SRAM T-type failure across all transmission type e-bikes

[steve_sordy]

Yesterday on the trail at Sherwood Pines my bike (Santa Cruz Vala) suddenly became sluggish. I checked all the usual things: Motor, was I dragging anything, obstruction, brakes binding and so forth. I came to the conclusion that the freehub was at fault. Pines bike shop are a Santa Cruz dealer so I went straight there.
Half an hour late I was told the following: The e13m freehub has seized and unwound the Sram Cassette. The cassette has been rubbing against the inside of the frame (fortunately, up against a metal piece that looks to have been put there for that purpose). The cassette is scrap. The wheel bearings were OK, but the hub was solid. Not e13 again I thought. So I wrote to the head of customer support in the USA, someone that had contacted me on another thread on this Forum about e13 hubs.
This was his response (spoiler alert - Not the fault of e13, but SRAM!)

Chris Costello (e13 Support)​

​

Jun 23, 2026, 15:49 PDT​

​

Hi Steve,​

Sorry to hear about this. Ive added James at Sherwood Pines Cycles to this email. ​

​

Unfortunately the hub failure was the result of your SRAM Transmission cassette loosening under normal use, contacting the derailleur mount and creating extreme inward force on the driver body. This issue is starting to be seen more and more on all Transmission spec ebikes despite it likely being installed to correct torque specification. ​

​

The cassette loosens to the point that it contacts the derailleur mount, and then the contact with the cassette lockring end causes a rapid loosening and heavy inward force on the driver. With some hubs it will cause excessive binding and lock the wheel up. With others it will cause the driver shell to push inward ​

​

Here is a Facebook post in the SRAM Transmission FB group where many riders of different model hubs are experiencing the issue: ​

​

We are in the process of drafting a Technical Service Bulletin about it. Despite the issue not being caused by our hub and being a direct result of the cassette loosening, we are helping riders with hub parts and SRAM should be contacted about parts and labor outside the hub. Ive been in contact with SRAM's USA Customer Experience Manager and he asked that cases be directed to SRAM. ​

​

Im going to pass your ticket to Joe at our UK office and he can work with James to get you sorted as quick as possible. From our end, I would suspect we can get something out to you quickly but need to confirm with Joe. The rest of the timeline would depend on SRAM and Sherwood Cycles service availability. ​

​

You guys should hear from Joe shortly. If you need anything further from my side, please send me a message .........​

​

Thanks,​

​

Chris​

I am happy about that response from e13. Not so happy that SRAM have this issue and are waiting for riders to experience the problem for themselves, rather than doing a recall or announcing a fix whatever... But maybe they have and I just am unaware of it. I will keep you informed.

 

[russ_e]

Maybe the new latest power updates are working things loose

 

[Fangs2k]

Good service Steve, but yes I hate the ‘wait for customers to experience the issue’ before companies act.

Somebody will be along soon to tell you a gearbox bike is the way forward. Just drop a few £k and ‘problem solved’!

 

[levity]

Thanks for the heads-up @steve_sordy !

Haven’t heard of this before. Do you know which freehub driver(s) are involved?

In any case, I’m going to check the torque on our T-type cassettes. However, I would think that the Avinox M2S we have would be keeping things snug.

 

[steve_sordy]

Thanks for the heads-up @steve_sordy !

Haven’t heard of this before. Do you know which freehub driver(s) are involved?

...........

E13 SL E-Spec, 12×148, XD with a SRAM XS 1275 Eagle T-Type cassette.

I'm guessing that the different cassette fastening design used by Shimano is proof against the problem experienced by SRAM.

 

[Zed. (Justin is short)]

Yesterday on the trail at Sherwood Pines my bike (Santa Cruz Vala) suddenly became sluggish. I checked all the usual things: Motor, was I dragging anything, obstruction, brakes binding and so forth.

about a month ago a friend had similar when riding, the casette had loosened on the freehub and was rubbing against the derailer hanger

repaired by tightening the casette locknut thing

bike is a SC somethingorother with t-type cable derailer

 

[steve_sordy]

I said that I would keep you updated.

