What’s the difference between a gravel groupset and a road groupset?
There’s a whole array of gravel bike groupsets available from all the major brands. But why do you need a gravel-specific groupset and what are the options?
Can you run road gears on a gravel bike?
Actually, for the first generation of gravel bikes, that’s exactly what manufacturers did, as there were no two chainring gravel-specific alternatives.
A few years back I rode plenty of gravel bikes with Ultegra groupsets. The mix of a 50/34T chainset with an 11-34T cassette gives adequate range if you’re riding mixed off/on-road. Some came with a 46/36T cyclocross chainset. One gravel bike I rode even came kitted out with a 52/36T chainset and an 11-30T cassette, upping my hillwalking quotient.
But there are good reasons for going for a gravel-specific groupset.
What’s different about a gravel groupset?
Modern gravel groupsets have features, often shared with MTB gearing, that make them a better choice for riding off-tarmac than a road bike groupset.
That starts with their clutched rear derailleur. The clutch helps keep the chain under tension when you’re riding over uneven surfaces, thus preventing your chain from slapping against the chainstay. That makes for quieter running and helps keep the chain planted on the chainring, meaning that you’re much less likely to lose your chain.
Gravel groupsets give you much lower gearing options too. A 1:1 ratio is fine if where you’re riding is fairly gentle, but as soon as you try to ride a hill off-road, particularly if the surface is loose, you’ll benefit from something lower that lets you spin up rather than trying to ride out of the saddle. Try to power up a loose, muddy climb and you’ll probably lose traction and spin your rear wheel and you may end up having to give up and walk.
How much lower than 1:1 you need obviously depends on the conditions and how fit you are, but particularly if you want to use your bike for a bikepacking adventure you’re gonna need a bigger sprocket. Take a look at our guide to bikepacking to see just how much you might need to carry.
Actually, it’s not just bigger sprockets but also smaller chainrings that gravel groupsets specialise in. The “super-compact” chainset is now a feature of most two ring gravel groupsets. That usually means either a 48/32T or 46/30T chainset (or something similar) paired with a conventional 11-34T cassette.
Coupled to those low ratios to tackle off-road obstacles, once you hit tarmac you want enough top end gearing to ride at pace, so gravel groupsets will be designed to offer a wide gear range. That’s usually expressed as the percent difference between the highest and the lowest ratio and will often exceed 500% for the widest range options.
It’s also useful to consider gear inches to make sure your available gears will work for your riding. With the smallest super-compact chainsets it’s relatively easy to spin out on faster road sections, but they can be a godsend on muddy tracks. There’s a good gear inch table here.
The chainline of gravel groupsets tends to be slightly wider side-to-side than road groupsets too. That means that you can’t always mix and match road and gravel components, but it does give a bit more clearance for wider tyres.
We’ll get onto single chainrings next and the gravel groupset options from Shimano, SRAM and Campagnolo afterwards.
Why go single ring?
Single ring (also called “one-by”) has the advantage that there’s less to go wrong and to collect mud than with a front derailleur. There’s less to interfere with tyre clearance and it’s lighter too.
A big plus of single ring groupsets is that, since the chain isn’t expected to jump between rings, the chainring can be designed so that it shouldn’t jump off the ring at all. A single chainring has much deeper teeth than a double set-up and alternate teeth are wide and narrow, so that they mesh more precisely with the chain links and also help shed mud. You could fit a chain guide to improve chain retention even further, although that’s not usually needed.
Another advantage of going single ring is that you only have one shift lever to deal with. The left lever is often a “dumb” brake lever that’s much less expensive than a combined brake lever and shifter. But it’s also freed up to operate a dropper post, which is becoming a popular option on gravel bikes.
The downside of single ring groupsets is that you have fewer gear ratios to play with and larger jumps between them. The difference to double ring groupsets is actually less than it first appears though, as two rings tend to give you some gear ratios on the large ring that are close to those on the small ring, so the actual number of discrete, different gear ratios is a lot less than the 20, 22 or 24 permutations that the gears offer.
With those ratios spread over 12 or 13 speeds, the jumps between them are getting ever-smaller too and the overall gearing range of some single ring groupsets can approach or better two ring set-ups.
Shimano or SRAM or Campagnolo?
Shimano’s gravel specific GRX groupsets come in 10-speed and 11-speed format. 10-speed is designated RX400. 11-speed comes in two spec levels, RX600 equivalent to 105 and RX800 equivalent to Ultegra. RX800 offers a mechanical and an electronic Di2 option, the latter designated RX815. All come in single chainring and double ring flavours.
Do the maths and GRX doesn’t offer quite the range of SRAM and Campagnolo’s options: 380% for single ring and a best of around 475% for two rings. That’s largely due to the cassettes starting with an 11 tooth smallest ring rather than 9T or 10T, but it’s probably enough for the majority of riders in most conditions and you can go below 1:1 for both single and double rings.
