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Discussion Starter · #1 ·
Hi all,

I've been riding SS for yonks but I've never had a round chainring with quite a much chain tension variation as this one. It is a SRAM direct mount so there is no scope for a bit of wiggling and correcting.

What do you reckon (it is a bit clearer viewed in full screen)?

I know I am being a bit precious and functionally it will be sound as people live with oval rings buuuuuut ..... :)

The main reason to ask the question is I've never had tension variation this bad before and also that the chain/ drivetrain is damned noisy coasting in the slackest orientation which takes away half the joy of a lovely smooth, peaceful drivetrain! It's just not cricket SS :)
 

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Can't tell exactly what you have there by gave up up SRAM GXP stuff for SS long ago, the plastic(not sure what to call lt between axle and outer axle) on the drive side would basically disintegrate and grind to a halt. [email protected] it happen 3 times moved on. Unless you're super tight which is not good some play is expected.
edit:
 

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Rippin da fAt
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Frankly, the tolerances in chainrings is atrocious regardless of mount type.
Small runout, ignore it and set tension at the loosest point in the system rather than tightest. Oval rings and a tensioner are unacceptable since the tensioner was made obsolete by sliding dropouts.
 

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Discussion Starter · #4 ·
The GXP bashing is a bit OT, but I've run XX1 GXP cranks on SS pretty much since they came out and never had any BB issues. I have always run Hope BB's though so that may help. There isn't any other crank that has been so fit and forget for me, has such a range of chainring options (spider mounted power meter/ 104bcd spider/ direct mount/ etc) and nothing comes close to the weight to cost ratio.

Anyways.... this round ring reminds me more of an oval :)

I've had Hope, Renthal, SRAM, Absolute Black, Works, VeloSolo and probably a dozen other rings I am forgetting mixed between 104 and direct mount on GXP cranks and never had such variation in tension.

I can tension to the loosest point but in this case the tightest point feels way too tight. I can't get a balance between where the tightest point isn't too tight but the loosest point isn't rattling around making the bike sound like a shopping trolley when coasting.

I guess I'll see what the manufacturer says but I don't hold out a lot of hope (mainly bought in the first place from Unite Co as they were the only ones with stock!)
 

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Hi all,

I've been riding SS for yonks but I've never had a round chainring with quite a much chain tension variation as this one. It is a SRAM direct mount so there is no scope for a bit of wiggling and correcting.

What do you reckon (it is a bit clearer viewed in full screen)?

I know I am being a bit precious and functionally it will be sound as people live with oval rings buuuuuut ..... :)

The main reason to ask the question is I've never had tension variation this bad before and also that the chain/ drivetrain is damned noisy coasting in the slackest orientation which takes away half the joy of a lovely smooth, peaceful drivetrain! It's just not cricket SS :)
It could be the chainring, but it also could be an unevenly stretched chain.
 

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Discussion Starter · #6 ·
Chain is new so it will need some time to bed in but the tension is related to crank position only.
I don’t know how the oval ring folks cope when I get precious about a round ring :)
 

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It could be the chainring, but it also could be an unevenly stretched chain.
I don't think so. The problem could be partially due to a slightly out of round rear cog too. Either way I'd set the max tension on the tightest spot and call it good, really it shouldn't cause any issues.
 

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Discussion Starter · #10 ·
I agree with JB- make sure the tightest spot isn't too tight and have to put up with the loosest parts.

Different from the above advice of tensioning to the loosest spot which I can see being bad for wear
 

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Rippin da fAt
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From a too loose chain?
If a fella sets the chain at the loosest point in the setup, and does so on the tighter side of tension, it will cause driver wear at a rather fast pace. Going to the loosest point and snug, it should serve fine at the tight spot in the system. If the chain is sloppy loose, gotta find out why and replace faulty parts then tension properly. I do not consider tensioners since I only run sliders, so that is not an integer in the equation. Never shall tension be bow string tight, ever.
Damn chemo... Mistated in my previous post and intentionally left it unedited since the correction is right here...

**** covid, cancer is far worse!
 

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Hi all,

I've been riding SS for yonks but I've never had a round chainring with quite a much chain tension variation as this one. It is a SRAM direct mount so there is no scope for a bit of wiggling and correcting.

What do you reckon (it is a bit clearer viewed in full screen)?

I know I am being a bit precious and functionally it will be sound as people live with oval rings buuuuuut ..... :)

The main reason to ask the question is I've never had tension variation this bad before and also that the chain/ drivetrain is damned noisy coasting in the slackest orientation which takes away half the joy of a lovely smooth, peaceful drivetrain! It's just not cricket SS :)
It almost looks like the chainring in the video has shift ramps. For multi-speed rings I doubt the mfg puts much if any emphasis on roundness as there's so much slack in the system anyway. Maybe post a vid that's not so cropped.
 

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Combat Wombat
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I have used several of the round Sram DM steel chainrings on a couple different bikes and found them to be a great deal, typically getting them shipped to the front door for about $19. They last a long time and if it turns out that particular size is not what I want, not out the $70 or so that most nice aluminum rings go for. I recently changed out the 34T chainring to a 32T on my KM and went with another Sram DM steel Chainring. I found it was about the same as the OP's as far as roundness. Not a big deal and have never had a problem with dropping a chain. Ran this chainring for a couple months and then replaced it with a round Wolftooth. Anybody wants a semi-oval 32T chainring, you can have it for shipping. It is kind of like the 27.5 of the chainring world. :p
 

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Rippin da fAt
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Totally agree. I probably wasn't clear in my post, I meant what Dan-W said.
I too stated it bass ackwards in my previous post and lead to confusion. Chemo has its moments!
Too much tension.. Try that with a timing belt in a car and get ready to replace pistons and valves when the belt breaks while putting some leg in it! Same happens when the chain on our bikes lets go, 'ceptin for that voice changeup by 10 octaves!
 

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Discussion Starter · #17 ·
So I got a reply which says my video is bobbins because I back pedaled to show the difference in tension. I need to pedal forwards to tension the chain. Where is the facepalm emoji? Of course the top of the chain is under tension pedaling. Arguing silly points aside, hopefully I'll get a refund.

Anyway, of course squeezing both top and bottom sections of the chain together to account for any differences between top and bottom tension shows exactly the same thing- one crank position is much more in tension compared to the other crank position where the chain is really floppy.

There is also ~2mm difference in the tooth tip position when measuring the two different parts of the chainring at the same point on the chainstay and the chain rises and falls (eg up and down the seat tube) a few mm. There is definitely something not quite right.

I'll will write this one off to experience and a use more familiar brand next time that I have had better experiences with in the past.
 
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