Anyone have experience with SRAM Eagle Transmission on any Specialized e-bike?

[dynamic]

The turbo levo/sl and kenovo/sl as well as the tero x all have udh. Has anyone put sram transmission on them and can provide an experience report?

I am looking at getting a tero X and then putting on an X0 transmission drivetrain. I still don't love chains, but what I don't love about the ones I have experienced is what happens after you attempt to shift. While I loved the enviolo automatic, I don't think it was the automatic shifting I really cared about. It was that shifting was a *completely* smooth experience. Nothing interfered with what I was doing. My understanding is Transmission actually works better when under power. This should make it a very good pairing for e-bikes.

I can't ride any transmission bike locally. At least not until it hits some more common models. The only specialized bike I am aware of is the epic world cup edition and I can't get a test ride on that here. Same with trek top fuel. I don't know of any other bike that could have sram transmission at a local dealership. Or I would just go try those bikes.

How does it change your shifting experience?

 

[dynamic]

Not sure I follow. The Tero X uses all SRAM in the drivetrain. It's a bit of a mix instead of a straight trim level. For example, Tero X 6 uses the X01 shifter and derailleur, but a lower trim cassette because the wheel has an HG freehub.

Actually, their specs are inconsistent. It claims a gx cassette but that is only on xd hubs. But the hub claims to be hg. Which, as far as I can tell, no version of the 1275 cassette is hg compatible.

None of that is the point though. SRAM has a new transmission drivetrain. It is only compatible with udh frames and I want to know if anyone has tried it on any of the specialized ebikes. X0 transmission supposedly shifts smoothly while under power.

 

[Rider777]

I guess we're (yes, me too) supposed to know what "udh" means?
For most of us that don't here ya go:

What is UDH? UDH is short for Universal Derailleur Hanger. It is an attempt to standardize on one derailleur hanger design and eliminate hundreds of existing standards. Today each bike brand designs their own hangers, and may have multiple incompatible hangers across their own models.

 

[McCorby]

Can we save everyone some time and just skip to the end……that it will fall woefully short of your expectations! You can’t tell me that others aren’t thinking the exact same thing!

 

[dynamic]

Can we save everyone some time and just skip to the end……that it will fall woefully short of your expectations! You can’t tell me that others aren’t thinking the exact same thing!

I mean, I know in this day and age, expecting stuff to work on delivery is a high standard. I will, however, maintain that standard.

Seriously though, I want to set the appropriate expectation. I have read quite a few positive reviews of the transmission system with many experiences aligning with a far better hill climbing shifting experience under power.

I have not heard much on the e-bike front. Hoping to hear some feedback here.

 

[Stefan Mikes]

You perhaps should write "SRAM Eagle Transmission" @dynamic as the word "transmission" might not be understood by the readers of this thread
I am not sure what actual benefits the new system (using the Universal Derailleur Hanger) can bring to the table (unless you are bombing technical singletrack on an e-MTB).

 

[dynamic]

You perhaps should write "SRAM Eagle Transmission" @dynamic as the word "transmission" might not be understood by the readers of this thread
I am not sure what actual benefits the new system (using the Universal Derailleur Hanger) can bring to the table (unless you are bombing technical singletrack on an e-MTB).

Good point. Fixed the title.

Durability is one benefit. But the main thing for ebikes is the way it manages shifting. It is an electronic system that times shifts at the exact right point where the chain can move from one gear to the next with the smoothest possible change. The derailleur won’t move gears until the cassette is oriented for the right transition point for that specific gear change. The shifting is so smooth that it supposedly works better while under power. No letting off the power is necessary (or even desired) while grinding uphill. It should also help ebikes not chew through chains and cassettes so quickly due to poor shifting. There is no poor shifting on this system.

Anyway, reviews on regular bikes appear to be confirming that info. E-bikes, of course, put a lot more stress on the drivetrain. I am hoping to confirm it works well by people who have tried it on ebikes.

