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I've just acquired a 2019 Scott Spark RC with SRAM XX1 Eagle 1x12 drive-train. I ride in SE Texas and only use the bottom 4 cogs on the cassette - that huge pie-plate is worthless down here, while I spin out on fast sections with 32x10 biggest gear available. I want to install a smaller range cassette - one that I'll use all the cogs - cheaper and spread the wear - along with a bigger chain ring. The chain ring is easy. Anyone done this? I guess I'll need a new derailleur as well. I'd like to keep the Eagle to install on trips to the mountains when I actually need that pie plate! Thanks!!
 

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Install a 34t chainring, if you find yourself consistently spinning out with that seek professional sponsorship.

You could install a different drivetrain, maybe 10 speed that has less range but you'd need a different freehub and I don't see what there is to gain by doing that.
 

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Use a 12 speed Force cassette - 10-36 or 10-33 - assuming you have a freehub which is XD-R compatible. Otherwise - larger chainring - as large as you can fit. Which is most likely going to be 34T.
 

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I've just acquired a 2019 Scott Spark RC with SRAM XX1 Eagle 1x12 drive-train. I ride in SE Texas and only use the bottom 4 cogs on the cassette - that huge pie-plate is worthless down here, while I spin out on fast sections with 32x10 biggest gear available. I want to install a smaller range cassette - one that I'll use all the cogs - cheaper and spread the wear - along with a bigger chain ring. The chain ring is easy. Anyone done this? I guess I'll need a new derailleur as well. I'd like to keep the Eagle to install on trips to the mountains when I actually need that pie plate! Thanks!!
If you only use the bottom 4 cogs, you have the wrong drivetrain. Why did you buy a bike with an XX1 if you ride somwhere where it's flat?
 

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With a 2019 Scott Spark RC frame you can fit a 38 tooth large chainring on the front:


For the rear gearing it depends on what hubs you have. You've got a SRAM XD driver freehub at the moment, which limits your choice of narrow cassettes.

To get tighter gearing you could change that to a Shimano HG freehub body and then fit an 11 speed Shimano road cassette such as an Ultegra 11-32 cassette or 11-36 cassette.

That will actually work nicely with your existing SRAM 12 speed chain and 12 speed SRAM Eagle XX1 rear derailleur and shifter as the sprocket spacing is the same. All you would need to do is screw in the lower limit screw on the rear derailleur, so that it doesn't shift further across than the 11 clicks. That gets you a close ratio 1x11 setup that can be quickly converted back to 1x12 wide ratio when needed.:)

In theory you could do uzurpators suggestion of using a SRAM Force 12 speed 10-33 road cassette but it looks to get a bit complicated on the freehub compatibility. Your current freehub is going to be SRAM XD which is the mountain bike version. SRAM XDR road is very close but it has a longer spline than a SRAM XD freehub. You can fit a MTB SRAM cassette onto a SRAM XDR freehub by using a spacer. I don't think you can fit a SRAM XDR road cassette onto a MTB SRAM XD freehub though, as the splines on the MTB SRAM XD freehub would be too short and it wouldn't thread on fully.

You can get replacement DT Swiss star ratchet SRAM XDR freehub bodies for 12x142mm rear spacing but I think a 2019 Scott Spark RC is the wider 12x148mm boost spacing. The current version of the Scott Spark RC is definitely 12x148mm boost spacing.

SCOTT Spark RC 900 SL AXS Bike

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That will actually work nicely with your existing SRAM 12 speed chain and 12 speed SRAM Eagle XX1 rear derailleur and shifter as the sprocket spacing is the same.
Mnior note - I am almost certain ( as in: I've got a few 12 and 11 speed cassettes ) that spacing of 11 and 12 speed is different. So if OP goes this route, then he also needs to replace the shifter with a 11 speed one.
 

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Mnior note - I am almost certain ( as in: I've got a few 12 and 11 speed cassettes ) that spacing of 11 and 12 speed is different. So if OP goes this route, then he also needs to replace the shifter with a 11 speed one.
The combination above is one I tried last year, not expecting it to work, but to my surprise it did. :)

Specialized Turbo Levo SL Turbo 1.jpg


I had a Specialized Turbo Levo SL demo bike for a few days so put it on my Tacx Neo 2T turbo trainer to compare the readings from the built in power meter of the Specialized Turbo Levo SL's Mahle motor against the power readings from the Tacx Neo 2T.

The cassette on the turbo trainer was a Shimano Ultegra CS-R8000 11 speed 11-32 road cassette.

The Specialized Turbo Levo SL had a SRAM NX Eagle 12 speed chain, SRAM NX Eagle 12 speed rear derailleur, SRAM NX Eagle 12 speed trigger shifter. Its actual rear wheel came with a SRAM NX 11-50 12 speed cassette fitted and the gears were indexed for that 12 speed cassette.

SRAM NX Eagle is a low end group but functionally the same as SRAM XX1 Eagle. The indexing using the 12 speed SRAM NX Eagle MTB drivetrain on the 11 speed road cassette was spot on with smooth shifts across the entire cassette! All it required was remembering not to shift into the missing largest 12th rear sprocket (fixed by screwing in the limit screw if it was for regular use).

If you've got the parts to hand give it a try.:)
 

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Install a 34t chainring, if you find yourself consistently spinning out with that seek professional sponsorship.

You could install a different drivetrain, maybe 10 speed that has less range but you'd need a different freehub and I don't see what there is to gain by doing that.
This, go pro. I do 28 mph on a 30x10 and you're spinning out on a 32? Sheesh!
 

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If you've got the parts to hand give it a try.
I have the parts and I tried it. I also, literally, measured 11 and 12sp cassettes and they are down to the tenth of a milimeter identical width wise. 12 speed just crams more cogs in the same space. I can believe that running 11-over-12 is possible considering how minor the difference is ( 0.38mm over one cog ). Strictly speaking, those systems are not compatible.

Unlike 10 over 11 or 11 over 10 - which works either way - either with a spare shifter click or one cog too many.
 

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Just install 36 or even 38 - use round chainrings - oval may not fit.
XC bikes usually come from the shop with 34 or 36 chainring anyway.

I use 36 on my oiz when I go racing and have backup 32 for mountains.
 

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I have the parts and I tried it. I also, literally, measured 11 and 12sp cassettes and they are down to the tenth of a milimeter identical width wise. 12 speed just crams more cogs in the same space. I can believe that running 11-over-12 is possible considering how minor the difference is ( 0.38mm over one cog ). Strictly speaking, those systems are not compatible.

Unlike 10 over 11 or 11 over 10 - which works either way - either with a spare shifter click or one cog too many.
Rather than more cogs being crammed into the same space a 12 speed MTB cassette is wider than a 11 speed road cassette. In order to fit that additional largest sprocket it is dished inboard, closer to the spokes. If you want to check this the easiest way is to stand a 12 speed MTB cassette and 11 speed road cassette (without lockring) on a flat surface and then put a straight edge across, as in the picture below.

Shimano 12 Speed 11 Speed Cassette Width.jpg


J_Westy posted a link to this Google docs sheet in another thread which has detailed sizing specs for many cassettes. That's a really useful resource as someone has spent ages collating the details for lots of different cassettes.


If you look at the "Sprocket Pitch Calculated" column for the specific combination I tried Shimano 11 speed road (sprocket pitch 3.69mm) and SRAM 12 speed MTB (sprocket pitch 3.65mm) they are very close. Both Shimano 11 speed road and SRAM 12 speed MTB have identical 1.6mm width sprockets per that chart also, which explains why it shifted properly.:)

Shimano SRAM Sprocket Pitch.jpg
 
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