SRAM RED AXS & Power Meter (2024) In-Depth Review

SRAM has announced their new SRAM RED AXS system, complete with a Quarq-based power meter. Depending on your perspective, you’ll either be focusing on the weight savings, or the tech integration. Around these parts, it’s gonna be the tech integration aspects rather than weight bits. After all, I can save weight (and money) by just eating less ice cream. However, I’ve been riding with the new system for over two months now, and so I’ve got some thoughts – both on the SRAM RED AXS system as a whole, as well as all the tech integration components.

The new system increases integration of shifting and control components to bike computers, allowing not just Hammerhead, but also Garmin & Wahoo to integrate more deeply for controlling your bike computer from your handlebars. Of course, Hammerhead also announced their new Karoo 3 unit, which I reviewed separately here. The focus of this review is primarily the tech side of it, rather than things like braking performance or weight components. That’s just what I do.

Further, this review will cover the power meter within the 2024 SRAM RED AXS groups, and dive into the accuracy of it. Given roughly half of the pro-level WorldTour teams are using it, we better make sure it’s accurate. Wouldn’t want WorldTour teams using inaccurate power meters now, would we?

Finally, as usual, note that this review isn’t sponsored by anyone. I was provided a loaner Specialized Roubaix bike from SRAM, with the new groupset installed (along with a loaner Hammerhead Karoo 3). That’ll all go back to them soon. Likewise, I attended a media event a few months back, but paid for all my own travel & accommodations to/from said event. If you found this review useful, you can use the links at the bottom, or consider becoming a DCR Supporter, which makes the site ad-free, while also getting access to a mostly weekly video series behind the scenes of the DCR Cave. And of course, it makes you awesome.

The Geeky Specs:

The big ticket story on the SRAM RED AXS (2024) system is the weight reductions, reducing it by 150g compared to the previous groupset. From a power meter standpoint, the unit claims +/- 1.5% accuracy, and has chainring options for 50/37T, 48/35T, and 46/33T, using integrated chainrings. It’s available in 160, 165, 167.5, 170, 172.5, and 175mm crank lengths. SRAM notes the entire power meter setup is now 29g lighter than previous.

Now, as stated above – I’m not a weight weeny geek. I’m a chipset geek. But, I know a lot of you are. And equally, SRAM produces (by a massive margin) the best media kits out there in the entire sports tech industry, in terms of geeky tech specs. Seriously, I have like 6 different absurdly deep tech guides in half a dozen languages, and it seems a waste of some poor person’s work to not let others see that. On past SRAM reviews I’ve simply uploaded these, as people have said they really enjoy the geekery. Thus, I’ll do that here as well. Here’s the main product spec book (including prices and more):

In terms of the test bike I was riding, it was the also-just-announced Specialized S-Works Roubaix SL8. It starts at $13,000USD, though as configured would undoubtedly be more, given it had Zipp’s wheel set on it, which runs roughly double the Roval Terra CLX II on the stock Roubaix. So I’d guess this is a $15,000+ bike. Or roughly, 3x the price of my cargo bike.

Here’s a small gallery of it:

I know a lot about sports tech that has chipsets and transmission stuffs in it. However, when it comes to things like tension of the Future Shock system on the Roubaix, or ride firmness, it’s all greek to me. Instead, my friend James over at Escape Collective actually writes about that stuff in-depth, and specifically this exact bike. He and I tested the same bike, except his is matte black, whereas mine was “Gloss Taupe/Gunmetal Strata/Charcoal”. Relatedly, my 7-year daughter asked why my bike looked like it went through a puddle. I didn’t have a good answer there for her.

As I said though, I don’t review ‘bikes’. I review the connected tech on said bikes. But, the bike was a nice ride over the nearly 1,000km I put on it. When I pedaled it moved forward, when I braked it stopped, and ultimately I didn’t crash. The bar for my bike review success is very low. Inversely, the bar for my power meter and connected tech reviews is very high. However, I will talk about the new SRAM RED AXS shifters down below, notably the bonus button bits.

