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Sora shifters can be used with a Tiagra derailleur from the 4500 and 4600 series because 9 and 10-speed Shimano rear road derailleurs have the same rear shift ratio (1.7:1).

The Tiagra 4700 components have unique characteristics and are NOT compatible with Sora shifters of any sort.

Sora’s new front shifters (3000) are not compatible with any Tiagra front derailleur.

Sora’s old front shifters (3500) are compatible with Tiagra 4500 front derailleurs.

The Factors That Influence Shifter and Rear Derailleur Compatibility

The drivetrains on modern bicycles are indexed. In simple terms, this means that each click of the shifter results in a shift up or down the cassette.

The rider is not required to position the shifter “at the right location” as it was with fiction shifters.

If the gearing is indexed properly, one press of the shift lever should result in an instant shift without any guesswork.

This is achieved via pre-determined jumps of the rear derailleur.

How?

The derailleur moves as much as the shifter wants. The control is achieved by pulling or releasing the gear cable (electronics shifters don’t use cables but e-motors).

Therefore, if we control how much cable the shifter pulls per 1 click and how much the derailleur moves per 1mm of cable movement, we will pre-determine where the derailleur will be after each shift.

This is exactly how modern drivetrains work.

Shifters have a pre-determined cable pull value (the amount of gear cable pulled or released by the shifter) whereas derailleurs have a rear shift ratio – the travel of the derailleur per 1mm of pulled or released cable.

For instance, Sora derailleurs have a 1.7:1 cable pull. In other words, Sora rear derailleurs move 1.7mm per 1 mm pulled or released by the shifter.

If another derailleur has the same rear shift ratio and the capacity to cover the cassette that we are using, it can replace the existing Sora derailleur.

Do Tiagra derailleurs fit the bill?

Yes and no. (Don’t worry. It will all make sense in the end.)

There are three Tiagra series:

• Tiagra 4500
• Tiagra 4600
• Tiagra 4700

Tiagra 4500

Tiagra 4500 goes back to 2006 and is therefore considered the “old Tiagra”. Just like Sora, the Tiagra 4500 is designed for 9-speeds. Consequently, Tiagra 4500’s rear derailleur has the same rear shift ratio as Sora (1.7:1) and can therefore be combined with a Sora shifter.

That said, the derailleur’s capacity and max cog limit will be an issue when coupled with larger Sora cassettes with a 34T large cog.

Why?

According to Shimano’s official manual, Tiagra 4500 RD models (RD-4500-SS, RD-4500-GS) max out at a 27T large gear. The GS (medium cage) model has a larger total capacity but the large cog limitation is the same.

If you want to use this derailleur with a large cassette, you will need to install a derailleur hanger extender to make the derailleur longer and capable of reaching the largest cog.

Tiagra 4600

As one might expect, Tiagra 4600 is an upgrade from the 4500. The groupset was introduced in 2011 and offers 10 speeds instead of 9.

Nonetheless, the Tiagra 4600 rear derailleur is still compatible with Sora shifters because it has the same rear shift ratio as the 9-speed models – 1.7:1.

Therefore, if the model in question can cover your cassette, it can be added to a 9-speed Sora drivetrain.

Remember that derailleurs do not care about the number of speeds on the cassette. They simply move when the shifter tells them to. In other words, they are not gear-limited like the shifter. Thus, the only requirement for them is to have the correct rear shift ratio.

The table below contains the basic characteristics of Tiagra 4600 derailleurs:

Tiagra 4700

Tiagra 4700 was introduced in 2015. It’s the youngest Tiagra group set at the moment. Just like the 4600 series, it’s a 10-speed system. It’s considered lighter and stiffer than the previous generations.

However, Tiagra 4700 derailleurs are not compatible with Sora shifters because they have a different rear shift ratio.

Tiagra 4700 derailleurs are 10-speed, but they have the rear shift ratio of Shimano’s 11-speed road derailleurs (1.4:1).

Tiagra 4700 shifters have a unique cable pull (different than both 10 and 11-speed shifters) so that the 4700 derailleur moves accurately across a 10-speed cassette.

In short, if you have Tiagra 4700, you won’t be able to use it with a shifter outside of the group set.

What About The Front Derailleur and Shifter?

For better or worse, front compatibility is very limited.

Here’s what we know at the moment:

• The front shifter of the older Sora series (3500) should be compatible with the older Tiagra 4500 front derailleur.
  
• The new Sora series (3000) shifter is not compatible with the old Tiagra front derailleurs because it has a longer cable pull than the old series. The new Sora front derailleur has a longer swingarm than the old ones. The longer arm changes the mechanical advantage of the shifter and requires a longer pull.

• Sora shifters are not compatible with the newer Tiagra series (4600 and 4700) due to the dissimilar cable pulls and shift ratios.

In short, the only compatible option at the front is Sora 3500 + Tiagra 4500.

Summary: Compatability Chart

Frequently Asked Questions

What are the advantages of using Sora shifters with a Tiagra derailleur?

I can think of only 2, one of which is subjective:

1. You like how Sora shifters feel.
2. Extra options to choose from.

Is a complete transition from Sora to Tiagra worth it?

If we are talking about the old Tiagra 4500, the answer is no as it simply doesn’t offer anything new.

However, Tiagra 4600 and 4700 have notable advantages:

• One extra speed

The benefit of the additional gear is that it reduces the jumps between the cogs. Smaller jumps between the cogs allow the user to make smoother transitions making it easier to maintain a higher cadence continuously. The term cadence refers to the rotations of the crank per 1 minute.

Higher cadence (e.g., 90RPM+) is associated with increased pedaling efficiency, reduced fatigue, and greater average speed when covering long distances.

• Compatibility with 11-speed shifters

The Tiagra 4700 products are essentially “downgraded” 11-speed units. The rear derailleurs can be used effectively in an 11-speed drivetrain.

Thus, a switch from Sora to Tiagra 4700 will also give you the option to upgrade to an 11-speed drivetrain eventually.

That said, it would be cheaper to go from Sora to 11-speed right away rather than to introduce a middle stop.

Is it worth it?

It could be if you have the funds. But if your Sora setup is working fine, don’t think that you need something better to get better.