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Will a SRAM X-Sync chainring align to the driveline center on a 2x crankset?

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Will a SRAM X-Sync chainring align to the driveline center on a 2x crankset?

Old 02-04-16, 08:02 PM
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RoadLight
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Will a SRAM X-Sync chainring align to the driveline center on a 2x crankset?

Greetings,

I road my road bike all last year (2015) without ever shifting my front derailleur. I used my 50T large chainring for 4100 miles, including two centuries. This test has given me the confidence to convert my bike to a 1x drivetrain for the upcoming year.

I'm using a 2x SRAM Force 10 drivetrain now. Unfortunately, I do not have access to SRAM 1x components at my location---so I can't measure their 1x crank or X-Sync chainring before I order parts.

My goal is to center the teeth of a single 50T X-Sync chainring on the exact centerline of my bike's driveline. That way the chain deflection from the driveline at the cassette is the same when the rear derailleur is shifted to either the smallest cog or the largest cog. I assume that the Force CX1 crankset will do this with an X-Sync chainring designed for this purpose.

Question: Can I add an X-Sync chainring to any SRAM 2x crankset and achieve the same thing?

If the answer is "yes" then it would mean that the outward-facing chainring mounting points of a Force CX1 crankset are located the same distance from the centerline of the bike as a regular Force 10 or Force 22 crankset. And it would mean that the X-Sync chainrings are slightly dished in order to center the teeth in the middle of the driveline. This would locate the teeth of a 1x X-Sync chainring in the middle between the outer and inner chainrings of a 2x crankset. It would also mean that I don't need to buy a Force CX1 crankset---I can simply install an X-Sync chainring on my existing Force 10 crankset.

Advice from a member with first-hand experience with SRAM 1x components would be greatly appreciated. Thanks.

Kind regards, RoadLight
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Old 02-05-16, 12:15 AM
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I have not personally installed a SRAM x-sync chainring, but instead it was a 38t assymetrical 110bcd for use on a shimano crank. The customer wanted to run cx-1 and keep his stages power meter. On that particular one, the ring was happiest in the inner position, which has a more centered postion. However, you might not have a choice because chainstay clearance may not allow you to run the 50t chainring in the inner position... The wolf tooth 50t chainring is offset 2 mm towards the frame from most stock chainrings as a result. Not completely sure about the SRAM ring, but you don't necessarily have to run that particular ring either. Hope this helps

110 BCD Cyclocross & Road Chainrings ? wolftoothcomponents.com
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Old 02-05-16, 09:53 AM
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If you look on the SRAM site for the Frame Fit Specifications it looks like the inner ring position is the same on the 2X and 1X cranks - 38 mm. The ring must be dished since the inner ring on the 2X shows 40mm and 43 mm on the 1X.
Look through the doc and see what you think. If I'm reading it right the IX ring will work - assuming it will physically fit. Don't know anything about bolt circle etc.
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Old 02-05-16, 02:40 PM
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I don't know specifically, but X-sync rings are available in different offsets, so one of them may be close enough. You might contact Wolf Tooth Components and ask them. They make a wide variety of rings including X-sync compatible rings so certainly know the answer. You might check their tech faqs first. They helped me out with a similar ring offset question.
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Old 02-05-16, 03:46 PM
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I've been looking at 1x conversions and recall SRAM's marketing materials saying that they provide spacers with their X-Sync chainrings that provide correct positioning of the ring between where the inner and outer rings would be on a conventional 2x.

https://www.sram.com/stories/simplif...ke-sram-1x-hop

I'd like to buy a Rival 1x X-Sync 40T right now and none of the online shops are carrying it - just Force. I thought SRAM had been shipping Rival 1 stuff for over a year. As to the rings being available in different offsets, that would be news to me at least if you're getting them from SRAM.

SRAM has sown a bunch of confusion with all their changes in marketing terms (e.g., CX1, Force 1, Rival 1, XX, X1, XO1, etc.).

- Mark

Last edited by markjenn; 02-05-16 at 03:50 PM.
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Old 02-05-16, 06:57 PM
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Hi all,

Thanks everyone for the response---much appreciated!

@markjenn: Thanks for the SRAM stories link---it was very helpful. I can't believe that I didn't find it, myself. I've poured over the SRAM website many times and done more google searches on this subject than I'd care to admit. However, I didn't interpret SRAM's write-up the way you did. What they wrote is that the spacers are provided so you don't have to buy new chainring bolts when converting your two-ring crank to a one-ring crank. The spacers take up the space that the inner chainring formerly occupied. I don't believe that the spacers are intended to center the X-Sync chainring to the driveline. My guess is that the X-Sync chainring will center to the driveline by virtue of its design.

