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Chainring wear on sram 1x

Old 08-11-20, 10:30 PM
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TimJ
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Chainring wear on sram 1x

Hello,

I recently converted my 2x9 raleigh Willard to 1x11, I started with a 42t gxp rival crankset (73mm shell, no spacers) with 11-42 sunrace cassette, apex 1x derailluer, and everything worked perfectly. I wanted a slightly lower gear so I got a 40t force chainring but when riding in the 42 cog the drivetrain was noisy (both rings are the correct 6mm offset). After only 2 rides I looked at the ring and there was a lot of wear. I asked sram about this and they had me check everything was setup correctly, everything is so they didn't have anything to say about the wear.

The chainline of the crankset is biased toward the smaller cogs, it's lined up with the 5th cog up, so the angle of the chain in the 42 cog is more extreme than in the 11t cog. I did an experiment and installed the 40t ring backwards on the inner side of the spider, and this lined the ring up with the middle (6th) cog. A couple rides on this and the wear on the ring is reduced, though still a little more than where the original 42t cog was after about 8 rides.

My question is- has anyone else had the same setup without experiencing the quick wear on a 40t or less chainring? If so I'd like to know what's different, or if I'm missing something.

Pics show the 42 and 40 chainring. 42t was used for about 8 rides, 40 was used only for 2 rides to get as much wear as shown in the pic.



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Old 08-12-20, 05:22 AM
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I have a 2x bike that I converted to 1x. I'm running:
Force 1x rear derailleur
Race Face 42T front chain ring attached to the original 2x crankset "small ring" location with shorter 1x bolts
11-32 Force cassette
SRAM Red chain

I've never measured it, but the chain line appears to be roughly centered on the cassette. When I first set it up, it shifted fine but ran a bit rough in the 32 cog. I added a link to the chain and now it shifts and runs smoothly throughout the range.
I haven't noticed any unusual wear on the front chain ring, which has around 2500 miles on it now (including a dozen or so CX races), but I also don't use the 32 cog very often.

In general, this 1x SRAM setup is noisy compared to the Shimano 2x that it replaced. It's also more noisy than my other bike which has Shimano GRX 1x.
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Old 08-12-20, 07:25 AM
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Guessing-- that either
  • you spend a lot of time in the 11T and the 42T
  • the X-Sync rings just fit tighter in the chain than others
  • That 5mm of shell width must really make a difference

Because the amount of "wear" on your 42T is similar to the condition of my USAMade 44T (on a 68mm BB) that has about 1,900 miles on it.
I put ~6,000 miles on a RaceFace 42T and it's still in good condition, only replaced because I wanted a 44T.
I've never paid attention to chainline on any bike other than my single-speed.

What brand/model of chain are you running?
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Old 08-12-20, 08:00 AM
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That wear doesn't look that bad to me. The main concern that I have is a Rival crankset installed in a 73mm bottom bracket shell. Rival and all other SRAM road cranksets are designed to work with a 68mm shell. They did make some "wide axle" versions, but I believe that they are OEM only and not for sale to the public. A standard Rival crankset doesn't have a long enough axle to be properly installed in a 73mm shell. The non-drive crankarm will bottom out on the bearings and the shoulder on the axle won't reach the inside face of the bearing. You should be able to tighten that non-drive arm down hard and not cause any drag on the bearings.

In the unlikely event that you were able to tighten the non drive arm completely without causing drag(or locking it up completely), your crankset will be offset 2.5mm to the non drive side.
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Old 08-12-20, 12:50 PM
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I Run 1x11 APEX1. I wouldn’t think the chainring moving in/out a few mm off center Would make much difference. I installed a boost spacing SRAM NX crankset (moved 2.5mm outward) this year and cant say wear Is any worse.

if you ride moreso in the extremes the lowest or highest gears, than maybe more wear I figure my riding is pretty balanced all up and down my 11 gears due to lots of hills where I live.
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Old 08-12-20, 01:22 PM
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TimJ
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Ultegra chain. I spend a lot of time in the 42 cog because my rides are all uphill until it's time to come down.

Originally Posted by DrIsotope View Post
Guessing-- that either
  • you spend a lot of time in the 11T and the 42T
  • the X-Sync rings just fit tighter in the chain than others
  • That 5mm of shell width must really make a difference

Because the amount of "wear" on your 42T is similar to the condition of my USAMade 44T (on a 68mm BB) that has about 1,900 miles on it.
I put ~6,000 miles on a RaceFace 42T and it's still in good condition, only replaced because I wanted a 44T.
I've never paid attention to chainline on any bike other than my single-speed.

What brand/model of chain are you running?
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Old 08-12-20, 01:24 PM
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It's designed for 68/73. Maybe previous models weren't but this crank is. In fact, Sram, assuming I had a 68mm shell, asked me if I had the proper spacers installed for the crank.

Originally Posted by dsaul View Post
That wear doesn't look that bad to me. The main concern that I have is a Rival crankset installed in a 73mm bottom bracket shell. Rival and all other SRAM road cranksets are designed to work with a 68mm shell. They did make some "wide axle" versions, but I believe that they are OEM only and not for sale to the public. A standard Rival crankset doesn't have a long enough axle to be properly installed in a 73mm shell. The non-drive crankarm will bottom out on the bearings and the shoulder on the axle won't reach the inside face of the bearing. You should be able to tighten that non-drive arm down hard and not cause any drag on the bearings.

In the unlikely event that you were able to tighten the non drive arm completely without causing drag(or locking it up completely), your crankset will be offset 2.5mm to the non drive side.
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Old 08-12-20, 02:05 PM
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Originally Posted by TimJ View Post
It's designed for 68/73. Maybe previous models weren't but this crank is. In fact, Sram, assuming I had a 68mm shell, asked me if I had the proper spacers installed for the crank.
That is unusual. The SRAM website still indicates that Rival 1 is only compatible with 68mm bottom brackets. The 2020 SRAM Road frame fit specifications manual also states that the only road cranksets that are compatible with a 73mm bottom bracket are the Wide Axle versions. The only Wide Axle crankset listed in the manual is the Rival S552 double.
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Old 08-12-20, 02:10 PM
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dirt should cover where the black finish was gone..

lay a brand new chain on it to see if it actually wore where it counts..
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Old 08-12-20, 02:28 PM
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You know what, you're right. It's 68mm. I confused myself.

Originally Posted by dsaul View Post
That is unusual. The SRAM website still indicates that Rival 1 is only compatible with 68mm bottom brackets. The 2020 SRAM Road frame fit specifications manual also states that the only road cranksets that are compatible with a 73mm bottom bracket are the Wide Axle versions. The only Wide Axle crankset listed in the manual is the Rival S552 double.
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