So, let’s get into it!

Shifting App Integration & Options:

Starting off with the shifting side of things, we’ve got the new shifters alongside the new front and rear derailleur. Setting aside weight savings and material changes, the biggest and most obvious tech improvement here is the addition of the new ‘bonus button’ on the  inside of the hoods. Alongside that, is the ability to now set this button, as well as the Blips, to control various functions on your Hammerhead, Wahoo, and Garmin bike computers.

However, as with before, all of this is tied into the SRAM AXS app. That’s SRAM’s app for configuring all of the shifting options, including more mundane things like which cassette you’re using, the shift preferences, and so-on. However, the app also now pushes these details to the Hammerhead platform/bike computer, which enumerates pretty cleverly as I’ll show in a second.

First though, diving into the app you’ve got your bike garage. In this case, I set up the Roubaix as a new bike, and then scanned for the nearby components, which requires confirmation by physically pressing buttons on the bike itself. The AXS app supports multiple bikes, so I’ve got some of my other bikes in there as well.

Once added in, you can see each of the components listed and their battery status (RD = Rear Derailleur, FD = Front Derailleur).

If we tap into the configure controls menu, you can see each portion of the controls broken out. It’s here that I can vary the shift methods, as well as the bonus buttons. Same goes for the blip buttons.

With SRAM AXS, the default method is that you use the right paddle to upshift the rear cassette, and the left paddle to downshift the rear cassette. To shift the front derailleur, you hold both together (hence the ‘Combination Actions’ term). It works well of course, and is one of the things SRAM likes to say makes the system easy to use.

I go back and forth between Shimano Di2 and SRAM AXS depending on which bike I’m on, and both systems are perfectly easy to use, and perfectly fast. There’s just no meaningful difference between the two in terms of responsiveness or reliability. They just work.

Within the SRAM AXS app, you can micro-adjust directly from the app:

The other big difference between Shimano/SRAM is really the battery tech/design. In the case of Shimano, you’ve got a singular battery that’s connected via wire to all components. Whereas in the case of SRAM, it’s totally wireless with the two derailleurs having small batteries at each point, and the front shifters relying on coin cell batteries that should get about 2 years of usage. Whereas, the stick-on shifting Blips have non-removable batteries (though claim a 4-7 year battery life). Here’s the SRAM AXS/eTap battery (which has remained the same since the eTap days):

Shimano, for their DuraAce system, claims a battery life of 1,000km between charges, whereas SRAM claims 60 ride hours between charges (assuming 25-30KPH average speed, that equals 1,500-1,800km. But practically speaking, I find that SRAM’s batteries tend to slowly de-charge when not in use faster than Shimano’s. Still, both batteries are silly easy to charge, I appreciate that I can easily have a spare battery on on a shelf when I need it.

SRAM still uses micro-USB in their charger though, which is annoying:

However, that’s very easily solved by picking up this cheap $19 one on Amazon, which is a double-charger, and is USB-C:

SRAM also sells a quad-charger, but I don’t have that. That’s more useful for (mostly gravel/MTB) folks with other SRAM components that leverage the same battery.

In any event, we got distracted with our battery sidebar here. So, let’s get back to the shifting, and in particular, the new bonus button. This new extra button is located on the inside of the shifter, near the top, it’s the little square you can see here (there’s one on each side):

By default, this button will essentially just act as another shift button. But for most people, that’s not super useful. Instead, you want it to do something else. For many years Shimano has had the same concept, which bike computer companies have then been able to assign to various actions – the most common of which is changing your display pages on your bike computer.

