Shimano R785 disc levers have excessive free stroke

warx · Jan 19, 2015

Hi,

I've bled these things several times with all the tricks (removing so hose is dead vertical, flicking hose, tilting etc.) but I realized my problem is the free stroke at the caliper is too much. Looks like they back off from the pads a lot so much of the stroke is just closing the gap. The free stroke adjustment is all the way in (least free stroke) but the lever still moves 25mm before pads engage so I have to leave the reach at maximum to ensure they don't bottom out. I read the road.cc review which mentions this. I just don't see a way I can do anything about it except mount the hoods on my drop bars where they have the most room to pull in. Crazy.

I can actually get enough braking force out of them but as also mentioned if doing a cross race and braking into barriers you trap your non braking fingers under the lever every time. Might try the stiffer BH90 hose to at least make the lever firmer once the pads have moved in to the disc and reduce travel that way.

cxwrench · Jan 19, 2015

Sounds to me like you're not bleeding them correctly. I've installed them on lots of bikes and have had no problems like this.

warx · Jan 19, 2015

That's what I thought but the pads start moving immediately the levers move. It just takes a lot of travel to move the pads in. Once they're touching the disc they are pretty firm just a half of the lever movement is already used up. There's like 1mm of clearance of pad and disc which seems a lot to me. If they just stopped backing off the disc so much they would be great.

ghettocop · Jan 19, 2015

After you do a complete, thorough, and correct bleed, pump the lever a few times with the system closed. Then (keeping the lever end closed) open the bleed valve at the caliper and force some more fluid into the caliper. Don't push the syringe as hard as you can or anything, but push hard enough that you can see and feel a small amount of fluid enter the caliper. Close valve and check lever pull now. I have done this a few times on various shimano systems to get a really "high and hard" lever. Seems to work.

warx · Jan 19, 2015

OK. Thanks. Will try that. I bleed as the manual instructs and did the final hold lever and open bleed port for half-second to squirt some liquid back into the syringe. Did this twice as I noticed if you do it more then it starts to get worse even though there's no re-introduction of air anywhere.

I guess what you're doing with one-last syringe plunge is sort of pre-loading the pressure a bit and perhaps closing the pads in. Do you find you have to repeat this once the pads wear a bit? I don't really know how the reservoir works on these levers and when is shuts it off and starts pressurizing but felt like that was too far into the lever travel.

nhluhr · Jan 19, 2015

If you're following the correct procedure ( http://si.shimano.com/php/download.php?file=pdf/dm/DM-BR0004-02-ENG.pdf ) it sounds to me like maybe you're either missing steps like forgetting to turn the freestroke/reach adjustment screws to the correct position before bleeding or maybe you're forgetting to use the red pad spacer to properly space the pistons before installing the wheel.

Special Eyes · Jan 19, 2015

I have a similar situation that I live with successfully. After adjusting the free stroke on the lever itself, there is still too much movement before the brakes kick in. The stroke adjustment on the lever if fairly useless, it is so small. I set the brakes up new on a new build and bled and checked. No air bubbles were ever introduced. I don't believe there are any other adjustments or methods to reduce the 2" of useless stroke of the lever before the brakes apply.

What red pad spacer are you talking about? None included or shown in the documentation. Also, I don't believe shimming the pad will lessen the free stroke.

nhluhr · Jan 19, 2015

Special Eyes said:
What red pad spacer are you talking about? None included or shown in the documentation.

Shimano hydraulic calipers come with the red pad spacer to ensure proper gapping for the standard 1.8mm rotor. In fact, all hydraulic brakes come with a spacer of some kind but Shimano's is red. This goes along with the yellow bleed block that you also use (if doing the job correctly).

http://youtu.be/9JrDwRuu8Gw?t=36s

cxwrench · Jan 19, 2015

nhluhr said:
Shimano hydraulic calipers come with the red pad spacer to ensure proper gapping for the standard 1.8mm rotor. In fact, all hydraulic brakes come with a spacer of some kind but Shimano's is red. This goes along with the yellow bleed block that you also use (if doing the job correctly).

http://youtu.be/9JrDwRuu8Gw?t=36s

^This^ Hopefully you're not bleeding them w/ the rotor and pads in place. Bleed them w/ the yellow bleed block, then install the pads. Then use the red pad spacer to set the pistons. And follow all the other instructions in the linked Shimano doc provided.

warx · Jan 19, 2015

Interesting. I understood the red spacer was used solely for checking the piston movement. It is only mentioned in the notes when there's no wheel/disc and you don't want the brakes applied accidentally and the sections "Adjustment when the pistons are not operating correctly" and "Replacing pads" under maintenance. They should really mention this in the "Installation" part.

I will use it to set the gap. I presume the spacer is thinner than the disc standard. A question I would ask is that do the pads stay gapped correctly as they wear if they need to be gapped by something thinner than a disc itself? Or must you regularly pop the red spacer in there to set it tighter again?

I ran into a Roubaix SL4 disc at Pantoll Station (Mt Tam, Norcal) today. Nice deep Roval carbon wheels, freeza centerlock rotors. I asked to feel his brakes (whoa!). He obliged and let me try and as I was he said "sometimes I pinch my fingers under the lever." This was a bike built by Specialized. Maybe this is a communication thing...

cxwrench · Jan 20, 2015

warx said:
Interesting. I understood the red spacer was used solely for checking the piston movement. It is only mentioned in the notes when there's no wheel/disc and you don't want the brakes applied accidentally and the sections "Adjustment when the pistons are not operating correctly" and "Replacing pads" under maintenance. They should really mention this in the "Installation" part.