E13 have been in contact with Sherwood Pines Cycles and had a long discussion with the mechanic there, Darren.

Joe from e13 told me this:

“Whilst the root cause does not appear to be with the hub itself, we're more than willing to help where we can and support Sherwood Pines in getting you back up and running as quickly as possible.​

​

I'll continue to support them from our side and assist with any parts requirements as needed.”​

SRAM have yet to reply to Sherwood Pines Cycles. But the e13 guy in USA has been in contact with his opposite number at SRAM in USA.

Darren told me that there have been nine similar cases in the UK. I don’t know whether that is since T-type was introduced, or this year so far.

Who knows how this will resolve itself? Sherwood Pines Cycles are predicting it may take time for the dust to settle. So they have fitted a spare wheel to my bike to get me up and running! The bike is ready for collection now. It is a Santa Cruz wheel and will fit right in and will feel the same. The hub is not an e13 hub, just the hub that was already on the wheel. I can keep this wheel until my own can be returned.

WOW!! What fantastic customer service from Sherwood Pines Cycles. BIG UP TO THEM!

Big thanks also to e13 for a very fast and supportive response.

PS: SRAM must be aware of the possibility of this because according to Darren, they have fitted a clip inside the cassette that is supposed to stop this happening.

 

[Fangs2k]

Santa Cruz, e13 and not least Sherwood Pines Cycles getting a big for their service to you.

Will bear that bike shop in mind for my next bike, it’s only up the A1 from me.

 

[RustyIron]

I am happy about that response from e13. Not so happy that SRAM have this issue and are waiting for riders to experience the problem for themselves, rather than doing a recall or announcing a fix whatever... But maybe they have and I just am unaware of it.

Hey, Steve. You've been around the block enough times to know that accurate failure analysis requires keen observation and thought. I haven't observed the failure at all, but I do have some thoughts on your situation.

First, let's not lose sight of the bigger picture: You bought a nice bike from Santa Cruz, the bike fell apart, and they should warranty the damaged parts. Go to the bike store and ask them to handle the warranty repair. If they're dicks about it, call or email Santa Cruz. It's only eight hours difference. Their customer service rocks.

Back to the failure. The bike store boy says the failure was the result of the hub seizing. I suppose it's possible, but not probable on a new bike. E13 guy says that the threads on his hub are good, but the threads on the cassette are bad. I suppose that's possible, too. Possible, but not probable.

If I was a gambling man and was offered even odds, I'd bet that the original bike store boy just slapped it all together. It takes a lot of time to clean the splines and threads, and then get out the torque wrench. Put my money on faulty assembly.

 

[steve_sordy]

Hey, Steve. You've been around the block enough times to know that accurate failure analysis requires keen observation and thought. I haven't observed the failure at all, but I do have some thoughts on your situation.

First, let's not lose sight of the bigger picture: You bought a nice bike from Santa Cruz, the bike fell apart, and they should warranty the damaged parts. Go to the bike store and ask them to handle the warranty repair. If they're dicks about it, call or email Santa Cruz. It's only eight hours difference. Their customer service rocks.

Back to the failure. The bike store boy says the failure was the result of the hub seizing. I suppose it's possible, but not probable on a new bike. E13 guy says that the threads on his hub are good, but the threads on the cassette are bad. I suppose that's possible, too. Possible, but not probable.

If I was a gambling man and was offered even odds, I'd bet that the original bike store boy just slapped it all together. It takes a lot of time to clean the splines and threads, and then get out the torque wrench. Put my money on faulty assembly.