SRAM does the same here, and there’s a bunch of ways you can configure it. Starting off from the AXS app, you’ve got 8 different morse-code style patterns you can use. The default of course is just tapping it once, but you can do all sorts of other combos, as you see below:

From there, you’ll go over to your bike computer and set up what you want it to do. If we look at the Hammerhead Karoo 3, it’s very deep on the list of options. First though, notice how I’m looking specifically at the shifter bonus buttons here, but I can also do the Blips individually as well. To get there, you’ll see your groupset listed:

And then tap the AXS system, where you can change gearing and controls:

You’ll choose the exact button you want (bonus or blips), and then choose which action you want. This could be an AXS Action (e.g. shifting), or a Karoo action (a gazillion other things):

Just a smattering of the options:

From a technical standpoint, all of this works great. You can see it in my Hammerhead Karoo 3 video, where I show changing data pages with the bonus button (and, of course, just using the buttons on the bike computer itself).

Also, before I forget, you can see battery and shift status on virtually all bike computers out there. SRAM uses open standards (the ANT+ Shifting standard), and doesn’t block any companies from accessing it (that’s kinda the magic of using open standards like the rest of the industry). Here’s a photo from my ride a few weeks ago:

That said, from an ergonomics standpoint, I didn’t love the button. There were two specific things I didn’t love. First is that it felt like it was a bit of a reach from my usual position on the hoods, to that (keeping in mind that as a 6’2” tall dude I’ve got pretty big hands). Of course, that could be more specific to my exact hand placement than anything else. When I asked SRAM why the buttons weren’t in a bit lower and easier to access placement (like other indoor bikes have it, which is more natural), they said they “Really wanted to stay out of the unintentional shift area”, noting they didn’t want a scenario where someone hit a bump while sprinting and then accidentally shifted due to the hands pressing down on the button. Which is fair enough.

But that piece doesn’t really answer the next aspect – which is the tactile feel of the button: It’s not easy to detect blindly while riding. If you were wearing bigger gloves, it’d be very hard to make out the button, let alone try and press that tiny thing. Thus, while I (very much) appreciate SRAM adding said button, I just wish the ergonomics of it were a bit improved.

In addition to the bonus button, you can configure the Blips the same way, to control specific items on your Hammerhead (see above for those photos). As a reminder, the Blips can be placed wherever you want. Here’s one underneath the handlebars:

Now, as noted above, the new Bonus Button shifting isn’t limited to just Hammerhead. SRAM says that Garmin integration is coming very soon, and Wahoo already announced theirs concurrently yesterday.

Here I’ve configured the Wahoo ROAM V2, to use the Blip buttons to change data pages. The entire setup process took like 7 seconds, given I already had the ANT+ gear shifting info configured on the ROAM.

Lastly, it should be mentioned that there’s more than just the SRAM AXS app. Sure, that’s kinda critical for configuring this whole thing, but SRAM actually has a full dashboard too. That dashboard will show all your shifting history and ride data. This data gets synced from your Hammerhead Karoo, Garmin Edge, or Wahoo Bike computers, and there’s some shifting-focused stats here (here’s one of my rides):

It’ll also then look at the battery information in those ride files, and alert you after the fact via the app (and e-mail), reminding you to charge batteries as needed.

The SRAM AXS site hasn’t really been upgraded much in the last few years since launch (or at least, that I can tell), and probably is a prime candidate to somehow share the same platform/site as the Hammerhead one. That said, you do get roughly the key shift data over on the Hammerhead site, here’s that same ride displayed there:

But of course, I appreciate that for Garmin/Wahoo users who don’t have Hammerhead, you can still do that on the SRAM side directly.

Finally, if you’re looking for a more bike shifting type review though, I encourage you to read Dave Rome’s review of it. He and I spent some time riding in the cold rain in Italy together on the new groupset, and he is much more keen on the nuances of non-chipset bike components and geekery than I am.

SRAM/Quarq Power Meter:

Next up is the SRAM RED AXS power meter, which is powered by Quarq technologies. Though, this is the first time you’ll notice that the Quarq logo is gone, replaced by just the SRAM logo. There’s also no external visual mention of it being a Quarq power meter (the app does still call it Quarq however).

