Super summary: Sora is a very good choice for a budget gravel bike. It’s sufficiently tough, affordable, and compatible with MTB parts.
To learn more, keep reading.
In descending order, Shimano’s road bike group sets rank as follows:
1. Dura-Ace – Shimano’s top-of-the-line road group set (offers electronic shifting too).
2. Ultegra – Like Dura-Ace, it’s designed for serious cyclists. Some components are slightly heavier than those of Dura-Ace but the overall performance is similar.
3. 105 – The ultimate group set from a cost-to-benefit perspective. It’s not as shiny as the higher-end, but the performance is so good people argue whether anything better is needed.
4. Tiagra – the most sophisticated group set in the “beginner’s” club”. The Tiagra 4700 series are essentially 11-speed units downgraded to 10-speeds.
5. Sora – beginner group set designed for 9-speeds. Nothing fancy. Just works.
6. Claris – almost the same quality as its brother Sora but designed for 8-speeds and weighs slightly more.
Some people may be hesitant to use an entry-level level group set such as Sora for grave riding, but that indecisiveness is unjust. The truth is that Sora’s components function well even when put in gravel settings.
Below are the advantages of using Sora on a gravel bike:
Compatibility with 9-speed MTB Rear Derailleurs
One of the strongest advantages of using Sora in a gravel setup is that its shifters are compatible with 9-speed MTB derailleurs such as Shimano Alivio.
How is that possible?
The movement of modern shifters is segregated into clicks depending on the number of gears. For instance, Sora shifters have 8 clicks (the clicks are n-1 where n is the total number of gears that the shifter is made for).
Each click pulls or releases a pre-determined amount of gear cable to trigger a shift. The value of the cable pull is carefully chosen in conjunction with the derailleur’s rear shift ratio.
The rear shift ratio indicates how much a derailleur moves per 1mm of cable that’s pulled or released by the shifter.
The rear shift ratio of Shimano Sora derailleurs is 1.7 and matches that of 8/9 MTB derailleurs. This means that the derailleur moves 1.7mm per 1mm of cable pulled or released by the shifter.
The cable pull and the rear shift ratio allow engineers to move the derailleur accurately across the cassette.
Derailleurs with the same rear shift ratio are essentially interchangeable under one condition – they should be large enough to cover the entire cassette.
For instance, a short cage road derailleur cannot be combined with a massive MTB cassette even if it has the correct rear shift ratio because it won’t be able to reach the largest cog.
The matching rear shift ratio of Sora and 8/9-speed MTB derailleurs make it possible to use larger cassettes.
The maximum sprocket capacity of Sora’s long cage derailleur is 34T. Meanwhile, the maximum sprocket capacity of most long-cage Shimano 9-speed MTB rear derailleurs is 36T.
The increase offers lower gearing which in return facilitates hill climbing.
9-speed MTB Derailleurs For Ulta-Low Gearing On a Gravel Bike
Below is a list of 9-speed MTB derailleurs that have the highest low sprocket capacity:
|Max. Low Sprocket*
|Shimano Deore RD-M592
|Shimano Alivio RD-M3100
|Shimano CUES RD-U3020
|Shimano Altus RD-M2000
|Shimano Deore XT M771
|Shimano Alivio RD-T4000
Note: Sora shifters are compatible only with 9-speed Shimano MTB derailleurs. SRAM 9-speed MTB rear derailleurs have a different rear shift ratio (1.1) and cannot be combined with a Sora shifter. The derailleur simply won’t move accurately.
Entering the World Of Gear Ratios
The gear ratio reveals the number of rotations that the rear cog and respectively the rear wheel make per 1 full revolution of the cranks.
The average gravel bike uses a 42T chainring. (Of course, some people prefer a larger chainring such as 46T when covering flatter terrain, but for the sake of simplicity I will use the average size to calculate how low of a gear a larger cassette can provide.)
The gear ratio is derived from the number of teeth on the chainring and cog.
For example, if the chainring has 42 teeth and the rear cog has 11, the gear ratio is 42:11= 3.8.
In this, case the rear wheel makes 3.8 rotations for every revolution of the cranks/chainring.
The higher the gear ratio, the greater the potential speed of the bike.
The lower the gear ratio, the easier it is to conquer hills.
A higher gear ratio indicates that the rear wheel makes many turns per 1 spin of the cranks.
Therefore, when the rotations of the cranks are the same and performed within the same time frame, a bike in a gear with a higher ratio will cover a greater distance.
A greater distance within the same time frame can only be achieved via higher speed. (The formula for speed is speed = distance/time.)