It's a reasonable proposition.
A few facts.
I bought the bike from Big Bear Bikes in Pickering. That is a two and half hour drive from me on a good day. BBB is a Santa Cruz dealer and has a good reputation. I ordered a Santa Cruz Vala from Sherwood Pines Cycles who are also a Santa Cruz dealer (but a smaller operation than BBB). They accepted the order, but soon told me that they could not deliver, they had been misinformed by their SC rep as to availability and SPC advised me to look elsewhere. I was sad about that because they are good guys (as we have seen), but there was nothing they could do. I was in New Zealand at the time, with intermittent wi-fi and yet somehow managed to find exactly the bike that I was looking for. It had just come onto the market because it had been a demo bike. It had 250 mies on the clock and it was immaculate. It also already had the Kiox 400c display and was fully framewrapped. They applied the Bosch update 2.0 as part of the deal. All for £6000 vs £7799 rrp plus the Kiox and the framewrap. It also had a new chain, cassette, brake pads, saddle, grips and rear tyre. I thought it was a cracking deal.

My opinion. I have no reason to suspect that the mechanics at BBB were shoddy in their initial assembly or indeed any subsequent work. It is not practical to take my bike all the way back to BBB for every warranty claim and they appreciate this. They have already agreed to one minor claim for a seized bolt on the rear brake calliper that was fixed by a local bike shop. When I took the bike in to Sherwood PInes (a SC dealer don't forget), I had no idea of the issues I was about to unleash/uncover/reveal/start up/whatever. I just wanted to know what was wrong. I was told it was the e13 hub. I contacted e13 who said it was the SRAM cassette. SRAM have yet to make their views known, although they have been informed.

As far as I am concerned a Santa Cruz dealer IS handling the warranty repair. Because of the potential bunfight between e13 and SRAM (and maybe also Big Bear Bikes, to take your point) it may take time to settle. So I am enormously grateful to Sherwood Pines Cycles for taking the supportive stance that they have. I would feel a lot better about it though if I they had actually been able to supply me with a bike!

 

[Mikerb]

I am also a little sceptical a bout the fault analysis. I have ridden SRAM T Type AXS for over 2 years with no issues. In my case the hub and freehub are DT Swiss (ratchet freehub). I service the freehub probably 3 times a year on all my bikes. Never experienced a loose cassette and I tighten to 50nm. Considering the cassette locknut is tightened clockwise the only component I can see that would loosen that nut is the freehub. If the freehub is partially seized, any attempt to freewheel could then loosen that locknut. If there is too much resistance between the axle and the freehub.....and the cassette was not properly torqued.....same result. Either way the freehub is the most probable culprit. SRAM Transmission whether AXS or cable must have been installed on thousands of bikes and there have been no reports on here or elsewhere that I have seen of such a problem.

 

[steve_sordy]

@Mikerb I'm not disagreeing with you one bit, it sounds very plausible. This is why when this started happening, E13 took the hit and paid the associated costs. But when it kept happening, they took a closer look and decided that it wasn't quite so simple. They are now adamant that it is not their fault. They have already engaged SRAM in discussion and they have a channel of communication.

I can see that SRAM would not want to accept liability; how many T-type transmissions are out there?

 

[Mikerb]

@Mikerb I'm not disagreeing with you one bit, it sounds very plausible. This is why when this started happening, E13 took the hit and paid the associated costs. But when it kept happening, they took a closer look and decided that it wasn't quite so simple. They are now adamant that it is not their fault. They have already engaged SRAM in discussion and they have a channel of communication.

I can see that SRAM would not want to accept liability; how many T-type transmissions are out there?

Ttype or not, SRAM cassettes fit in the same way and there are many thousands of them out there on bikes. I have seen no significant reports of any generic SRAM cassette issues.I have used various SRAM cassettes on all my bikes for more than 7 years T Type and standard. No issues. Meanwhile I have seen reports of E13 pedals, cranks, freehubs and chainwheels failing. Of course they will look to blame SRAM...............sorry I dont buy it. As I said previously any failure such as the one you experienced can , in my opinion only be rationally explained if the freehub seizes or has high resistance under freewheel conditions. The lock nut is standard thread and torqued to 40-50 nm.

Potential issue could include:-
hub arrangements that require a spacer behind the cassette, not fitted.
Cassette lock nut not properly torqued.
Freehub pawl fail to disengage due to poor assembly or poor maintenance
Freehub bearings failure.