While the groupset can be purchased without the power meter option, the assumption is that most OEMs will spec a bike with this price with the power meter. This unit maintains SRAM’s existing (controversial) integrated chainring. Meaning, if you need to replace the chainring, the power meter goes with it too. How long chainrings last is up for internet debate, though the general consensus is 20,000-30,000 miles (32,000-48,000KM). For SRAM RED AXS, SRAM offers 50% off for the replacement of said combined rings+power meter, though, that’s only good if you do it in the first 5 years.

In any event, the battery on these is user-replaceable, and is a standard CR2032 coin cell battery that should get you about a year or so of usage before simply swapping it out. That’s done via the little battery compartment on it.

Note that a key difference between the SRAM RED AXS power meter, and SRAM’s other RIVAL-based power meters, is that the SRAM RED AXS unit captures your total power. It doesn’t technically measure left and right power independently, but rather estimates it based on upstroke/downstroke. Still, the total power is absolutely measured. Whereas for SRAM’s RIVAL-based power meters (including the default units in a FORCE/APEX/RIVAL/XPLR), those measure only the left-side power via a bottom bracket power meter. They then take that left-side power and double it. With the SRAM RED AXS unit, it’s instead measuring it via the chainrings, and thus can measure total power from your legs.

The SRAM RED AXS power meter broadcasts across both ANT+ & Bluetooth Smart as a power signal, this means it’s fully compatible with pretty much every bike computer and watch on the market. During my testing timeframe, I used it on rides with: Hammerhead Karoo 2, Karoo 3, Garmin Edge 840, Edge 1040, Garmin Epix Pro, Apple Watch Ultra 2, Polar Grit X2 Pro, COROS Vertix 2S, Wahoo ROAM V2, and undoubtedly more watches and bike computers that I’m forgetting.

Within those ANT+ & Bluetooth signals are the following data metrics:

– Total Power (ANT+ & Bluetooth Smart)
– Power Balance (ANT+ & Bluetooth Smart)
– Cadence (ANT+ & Bluetooth Smart)
– Power Meter Battery Level (ANT+ & Bluetooth Smart)
– Torque Effectiveness (ANT+)
– Pedal Smoothness (Bluetooth Smart)

Technically speaking, it actually transmits torque and calculates watts, but for the purposes of simplicity on your head unit, you’re going to see watts.

To pair it up, depending on your head unit, it’ll either be automatically paired as part of your RED AXS set (if Hammerhead), or you’ll manually pair it as a new power meter (every other bike computer). In the case of Hammerhead, it’ll show up with the bike computer name (Roubaix), though does technically split it out of the larger AXS group. Personally, it’d be a bit cleaner to put it in (like the AXS app does). But hey, I’m pretty happy with the big group of components as is.

I will say, as I said in the Hammerhead review, this grouping of components by bikes is a super clean way to display groupset/power meter pieces. Nobody else does it this way, and it helps to avoid the messiness found on other units with tons of sensors. I’d love to see Garmin & Wahoo use that already-existing SRAM AXS platform/API connection, and get this data from SRAM, and do something similar. Of course, that’d take SRAM opening up their API, but it’s just presented very well.

Old timers might think this harkens back to the days of per-bike sensors, and while there are similarities there, I’d argue this is better. The key difference is this isn’t limited to a specific ride profile (though on the Hammerhead you can do that). Instead, it’s just logically grouped as a collection of parts that stick together, and tracked together.

Anyway, back on the power meter side again, if pairing on a Garmin/Wahoo/etc. unit, it’ll look just like it does for other power meters. From all of these units you can do a zero offset (calibration) at any time:

And a few seconds later, it’ll complete:

And likewise, you can do so from the SRAM AXS app as well. Further, the SRAM AXS app also lets you do static calibrations, and validations of the torque values. Additionally, it can perform power meter firmware updates.

