Rear derailleur and Rear Shifter
Shimano Sora’s rear derailleurs and shifters are compatible with those of Shimano Alivio because both are 9-speed group sets from Shimano. Before the appearance of 10/11/12-speed drivetrains, there was no major differentiation between Shimano’s MTB and road parts.
Front Derailleur and Front Shifter
The front shifters and derailleurs of Sora and Alivio aren’t compatible due to dissimilar cable pulls and shift ratios.
The front derailleur and the shifter will have to be of the same group set for a good shifting experience to take place.
Rear Shifters and Derailleurs Compatibility
Modern indexed drivetrains allow the user to shift with a simple click.
If the limit screws of the derailleur and the tension of the gear cable are set properly, shifting is fast, accurate, and easy as long as you remember to reduce the tension on the cranks/chain when shifting.
Accurate shifting requires accurate engineering. The only way to ensure the predictable behavior of the rear derailleur is to control it.
The predetermined movement of the derailleur is achieved via two values:
a. Cable pull – the amount of gear cable pulled or released by the shifter with each click/shift.
b. Rear shift ratio – the rear shift ratio indicates how much the rear derailleur moves per 1mm of cable pull.
If the rear shift ratio is 1.7:1 the derailleur will move 1.7mm per 1mm of cable pulled/released by the shifter.
The cable pull and the rear shift ratio are influenced by the following factors:
- Bike type (road or MTB)
- Number of speeds on the cassette
- Number of gears on the shifter
- Brand subcategory
In the case of Shimano Sora and Shimano Alivio, the front cable pull and the rear shift ratio share the same values (table below).
|Rear Shift Ratio
Since SORA and Alivio have identical cable pulls and rear shift ratios, it’s possible to combine Sora shifters with an Alivio rear derailleur or vice versa.
Derailleur Maximum Cog Capacity
All derailleurs have a maximum large cog capacity that shouldn’t be exceeded. If a derailleur with a low max. cog capacity is coupled with a very large cassette (e.g., 11-42), it will fail to reach the largest cog.
In our scenario, however, this outcome isn’t possible when using an Alivio derailleur because the largest Sora cassette is 11-32/34.
Alivio rear derailleurs have a long cage since they are designed for trekking/MTBs and can handle a cassette with a 36T large cog.
If you try to do the opposite, however, namely combining a Sora rear derailleur with an Alivio cassette, you will be limited.
The largest Alivio cassette has a 36T big cog whereas the longest Sora derailleur caps out at a 34T. With some tinkering, it may be possible to get the combination to work, but the shifting experience won’t be satisfying.
That said, you can still use Alivio cassettes with 28T, 32T, and 34T first gear.
Conclusion: It’s fine to mix SORA and Alivio rear derailleurs and shifters.
Front Shifters and Derailleurs Compatibility
Modern front shifters and derailleurs follow the same principles as the rear ones.
However, there’s a major difference between road and MTB derailleurs.
Most road derailleurs are bottom pull models while MTB models are top pull.
As one may guess, that classification is determined by the angle from which the gear cable pulls the arm of the derailleur.
Bottom pull (road) models have the gear cable under the downtube and then up (image below).
Top pull (MTB) front derailleurs have a gear cable going along the top tube and then down the seat tube. Thus, they pull the derailleur from the top.
MTBs use this setup because the riding is more extreme and there’s a higher chance for the downtube to come in contact with a branch or another obstacle. Thus, it’s more logical to route the cable through the top tube as the location is more isolated.
The pulling angles result in different leverages and thus require shifters with dissimilar cable pulls. The shift ratios of the derailleurs are different too.
For that reason, it’s not possible to mix Sora and Alivio front shifters and front derailleurs.
Shimano Alivio cranks can be installed on a road bike but only when the bottom bracket and the cranks match.
Alivio cranks are divided into three groups when it comes to bottom bracket compatibility:
- Square taper
- Press Fit
The same applies to Shimano Sora cranks, albeit only the older models operate with a square taper bottom bracket.
One may conclude that if the bottom bracket type matches, the cranks are interchangeable, but that isn’t correct.
You can install Alivio cranks on a Sora bike right away ONLY when the bottom bracket is a square taper model.
In all other cases, it will be necessary to replace the bottom bracket with an MTB one for two reasons:
- The Octalink bottom brackets are road and MTB specifics. You can’t use an Octalink bottom bracket designed for road cranks with MTB cranks.
- MTB axles and bottom brackets are longer than their road equivalents.
If you install MTB cranks on a road frame with a road bottom bracket, there will be two gaps. In other words, the connection will not be secure.
That is why it’s necessary to install and use an MTB bottom bracket.
However, road frames have narrower bottom bracket shells than MTB frames. Thus, you will also have to add two spacers to each side of the bottom bracket to make up for the wider bottom bracket.
For more information, consider reading the full post on the topic.
The above may seem slightly too chaotic. But ultimately, you have to remember the following:
- If the old cranks use a square taper bottom bracket, you can install the new ones right away (as long as they’re designed for a square taper BB too).
- If the old cranks use a non-square taper road bottom bracket, you will have to replace it with an MTB model with 2 spacers on each side if you want to use MTB cranks.
Truth be told, in most cases, it’s better to stick with the original cranks precisely because of compatibility issues.
If you have a road bike and want to lower its gearing, I would simply replace the chainring(s) with a smaller one(s) instead of trying to install a set of Alivio cranks.
If the cassette is fairly large (e.g., 32T+), a set of compact road cranks will offer plenty of low gearing for a fairly trained cyclist.
Alivio brake levers aren’t compatible with any road system including SORA.
The disc brake levers cannot be used on a road bike because road disc models are flat mount whereas most MTB disc brakes are post mount.
Trying to make an MTB disc brake system work on a road bike will be quite difficult and can result in frustration.
Alivio’s mechanical brake levers aren’t compatible with road brakes either because of dissimilar cable pulls.
Road rim brakes have a smaller mechanical advantage than V-brakes (the standard MTB rim brake.) Consequently, road levers pull less cable than V-brake levers. Switching between the two will result in poor performance. (read more)
The spacing of a front MTB hub is 100mm and matches that of road hubs. Thus, a basic MTB front hub can be installed on a road bike.
Rear MTB hubs are wider than rear Road hubs designed for bikes with rim brakes. Therefore, rear road wheels built around MTB hubs won’t fit on a modern rim brake frame.
However, disc-brake-ready road frames have a 135mm rear O.L.D. and can therefore accept a wheel with an MTB hub.
The cassettes of Sora and Alivio are interchangeable. The only potential issue would be to have a short cage Sora derailleur combined with the largest Alivio cassette. In that scenario, the derailleur will be unable to cover the entire cassette.
FAQ: What about installing road (e.g., Sora) cranks on an MTB frame?
MTB frames aren’t designed for road cranks. The chainstays are wide to accommodate fatter tires and often create clearance issues (read more).