 

[steve_sordy]

Ttype or not, SRAM cassettes fit in the same way and there are many thousands of them out there on bikes. I have seen no significant reports of any generic SRAM cassette issues.I have used various SRAM cassettes on all my bikes for more than 7 years T Type and standard. No issues. Meanwhile I have seen reports of E13 pedals, cranks, freehubs and chainwheels failing. Of course they will look to blame SRAM...............sorry I dont buy it. As I said previously any failure such as the one you experienced can , in my opinion only be rationally explained if the freehub seizes or has high resistance under freewheel conditions. The lock nut is standard thread and torqued to 40-50 nm.

Potential issue could include:-
hub arrangements that require a spacer behind the cassette, not fitted.
Cassette lock nut not properly torqued.
Freehub pawl fail to disengage due to poor assembly or poor maintenance
Freehub bearings failure.

You make a convincing case. I am in the position of having no particular experience (therefore no expertise) in Sram transmission, having always had Shimano. I did have one bike with XO transmission, but it never went wrong before I sold it and I never had to take it apart, not even to fit a cassette!
I will be sure to mention your points next time I am in conversation with e13 on this topic.

 

[John_likes_bikes]

Simplest explanation is usually the right one, cassette not torqued correctly. Transmission cassette is 40nm, that's 354 in-lbs. No way that's just coming loose on its own.

 

[Arminius]

Steve,
I find this interesting and thank you for sharing the details, including the great support you received, as well for the way you are dealing with it here.

Not having a transmission system yet but looking for new bike that may have that system I became nosy and looked around a little bit. It appears to me that the installation of the rear hanger is way more complicated than what I am used to. Some say this may lead to loose rear derailleur or cassettes, i.e. if not done properly.

Is it a must to do it that accurate. Have you been following all these instructions when reinstalling the rear wheel? Could it have such effect?

https://www.sram.com/en/learn/eagle-transmission-welcome-guide/installation-overview

 

[xtraman122]

Simplest explanation is usually the right one, cassette not torqued correctly. Transmission cassette is 40nm, that's 354 in-lbs. No way that's just coming loose on its own.

In the case of OP’s Santa Cruz bike, wouldn’t the cassette have come installed on the wheel already when his LBS got it, or is that part of the assembly the shop has to do? I figured they came mostly assembled and shop just did some basic assembly, but I’m not familiar with SC in particular.

 

[John_likes_bikes]

In the case of OP’s Santa Cruz bike, wouldn’t the cassette have come installed on the wheel already when his LBS got it, or is that part of the assembly the shop has to do? I figured they came mostly assembled and shop just did some basic assembly, but I’m not familiar with SC in particular.

I don't know either. Years ago when I worked in a shop I vaguely recall that being a part already installed but I trust myself just a little bit more than anyone else assembling my bike so I've made it a habit to disassemble anything and doing it "right" (or wrong) myself.

 

[xtraman122]

I don't know either. Years ago when I worked in a shop I vaguely recall that being a part already installed but I trust myself just a little bit more than anyone else assembling my bike so I've made it a habit to disassemble anything and doing it "right" (or wrong) myself.

Actually, is OP had an e13 hub that presumably would have been installed after the fact, and improper torquing as the cause might explain why an aftermarket hub manufacturer like e13 would be seeing a lot of it because it might be something not many people torque correctly. Just a theory, but I could see someone like them suffering the consequences of the Wild West of bike techs more than an OEM who probably has an assembly line where they all get torqued to an exact spec consistently.

 

[John_likes_bikes]

Actually, is OP had an e13 hub that presumably would have been installed after the fact, and improper torquing as the cause might explain why an aftermarket hub manufacturer like e13 would be seeing a lot of it because it might be something not many people torque correctly. Just a theory, but I could see someone like them suffering the consequences of the Wild West of bike techs more than an OEM who probably has an assembly line where they all get torqued to an exact spec consistently.