 

[Douglas Ruby]

I have a fair amount of experience. My 2022 Turbo Vado SL 5.0 EQ came with SRAM Eagle GX shifter and derailleur. It had an HG freehub with SRAM PG-1230 11-50T classette and a 44T 110 BCD chain ring. I like to gear my Class 3 e-bikes such that the next to tallest gear (11th speed in this case) will max out the assist at 28 mph and a cadence of just over 90 rpm (comfortable for me). With the 44T ring and the 11T (12th gear) and 13T (11th gear) of the PG-1230, I found I was spinning too high on the 13 and the 11 was required for 28 mph, with nothing left over for descents at 30-35 mph.

I first upgraded my chain ring from the stock 44T to a Wolf Tooth 110 BCD 46T. I then found out that I could purchase an XD driver freehub from Specialized for around $75 and replace the freehub myself. Replacing the HG freehub with XD is as simple as removing the rear wheel and cluster. Then give a good yank on the freehub and it comes right off. The replacement slips back on (3 pawl ratchet) after thoroughly cleaning and greasing the ratchet and pawls. Next, install the 10t-52T SRAM XG-1275 cluster. I get better gear spacing and ratios on the top end (9th - 12th gears) with a lower "Granny" gear (52T/46T) in 1st. I also upgraded from an SRAM NX Eagle chain to an SRAM GX Eagle chain and used all 126 links instead of the stock 124 links. The last change (and a welcome one) was to switch from the standard GX shifter to a "single click" shifter. This makes both upshifting and downshifting sequential, with no "skipping" gears or accidental over shifting. This shifter is designed to help reduce stress on the chain and sprockets and provide a bit smoother more accurate transmission. I am very pleased with this conversion, even though the upgrades cost around $460 - tax and shipping where required.

Using the XG-1275 cassette, Wolf Tooth chain ring, and GX chain also saves a few grams over the stock Vado SL 5.0 and SRAM NX components. Since I added a fair amount of weight elsewhere to my bike, I haven't bothered to do any fine calculations.

The Parts List:

Wolf Tooth 46T 110 BCD chain ring - $69.95+shipping+tax (eBay)
SRAM XD-1275 cassette 10t-52T - $231 (list price) - multiple sources
XD Driver for Specialized hub - approx. $75 - Specialized shop
SRAM GX Eagle 12-speed chain - $36 - multiple sources
SRAM GX Eagle Single Click Shifter - $49 - multiple sources

 

[Ben J]

Skip about 8 minutes (past the teardown/install) and there are some examples of it shifting under load on a regular MTB:

 

[dynamic]

Did they just release the gx version? UGH. I wish my bike has UDH.

 

[mschwett]

Good point. Fixed the title.

Durability is one benefit. But the main thing for ebikes is the way it manages shifting. It is an electronic system that times shifts at the exact right point where the chain can move from one gear to the next with the smoothest possible change. The derailleur won’t move gears until the cassette is oriented for the right transition point for that specific gear change. …

the net result may be the same, but that isn’t what it does. the derailleur has absolutely no idea where the cassette is in the rotation - there’s no sensor in either to do so, and the relationship between any position of the chain, cranks, wheel to the cassette are always changing due to gearing and the freewheel. The derailleur does not wait to do anything - you push shift, it moves. Immediately.

the electronics have nothing to do with the shifting under load thing. It’s the result of the newly designed little bumps/ramps on the cassette that have specific relationships to many pre-determined shift points around each cog, so while the derailleur has in fact already moved to the new position, the chain actually doesn’t pop over until it gets to the right bump. the new UDH design facilitates this because it’s so much stiffer. with a flimsy little derailleur hanger, all that stress created by the chain on the cassette and the derailleur being misaligned, under load, would be a huge problem. Derailleur would bend, shifting alignment would go south.

it’s actually the exact same concept as shimano’s hyperglide+ cassettes, which claim similar benefits but without the complete package including hangar, haven’t gone quite as far. I will say that my 12 speed shimano di2 bike shifts flawlessly and incredibly quickly under load, but i still tend to ease off a bit because it just SEEMS wrong.

here’s another explanation of SRAM’s new version of it:

What really makes Transmission shine is how you can just keep putting down power as you move through the gears, a feature that comes about because of all the new ramps that SRAM’s engineers have added to the cassette, and how they interact with the chain. They call this technology “cassette mapping,” and it’s a series of points around each cog where the chain encounters a little ridge that help bump it up or down the cassette. The additional stiffness of the direct mount system is a necessity to allow you to maintain your power output to move through your gears. All that extra torque being put through this drivetrain wouldn’t fly with the amount of flex that is inevitable with a hanger.

so far the couple people i know who have ridden bikes with transmission say it’s really great.

