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Shimano road disc brakes for a tandem - brake models and hose lengths

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Shimano road disc brakes for a tandem - brake models and hose lengths

Old 04-27-20, 04:47 PM
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Chris_W
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Shimano road disc brakes for a tandem - brake models and hose lengths

I just went through the process of putting Shimano road hydraulic brakes on our 12-year-old Co-Motion Speedster tandem and learned a few things that I thought others could benefit from:

Not many tandem forks or frames use the newer road-style "flat-mount" brakes, which is probably not a bad thing because flat-mount only allows up to 160mm rotors, and most tandem riders will choose larger rotors than that. Post-mount or IS mount disc brakes is the norm for tandems and although post-mount to flat-mount adapters do exist, they are not common and might not work in all cases.

Fortunately, although when sold in a lever-brake kit, current generation Shimano road hydraulic disc brakes only come with flat mount brakes, Shimano sells the levers separately and still sells the previous-generation RS785 road disc brakes that use post-mount fittings. Just be careful not to get the really early version of the RS785 that had the "banjo" hose fitting on the side, get the newer RS785 where the hose plugs directly into the caliper (shown below). Shimano's current compatibility table lists the RS785 as being fully compatible with the newest generation of road hydraulic levers (i.e., 7000 series 105, 8000 series Ultegra, 9100 series DA) because Shimano knows that there are still road disc bikes that don't have flat-mounts.

To connect the newer levers to the RS785 brakes, you need the BH90 hose, and if you buy the "SSR" version of the hose kit then you get all of the correct connectors. However, the SSR kit only comes in 1.0 or 1.7 meter lengths, which is a problem for the rear brake on a tandem. Shimano doesn't care because they've officially stated that their hydraulic disc brakes are not rated for tandem use (but what else are we supposed to use?). After some searching, I found the "SS" version of the BH90 hose kit is available in a 2.0 meter length, which is the same hose but not the right connectors, so I ordered the 2.0m SS kit plus an extra 1.0m SSR kit so I'd have the connectors (maybe you can buy the connectors separately, but the extra SSR kit wasn't very expensive and maybe I'll need that extra hose one day). Some bike shops may have the bulk roll of BH90 housing and you could then buy the length you need, but even in the high-end shop that I used to work in the boss refused to buy that bulk roll when a customer asked because he couldn't imagine ever being able to sell the rest of it.

But, 2.0m is still a bit too short for the rear brake on a tandem! No problem, because Shimano now sells hydraulic interruptor brake levers in the GRX series (model BL-RX812) that mount next to the stem (shown below). These allow you to brake when holding the bar tops, which is quite useful when riding and great for holding the bike steady when stopping briefly. The interruptor levers are also really handy hose connectors and are again officially compatible with all the current road hydraulic levers (not only the GRX versions). The 2.0m hose is long enough to reach from the rear brake to the GRX lever (I had to trim it by about 10 cm on our small-size tandem) and then the GRX lever comes with a short section of BH90 hose and all the connectors to go between the extra lever and the regular brake lever - just be careful when trimming that down because it needs to be close to the perfect length to hide neatly under the bar tape.

These parts are delivered with no hydraulic fluid inside, so the next complication is filling the system with fluid and getting all of the air bubbles out, which isn't simple, especially with the extra lever also needing to be air-free. If you don't have the proper syringes, funnels, adapters, and a bit of experience then I'd recommend getting a professional to do it. To do it yourself properly, download Shimano's dealer manual and follow the instructions starting on page 70 and especially the part starting on page 75 for the extra steps with the interruptor lever. I've now setup a total of 4 brakes with the interruptor levers and on half of them I've been successful the first time, the other half I've immediately had to do a second bleeding of the fluid because there was too much air in the system. After getting each of them bled properly at the beginning, everything has continued to work well since.

I only installed a right-hand interruptor lever because that's all we had when we had mechanical brakes. I mainly just use that lever for holding the bike steady when stopped and we already have the Di2 gear display (SC-M9051) on the left side of the stem which would need to be moved if we had another lever there, but you may prefer to have a pair if you plan to use these levers much when actually riding.