I'll know the truth soon enough because: Today I ordered the X-Sync 50T chainring that I'll need. My purchase was made at Berman's Bicycle (Keene, NH) via their online eBay store (discountbicycle603) for $70.33 shipped. The chainring has a 110 mm BCD which matches my compact Force 10 crank. I'll report back what I find once I receive it and can do some test-fitting and driveline measurements.

One of the reasons that I want to use the X-Sync chainring is because of its wide-narrow teeth that are designed to match the alternating gap width between chain links. From what I've learned, there is no better 1x chainring tooth design at present. My bike has a carbon frame and I'd hate to lose a chain on the inside and cut my bottom bracket shell---I've seen it happen to other carbon bikes and it ain't pretty!!! I have a chain catcher to prevent that now with my current drivetrain and I plan to rig up something for the 1x as well to be extra safe. But I doubt that I'll have as much to worry about with the X-Sync because of its unique tooth design.

One thing I noticed while searching for X-Sync chainrings is that there is an all-black version. The SRAM website only shows the grey+black version and this is what most bike shops are selling. Evidently there are a few more options than are listed on the SRAM website. I ordered the all-black one.

I'm very excited that this chainring may work fine with a 2x crankset. It offers many more crank choices. I've been wanting to move to a 165 mm crank arm length (at present, I'm using 170 mm on one bike and 172.5 mm on another). It's much easier to find a 165 mm crank arm length in a Force 22 or Red 22 crankset. And, if the X-Sync chainring doesn't center to my driveline with a 2x crank, then I'll be looking for a Force CX1 crank for my GXP bottom bracket. In the latter case, I'll probably have to settle for a 170 mm crank length because the 165 mm Force CX1 crank, although listed on the SRAM website, has been impossible to find. It may be an option that is only available to bike manufacturers.

Kind regards, RoadLight
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Old 02-05-16, 07:58 PM
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Awesome, let us know how it goes! For what it's worth, they didn't patent the wide/narrow tooth profile... So there are tons of options from wolftooth, raceface, 1up (and many others I can't think of immediately) that also make those 1x rings with that profile. So far I like the one I got for my mountain bike from race face... All good stuff!
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Old 02-07-16, 02:24 PM
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Yes, do report back on what the chainline looks like. It sounds like you're just going to run your existing Force RD. I was probably going to ante up to buying the 1x RD too.

- Mark
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Old 02-08-16, 09:03 AM
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Originally Posted by RoadLight View Post
One of the reasons that I want to use the X-Sync chainring is because of its wide-narrow teeth that are designed to match the alternating gap width between chain links. From what I've learned, there is no better 1x chainring tooth design at present. My bike has a carbon frame and I'd hate to lose a chain on the inside and cut my bottom bracket shell---I've seen it happen to other carbon bikes and it ain't pretty!!! I have a chain catcher to prevent that now with my current drivetrain and I plan to rig up something for the 1x as well to be extra safe. But I doubt that I'll have as much to worry about with the X-Sync because of its unique tooth design.
Keep in mind that the clutch rear derailleur is a key part of a reliable 1x setup. The narrow/wide rings help, but I know from personal experience that without a clutch RD, you're still at risk of chain drops. Some folks will tell you they've been running 1x with a standard RD forever with no problems, but that doesn't mean it won't happen.
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Old 02-08-16, 09:30 AM
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I would expect that a road bike would not need a clutch derailleur. For that matter, I'd think that a normal single speed chainring would work and a N/W would not be necessary.
Does your experience on a 1X road bike disagree with that?
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Old 02-08-16, 03:52 PM
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Originally Posted by Kopsis View Post
... I know from personal experience that without a clutch RD, you're still at risk of chain drops. Some folks will tell you they've been running 1x with a standard RD forever with no problems, but that doesn't mean it won't happen.
Hi Kopsis,

Thanks, I am aware of the issue. However, I'm not sure about the way you've characterized it. I haven't seen a clutch derailleur yet but my understanding is that it improves the shifting---especially when using a wide range of gear sizes in your cassette. But I don't think that it is the reason why SRAM's 1x rear derailleur helps prevent chain drop. My understanding it that the 1x derailleur employs a new method of maintaining chain tension so the tension isn't momentarily lost when hitting hard bumps and such. Again, since I haven't seen a 1x derailleur, I haven't had a chance to see how it works, but that's my impression. Please correct me if I'm wrong about this.