 

[dynamic]

the electronics have nothing to do with the shifting under load thing.

There is also talk of the electronics queuing shifts creating potential delays. Multiple sources talk about electronically delayed shifts (I am not saying they are right, only that others have a different view, no idea what the truth is). My assumption was that the system knows the relationship of the cassette to the shifter since all distances are now fixed due to udh. As such, the shifter doesn’t need sensors, it knows the exact location of the cassette at all times from calibration. So it can perform the shift at the exact point when the cassette would catch smoothly.

Again, if it is purely mechanical, great, but quite a few sources might be wrong. It is, however, inline with lots of feedback.

 

[mschwett]

There is also talk of the electronics queuing shifts creating potential delays. Multiple sources talk about electronically delayed shifts (I am not saying they are right, only that others have a different view, no idea what the truth is). My assumption was that the system knows the relationship of the cassette to the shifter since all distances are now fixed due to udh. As such, the shifter doesn’t need sensors, it knows the exact location of the cassette at all times from calibration. So it can perform the shift at the exact point when the cassette would catch smoothly.

Again, if it is purely mechanical, great, but quite a few sources might be wrong. It is, however, inline with lots of feedback.

early reviewers have mentioned that it couldn’t yet do multiple shifts at once because the latest derailleur was embargoed in the app until
the official release date, so it couldn’t be set up to do so.

think about what you’re saying. how on earth does the spacing between the cassette and the RD mean that the RD knows what position in rotation the cassette is in at any time? totally unrelated. you can walk up to the bike and spin the cassette backwards without the bike moving, and depending on what gear, it’ll result in a different amount of crank movement. similarly roll the bike and the wheel moves but the cassette does not. watch the tear down and install reviews - there is no sensor in the RD / cassette to somehow tell it where in the rotation it is.

it seems like a huge improvement but not because they’re added more electronics to it

 

[dynamic]

think about what you’re saying. how on earth does the spacing between the cassette and the RD mean that the RD knows what position in rotation the cassette is in at any time?

That's a good point. The derailleur would have to be able to track chain movement via its sprockets rotation or equivalent. Otherwise it really needs to be purely mechanical. However, reviews are not corroborating that.

The delays people report in shifting don't seem like delays that can be *purely* mechanical given how many shift points are on the cassette.

ANyway, here is a review: https://enduro-mtb.com/en/sram-eagle-transmission-groupset-review/
with this quote:

If you shift more than three gears in quick succession, the shifting process is noticeably delayed, ensuring that the chain is always securely meshed with a maximum of two different cogs, thus allowing you to keep pedalling at full force without putting your drivetrain at risk. Due to this delay, it skips shifting ramps and thus allows the chain to catch up before starting the next shift. However, the shifting speed – or rather the delay – differs depending on which gear you’re shifting from and the number of gears you’re shifting.

This site suggests it is a purely programmed delay to give the chain the time it needs to settle to the new gear and then goes on to the next shift. If it *is* purely mechanical with a programmed delay, then great. Seems to be working brilliantly. The other issue I have read is reports that the delay isn't identical. Meaning, sometimes the shift just takes longer than other times. Now, the delays would *have* to be different between different gears. But if one went longer than normal (missed one or more ramps for whatever reason) That could be bad for a purely programmed delay.

This programmed delay also helps explain the lack of a mechanical version of this shift system. I still think the electronics is doing *something* even if it is a simple shift delay.

I am curious what this thing does when shifted while stopped. If it has zero sensing, it should be amazingly easy to confuse in that scenario. I suppose the chain would eventually catch up just like a normal bike.