We've gone with 180mm rotors front and rear and changed the stock resin brake pads to Shimano's metal pads and so far we are very happy with the performance.

If you want advice about installing non-Shimano hydraulic brakes then you'll have to ask someone else. I've been a professional bike mechanic for 8 years and based on my experience, I'll never touch any hydraulic brakes other than Shimano when I have the choice - Shimano are the only hydraulic brakes that I can bleed reliably, change brake pads easily, and I also hate the idea of using corrosive DOT fluid. Also, Shimano offers far more versions and accessories for all of their products than other brands do, which is what allowed all of this to go together so flawlessly for us.

Last edited by Chris_W; 05-17-20 at 10:26 AM.
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Old 04-28-20, 03:04 PM
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Nice long write up

FWIW, originally we had the RS785 brake set on our road tandem. I never liked those levers, both because of the large shape, but more importantly the poor bleeding and lever feel. These came spec'd with BH59 hose. When the newer ST-6870 levers became available I bought a road kit set including new calipers at a good price. Didn't immediately need the calipers, but it was just a few buck more to get another set as spares (my parts bins are full of "spare" stuff never used :/ ). On the down side, these new calipers came with a banjo fitting requirement, and single bike length hose with the banjo at one end.

I then sourced a bulk box of the SS BH90 hose because the 2.0m max hose length was around 15cm too short for a full run up to my road bars and leave appropriate slack for turning. Also bought some extra end pins and proceeded to install the new levers + BH90 hose + the old RS785 calipers. I was very surprised to learn there is no such thing as an after market banjo fitting for Shimano hose. All Shimano hoses that require banjos, come with those attached and that is your only choice.

Happy with the results as the lever feel is better both in firmness and power, plus they look much nicer.

RS785 hacks:

1. eliminate annoying rattle of the RS785 brake pads. Search online for a tip to create a couple rubber belts from cutting an old road inner tube, then wrap the belt strip around the ICE fins+retainer pin.

2. sticky RS785 caliper pistons. Get some Q-tips, clean the pistons, then apply mineral oil to the piston base where it enters the caliper body. Work the pistons in/out to spread the oil inside, then wipe off all excess. Pistons now move freely.

Last edited by twocicle; 05-11-20 at 08:37 AM.
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Old 05-01-20, 06:05 PM
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We previously had only the front brake as hydraulic, using the RS785 with the banjo fitting, BH59 hose and an ugly R785 lever. I also never liked the lever feel on that, and so I decided to upgrade another bike to GRX levers from Ultegra so the tandem was going to get the pair of almost new Ultegra hydraulic levers. It's then that I went down the rabbit hole of figuring out that I should change to a non-banjo RS785 so that I could use the required BH90 hose ...... Fortunately, the banjo RS785 found a new home on a bike that I've been fixing up to sell, which someone is collecting tomorrow, so the parts bin isn't any fuller, yet
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Old 05-11-20, 08:49 AM
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Ultegra Di2 shifters just got really cheap. Upgrade from RS785
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Old 05-13-20, 01:21 AM
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Unfortunately, that's for cable-actuated brake levers, not hydraulic, so not a RS785 alternative.
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Old 05-14-20, 11:22 AM
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Corrected the info in that posting. Thx.
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Old 05-28-20, 02:35 PM
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Can you find Shimano hydraulic shifters for a triple front?

<eom>
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Old 06-02-20, 07:04 PM
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Just thought I would add a couple of thoughts to the thread regarding hydro brakes and XTR 3x shifting

I had a spare set of ST-R785 di2 brifters lying around (not super comfy, but available for this experiment) and decided to go all in with 3xXTR + hydro brakes. some serious $$...be warned.

Shimano hydro road calipers/pads make me nervous with the small housing, small pads and small banjo fitting, so I picked up a set of Saint four piston post mount calipers, Shimano saint hose with a 2-inch banjo fitting installed and the Ti-Cycles hose coupler. The Saint pads are probably 2.5x the surface area compared to the road pads and they have a huge heat sink. Sure enough it all works, and better than I had imagined. Install was simple, and bleeding the system was easier than I anticipated. These can stop with serious force. Heat seems to not be a problem. The stopping power is still super impressive. No fade at the levers either. The rotors do warp when they are hot, so the next step is floating 203mm rotors for e-bike/cargo bike.

