Eagle PG1230 NX Eagle 3rd cog bent / Stiffer 12x cassette EMTB specced

[sandyman44]

my EMTB, scott e-genius, has sram nx eagle 12x PG1230 cassette. standard splined freehub. recently towards the end of a ride I noticed some gears become unusable, it turned out the 3rd largest cog (36T) has a significant (about 4mm) away-from-the-wheel bend in it for about 3 teeth-worth, almost overlapping the adjacent 4th largest making both unusable. Only explanation that is likely is that this ring was taking too much torque at some point on my ride , perhaps after a less-than-perfect shift, and got bent. there was no crash.
After I took it off the bike and had a good look at it, this one cog is very flexible, you can push it sideways with finger, its only built from a single ring of metal for large sections of the arc.if I can bend it with a finger, sure as heck a bosch motor in turbo pulling 120kg's up a hill can potentially do so.
All the other large cogs are built from two concentric rings with structural triangles joining them all the way round the arc, and are much much stiffer. seems like a design flaw in this cassette that this one cog is very flexible. I've whacked it with a hammer and got it more or less back to straight but I don't know how long it will last.

anyone found a way to replace the large rings only , I don't see anyone listing sram cassettes piecemeal?
Is there an alternative EMTB rated stronger 12x cassette that fits a standard freehub?

 

[Jackware]

www.servicearchive.sram.com › ...PDF
Compatibility Map MTB Components 2018 - SRAM

To change the cassette from either the 1210 or 1230 you'll need to change the hub as well.

Maybe put it down as a learning experience rather than a design fault that you've discovered.

 

[>moto<]

Might have been a stick or something that got caught and caused the bend. Most cassette's are made from similar materials, even the expensive ones, though they are constructed differently.

I'm 100Kg's and don't go light on my bike and the cheap ass SX cassette has held up so far.

 

[Gary]

anyone found a way to replace the large rings only

you don't need to. simply return it and have the seller/supplier warranty it for you.

it happens. and not just to lower end sprockets

 

[Drsooty]

you don't need to. simply return it and have the seller/supplier warranty it for you.

it happens. and not just to lower end sprockets

This happened to me, same cassette, same ring bent. SRAM would not repair or replace under warranty.

In terms of prevention, I am now keeping a closer eye on chain wear. My gear changing is not perfect but I had no issues for 6 months until my chain wear got higher.

I've replaced with a Sunrace MZ90 cassette. Not sure if it is stronger but got a good deal.

 

[Jackware]

This happened to me, same cassette, same ring bent. SRAM would not repair or replace under warranty.

In terms of prevention, I am now keeping a closer eye on chain wear. My gear changing is not perfect but I had no issues for 6 months until my chain wear got higher.

I've replaced with a Sunrace MZ90 cassette. Not sure if it is stronger but got a good deal.

The Sunrace uses aluminium for all except the 2 largest cogs while the Sram cogs are all steel, so the Sunrace may wear sooner but YMMV literally.

 

[Drsooty]

The Sunrace uses aluminium for all except the 2 largest cogs while the Sram cogs are all steel, so the Sunrace may wear sooner but YMMV literally.

Cheers.

Yes, after my second SRAM cassette bent only 2 weeks after installation, then SRAM would not replace it, I decided to go for a cheaper option. The Sunrace was on offer at my LBS.

In retrospect the chain wear was the likely culprit. Had no issues with Sunrace so far. Also upgraded to a GX chain. You live and learn.

I'd only had budget hard tails prior to this bike! Never had any problems with them!

 

[sandyman44]

this isn't tooth wear, its the actual cog bending. although wear could be a contributor to less-than-perfect shifts that could have caused the bend itself, I'm convinced its the construction method that allows the bend to happen.

I've compared the PG-1230 to an XG-1275 cassette and the construction method is totally different. on the more expensive cassette every cog has an independent "truss" construction i.e. two concentric rings with triangle braces between them. they are all very very stiff. Plus, every cog is pinned to the next one at quite small distance intervals, so there is no large sections of cog that can move independently. on the PG1230 on this one 36T cog that got bent there is a fairly large arc, that is both a single ring of metal with no truss bracing, and unsupported by pins, able to move quite freely and thats where mine got bent.

I have no illusions about trying to get a warranty claim on it, clearly it will be put down as fair wear-and-tear and/or riding damage, its done 1000 miles.

anyone know if there is a conversion for this hub to XD?

 

[salko]

anyone know if there is a conversion for this hub to XD?

Well that depends on which rear hub you have ...

 

[Drsooty]

this isn't tooth wear, its the actual cog bending. although wear could be a contributor to less-than-perfect shifts that could have caused the bend itself, I'm convinced its the construction method that allows the bend to happen.

I've compared the PG-1230 to an XG-1275 cassette and the construction method is totally different. on the more expensive cassette every cog has an independent "truss" construction i.e. two concentric rings with triangle braces between them. they are all very very stiff. Plus, every cog is pinned to the next one at quite small distance intervals, so there is no large sections of cog that can move independently. on the PG1230 on this one 36T cog that got bent there is a fairly large arc, that is both a single ring of metal with no truss bracing, and unsupported by pins, able to move quite freely and thats where mine got bent.

I have no illusions about trying to get a warranty claim on it, clearly it will be put down as fair wear-and-tear and/or riding damage, its done 1000 miles.

anyone know if there is a conversion for this hub to XD?

Interesting about the construction of the 2 cassettes. Maybe they have cheaped out on the entry level.

Totally understand it wasn't tooth wear. I'm saying that a worn chain makes it more more likely to bend a cassette. Possibly due to the gear change inefficiencies. At least I believe that's what happened in my case. Although I did hope that as it was only 2 weeks old SRAM would have allowed a warranty claim.

 

[GrumpyMTB]

Old thread but thought I'd chip in. Just bought a Whyte E-180S with a Bosch/SRAM drivetrain. It has an NX 12 speed casstte, and on only my second ride after about 30 miles of total riding on this new bike I also had the third sprocket bend in the way you described; banana shaped between two pins, about 3 teeth affected, bent outwards from the centre of the hub making 3rd and 4th unusable. It happened on a fairly flat section of trail, not especially putting a huge load through the drive train and no under-load changes as far as I remember. My initial thought was a twig stuck in the cassette, but when I stopped and looked, the bend was clear to see and nothing was stuck in the cassette. I took mine back to the retailer (Leisure Lakes) as I'd only had it for 6 days and they replaced it at no charge.

It does sound however like this is a design flaw of the NX and it probably should not be being utilised on eBikes. I've also had a YT Decoy for about 3 years powered by a Shimano E8000 with Shimano XT 12 speed cassette. On that bike I've done 5500Km across about 3 cassettes and have never had such an issue, I have had entire teeth ripped off on two occasions from badly timed shifting under load, but never experienced a bent sprocket. Even those damaged Shimano cassettes continued to work absolutely fine until eventually wearing out and needing replacement.

My riding buddy has a Whyte E-160S, also with the same Bosch motor. He puts SRAM SX cassettes onto his and hasn't had any similar issues. I wonder if the NX, also being steel but being lighter than the steel SX has been slimmed down to save a little weight but at the cost of stiffness.