 

[mfgrep]

I haven't been a member here for long but have noticed that you don't like chains and you demand/expect crisp and precise shifting.
As a result you seem to be drawn to some complex bicycle transmission types.....some of which are quite new.
Given your apparent propensity to seek some 'perfection'.....have you ever considered that the more complexities within any given 'system'.... the more mechanical/electronic troubles you are likely to experience?

I am a bit OCD myself but try to limit those tendencies with a healthy dose of reality based common sense.

 

[dynamic]

have you ever considered that the more complexities within any given 'system'.... the more mechanical/electronic troubles you are likely to experience?

Every day. But, honestly, mostly that's not a valid statement. Lots of complex things *can* be reliable. The real problem tends to be early versions of those things. How reliable do you think the first chain derailleurs were?

What I want is a shifting experience that doesn't interrupt the riding experience. I have yet to experience that on any bike with a chain. I suspect the pinion smart shift system would be nearly as good as the enviolo automatic in that respect.

Again, I don't bike to ride a bike. I bike to be outside and see the country while getting some good exercise. If there were another way to do that and not bike, I would go try it.

 

[mschwett]

That's a good point. The derailleur would have to be able to track chain movement via its sprockets rotation or equivalent. Otherwise it really needs to be purely mechanical. However, reviews are not corroborating that.

The delays people report in shifting don't seem like delays that can be *purely* mechanical given how many shift points are on the cassette.

ANyway, here is a review: https://enduro-mtb.com/en/sram-eagle-transmission-groupset-review/
with this quote:


This site suggests it is a purely programmed delay to give the chain the time it needs to settle to the new gear and then goes on to the next shift. If it *is* purely mechanical with a programmed delay, then great. Seems to be working brilliantly. The other issue I have read is reports that the delay isn't identical. Meaning, sometimes the shift just takes longer than other times. Now, the delays would *have* to be different between different gears. But if one went longer than normal (missed one or more ramps for whatever reason) That could be bad for a purely programmed delay.

This programmed delay also helps explain the lack of a mechanical version of this shift system. I still think the electronics is doing *something* even if it is a simple shift delay.

I am curious what this thing does when shifted while stopped. If it has zero sensing, it should be amazingly easy to confuse in that scenario. I suppose the chain would eventually catch up just like a normal bike.

right, the delay varies because the system knows that it takes time for the cassette to go around to the point where the chain hits one of the shift points. of course it knows what gear you’re in, and how many ramps there are in each gear, but there is absolutely no evidence or claim that it knows how fast the cassette is going around or in what position it is.

i think it’s pretty smart that they designed the ramps to shift better and faster under load.

since it’s just a dumb “delay” what happens if you shift while stopped is that the derailleur moves over after a tiny delay, and it sits there with some sideways tension on the chain until you start moving, at which point it shifts. if you keep shifting, the tension becomes too much to overcome in such a short angle and it just won’t move any further. the RD a knows what position it is in, so it knows what’s going on and either gives up or queues it, not sure which.

 

[rochrunner]

right, the delay varies because the system knows that it takes time for the cassette to go around to the point where the chain hits one of the shift points. of course it knows what gear you’re in, and how many ramps there are in each gear, but there is absolutely no evidence or claim that it knows how fast the cassette is going around or in what position it is.

I'm pretty sure that I listened to a podcast where a guy from SRAM explained the system in such a way that it somehow *does* know the position of the cassette and then moves the derailleur at just the right time to catch the ramps. I'll do some digging on this when I get a chance...

 

[dynamic]

I'm pretty sure that I listened to a podcast where a guy from SRAM explained the system in such a way that it somehow *does* know the position of the cassette and then moves the derailleur at just the right time to catch the ramps. I'll do some digging on this when I get a chance...

Exactly. Same for me. And I have seen that implication passed on by various forums and blogs.

For me, it doesn’t really matter as long as the transition is smooth and doesn’t interrupt my pedaling. If my sirrus x 4 were compatible with the gx eagle transmission, it would be ordered already. To try it before buying an ebike to put it on.

 

[Ben J]

I don't see why people would find it unlikely. I can think of lots of ways that the derailleur could know the phase of the cassette. And given the way they are designed with optimal shift points, it's an obvious feature to add to an electronically actuated derailleur.