I know the 1x or 2x gravel question has come up a few times in the past but I have a slightly different take on the question. I’m looking at buying a Cervelo Aspero and trying to decide between one with a 2x GRX Di2 and 1x Rival XPLR. I plan on using this bike as both a road bike and gravel bike in Minnnesota, where the terrain is mostly flat and I’m worried about the gearing limitations of a 1x when riding on the road. That said, I do plan on having two sets of wheels so I’m wondering if there are specific thoughts on maybe doing a road set of wheels with a different cassette that is more geared towards road riding or if that would be insufficient and people still think going 2x is better if I plan on doing more road riding? Has anyone done something like this with a 1x SRAM? If so, what did you choose in terms of your cassette and gearing set up for the road set up?
If you are going to be doing group rides with the Aspero, chances are pretty high you will not have enough top end gearing.
If you are just going to be riding solo and relatively casually, you can probably make do with a gravel 1x system on the road.
Hey @dthansen,
This is a great question and one I’ve pondered for quite a while myself.
After having many, many bikes with all sorts of different setups, I’ve come to this realization:
1x works well in situations where you’re not constantly pedaling (XC MTB, some technical gravel, etc.), but when consistently pedaling, I find that I much prefer to be able to keep my cadence where I want it and make smaller shifts to adjust to the terrain. Otherwise, I’m finding myself at either the wrong cadence or sacrificing power when the terrain subtly shifts.
I’ve never had any issues running 2x on rough roads or gravel, so I’m not sure what the advantage of the 1x system is. 
Some say simplicity, but we’re still talking about bikes here. Learn your drivetrain and set it up well, and I don’t see where the issues could come from. The front derailleur has been around for a long time – we should all know how to use them! Besides, many gravel-specific rear derailleurs have plenty of tension to keep your chain snug nowadays.
My issue with 1x is that I always feel like there is a compromise. I’ve built up gravel bikes for fast road riding with bigger chainrings and smaller (11-34ish) cassettes, which work fine around here (I’m in northern Wisconsin) since there aren’t any sustained climbing efforts. The gearing isn’t as low as it is with a 2x system, and I’m left muscling up the punchy climbs, which, in all honesty, I love doing, but the question I’m left with is why? I could still do that with a 2x system if I wanted, and I have backup gears too! They’re there for me if I want to ride easy and stay seated throughout all of my “climbing.” 
So much tech trickles down from MTBs, and 1x is just another example. It can be a great option for some of the examples I listed earlier, but I just don’t see any benefit to having a huge chainring and a 52t cog on my gravel or road bike. In my honest opinion, I think it’s a trend that is likely here to stay but will find its place before long. The pendulum has swung in one direction, and it will settle down soon.
The nail in the coffin in terms of your decision here is Sram vs Shimano. I’ve worked in shops and built, serviced, and warrantied everything from both brands, from new out of the box and bikes with 10s of thousands of miles on them. In my opinion, there is no comparison in terms of quality or performance. Sram looks cool and has a good design philosophy, but Shimano works better and is built wayyy better. I’ve owned bikes of every kind with groupsets from both brands, and I made the decision a few years ago to only move forward with Shimano. I don’t think that every single part of my bike needs a lithium battery, or to be hidden inside of carbon fiber, or wireless, and Sram is definitely going that route. 
I’m sure this will go against the grain for some, but I have a good hunch that if you asked any truly seasoned mechanic which they prefer, you’d get Shimano 9 times out of 10.
My latest bike that I built for the type of riding you’re planning on doing had GRX 46/30 chainrings and two wheelsets. One with an 11-30 cassette (1:1 is plenty good for road riding around here), and the other with an 11-34, just for a little extra when I want to take that bike on the unmaintained rocky gravel roads (Shimano also makes an 11-36 now too!). If you’re stronger than me, then a 48/31 would work, or even a 50/34, which is what’s on my road bike.
Either way, you’ll probably be happy with your bike, but my opinion is: 1x on my MTB and 2x on most everything else. A drop-bar bike is supposed to be versatile, and you’re losing some of that with a 1x setup. It’s either not fast enough on the road, not slow enough on the climbs, or your jumps between gears are truly enormous.
Get your GRX dialed in and you won’t have any issues. 
Existing topics worth look:
- 1x curious, let's talk about it (road bikes only)
- Basic 1x Road conversion
- Sram axs 1x for all things road
- 1x vs 2x on gravel bike
- Gravel Bike Set up: 1x or 2x
- Gravel bike -- 1x vs 2x
Personally, I couldn’t imagine using 1x for road and I also prefer 2x for gravel for the tighter steps in the rear.
