Shimano R-785 Hydraulic Disc Setup

By: Brandon Mar 12

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The Shimano R-785 hydraulic Di2 setup has been a long time coming. Let's say you're the early adopter, or just lucky and were able to land a kit early. It's not uncommon for guys to come from the road to cyclocross, or to be curious about road hydro disc, but not have a ton of experience with hydraulic brakes. They've been commonplace for years on the trails, and because of that mountain bikers tend to be a bit more familiar with the bleed process for their disc brakes.

Have no fear, though. The bleed process for Shimano disc brakes really is relatively painless once you've done it a few times, it's those first few times that can get you. Shimano does publish a really good step-by-step manual, even though they make it a bit hard to find. Including this manual in the packaging with your new brakes seems like smart move.

Now I've told you it's not that hard to bleed your new brakes. I've shown you where to find the manual to properly bleed your brakes. Next step? Take them to a professional. You heard that right. The bleed process is not that hard, but a professional mechanic, a good mechanic, can ensure it's done right the first time, that your brakes work well from the get-go, as well as stand behind their work.

The pictures above give a few notes into the process:

1. You need the full Shimano bleed kit, TL-BT03. It's $105. Do not bleed your brakes without it. I have no doubt it's possible to bypass using this kit, but I feel confident in saying the bleed will either be less optimal, messy, or both.

2. ALWAYS remove the wheel/rotor and pads and use the supplied bleed block. Even a drop or two of mineral oil will leave your brakes howling uncontrollably and reduce their power.

3. Have some disc brake cleaner and alcohol ready to clean any messes. A little drop here and there of spillage happens during bleeding brakes, cleaning everything to spotless before inserting pads/rotors is essential.

4. Gloves. Wear them. Always. Mineral oil and disc brake cleaner, it's probably not a good idea to get all over yourself. Play it safe.

5. Follow the recommended bedding procedures. Your new disc brakes will be less than wonderful out of the stand. The pads and rotor need to break in during bedding, when the pads leave material on the rotor. Properly bedding your brakes will make or brake (see what I did there?) the performance of your brakes.

The final picture in the gallery (also shown below) shows what happens when the pads get contaminated. In the middle of the photo you'll see a torn o-ring. That tiny o-ring allowed fluid to leak from the system and coat the pads. The honking was unreal, but more importantly enough fluid was gone from the system that the lever could be pulled to the bar without really providing any meaningful amount of stopping power.

This picture below is particularly important because it shows how important every last piece is when it comes to hydraulic brakes. That tiny o-ring rendered the entire front brake useless.

If you have questions, contact us here. We'd be more than happy to shed some light when we can on the setup of your new brakes.

photos and words by Brandon Elliott



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