I don't anticipate a problem because I'm strictly a roadie and I stick to good paved roads. I like to go fast and I like to keep a good speed throughout my 35-mile workouts. SRAM's 1x rear derailleur was designed primarily with the rigors of cyclocross in mind where things are obviously a bit bumpy in places---to understate it. :-)

My ultimate goal for my main roadbike is somewhat specialized. What I really want on the rear is a medium or long-cage SRAM Red eTap derailleur. But SRAM is only offering a short-cage at this time and that won't do for my long-term plans because I anticipate moving to a 11x32T cassette whenever I change my rear derailleur (I'm using an 11x28T now with a Force rear derailleur). Why an electronic rear derailleur on a 1x drivetrain? Answer: Because I would like multiple shift points. The most important is my aerobars where I spend most of my rides. But I also need to shift from the handlebars when I'm in traffic. I'm not aware of any way to do this with a mechanical system. I really don't want to use an electronic system---a mechanical 1x is excellent---but the desire for a second shifter at the front of my aerobars is pushing me to it.

With that in mind, my plan is to convert the crank first and wait on changing the rear until SRAM has more to offer. Plus, I have another reason pressing me to change the crank soon. I'm adding a Stages power meter and I'm changing my crank arm length. Since the Stages power meter needs to match the crank length, I need to replace my crank first. Why change the crank length? I'm getting old. I'm chasing 60 and find that my knees are more comfortable now with a 165 mm crank arm length. I've used 170 and 172.5 mm cranks most of my adult life but I can't quite keep my cadence up like I used to. It isn't a fitness issue as much as it's an "old knee" issue.

So I'll convert to a 1x without touching the rear this year. And I'll add the power meter. Then I hope to replace the rear next year if SRAM has a suitable eTap rear derailleur by then.

Kind regards, RoadLight
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Old 02-08-16, 04:13 PM
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Originally Posted by RoadLight View Post
I haven't seen a clutch derailleur yet but my understanding is that it improves the shifting---especially when using a wide range of gear sizes in your cassette. But I don't think that it is the reason why SRAM's 1x rear derailleur helps prevent chain drop. My understanding it that the 1x derailleur employs a new method of maintaining chain tension so the tension isn't momentarily lost when hitting hard bumps and such.
Clutch derailleurs have nothing to do with improved shifting or gear sizes, they're all about keeping the chain from going slack (what you describe for SRAM's 1x RD). But but the tech in SRAM's 1x RD isn't new -- it's the same tech that's been in the MTB RDs for years (a clutch in the cage pivot).

You probably won't have any problems riding road on a 1x with a standard RD. But if I were you, I'd throw on a chain keeper in place of the FD. They're way cheaper than a new carbon frame.
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Old 02-08-16, 04:31 PM
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Originally Posted by Kopsis View Post
... But if I were you, I'd throw on a chain keeper in place of the FD. They're way cheaper than a new carbon frame.
Hello again,

I'm way ahead of you on that. I have a chain catcher on it now and I plan to rig a new one after converting to 1x, too. I've seen carbon bikes after their bottom bracket shell has been cut by a derailed chain and it's scary. :-(

Thanks for the enlightenment about the clutch derailleur.

Kind regards, RoadLight
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Old 02-12-16, 10:58 PM
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The X-Sync chainring arrived -- Here are some preliminary observations...

Greetings all,

My new X-Sync 50T chainring arrived today. Hurrah! I've made some preliminary measurements. A summary and details follow...

Summary
The rear of my driveline appears to be 43 mm from the center line of my frame at my 10-speed cassette. The front of my driveline also appears to be 43 mm from the center line of my frame (measured to the center of the space between the outer and inner chainrings of my 2-ring Force 10 crank. If I were to mount the X-Sync chainring to this same crank, it would probably move the front of my driveline out to 44.5 mm. This seems acceptable to me. But I'm not planning on using my existing Force 10 crank because I need shorter crank arms.

I'm waiting for a SRAM Red 22 crank to arrive. Since it is made for an 11-speed system, its chainring spacing will be different. Once it arrives and I begin to disassemble my existing crank, I'll be able to make accurate measurements of both and see how they compare. Why Red? Simple: I discovered a nearly unbelievable sale and the bike shop had the Red with the 165 mm crank arm length I needed but they were out of stock on the 165 mm Force 22 crank. Plus, I eventually plan to switch my rear derailleur to a Red eTap after SRAM supports larger cogs with a medium or long cage version. Why eTap? Answer: So I can have a second set of shifters for my aerobars.

