Custom Di2 build

hero0bun
hero0bun Posts: 2
in Road general
Hi Dear BikeRadar community members,

I have been trying to figure out a way to set up a Di2 system on an unique TT bike.

The question began with the brake system.
Front: TRP TTV Aero TT Brake: linear pull
Rear: BR-5810-R : caliper brake
So, I needed to use different brake levers for each brakes.
Because there is no choice, I bought a pair of V-Brake lever (TTLVR) knowing that I would not use one side.

Now, I began wondering on shifting.
Option 1. If I buy a Single Di2 lever (ST-6871, which has two buttons,) could I shift up/down front/back Di2 R8050 derailleurs via their synchro-shift?

Option 2. I could shift using a brake lever: ST-R8060 and SW-R9150. Each of them has single button. I have called Shimano USA and they said basically "a switch is a switch".

These buttons will be connected through Junction A: SM-EW90- (A or B)(3 or 5 connections).

Shimano USA did not explain at all but I am assuming that "a switch is a switch" means that I could customize the switch configuration via a software "E-TUBE".

I was wondering if there is anyone who have been through the same situation and figure out the solution.

Thank you so much






Comments

  • StillGoing
    StillGoing Posts: 5,211
    Why do you need to use different brake levers for each brake? The brake lever is just that, a lever applying the tension to the cable actuating the brake calliper.

    Shimano Di2 has TT switches for the aero extensions and a brake levers with built in switches to operate the derailleurs. One operates the rear derailleur, one operates the front derailleur.

    Maybe I'm missing something here, but building a TT bike isn't that difficult. Plenty of TT bikes have TRP brake callipers and don't need special brake levers. Plenty have Di2.

    https://youtu.be/-aDase_vpBE
    I ride a bike. Doesn't make me green or a tree hugger. I drive a car too.
  • hero0bun
    hero0bun Posts: 2
    edited March 2020
    Thank you StillGoing for your comment.

    This is what I was puzzled first.
    It is not recommended to mix "Standard pull" and "Long pull" systems.

    • Standard pull: These are designed to work with caliper brakes (as found on a BMX or road bike) or with traditional centre-pull cantilever brakes (as found on Cyclo-X bikes).

    • Long pull: These work with direct-pull cantilever brakes such as the v-brakes found on many MTB bikes, as well as MTB cable disc brakes.

    Their lever ratios are different so that you will not have a good brake control with a "Standard pull" lever and "Long pull" V-brake. All Shimano Di2 levers are "Standard pull" and Shimano specifically stated that these levers can't be used with "Long pull" V-brakes.
    Of course, if you have strong grip, it may not matter.

    That's one thing.

    What I'm hoping to achieve a kind of a "hack" due to this need.

    When Shimano upgraded their Di2 system, they introduced "Synchro-Shift". In a sense, you can control both front and rear with one switch seamlessly. Now, you need only a UP button and a DOWN button. Then, they made single UP button on right brake lever and single DOWN button on the other, left brake lever.

    Also, via the firmware upgrade and e-Tube, Shimano let us use this "Syncrho-Shift" with the older Di2 system. So, you can shift both front and back derailleurs using the older brake lever with "two-buttons" that used to shift only one derailleur.

    Then, do you need another brake levers with "two-buttons"? If I want to keep the manual shift mode without Synchro-shift, yes. But, Shimano officially began using "single button on each brake lever" system.

    I'd rather try "two-buttons" on one side configuration and "save money" by buying a single brake lever instead of buying two expensive brake levers. Obviously, this is not a good option for Shimano. So, I was a little bit skeptical if their E-Tube system let me do this.
  • raisinberry777
    raisinberry777 Posts: 141
    The TRP TTV brakes use the same amount of pull as a normal road caliper. This type of brake is referred to as a 'mini-v brake'. The TRP TTLVR will work with either type of brake, which is noted on their website.

    Given that you've already got the brake levers, the most sensible solution is to buy the SW-R9160 or SW-R8060 and insert them in the bar ends of your aero extensions (as StillGoing said above). These two switches are designed to be used with the Synchro-Shift feature so that one button goes up, one goes down and you never (manually) control the front derailleur.

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