In this case, however, we are focused on low-gear ratios.
A low gear ratio makes it easier to climb hills because each revolution of the cranks equals a very small movement (sometimes not even a full spin) of the rear wheel. And since it takes a lot less effort to make one rear wheel rotation than 3 full spins, the rider can climb slowly but confidently.
The largest cassette that a Sora derailleur can cover has a 34T big cog. Meanwhile, a 9-speed Shimano MTB RD can reach a 36T cog. If the chainring of the bike is 42T, we have the following gear ratios:
- Sora: 42:34 = 1.23
- 9sp. MTB 42:36= 1.16
The discrepancy is 6%.
In other words, a 36T cog will allow you to cover the same hills with 6% less effort. 6% will quickly feel like a lot when you are on a long ride.
A Derailleur Hanger Extender = Even Larger Cassette
If you want an even greater range, you could add a derailleur hanger extender. This little piece of aluminum artificially elongates the derailleur cage and makes it possible to reach an even larger cog.
For instance, a 9-speed MTB derailleur with a 36T maximum large cog capacity can cover an 11-42 cassette with this extra link.
FAQ: What if I don’t want to change my original Sora derailleur?
A Sora derailleur can handle “standard” gravel riding adequately even though the derailleur isn’t labeled as “gravel-ready”. However, an MTB derailleur is expected to outperform a Sora model on rough terrain and isn’t nearly as affected by dust and other contaminations.
In other words, the important question is how aggressive is your gravel riding. If the terrain that you cover is on the line between gravel and light XC, then a Sora derailleur will struggle. It won’t be terrible, but it won’t be ideal either. In that case, an Alivio or a Deore rear derailleur will provide a much better experience.
If the terrain isn’t all that “scary”, a Sora derailleur will be enough.
Truth be told, I’ve covered light gravel terrain with a retro road bike with 25mm tires and a Suntour rear derailleur from 1987. I had no issues. That said, I wasn’t trying to win a race. I was simply commuting.
Maximum Affordability + Decent Quality
A Shimano Sora groupset is substantially cheaper than a dedicated “gravel” one. The price remains similar even if you go for the MTB derailleur upgrade.
The price of Sora and Alivio derailleurs is almost the same depending on the dealer. The Deore options are about 10-15% more expensive. Their advantage is that they’re considered tougher and thus more MTB-oriented. From a “gravel” perspective, the extra toughness doesn’t matter much.
Cheap and Efficient Drop Bar Shifters
Even though Sora shifters are not perfect (some criticize them for being unfriendly towards small hands) they offer an affordable way to enter the world of drop bars.
Cyclocross bikes use drop bars because the Union Cycliste Internationale (UCI) has a strict rule for keeping the width of the cyclocross bicycle under 50cm. This requirement alone eliminates the possibility of implementing flat or riser handlebars while preserving their full functionality (read more).
Why Not Claris?
There’s nothing wrong with Shimano Claris, but Sora is simply better and doesn’t cost a lot more. The advantages of Sora are:
- Smoother shifting
- 9-speeds (smaller jumps between the gears = smoother transitions = easier to maintain high cadence)
- Internal cable routing
- Partial compatibility with the Tiagra series
Frequently Asked Questions About the SORA Groupset
Is it true that Sora shifters get unresponsive?
They don’t get any more unresponsive than the other shifters out there. If a shifter is not performing well, the usual culprits outside of a mechanical failure are:
- Contaminated or worn/damaged gear cables and housing
- Contaminated shifters
- Poorly adjusted derailleur
- Improperly installed derailleur
- Using the wrong derailleur for the cassette
- Bent derailleur hanger
I have a Sora crankset. How can I convert it to a 1x drivetrain?
This question requires an article on its own, but I will try to provide as much information as possible nonetheless.
To transition from a 2x Sora to 1x, the following conditions have to be met:
1. Remove the original chainrings from the cranks by unscrewing the crank bolts.
2. Install a narrow-wide chainring with a 110mm BCD. The term BCD refers to the distance between the centers of two adjacent chainring bolts/holes.
The narrow-wide chainring’s bolt entrances should match the number of crank arms that your particular Sora crankset has (either 4 or 5)
The chainring’s number of teeth should be chosen carefully and according to the gearing that you need.
You will have to use chainring bolt spacers to make up for the absence of a second chainring.
Shorten the chain as needed for the new drivetrain.
Adjust/re-index the gears.
You can keep the front derailleur as a chain guide if you want. But if the chain is of the right size, the narrow-wide chainring should be enough to prevent the chain from falling. After all, improved chain retention is the main function of narrow-wide chainrings.