You can also turn on/off auto zero from the Karoo as well:

With that all set, you’re off to ride as normal. You’ll see your power displayed, based on whatever you’ve configured on your specific bike computer. This includes any of the aforementioned metrics. Here’s a shot of what they looks like on the Hammerhead Karoo 2, as I rode along the other night:

And again, a different page from a few weeks ago:

For metrics like normalized power, average power, etc… All these are calculated from your specific bike computer. The SRAM/Quarq unit simply transmits this data over, and your bike computer does the work of figuring all that out.

Ultimately, from a user/riding standpoint, the unit worked flawlessly. As one might expect, given SRAM confirmed there are zero changes to the power meter side of the 2024 SRAM RED AXS unit compared to the previous SRAM RED AXS power meter. The only changes are external and cosmetic material-related changes, that’s it.

Power Meter Accuracy:

As noted just a sentence ago, the 2024 edition of the SRAM RED AXS power meter is identical to the previous edition – and thus should be equally solid in accuracy. But I’ve been around the block long enough to never quite trust any power meter company, no matter how big or well-known. In the case of manufacturing power meters, it’s always the tiny changes that get you in trouble, even unrelated changes.

So, I simply went out and tested the unit like I normally do. In this case, I’ve got a boatload of outside data across a number of different environmental conditions, and compared to a number of different power meters. I’m just gonna pick the most interesting/complex data sets though, as the rest are quite boring.

First up we’ve got an indoor trainer ride against a trusted trainer, the Tacx NEO 3M, which I’d argue is the most accurate indoor trainer on the market today. That’s compared with the also trusted Favero Assioma MX Pro power meters. As you can see, things line up quite nicely!

Same goes for the zoomed in look at one of the intervals:

The cadence is equally spot-on:

As is the mean-max graph.

Thus, let’s head outside.

Next, we’ve got a 100KM outside ride in the 93°F heat of Florida. This was a spicy one. The units had at least 15-20 minutes to get stabilized in the heat after getting to the ride location, and then a zero offset was done. This is compared to the also-new and the Favero Assioma MX Pro units:

One of the things I pointed out on my initial Favero MX review was that the Favero MX units had a slight tendency to smooth out more variable power, which in turn results in a slightly lower value. This isn’t as noticeable indoors, but seems to happen outdoors on roads that are more bumpy (in this case, very cracked concrete). It’s hard to see this above in a 3.5hr long graph of scribbles, but down below you can see it quite clearly:

And again here:

Whereas here’s a ride I did in Gran Canaria on mostly brand-new pavement, and thus far smoother. In that case you don’t notice the over-smoothing of the Favero MX Pro, and thus the Quarq and it are very closely aligned on this punchy interval workout along the coastline in the evening:

And here’s a random interval showing that off as well. Of course with surges like this you’ll see slight variations in transmission, but these are actually quite close:

And then looking at cadence, again, you can see it’s identical:

And the mean-max graph looks pretty good too:

Here’s another interval workout, this time on a very windy day, so a bit more variability in my powers, but still very close alignment again in this data set:

=

And here’s a close-up of one of the intervals:

And the mean-max looks good too:

Next, we’ve got a long climb in Gran Canaria up into the mountains. Here we can see that, on the whole, things look very close comparing these two:

Though interestingly, you can see some of the slight lowering of the MX power here and there as I’d hit minor sections of pavement that wasn’t as silky smooth:

Still, the cadence looks spot-on (the wonky stop/go section is the descent of course):

And the mean-max power looks pretty solid:

Next, I switched pedals to the Look pedals, so just a quick baseline against a trusted indoor trainer, the Wahoo KICKR MOVE/V6 (the V6 is the unit that slides atop the MOVE), with LOOK’s new power meter pedals on them:

As you can see above, the Quarq very nicely matches the Wahoo KICKR, which has proven itself accurate in countless other power meter tests. However, the Look pedals appear to be reading a bit lower than I’d expect.