If terrain is flat, there should be zero gearing limitations for road with 1x if you size your chainring properly. I’ll run a 42 or 44 on my gravel bike and use it for fast group rides all the time. Sure, there are times a 46 would make my cadence more comfortable, but you aren’t getting dropped due to gearing if you are running a 44 (or even a 42) ring up front with a 10 cog in the rear (Unless you are racing at the very pointy end with the pros). But if you are that strong, you are strong enough to turn a 46 or 48 ring without issue. The biggest advantage of 2x in my opinion is the smaller gear jumps. I used to be a die hard 2x guy and pretty sensitive to gear jumps, but after swapping between 1x and 2x on the gravel bike for a year or so, I prefer the 1x and don’t even notice the gear jumps. The flexibility is a big selling point for SRAM in my opinion. With the AXS system, you can swap between 2x road, 1x xplr, and 1x Eagle setups in a matter of minutes. Best of all worlds. I still have 2x on my road race bike and don’t really have a desire to go 1x there, but I hardly ever use that bike because the gravel bike is more comfy and plenty fast for road. As a guy who runs both Shimano di2 and SRAM AXS for multiple years (and do all my own wrenching), they are both great and I’ll never go back to mechanical. That said, I prefer SRAM AXS these days based on the wireless aspect and flexibility to mix/match road/gravel/MTB groups.
I bought a trek Boone last year that came 1x GRX. I paid to buy a left shifter, front derailleur, and 2x crank to have it as 2x and ride it as both my road bike and for CX/gravel. Financially, it wasn’t the smartest idea but I was used to the geometry so wanted to stick with the brand. I’d recommend the 2x - you can always run easier gearing. 1x is a gimmick
This^^. If you are more on casual side you could make it work.
Went through this exact debate and also ride in MN. Got an Aspero
Largest chainring you can get is a 44t on the Aspero. Shop said they wouldn’t install larger and warranty would be invalidated.
I have another groadie bike with 46T and 10-42 cassette. I did the one bike for both road and gravel with two wheel sets. Worked fine in very fast group rides and gravel. Even worked in mountains of CO. Never got spun out on either side of the cassette. However, chainline not optimal unless you are climbing (which is mostly rare in MN)
Long story short. This one is easy. Get the 2x. Also, the DI2 hoods are really, really nice in comparison to the 1x SRAMs (whose primary benefit is dead simple to use)
I’m a big fan of mullet gearing (big 1x chainring in the front and a mountain cassette in the back) for mixed road and gravel riding. The compromise with this setup is you have to be a little more flexible with your cadence due to the bigger jumps between gears, which in my opinion is really not a big issue. Given the options you listed though I would go with the 2x GRX for sure.
I have 1x13 on my gravel bike (3T Exploro Racemax eKar) and absolutely love it.
I use it for road and gravel with different wheelsets and don’t feel like I am missing any faster gears.
What you will miss, and @mcneese.chad alluded to this above, is the smaller jumps between the easier gears that you get with on a 2x bike.
I only find this a bit annoying on long steady ascents where sometimes I feel like I need to be between gears in order to ride at my preferred cadence and power.
A very handy guideline, IMO, is that for bikes that will largely have knobbly tyres, 1x arguably makes more sense, while bikes that’ll typically wear slicks usually make more sense in 2x.
I have Rival XPLR on my gravel bike (with a 42t up front), which I also use for audax with a second wheelset. For solo road riding I have no issues with the 1x setup whatsoever. I have used it in a fairly pointy group ride, and while it was ok, 2x would have been a definite advantage.
I’m going to play devil’s advocate slightly on the SRAM/Shimano front, though. Yes, Shimano does work slightly better in terms of shifting speed. I also think the brakes have more feel.
However - and I acknowledge I haven’t worked in a bike shop and hence seen the range that @eddiegrinwald has - I’m not convinced by the reliability and build quality argument. There seem to be recurring issues with leaky Shimano callipers, the 12sp pulley wheels last about 5 minutes, and we also know exactly what happened with the chainset issue.
I also think AXS gearing makes more sense for anyone south of 5w/kg, the shift logic is much more viable in gloves, the app is miles better and I really like being able to carry a spare battery.
Having said all that, for the OP’s stated purpose, I’d run 12sp mechanical GRX (2x, 48/21) with an AXS 10-36 cassette on the rear (yes, it’ll work well with an AXS chain). 
- likely a typo above and should be 48/31
- Flat top roadie AXS, original AXS MTB 12s, or new AXS Transmission flat top MTB 12s style?
Sorry, yes - 48/31 - typo.
And flat top road.
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I will just restate the fact that I think using that SRAM AXS Flat Top roadie chain (with oversized rollers) on a Shimano crankset designed for the most common 12s chains around is not ideal.
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It works in that the chain goes around everything but there will be wear on parts that is not intended with this suggested mix. Likely loser here would be the aluminum chainring teeth getting smashed from the larger steel chain rollers, but I could be wrong once you factor in the literal part strengths due to material shaping. Either way, not a match made in heaven IMO.
I’m a believer in 1X for all the bikes, but I don’t regularly ride road. And just about never do a group ride. Maybe I will ride with 2-3 friends on the road. So I would not say it’s a gimmick, it appears that it will be around for a long time.
Just installed the newish 12spd GRX RX820 on my gravel/CX bike. So far I really like it coming from SRAM 11spd. It also works well for me since I already have 12spd Shimano microspline drivetrains on my MTB’s. So I was able to swap over an XTR cassette and had spare HG+ chains. I went with the “Unbeatable” 10-45t RD offering.