The banjo fitting screw is the only are where I am a little nervous. It can't be super tight, so i'll be keeping an eye on that.

Regarding the 3x Di2 - I am running 52/39/30 + 11x42. Technically beyond the capacity of the XTR system, the inner ring should be a 34. I use Semi Sync shifting set up like eTap where right buttons are taller gears and left buttons are smaller gears. System beeps 1 shift before the FD changes rings. The FD needs a little plastic shim between the frame mount and the body of the derailleur to lift the cage enough to clear the 52t chainring. I had the eTap system , 48x30 or 52x34, and the lack of middle chainring was frustrating at times. Going back to 3x really is nice.
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Old 06-23-20, 05:42 PM
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Originally Posted by marcdanziger View Post
Can you find Shimano hydraulic shifters for a triple front?
Not for mechanical shifting that I'm aware of. Only Di2 can do both triple FD and hydro brakes. Perhaps there are 3rd party/non-Shimano?
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Old 06-23-20, 05:48 PM
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"Ti-Cycles hose coupler"

The above comes with some unspecified barb size. Just be certain to use the correct size barb for the ID of the hose type used as there is no "one-size" barb for all Shimano hose versions. For example, BH59 (comes with rs785 set) hose is 2.3mm ID; BH90 (stiffer) is 2.1mm ID. I am now using the BH90 and like the firmer feel.

Since the product indicates it uses a "standard compression nut" I would try using OEM Shimano barbs and olives in this coupler, as these parts are readily available and known to be hose model specific. The correct Shimano barb for BH90 is silver color, whereas the BH59 is gold (brass).
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Old 06-26-20, 11:27 AM
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Just to check, _any_ Di2 setup can be configured for a triple?
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Old 06-28-20, 11:17 PM
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Originally Posted by marcdanziger View Post
Just to check, _any_ Di2 setup can be configured for a triple?
I believe you'd need to have the XTR Di2 triple front derailluer plus clamp-on derailleur mount (it won't work with braze on mounts) plus the XTR or XT Di2 rear derailleur (a road rear derailleur won't work), plus any set of road shift levers.
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Old 07-16-20, 07:43 AM
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Originally Posted by twocicle View Post
FWIW, originally we had the RS785 brake set on our road tandem. I never liked those levers, both because of the large shape, but more importantly the poor bleeding and lever feel. These came spec'd with BH59 hose. When the newer ST-6870 levers became available I bought a road kit set including new calipers at a good price. Didn't immediately need the calipers, but it was just a few buck more to get another set as spares (my parts bins are full of "spare" stuff never used :/ ). On the down side, these new calipers came with a banjo fitting requirement, and single bike length hose with the banjo at one end.

I then sourced a bulk box of the SS BH90 hose because the 2.0m max hose length was around 15cm too short for a full run up to my road bars and leave appropriate slack for turning. Also bought some extra end pins and proceeded to install the new levers + BH90 hose + the old RS785 calipers. I was very surprised to learn there is no such thing as an after market banjo fitting for Shimano hose. All Shimano hoses that require banjos, come with those attached and that is your only choice.

Happy with the results as the lever feel is better both in firmness and power, plus they look much nicer.
I'm thinking about using the latest Ultegra R8070 shifters with the XT M8120 calipers. Will the shifters and calipers both use the BH90 hose?
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Old 07-16-20, 10:56 AM
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Originally Posted by mtseymour View Post
I'm thinking about using the latest Ultegra R8070 shifters with the XT M8120 calipers. Will the shifters and calipers both use the BH90 hose?
Originally Posted by mtseymour View Post
I'm thinking about using the latest Ultegra R8070 shifters with the XT M8120 calipers. Will the shifters and calipers both use the BH90 hose?
Yes, the BH90 is now used for the current the road (ultegra & dura ace) and mtb (xtr, xt, saint) hydro brakes. Jagwire has a "Pro" hose kit that works ok on the mtb rear hose run, but it is still a bit more mushy than the BH90. With the road levers, the best firmness with decent modulation is to use BH90.