Here’s a look at the cadence chart for this ride. Keep in mind that while the Wahoo KICKR Power is very accurate, the cadence is actually estimated and usually only accurate to within a few RPM. Thus in this case, the Quarq & LOOK power meters match exactly, which are both measured cadence.

Finally for that set is a mean-max graph. As expected, the Quarq & Wahoo units are virtually identical, while the Look unit is a bit lower. Given this was a relatively steady-state indoor trainer session, the scale of the graph makes the differences seem bigger than it is (since it doesn’t go down to 0w).

Lastly, one last ride I thought was interesting from earlier this week. This ride started in light rain, then I found myself in a thunderstorm for a bit (complete with lightning), before ending with light rain and mist. This was compared against the LOOK power meter pedals:

What caught my eye though were two brief moments after some form of stop (looks like a stoplight the first time, and not sure what the second time), where the two power meters differed very significantly. In this case, either the Quarq measured low, or the LOOK measured high. Without a 3rd source, it’s impossible to know:

Still, my gut here tells me the LOOK pedals were correct, and Quarq wasn’t. My rationale is that it’d be rare I’d be peddling at 80w for a minute or so. For my weight/etc, that’s well below easy-pedaling (which would be in the 130-180w range, as the LOOK pedals showed). Having taken a look at that portion of the route, I don’t remember anything distinctive/unique about it, though it was at the exact same time as a few lighting strikes (apparently about 2 miles away). Perhaps there was something wonky going on there. I have no idea. Nor can I say which one is right/wrong.

Here’s a look at the cadence & speed for that exact same snippet. As you can see, both before/after the ‘split’

Likewise, here’s the left/right balance, which shows evenly split, but just half the values on Quarq.

After seeing that quirk, I went back through every data set over the last two months, and haven’t found any other scenarios where it did that. Most of these data sets were on the Favero’s (with the Quarq), so that might be an indication the opposite of my thinking, and that perhaps it’s a LOOK issue. Again, I simply don’t have conclusive data one way or the other.

Setting aside that bolt from the sky-induced error, I see nothing of concern in any of my data on the new SRAM RED AXS power meter by Quarq. Which means that if you’re a UCI WorldTour Pro Team, you know your data is actually usable. Good luck to the rest of them!

Wrap-Up:

As is often the case in many established technological areas these days, we no longer see the major leaps in features or advancements. Instead, it’s more moderate and incremental changes. That’s mostly the case here with the new SRAM RED AXS as well. Individually, there are some nice upgrades in the system, but holistically, most existing SRAM AXS users won’t likely see a huge difference in daily riding – except the addition of the bonus button and customizable shift button integration with bike computers (or, lower weight if that’s your jam). Of course, depending on your perspective, that’s been a big item for many Shimano users for years – the ability to change data pages and such from their handlebars. While other never use it at all. Simply personal preference.

As I’ve said in my other reviews, when it comes to shift performance, almost nobody is going to notice the difference in the slightly tuned algorithms that SRAM says makes the rear derailleur shift slightly faster now. It was excellent in even their lowest level Apex AXS shifting system last year, and it’s still excellent now. Frankly, I’m happy with either. Which isn’t a slight on the RED AXS system (or my wallet), but rather, pointing out just how damn good Apex AXS is. Albeit sadly, minus the new bonus button.

Meanwhile, on the power meter side, it’s more of what we know. It’s not new, but equally, it’s not broken. It just works, just as it’s always worked for years. Quarq isn’t new to this game, and they demonstrate that accuracy and reliability here.

Ultimately, the vast majority of people aren’t going to go out and buy this groupset by itself to install on an existing bike (as the prices are quite high). Instead, it’s going to come on your next new bike at a price that seems acceptable. That’s simply the way the bike industry works, for better or worse. And if this ends up on your next bike, it’s a pretty solid product with plenty of tech integration.

With that – thanks for reading!