The clutch in Shimano’s GRX rear derailleurs can be switched on and off - there’s marginally less friction in the drivetrain with it off. GRX shift levers have a different design to Shimano’s road levers, with a little more to grab hold of and a matt finish that should stand up better to rough wear. Unique to Shimano, you can also fit an in-line hydraulic brake lever on the bar tops, to give you a second braking position.
With GRX having an 11-tooth smallest sprocket, a cassette will fit on a standard Shimano/SRAM 11-speed road freehub. Shimano doesn’t have specific GRX cassettes, but uses standard ones from its road and MTB groupsets.
SRAM was actually the early mover in gravel gearing and you can still buy its impressive single ring 11-speed mechanical Force 1, Rival 1 and Apex 1 groupsets. These run a 10-42T or 10-36T cassette with a clutched derailleur and a range of chainsets with between 38T and 44T suitable for gravel riding.
But SRAM has even more options for gravel riding with its XPLR 12-speed wireless electronic groupset range, available at Red, Force and Rival levels. XPLR repackages some of SRAM’s earlier eTap AXS components into a single ring gravel gearing ecosystem which uses a 10-44T cassette and can be paired up with a range of chainsets starting with a 36 tooth chainring. As with its road gearing, the 10 tooth smallest sprocket, rather than one with 11 teeth, lets SRAM use smaller chainrings to achieve similar gear ranges to Shimano’s.
If you prefer a two chainring groupset, SRAM’s got that covered off too with its eTap AXS Wide chainset. This has 43/30T chainrings, shifts the chainline slightly to the right for extra tyre clearance and gives you up to 516% gear range. It needs a specific Wide front derailleur. There’s also a wide single ring option, which again gives you a little more tyre clearance than a standard single ring chainset. Many of SRAM’s gravel chainsets can be upgraded to a power meter.
SRAM also gives you the option of a “mullet build”, where the shifters and single ring chainset from a gravel set-up are coupled with a SRAM Eagle eTap AXS 12-speed MTB rear mech and cassette, as the MTB rear mech uses the same wireless comms protocol as SRAM’s road and gravel groupsets. That gives you a huge 10-52 cassette for a 520% gear range - the largest available for your gravel bike. You may not need such low ratios or such a wide range, but it’s a useful option for extreme gravel riding and for bikepacking.
You’ll need a wheelset with an XDR freehub body to run SRAM’s cassettes, rather than a standard Shimano/SRAM 11-speed freehub.
Campagnolo was late to the gravel party, but its Ekar gravel groupset offers something different. For starters, it’s 13-speed and it’s very lightweight. It also has three cassette options, including a 9-42T that gives you a really wide 466% gear range with the first seven sprockets having one or two tooth jumps. There are also 9-36T and 10-44T cassettes available. At present Ekar offers mechanical shifting only.
Like SRAM’s gravel cassettes, you need a rear wheel with a specific freehub body to run Ekar though, in this case Campag’s new N3W standard. It is, though, backward compatible with 11 or 12 speed Campagnolo cassettes with an adapter and all Campag’s new wheels will come with an N3W freehub as standard.
Take a look at SRAM’s excellent post on gravel gearing options if you want more on gear ranges and ratios for different types of gravel riding.
Electronic v mechanical
If you want to go electronic with your gravel groupset, the top tier of Shimano GRX, labelled RX815, uses the Di2 shifting system and all SRAM’s 12-speed gravel options use wireless eTap AXS shifting.
The swift, precise shifting of electronic drivetrains is well adapted to off-road conditions. For two chainring set-ups, electronic shifting also gives you the option to set up compensating shifts in the rear mech when you swap between chainrings, which can be useful off road to help keep you in the best ratio so you don’t lose momentum.
SRAM’s single paddle per lever right to shift up, left to shift down system is handy off-road, as it reduces the chance of mis-shifts from hitting the wrong shift paddle. You can emulate it with Shimano Di2 and the spare button on Shimano shifters can be handy to control a computer or other kit if you add a DFly wireless unit to your bike. The option with electronic groupsets to add satellite shifters on your bar tops is also useful, so you can keep your hands on the bar tops as you ride.
Not just the shifting
Gravel groupsets aren’t just about the gearing: all come with hydraulic disc brakes too. We’ve not discussed this and although the different brands have their own take on the tech you get, they all work just fine if you look after them.
So which gravel groupset you choose is largely a matter of your preferences and how much you want to spend. SRAM definitely has the greatest number of options and the most versatility if you want to go electronic, whereas Shimano has more mechanical offerings. Campagnolo may only have one gravel groupset, but it has some unique features and comes with the brand’s customary flair.