Author Topic: 12 sp SRAM NX / SLX M7100 & Chainset limitations  (Read 258 times)

12 sp SRAM NX / SLX M7100 & Chainset limitations
« on: November 26, 2019, 12:19:44 am »
I have a question regarding chainring sizes as I'm hoping to make the change to a 12sp setup soon.

My current gear range in inches is 18-81 (using a 9 speed cassette and triple front combined with 24in wheels). If anything I'd want to lose something at the bottom end of the range so that I can get as close to 90in. Also I'm aiming more towards a touring setup than speed.

To get something like a gear range of 20-90in I was hoping to be able to use a 45 tooth chainring but notice with SRAM this is not possible with the 12 sp groupset, or even the 11sp groupset. Actually the single chainring setup with both Shimano and SRAM seem to top out at 34! Why on earth so they not have more options. I don't want to have to use a front derailleur and want to stick with solely a rear derailleur setup.

I'm posting this as I may be missing something so any input from those wiser than me would be appreciated.

Re: 12 sp SRAM NX / SLX M7100 & Chainset limitations
« Reply #1 on: November 26, 2019, 09:59:00 am »
I don't know 12 speed bits that well, but having looked at one-by for touring I'll make a couple of observations...

Single chainrings are mostly a mountain bike thing. That tends to mean low gears on 26 / 29 inch wheels. Your 24 inch will exacerbate that, so trading low gears for high isn't what manufacturers have designed (marketed) for.

That ought to mean that 24 inch wheels will get a typical road spec down to something sensible. But roadies seem to favour doubles still.

After market chainrings may be your friend. For instance, Absolute Black do one-by chainrings with 40 and 42 teeth.

I found it really hard to get the range I wanted from one-by. It seems to be a solution to a different problem than a bike that can work well both with and without luggage across a range of roads. But if it works for you, that's nice.


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Carlosfandango

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Re: 12 sp SRAM NX / SLX M7100 & Chainset limitations
« Reply #2 on: November 26, 2019, 10:05:42 am »
You need to use a road crankset with a MTB rear gearset, search "SRAM mullet build".

Re: 12 sp SRAM NX / SLX M7100 & Chainset limitations
« Reply #3 on: November 26, 2019, 01:36:59 pm »
AFAIK 12 speed chain has the same inner dimension as 11 speed, and with a single ring the outer dimension doesn't matter, so you can just use any of the numerous after market 11 speed 1x rings.

Most are narrow-wide, so you'll be stuck with even numbers of teeth.

Re: 12 sp SRAM NX / SLX M7100 & Chainset limitations
« Reply #4 on: November 26, 2019, 11:43:55 pm »
Thank you folks for your answers. So it sounds like I don't have to stick with SRAM for the up front single chainset and the only requirement is that the chainset is 11/12 spd compatible. If this is right that's fantastic and very exciting and I won't be held back/limited by the 24in wheels which I love on my bike :)