I will use it to set the gap. I presume the spacer is thinner than the disc standard. A question I would ask is that do the pads stay gapped correctly as they wear if they need to be gapped by something thinner than a disc itself? Or must you regularly pop the red spacer in there to set it tighter again?

I ran into a Roubaix SL4 disc at Pantoll Station (Mt Tam, Norcal) today. Nice deep Roval carbon wheels, freeza centerlock rotors. I asked to feel his brakes (whoa!). He obliged and let me try and as I was he said "sometimes I pinch my fingers under the lever." This was a bike built by Specialized. Maybe this is a communication thing...

Built by Specialized or since you're in the middle of Mike's Bikes territory, built by them? Must have been nice up on Tam today, it's been a perfect day in Marin.

warx · Jan 20, 2015

Rode from GGB, Headlands, Ten. Valley, Coastal, Deer Park, Pantoll, Coast View, Middle Green Gulch, Miwok, Headlands. Gotta love this place!

True about the stores - I guess a delivering bike store could be responsible. I am never sure if a bike arrives at a dealers with just the handlebars and wheels removed or separate parts. If so it is more likely a communications thing. Shimano needs to communicate to its dealer/assemblers better. Their docs leave a lot to be desired.

nhluhr · Jan 20, 2015

Shimano's docs are light years ahead of SRAM's cryptic pictographic flyers. I do find it odd the dealer manual doesn't mention the red spacer in the bleed instructions but on shimano' online tech videos they offer dealers, the red pad spacer is mentioned in every single video dealing with hydraulic braked to the point where it's drilled into your head.

cxwrench · Jan 20, 2015

warx said:
Rode from GGB, Headlands, Ten. Valley, Coastal, Deer Park, Pantoll, Coast View, Middle Green Gulch, Miwok, Headlands. Gotta love this place!

True about the stores - I guess a delivering bike store could be responsible. I am never sure if a bike arrives at a dealers with just the handlebars and wheels removed or separate parts. If so it is more likely a communications thing. Shimano needs to communicate to its dealer/assemblers better. Their docs leave a lot to be desired.

Jesus...you got all of it today. I, OTOH, went to lunch at Pacific Catch w/ mom and picked up a rental car. Also hit TJ's for some essential frozen treats. I am building a bike for a girl on Velocio today, but didn't get close to riding one.

The s-tec website that dealers have access to is very thorough as nhluhr posted. They really beat us to death w/ the red pad spacer stuff. But I wouldn't expect the majority of Specialized shops in Marin to even know about s-tec, much less actually log in and pay attention to the videos.

Special Eyes · Jan 20, 2015

OK I saw the red bleed block in that Art's Cyclery video. I built up a Vamoots DR recently with 2014 R785 disc brakes and Di2. There was a YELLOW bleed block in the brand new kit. Apparently they are the same. I was misled by mention of a red piston spacer.

cxwrench · Jan 20, 2015

Special Eyes said:
OK I saw the red bleed block in that Art's Cyclery video. I built up a Vamoots DR recently with 2014 R785 disc brakes and Di2. There was a YELLOW bleed block in the brand new kit. Apparently they are the same. I was misled by mention of a red piston spacer.

Nope. The yellow 'bleed block' is what you use when bleeding the brakes. It fills up the space between the pistons when the pads are removed. The red 'pad spacer' is what is used to set the pistons in the right place when you're done bleeding and the pads are installed. Not the same piece.

nhluhr · Jan 20, 2015

Special Eyes said:
OK I saw the red bleed block in that Art's Cyclery video. I built up a Vamoots DR recently with 2014 R785 disc brakes and Di2. There was a YELLOW bleed block in the brand new kit. Apparently they are the same. I was misled by mention of a red piston spacer.

The video link I posted puts you in the exact part of the video where the guys says they are two different tools.

Special Eyes · Jan 21, 2015

nhluhr said:
I do find it odd the dealer manual doesn't mention the red spacer in the bleed instructions but on shimano' online tech videos they offer dealers, the red pad spacer is mentioned in every single video dealing with hydraulic braked to the point where it's drilled into your head.

I guess that was the experience I was referring to, except for the video parts. It simply wasn't shown in the docs. I did not watch any videos, and nothing indicated that I had to find them independently. I thought the slim spacer was to be put in between the pads when the wheel was removed for transport in case the brake lever was pressed with no rotor in there. Made sense to me.

cxwrench · Jan 21, 2015

Special Eyes said:
I guess that was the experience I was referring to, except for the video parts. It simply wasn't shown in the docs. I did not watch any videos, and nothing indicated that I had to find them independently. I thought the slim spacer was to be put in between the pads when the wheel was removed for transport in case the brake lever was pressed with no rotor in there. Made sense to me.

That's what everyone thinks they're for, hell...that's what I thought they were for til a couple years ago. They come in new brakes, they come w/ new bikes...makes sense they'd be used as a 'travel spacer'. We just had the wrong meaning for 'travel'.

Special Eyes · Jan 21, 2015

cxwrench said:
We just had the wrong meaning for 'travel'.

Good point, CX!

Shimano R785 disc levers have excessive free stroke

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