The 2 piston r785 calipers work fine on our road tandem at a loaded team weight of maybe 280lbs. For our mtb tandem where we ride quite steep technical terrain, definitely that needs the 4 piston M8120 calipers along with the H03C metallic pads which don't fade or burn out as fast as the resin/organic pads. I would definitely use the 4 piston calipers for heavy use.

The big "gotcha" with the rear calipers is when they require a banjo fitting. Shimano only has this fitting factory installed on hoses up to maybe 2000mm which is just a touch too short for our tandems. The Jagwire Pro kit mentioned above does have a banjo fitting which is one reason why we use it on our mtb tandem. A new solution to this issue is to get a hose coupler to join a standard rear Shimano BH90 hose (w/banjo factory installed) to a supplemental length of hose running to your levers. Otherwise, more recently there are a few after-market banjo fittings becoming available, mostly from China and posted on eBay. Amazon is also showing some postings but limited availability.

Here is a view of the coupler :

Last edited by twocicle; 07-16-20 at 11:03 AM.
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Old 07-16-20, 04:52 PM
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Originally Posted by twocicle View Post
The big "gotcha" with the rear calipers is when they require a banjo fitting. Shimano only has this fitting factory installed on hoses up to maybe 2000mm which is just a touch too short for our tandems. The Jagwire Pro kit mentioned above does have a banjo fitting which is one reason why we use it on our mtb tandem. A new solution to this issue is to get a hose coupler to join a standard rear Shimano BH90 hose (w/banjo factory installed) to a supplemental length of hose running to your levers. Otherwise, more recently there are a few after-market banjo fittings becoming available, mostly from China and posted on eBay. Amazon is also showing some postings but limited availability.
The banjo is an unexpected complication. I didn't realize that Shimano crimps the banjo at the factory. I came across the Jagwire Quick-Fit option, but the TRP hose coupler is a good alternative because it's easier to combine two hoses rather than use an extra-long hose. Thanks for the tip.

I'm currently figuring out all the pieces (disc fork, shifters, brakes, wheels) for a conversion to hydraulic disc brakes for our Calfee.
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Old 07-16-20, 08:20 PM
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Originally Posted by mtseymour View Post
The banjo is an unexpected complication. I didn't realize that Shimano crimps the banjo at the factory. I came across the Jagwire Quick-Fit option, but the TRP hose coupler is a good alternative because it's easier to combine two hoses rather than use an extra-long hose. Thanks for the tip.

I'm currently figuring out all the pieces (disc fork, shifters, brakes, wheels) for a conversion to hydraulic disc brakes for our Calfee.
The simple solution is to use a set of dual piston rs785 calipers which take a compression nut instead of banjo. With this setup, you can simply run an unbroken length of BH90 hose from levers to caliper w/o need for a coupler or other alternatives.

This photo showing the rear brake is the closest I have to our current setup...
https://photos.app.goo.gl/TwVfLbHFSBxCZUiw7

4-Piston Hydraulic Caliper CAVEAT:
This caliper can generate more torque than what your frame was designed for and possibly break the chain stay (PM: AKEXPRESS). Unless you have the additional diagonal brace between the seat stay and the chain stay, you should probably go with the 2 piston caliper or contact Calfee to discuss options.

Last edited by twocicle; 07-17-20 at 12:08 PM.
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Old 07-17-20, 05:58 PM
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Originally Posted by twocicle View Post
The simple solution is to use a set of dual piston rs785 calipers which take a compression nut instead of banjo. With this setup, you can simply run an unbroken length of BH90 hose from levers to caliper w/o need for a coupler or other alternatives.

This photo showing the rear brake is the closest I have to our current setup...
https://photos.app.goo.gl/TwVfLbHFSBxCZUiw7
This is exactly what we are running on our tandem. Works awesome. We have a 180 mm front rotor and a 203 mm rear rotor. The rear might be overkill.
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