Shimano R785 disc levers have excessive free stroke

warx · Jan 23, 2015

I worked on my brakes a bit last night. It's funny as when the yellow bleed block in in the calipers the levers feel solid - mainly as the block is thicker than the pads and red spacer. I know the lever is functioning correctly and there's no air in the line.

Using the red spacer and a few hard squeezes does set the pads marginally closer to the disc and reduced the free-stroke a bit. Enough to where I could not squeeze the lever so tight I could bottom out (given the reach is set to max and free-stroke adjustment is min)

The one issue that remains is specific to cyclocross is that the front brake lever will still pinch any fingers left around the bar when braking hard into a dismount. But looking at this I realize those paddle buttons are pretty darn big! I am coming from TRP Hylex (single-speed) hydraulics where there's no gear shifter on the levers so plenty of room under. I think I just need to adjust my technique. Also I am going to be using a 1x11 (XTR) so could remove the left/front shifter switches anyways.

One final test is I made a spacer thinner than the red spacer and set the pads with that and it gave me a perfect tighter clearance gap and super-solid lever feel. I could even wind the reach in a little bit. I'll try with this and see how it fairs as the pads wear.

I did get some BH90 hoses (much stiffer and less compressible) and might still try this for the rear. I am more used to hydraulic discs than rim cables so don't need a particular feel to them.

bedwards1000 · Sep 14, 2015

warx, did you finally get this the way you like it? I just took delivery of a lightly used bike with R785s and have the same problem. The brakes engage just before the bars but otherwise work fine. I've done zero tinkering yet but was reading up on it to see what worked.

warx · Sep 14, 2015

Not quite the way I'd like it TBH. I do the trick with the shim to set them closer than just setting them on the disc and it's better - but still seams like too much travel. I guess I am used it now. I still might try using an even thinner shim to set them closer.

Now cross season is almost here I am practicing dismounts and this is where it feels the most wrong. I was used to having fingers under the lever during a dismount. I can't do that now. I suppose it was a bad habit.

bedwards1000 · Sep 14, 2015

Thanks for the quick reply. I haven't done or noticed it on the dismounts (only had the bike 2 rides) but on sketchy downhill stuff I hang onto the hoods with a finger wrapped around and the travel is too much. I haven't even played with the stroke adjustment. I've had the bike <24 hours and I've been riding it 5 or those and sleeping the rest.

Now I'm at work so I can do some research.

J.R. · Sep 14, 2015

Just use a shim to move the pads closer together. By using a thinner shim you can move the pads as close as you want which results in a "high and hard" brake lever.

bedwards1000 · Sep 14, 2015

Thanks, I'm glad I asked, I'll be way closer to getting it right than if I started tinkering blind.

Somebody suggested using playing cards as shims since you can get any thickness to get any lever feel you want.

I know enough to be dangerous!

J.R. · Sep 14, 2015

I thought it was pretty easy. Pull the wheel, insert spacer, pump brake lever until pads are against spacer, put the wheel back on and ride.

Playing cards should work. You may need to experiment a bit to get the right amount.

I just used a piece of brass stock I had handy.

wgscott · Sep 14, 2015

One thing I discovered the hard way is you don't want to do a bleed with worn pads in place. You need fresh pads, or a spacer to match, or there won't be enough expansion room when you go to replace your warn pads.

Conversely, I have noticed that the travel increases quite noticeably when the pads need to be replaced (you need to do so before they become as thin as the spring metal that hold them apart).

warx · Sep 14, 2015

Yeah - it's about getting the right thickness shim for your desired gap. I still think the stock gap setting it either on the rotors themselves or the shim (which pretty much measures almost the same as the rotor) is too wide. Never had disc brakes that separated before.

bedwards1000 · Sep 14, 2015

Unfortunately, I don't think I got the spacer in the box of goodies that came with the bike. Does anybody have a pair of calipers to measure the thickness? I think I'm on the right track.

warx · Sep 14, 2015

As I suspected, my orange/red spacers measure 1.82mm which is thicker than all my various rotors (1.71-1.74mm). So whatever gap I set with them is overridden by the first application on the rotor itself. I have been using some 0.040 (1mm) aluminum sheet instead although I might try some 0.025 sheet.

wgscott · Sep 14, 2015

bedwards1000 said:
Unfortunately, I don't think I got the spacer in the box of goodies that came with the bike. Does anybody have a pair of calipers to measure the thickness? I think I'm on the right track.