By the way, my Red crankset was purchased for US$241.71 from Merlin Cycles in the U.K. with free shipping to the U.S. Their sale is still on in case anyone else is interested in picking up a compact-size SRAM Red crank at a 45% discount. I plan to sell the new Exogram Yaw chainrings (50/34T) that come with it on eBay to further offset some of the cost.

Details
  • The X-Sync chainring appears to be designed for front mounting only. In other words, it needs to be mounted to the outside of the crank spider.
  • The X-Sync teeth are off-center toward the crank. In fact, the teeth appear to be centered precisely to the rear mounting surface of the chainring (they overhang it). This will cause the teeth to also be centered over the front mounting surface of the crank spider (since this is where the rear mounting surface of the chainring mates.)
  • Therefore, the teeth of the 50T X-Sync chainring will not center perfectly to the driveline---but they will probably be fairly close (within 1.5 mm, I believe).
The spider mounting tabs of my SRAM Force 10 crank appear to be 3.5 mm thick. I have two SRAM Powerglide chainrings on it and each is about 3 mm thick where they mount to the spider. The teeth of the outer chainring are centered to this---which places the center of the teeth about 1.5 mm outside of the spider's front mounting surface. The teeth of the inner chainring are not centered. Rather they are closer to the spider---I think they are about 1 mm away from the rear mounting surface of the spider. This means the center-to-center distance between the teeth of my two chainrings is 1.5 + 3.5 + 1 mm = 6 mm. (Remember, my Force 10 drivetrain is a 10-speed system.)

With the above dimensions, the teeth of the X-Sync chainring would need to be centered 1.5 mm to the inside of the spider's front mounting surface. Instead they are exactly centered over the spider's front mounting surface. Ergo, the teeth of the X-Sync chainring will be 1.5 mm outside of the driveline if I were to use my existing Force 10 crank. Would this be a "show stopper"? I'm not sure since I've never used a 1x system before---but I doubt it. If anything, it might be good because I spend most of my time in the outer five cogs of my 11x28T cassette. And the X-Sync chainring would place the chain 1.5 mm closer to the inside 28T cog than the outer chainring of my current 2x crank setup.

Obviously, I have more work to do before drawing any conclusions. I hope this is helpful for others who may consider a similar change.

Kind regards, RoadLight

P.S. I'm sorry for making the above description with words and not pictures. If I can make time, I'll try to include some illustrations in my final post after the new crank arrives.
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Old 02-12-16, 11:38 PM
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I recall reading somewhere else that X-Sync rings mounted to a standard 110 BCD crank will move the chainline 2mm outboard vs. a the standard 2x setup (midway between the two rings). I got the impression from the article that this is the way SRAM designed it and they thought it was more/less optimal for 1x. Why you wouldn't want the 1x ring to be centered between the old 2x rings which presumably would match with the center of the rear cluster, I don't know.

- Mark

Last edited by markjenn; 07-11-16 at 08:30 PM.
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Old 07-11-16, 08:35 AM
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Flipping the ring?

Has anyone flipped the CX1 ring? I have mine on a Sram 1x crank now and it lines up just fine, but I plan on moving the ring to a carbon bike with a Rotor 2x crank. From what I can see, the teeth are symmetrical in every way, so if I mount it on the inside of the crank, but flipped, the offset built into the ring should push the teeth closer to a halfway point between the outer and inner rings of a 2x setup.

Then I can add a bash guard on the outside and a chain catcher on the inside for extra insurance (the carbon thing is making me nervous, coming from an aluminum frame that I didn't really care that much about).