For sure every component manufacture has to weed through the sometimes impossible task of determining fault. Everyone is going to point the finger at the other.

 

[Mikerb]

There is n

Steve,
I find this interesting and thank you for sharing the details, including the great support you received, as well for the way you are dealing with it here.

Not having a transmission system yet but looking for new bike that may have that system I became nosy and looked around a little bit. It appears to me that the installation of the rear hanger is way more complicated than what I am used to. Some say this may lead to loose rear derailleur or cassettes, i.e. if not done properly.

Is it a must to do it that accurate. Have you been following all these instructions when reinstalling the rear wheel? Could it have such effect?

https://www.sram.com/en/learn/eagle-transmission-welcome-guide/installation-overview

There is no hanger. It also has no limit or b tension screw. Correct fitting and choice of settings on the derailleur mame them uneccessary. Each bike has those settings specified by the bike brand, together with chain length. That fitting process ensures the correct alignment of the derailleur across the cassette. It has nothing to do with how the cassette is fitted. The only aspect that is different in terms of wheel removal and refitting is concerned is that the wheel is removed as usual with the cage locked forward but when the wheel is replaced you merely snug up the thru axle, then release the cage before applying full torque to the thru axle.
If you do not follow that procedure the derailleur will not hang in its correct position..and not select gears correctly. .....still nothing to do with the cassette fitment

 

[Arminius]

There is no hanger. It also has no limit or b tension screw. Correct fitting and choice of settings on the derailleur mame them uneccessary. Each bike has those settings specified by the bike brand, together with chain length. That fitting process ensures the correct alignment of the derailleur across the cassette. It has nothing to do with how the cassette is fitted. The only aspect that is different in terms of wheel removal and refitting is concerned is that the wheel is removed as usual with the cage locked forward but when the wheel is replaced you merely snug up the thru axle, then release the cage before applying full torque to the thru axle.
If you do not follow that procedure the derailleur will not hang in its correct position..and not select gears correctly. .....still nothing to do with the cassette fitment

Thank you! It was just that acc. to some riders it sounded like a improper mounted transmission „derailleur“ could get loose and in consequence work on the cassette to get loose as well -> causing a damage. Seems to be not the case.

PS: Please have a little patience with non native speakers if „hanger“ was not the correct word for….

 

[steve_sordy]

Steve,
I find this interesting and thank you for sharing the details, including the great support you received, as well for the way you are dealing with it here.

Not having a transmission system yet but looking for new bike that may have that system I became nosy and looked around a little bit. It appears to me that the installation of the rear hanger is way more complicated than what I am used to. Some say this may lead to loose rear derailleur or cassettes, i.e. if not done properly.

Is it a must to do it that accurate. Have you been following all these instructions when reinstalling the rear wheel? Could it have such effect?

https://www.sram.com/en/learn/eagle-transmission-welcome-guide/installation-overview

I have done no installation on the bike.

 

[steve_sordy]

In the case of OP’s Santa Cruz bike, wouldn’t the cassette have come installed on the wheel already when his LBS got it, or is that part of the assembly the shop has to do? I figured they came mostly assembled and shop just did some basic assembly, but I’m not familiar with SC in particular.

The cassette may indeed have come already installed when it arrived at the dealer's shop. But I bought a demo bike that came with a new cassette as part of the deal (among other things).

 

[steve_sordy]

Actually, is OP had an e13 hub that presumably would have been installed after the fact, and improper torquing as the cause might explain why an aftermarket hub manufacturer like e13 would be seeing a lot of it because it might be something not many people torque correctly. Just a theory, but I could see someone like them suffering the consequences of the Wild West of bike techs more than an OEM who probably has an assembly line where they all get torqued to an exact spec consistently.

The Vala 90 has e13 hubs front and rear as standard from Santa Cruz. The T-type transmission is also standard spec.

 

[xtraman122]

The Vala 90 has e13 hubs front and rear as standard from Santa Cruz. The T-type transmission is also standard spec.

