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I have been riding SRAM GX 11sp on all my bikes since it first came out, prior to that I was riding SRAM 10sp.

Last year I bought a bike with GX Eagle 12sp, and to to put it simply, it was a finisky lil' biatch! I could never find a sweet spot where all the gears shifted well, the system was super fickle when it came to a dirty chain, and parts were not cheap for what is essentially a low level groupo. When I sold the bike I shitcanned the Eagle and went back to GX 11sp.

The one thing I missed about the GX Eagle was having the 50t bail out gear. I contemplated getting a Garbaruk 11sp cassette for the extended range, but the price, availability, and lateral nature of this purchase begged the question of why not wait for Shimano 12sp? Why, because Shimano is sooooo slooooow to get stuff to market!

So last month I ordered a complete Shimano XR 12sp drivetrain, an extra cassette, and two micro spline drivers. I got a great deal, the works for $500, but it shipped from Asia, so I have been waiting, and waiting, and waiting. It arrived Friday/Saturday, so I stayed up late to install it, set up was very straight forward, no need for a special "gap tool" like on Eagle, just set and forget.

Went for an all ride the next morning with no testing other than on my stand.

Bottom line: It works, I had no issues other than some fine tuning during the day as the system bedded in. It was a dusty ride, four hours of mixed use, never had a shifting issue, dumping multiple gears works well, no dropped chains, rode in both clutch and non clutch settings.

The Ebay deals are real! I bought two drivers for $75, an extra cassette for $115, all products were well made, came from three different countries, all properly branded, no issues with products being out of spec.
 

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gearing wise, the nicest thing about the shimano 12 speed IMO is that you can run 34T chainring with the 10-51 cassette and it's the same as a 32T 10-50T cassette in terms of climbing range for the last 4 sprockets at least.

The 34T advantage without losing the ability to climb is amazing for racing.
 

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gearing wise, the nicest thing about the shimano 12 speed IMO is that you can run 34T chainring with the 10-51 cassette and it's the same as a 32T 10-50T cassette in terms of climbing range for the last 4 sprockets at least.

The 34T advantage without losing the ability to climb is amazing for racing.
Is it? I do a lot of cat1 racing and I've found the opposite to be true, you really don't need very high gears, but having low gears is pretty important. The old "big ring" stuff was never really pedaled at the cadence that would give you any real efficiency, so it was always better to be in a lower gear spinning faster. Keeping your cadence high, although frustratingly unnatural at times, allows you to put out watts more consistently over time. People aren't spinning out the smaller gears/losing time on courses.

Also, I don't think 32 10-50 is the same as 34 10-51, the changing of the front ring would have a far great effect than 1 tooth on a 50t ring. % wise, 1 tooth on a bigger ring is a lot less than 1 tooth on a smaller ring, so you'd be making it harder to pedal and some people need the "bail out" gear of the 50t, a 32 10-50 actually gets you to the useful gear range that was had before on 2 and 3x systems IME, vs. 11 speed that doesn't quite match the low end, while still good for many people like myself.
 

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gearing wise, the nicest thing about the shimano 12 speed IMO is that you can run 34T chainring with the 10-51 cassette and it's the same as a 32T 10-50T cassette in terms of climbing range for the last 4 sprockets at least.

The 34T advantage without losing the ability to climb is amazing for racing.
2 teeth in the front will need 4 in the rear to compensate. The 51 teeth on the back might give way for an extra ramp to improve shifting. But your not really going to notice it helping on climbs.
 

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Is it? I do a lot of cat1 racing and I've found the opposite to be true, you really don't need very high gears, but having low gears is pretty important. The old "big ring" stuff was never really pedaled at the cadence that would give you any real efficiency, so it was always better to be in a lower gear spinning faster. Keeping your cadence high, although frustratingly unnatural at times, allows you to put out watts more consistently over time. People aren't spinning out the smaller gears/losing time on courses.

Also, I don't think 32 10-50 is the same as 34 10-51, the changing of the front ring would have a far great effect than 1 tooth on a 50t ring. % wise, 1 tooth on a bigger ring is a lot less than 1 tooth on a smaller ring, so you'd be making it harder to pedal and some people need the "bail out" gear of the 50t, a 32 10-50 actually gets you to the useful gear range that was had before on 2 and 3x systems IME, vs. 11 speed that doesn't quite match the low end, while still good for many people like myself.
Agreed. Low gear is definitely my priority but with mass start "races" we have here, getting to the front quickly and sustaining a high peloton speed at the front requires a lot of good top end gearing especially on the flats. Our terrain here is quite drastic, in terms of gradient change.

Running them through the calculators (29er)
32T with 10-50 Eagle Cassette, starting from the 1st Gear (Largest Sprocket), I get the following ratios:
0.7, 0.83, 0.97, 1.10..... (so on)

34T with 10-51 Shimano Cassette, starting from the 1st Gear (Largest Sprocket), I get the following ratios:
0.73, 0.83, 0.95, 1.13..... (so on)

As you can see, the 4 most important cogs align pretty well to each other.

For the stuff I do here, most of the time when I climb I'm in in the 42T most of the time and 50T for the long steep climbs where I can hammer it out. 0.7 and 0.73 is less than half a gear and it's not that noticeable considering how little time I spend on it.

2 teeth in the front will need 4 in the rear to compensate. The 51 teeth on the back might give way for an extra ramp to improve shifting. But your not really going to notice it helping on climbs.
See above calculations.
 

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Looks like you got a pretty sweet deal, and that is always good. Impressed me how good are the prices of the Shimano stuff. But this paragraph caught my attention:

I could never find a sweet spot where all the gears shifted well, the system was super fickle when it came to a dirty chain, and parts were not cheap for what is essentially a low level groupo.
I had a problem with my bike since I bought it, either would not shift from 5th to 4th cog, or would stutter shifting everywhere else. The solution given by someone here in this forum was to add a link (two links actually) to the chain. Working just as it should now.

BTW, I have GX eagle in one bike and SLX 11sp in the other, and shifting is about the same if you're not picky. I just miss the big cog on the SLX.
 

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Discussion Starter · #8 ·
Yeah, good prices, good function, good range, pretty much all I wanted but couldn't get with Eagle. Having to buy new drivers was a PITA, but then it was the same gig with getting XD to run GX.

You guys and those big chainrings! I run a 26t chainring, which may seem small, but my climbs are steep and sustained, and I prefer to sit and spin. I only use the 51t as a bailout, so on the last ride I used it once on a climb everyone else walked ;)

Looks like you got a pretty sweet deal, and that is always good. Impressed me how good are the prices of the Shimano stuff. But this paragraph caught my attention:

I had a problem with my bike since I bought it, either would not shift from 5th to 4th cog, or would stutter shifting everywhere else. The solution given by someone here in this forum was to add a link (two links actually) to the chain. Working just as it should now.
 
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