Thanks for any thoughts on this plan.
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Old 10-22-18, 09:52 AM
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Thanks for the details of the chainring. I'm experimenting with 1x road and started with a generic "rocket" 43t chainring and a long cage Deore 9 speed derailleur (shimano 10 speed shifters and cassette). It works but I threw the chain off the front ring a couple of time when shifting out of the saddle. I have since eased up a bit while shifting and have not had any more thrown chains. If I watch the chain when shifting it does wobble side to side and it gets worse with more force. So I figured a narrow-wide would help more than a clutch derailleur. I ordered a J&L narrow-wide chainring from ebay and it is thick with no offset. I have found that it's quite noisy in the largest cog (in the stand, have not ridden it yet). So my options are to try the inner little ring position assuming I have clearance and hope I don't have the same problem in the smallest cog, go with a square taper crank that will allow me different spindle lengths, or come off the hip and purchase an X-sync chainring (based on your information). I think the last option is best. As far as the clutch derailleur, I have found that when I stop pedaling in the 13 or 11, the inertia of the cassette along with the friction of the free hub will cause the upper run of chain to droop down and tap the chainstay. This is with a heavy, all steel 11-36 cassette. I am thinking with a lighter and perhaps smaller cassette (maybe 11-32 with aluminum spider), this will not happen as much. But I think to eliminate this, and well as chain bouncing over bumps, a clutch derailleur is the best option.

Roadlight wrote:
"My new X-Sync 50T chainring arrived today. Hurrah! I've made some preliminary measurements. A summary and details follow...

Summary
The rear of my driveline appears to be 43 mm from the center line of my frame at my 10-speed cassette. The front of my driveline also appears to be 43 mm from the center line of my frame (measured to the center of the space between the outer and inner chainrings of my 2-ring Force 10 crank. If I were to mount the X-Sync chainring to this same crank, it would probably move the front of my driveline out to 44.5 mm. This seems acceptable to me. But I'm not planning on using my existing Force 10 crank because I need shorter crank arms.

I'm waiting for a SRAM Red 22 crank to arrive. Since it is made for an 11-speed system, its chainring spacing will be different. Once it arrives and I begin to disassemble my existing crank, I'll be able to make accurate measurements of both and see how they compare. Why Red? Simple: I discovered a nearly unbelievable sale and the bike shop had the Red with the 165 mm crank arm length I needed but they were out of stock on the 165 mm Force 22 crank. Plus, I eventually plan to switch my rear derailleur to a Red eTap after SRAM supports larger cogs with a medium or long cage version. Why eTap? Answer: So I can have a second set of shifters for my aerobars.

By the way, my Red crankset was purchased for US$241.71 from Merlin Cycles in the U.K. with free shipping to the U.S. Their sale is still on in case anyone else is interested in picking up a compact-size SRAM Red crank at a 45% discount. I plan to sell the new Exogram Yaw chainrings (50/34T) that come with it on eBay to further offset some of the cost.

Details
  • The X-Sync chainring appears to be designed for front mounting only. In other words, it needs to be mounted to the outside of the crank spider.
  • The X-Sync teeth are off-center toward the crank. In fact, the teeth appear to be centered precisely to the rear mounting surface of the chainring (they overhang it). This will cause the teeth to also be centered over the front mounting surface of the crank spider (since this is where the rear mounting surface of the chainring mates.)
  • Therefore, the teeth of the 50T X-Sync chainring will not center perfectly to the driveline---but they will probably be fairly close (within 1.5 mm, I believe).
The spider mounting tabs of my SRAM Force 10 crank appear to be 3.5 mm thick. I have two SRAM Powerglide chainrings on it and each is about 3 mm thick where they mount to the spider. The teeth of the outer chainring are centered to this---which places the center of the teeth about 1.5 mm outside of the spider's front mounting surface. The teeth of the inner chainring are not centered. Rather they are closer to the spider---I think they are about 1 mm away from the rear mounting surface of the spider. This means the center-to-center distance between the teeth of my two chainrings is 1.5 + 3.5 + 1 mm = 6 mm. (Remember, my Force 10 drivetrain is a 10-speed system.)

With the above dimensions, the teeth of the X-Sync chainring would need to be centered 1.5 mm to the inside of the spider's front mounting surface. Instead they are exactly centered over the spider's front mounting surface. Ergo, the teeth of the X-Sync chainring will be 1.5 mm outside of the driveline if I were to use my existing Force 10 crank. Would this be a "show stopper"? I'm not sure since I've never used a 1x system before---but I doubt it. If anything, it might be good because I spend most of my time in the outer five cogs of my 11x28T cassette. And the X-Sync chainring would place the chain 1.5 mm closer to the inside 28T cog than the outer chainring of my current 2x crank setup.

Obviously, I have more work to do before drawing any conclusions. I hope this is helpful for others who may consider a similar change.

Kind regards, RoadLight

P.S. I'm sorry for making the above description with words and not pictures. If I can make time, I'll try to include some illustrations in my final post after the new crank arrives."

Last edited by 3speedcliff; 10-22-18 at 10:00 AM.
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