I didn't either. I had to wing it. The deck of cards idea sounds ideal. Then count the cards you need to get it right and save that info for the next time you have to bleed your brakes, so that [sarc]six weeks from now when you have to do it again[/sarc], you won't have to do all the experimenting again.

cxwrench · Sep 14, 2015

wgscott said:
One thing I discovered the hard way is you don't want to do a bleed with worn pads in place. You need fresh pads, or a spacer to match, or there won't be enough expansion room when you go to replace your warn pads.

Conversely, I have noticed that the travel increases quite noticeably when the pads need to be replaced (you need to do so before they become as thin as the spring metal that hold them apart).

You don't ever want to bleed a brake w/ the pads in. Too easy to ruin your pads.

wgscott · Sep 14, 2015

I was thinking more in terms of the final adjustment just before you take the upper syringe off.

jamesgumby · Sep 20, 2015

Quick question. I have new 785s and the same issue. It isn't too much 'freestroke' as the pads move with the lever from the word go.

So.... when bleeding with yellow block, do I back off the freestroke screw first? (It comes set to minimum, ie. screwed right in) and then screw it in after completing all procedures...or will this make no difference?

Cheers

Srode · Sep 21, 2015

Just got done installing a set on my new build and the front has very little travel before biting, feels nice and solid. The rear travels a long way, but still stops well. I read the thread, not sure I want to play with shims - shouldn't have to. Maybe I'll get another bottle of fluid and try again.

rcb78 · Sep 21, 2015

I just did a set of 685s that came completely dry, new lines, disconnected, etc. I tried it the Shimano way and it felt pretty good. Then I tried hooking up syringes to both sides and bleeding like I do my Avid brakes and 'vacuumed' out a few more bubbles giving a slightly better lever feel that was balanced left to right.
Having tried it both ways now, I think I'll stick to the dual syringe method. Seemed faster and more effective.
FWIW, the syringes I use are from the Jagwire universal kit for mineral oil. Very similar to the pro level Avid kit except the syringes aren't rebuildable.

wgscott · Sep 21, 2015

I don't know if this is an acceptable protocol, but I used the top syringe to generate negative pressure to suck out as much air as possible. I found in order for this to work, I had to put a thin layer of high vacuum grease in the Luer lock thread to keep it from leaking under negative pressure. Having said that, I have never gotten the back brake as nice and solid as the front. They guy who built my bike did, so I know it is possible.

Lelandjt · Sep 22, 2015

In the MTB world Shimano brakes are known for having lots of rotor clearance which is great for accomodating wobbly rotors. They also have a long free stroke. Some people overfill them to reduce this. How long it takes to go from the overfilled state to normal seems to vary from days to months.

jamesgumby · Sep 26, 2015

Ok, finally done my brakes. Bled according to Shimano instructions. Then closed all oil ports, attached syringe to caliper, undid caliper port and pumped in a bit more (with yellow block in).

Then....reset pistons with wheel in, by lightly pulling lever. Didn't use red spacer. Levers really firm now.

Shimano R785 disc levers have excessive free stroke

warx

bedwards1000

warx

bedwards1000

J.R.

bedwards1000

J.R.

wgscott

warx

bedwards1000

warx

wgscott

cxwrench

wgscott

jamesgumby

Srode

rcb78

wgscott

Lelandjt

jamesgumby

Top Contributors this Month

Recommended Communities