I work at a bike shop, and it amazes how much of a pain it can be working with front derailleurs. Despite servicing/adjusting several every week. Even on new builds, between them and low end hydraulic disc brakes it’s such a time suck
I much prefer the ‘simplicity’ (even if some of that is conceptual) of a 1x system, but I’d probably need a 1x14 to have a set of ratios that I’d be completely happy with for all the road riding I do without excessive gaps. Ekar is probably the closest but it’s definitely a quirky option.
I wonder if the Classified hub is really the best of both worlds for an all-road bike. Having said that, almost all higher end modern FDs work so well, there is a hint of a solution looking for a problem, and (for me) the fact they won’t make a cassette starting at 10t is the dealbreaker. I want a 2x AXS setup without an AXS FD, Classified!
I’ve thought about a Classified PowerShift hub to have 1x up front but a 2x in practice. I run XPLR with 10-44 and a 40t up front and the PowerShift doesn’t really get me much better range overall. The main advantage seems to have a bunch of close gearing available. Not a small thing if you are on the pointy end of things, but for me in the soft and creamy middle, hard to justify the incremental cost of PowerShift over a decent mid-range carbon hoops.
Fellow upper Midwest resident here, I’m in the northwoods of WI which is fairly flat. I ride my gravel bike almost anytime I’m out. I have a 46t in front and and an 11-40 in back. Once in a while on a long false flat or downhill I’ll spinout but nothing too bad. On the other hand, I haven’t had to deal with anything too steep for my 40t either. That said, I’ll probably go back to 2x. I like having the wider range and small jumps between gears.
I think you’ve got some Aspero specific comments above. Some of what I say below may not apply to Aspero on the max sizing of front chainring.
Recently purchased a Trek Checkpoint SL6, it can handle up to 46T on 1x setup, or 50/34 (Shimano) on a 2x setup. My Tarmac race bike is running a 46/33 2x setup. Going to be honest after 2 years with SRAM, there is very little difference between Shimano and SRAM. Although the 2015 vintage Shimano Ultegra shift levers would break cables after about 5000 miles / 1 year. Otherwise they both work fine, reliable, serviceable, etc. I’ve been told one advantage of SRAM is you can easily trim the derailleur while riding, but Shimano may have that now.
All that said, for 1x setup I have both 40T and 46T chainrings. The 46T is for flatland, and paired with a 10-52 cassette / rear derailleur. Same top-end gear as the Tarmac with 46/33 and 10-36 cassette, but the 1x has a lower gear which works out to something like +3 or +4rpm at 5mph when grinding up a steep incline. I’m not sensitive to large cadence jumps, and will typically wind out to 95-105rpm before shifting down into the 80s (depending on the ride). Apparently some people demand closer gear ratios.
Its completely flat where I live, with really bad roads (‘gravel’ can be smoother LOL), but within 60-90 minutes I can climb straight up to the summit of the Sierra Nevada mountains. Or drive to the CA coastal mountains, closest HC climb is 90 minute drive and its straight uphill for 3500’. In the past I’ve done gravel events on my Tarmac in the coastal mountains, it was fine and having some trim adjustment on the SRAM levers was nice because on climbs I slam it into the 33T chainring and then use a few of the lower gears on the cassette. Will be nice to have lower gearing on my 1x Checkpoint.
Back in March I rented a Checkpoint SL5 for BWR Arizona, it had Shimano GRX 2x setup with 46/30 crank and 11-34 cassette. It was fine on a couple steep gravel climbs, would have been better with a little lower gearing. As far as I’m concerned there is no real advantage of Shimano over SRAM, although I prefer SRAM’s left / right lever tapping approach to shifting up/down on gearing. Shimano hollow tech crank arms have some minor issues with power meter accuracy, and Shimano doesn’t have a good story on power meters.
I run a 40t up front and 10-44 rear for gravel and 10-36 rear for road on an Aspero. It’s realistically enough gears for me unless I want to push a downhill on the 40/10. Looking at the axs stats, I don’t nearly touch the 10 tooth as much as I expect. Imo it’s whether you like the front derailleur. I really dislike having the manage which front ring I’m using and would rather have a simple up/down at the expense of bigger gaps slightly less head room at the top end
A few other considerations on 1x vs 2x that I haven’t seen mentioned -
1x provides more tire clearance on many frames (the FD can be a limiter).
Simplicity of 1x - A modern 2x drivetrain is pretty reliable, but things can get tough when you are off road. Especially racing in serious mud.
Chain retention - A 1x setup will have a narrow/wide chainring which is less prone to drops. A 2x setup is more prone to drops, but the FD can be helpful retaining the chain and often get it back on the ring without stopping. I strongly prefer 1x for rough off-road situations and I’ve never dropped a chain on MTB or Gravel running 1x (not saying it doesn’t happen, just not to me yet). I could see a case for either 1x or 2x based on chain retention, I think it’s just preference.