to drop the chain between the frame and the smallest cog, tighten it until it stops doing that. Now hook up the cable. Pay attention to the curved routing "anvil" with the groove on the bottom. pass the cable along the groove and attach it to the top of the pinch bolt. Make sure the shifter is all the way out before pulling the cable snug and fastening. Adjust tension and there you are.
We're not done yet. Shift into your lower cogs and note the distance between the jockey pulley and the cog. If there isn't any, tighten the B-screw, until there's a little distance and the chain stops making noise. If the B-screw is all the way in and it's still making noise, your chain is probably too long. Also, standard (not WiFli) SRAM derailleurs nominally handle only 28t cassette cogs, so the 30 might be overreaching. If it works fine on cog 2 but not 1, this is probably the case.
You know, this whole thing would be a lot easier if you'd posted a few photos of the situation. They'd be a lot more helpful than outtakes from alfeng's lovely family album.
