The 105 ST-7170 Hydraulic Disc Brake levers weigh about 211 per lever.
Unlike its sibling 12-speed shifters (ST-R9270/ST-R8170), these 105 levers do not have 'hidden' hood buttons. They also don't have a satellite shifter port.
They do however support wireless shifting, and take two CR1632 batteries per lever. Also, the single E-Tube port (SD300 type) can be used to update and troubleshoot the levers, but you cannot use wired shifting with these shifters.
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Let's say you just bought a 105 Di2 bike, but really want the hood buttons or the ability to connect satellite shifters (SW-RS801-T / SW-RS801-S / SW-RS801-E).
For example, because you want to be able to shift from your clip-on aero bars.
These shift levers don't support any of those, but don't worry - 105 Di2 (R7150) is fully compatible with the DURA-ACE and Ultegra 12-speed shift levers.
You could upgrade the levers to (ST-R9270/ST-R8170), while keeping the other components at 105 level.
If you're looking to build a rim brake bike, you won't be able to use 105 shift levers.
Again, there are compatible Ultegra and Dura-Ace shifters, and these do support rim brakes. Note that 12-speed rim brake shifters can not be used for wireless shifting:
Updating 12-speed Di2 R9270/R8170/R7170 shift levers is not as straightforward as you might think. You need either the SM-PCE02, or connect the levers to the rest of the system using an EW-SD300 wire.
I'll show you two different methods of pairing 12-speed Di2 wireless shift levers - using the mobile app and using wires.
Just bought a new 12-speed Di2 bike? This page explains what the buttons do, how to charge, and what synchronized shfit does.
12-speed wireless Di2 shifter batteries last about two years, and this page will teach you how to check the battery level and replace the battery itself.
Unpairing 12-speed Di2 wireless shift levers can be done using the mobile app or using the SM-PCE02 and E-Tube Project for Windows. This page describes both methods of unpairing wireless shifters.
Cheat sheets to help identify button functions and explain what the LEDs mean.
Do you have small hands? Or extra large hands? Read this page to figure out how to change your Shimano Di2 shift lever (or shifter) reach.
Below is an overview of all known firmware updates for this component. The changelog texts are Shimano's, and quite often they're a bit cryptic - sorry!
4.3.0
General bug fixes.
4.2.1
■ ChangesSecurity performance for wireless communications between the shifter and rear derailleur has been improved.Click here to view FAQs for more information. https://bike.shimano.com/faq/DI20A#D-7030*The firmware for both the shifter and rear derailleur must be updated for proper operation of the Di2 system.* Wireless firmware update is not available for this product.Update the firmware over a wired connection or contact your place of purchase or a distributor. ■ OthersGeneral bug fixes.
4.2.0
- The FRONT SHIFT NEXT function is now supported.It is a function that allows you to shift up and down the front derailleur with a single button. * To use this function, assign “FRONT SHIFT NEXT” to a button on the wireless shifter/switch.* Wireless firmware update is not available for this product. Update the firmware over a wired connection or contact your place of purchase or a distributor. Click here to view FAQs for more information.(https://bike.shimano.com/faq/DI20A#D-7020)
4.1.0
EW-EX310 is now supported.
4.0.1
Firmware released.