Thanks, didn't realize Santa Cruz sold those from the factory on their bikes. But based on what you said it was replaced by the shop regardless in your case.

 

[steve_sordy]

Thanks, didn't realize Santa Cruz sold those from the factory on their bikes. But based on what you said it was replaced by the shop regardless in your case.

The spec is standard, I don't know to what extent they are shipped to the dealers. The dealer may have built up the bike.

 

[RickBullotta]

Yesterday on the trail at Sherwood Pines my bike (Santa Cruz Vala) suddenly became sluggish. I checked all the usual things: Motor, was I dragging anything, obstruction, brakes binding and so forth. I came to the conclusion that the freehub was at fault. Pines bike shop are a Santa Cruz dealer so I went straight there.
Half an hour late I was told the following: The e13m freehub has seized and unwound the Sram Cassette. The cassette has been rubbing against the inside of the frame (fortunately, up against a metal piece that looks to have been put there for that purpose). The cassette is scrap. The wheel bearings were OK, but the hub was solid. Not e13 again I thought. So I wrote to the head of customer support in the USA, someone that had contacted me on another thread on this Forum about e13 hubs.
This was his response (spoiler alert - Not the fault of e13, but SRAM!)

Chris Costello (e13 Support)​

​

Jun 23, 2026, 15:49 PDT​

​

Hi Steve,​

Sorry to hear about this. Ive added James at Sherwood Pines Cycles to this email. ​

​

Unfortunately the hub failure was the result of your SRAM Transmission cassette loosening under normal use, contacting the derailleur mount and creating extreme inward force on the driver body. This issue is starting to be seen more and more on all Transmission spec ebikes despite it likely being installed to correct torque specification. ​

​

The cassette loosens to the point that it contacts the derailleur mount, and then the contact with the cassette lockring end causes a rapid loosening and heavy inward force on the driver. With some hubs it will cause excessive binding and lock the wheel up. With others it will cause the driver shell to push inward ​

​

Here is a Facebook post in the SRAM Transmission FB group where many riders of different model hubs are experiencing the issue: ​

​

We are in the process of drafting a Technical Service Bulletin about it. Despite the issue not being caused by our hub and being a direct result of the cassette loosening, we are helping riders with hub parts and SRAM should be contacted about parts and labor outside the hub. Ive been in contact with SRAM's USA Customer Experience Manager and he asked that cases be directed to SRAM. ​

​

Im going to pass your ticket to Joe at our UK office and he can work with James to get you sorted as quick as possible. From our end, I would suspect we can get something out to you quickly but need to confirm with Joe. The rest of the timeline would depend on SRAM and Sherwood Cycles service availability. ​

​

You guys should hear from Joe shortly. If you need anything further from my side, please send me a message .........​

​

Thanks,​

​

Chris​

I am happy about that response from e13. Not so happy that SRAM have this issue and are waiting for riders to experience the problem for themselves, rather than doing a recall or announcing a fix whatever... But maybe they have and I just am unaware of it. I will keep you informed.

Before you put e*13 on too high a pedestal, keep in mind that there are other issues of e*13 components being off tolerance and causing issues with loosening - notably some of their carbon eMTB cranks. I personally wouldn't assume that this isn't the case here as well - keep an open mind.

 

[Mikerb]

All of my Bosch motor bikes have had DT Swiss wheels, hubs and freehubs. All xg...all with SRAM drivetrain, standard GX , Some T TYpe, both versions of AXS. No issues on any of them. Usual lifespan for chains on the standard GX (c 450 miles and 2 or 3 chains before a cassette change) . I have not yet had to change any T Type chains or cassettes. ......one bike with T Type is beyond 450 miles with no sign of wear yet. All degreased and lubed after every ride.

 

[Mikerb]

Heck....

The cassette may indeed have come already installed when it arrived at the dealer's shop. But I bought a demo bike that came with a new cassette as part of the deal (among other things).

a cassette should last 1000 miles ...more if it was T Type. Serious questions to be asked why that was needed.