Shimano hydraulic brakes - lever distance before biting

[wyre forest blues]

I have shimano ST-R785 Di2 hydraulic disc brake set. The levers (both) have to travel quite some distance before biting.. in fact now that the pads have worn the levers almost touch the bars before biting. The pads have not worn sufficiently to warrant changing. The system, both back and front has been bled. When new pads are inserted the levers dont have to travel quite so far before biting, but nevertheless IMO still need to be biting earlier. The pads are the resin type. (J02A). It has been suggested that the metal one (J04C) might be a solution.
One solution I have considered is to place shims between the pistons and the brake pads. Are any suitable available? Has anyone else had this issue? Can anyone help with a solution?. Views and opinions would be appreciated. Thanks in advance.

 

[Drago]

The system should self adjust for pad wear.

 

[wyre forest blues]

The system should self adjust for pad wear.

So why do the levers not have to travel so far before biting when i put new pads in? , and as the pads wear, the levers gradually get nearer and nearer to the handlebars before biting?

 

[I like Skol]

There is something very wrong here because the biting point should not change throughout the life of the pads even when worn down to the metal backing plate.
I have the 11spd cable/hydraulic road shifters (i.e not Di2) and the biting point is very consistant and I don't think I could bet the levers to touch the bars if I tried.
Why have the brakes been bled? This is not something that should need doing routinely but is often done in a futile effort to cure other braking issues by people that don't understand how these brakes work. Having said that, I wonder if there is insufficient fluid in the reservoir and as the pads wear some air is entering the system? It might be worth topping up the fluid (try this without rebleeding the brakes) and see if there is any change.
Just out of interest do you store or transport the bike upside down at all?

 

[I like Skol]

The pads are the resin type. (J02A). It has been suggested that the metal one (J04C) might be a solution.

Please slap whoever suggested that little nugget and tell them to stick to sharpening crayons because they certainly shouldn't be giving advice about brakes!

 

[wyre forest blues]

The bike was new 15 months ago and the brakes have always been like that. Ignoring the fact that the levers get closer to the bar after wear, the fact that they have always had to travel some distance is something I would like to correct, so that they bite within a cm or two of applying.
In an effort to correct the rear (as the pads had worn more than the front) it was thought that air might be in the system, hence bleeding the rear by the LBS. Recently I damaged the front cable whilst transporting it in a bike box and the front cable was replaced, hence bleeding the front.... There is no doubt the reservoir is full.

 

[I like Skol]

OK, the reach and free stroke at the lever can be adjusted according to this tech doc on page 47, but there is an interesting footnote which states that the free stroke is set to the minimum amount at the factory. Has someone altered these settings?

 

[lpretro1]

I like Skol is correct in his statements above. People often mess about bleeding when it is not necessary. Some brakes you can adjust both the reach and the bite point - I know on Hope brakes you can as on yours. Reach is simple that is to adjust for hand size. The bite point is a personal preference - some like them to bite very quickly and others prefer a more progressive feel. Adjust reach before adjusting bite point.

 

[Drago]

Adjusting reach doesn't alter bite point. You'll still have Xmm of lever movement before pad contact. Presumably you mean a separate adjustment for bite on Hopes?

 

[rusty bearing]

Yep, the Hope mtb brakes have separate adjustment for bite and reach.

 

[wyre forest blues]

Thanks guys for your advice. It appears that the pistons have to be 'set' from the outset so that the distance between the pad surfaces is slightly more than the disc rotors. If the gap is too large then the pads have to move further before biting. In other words the levers have to travel further before biting. To achieve this I removed the wheels and inserted the red pad spacer, then pumped the lever to reset the pistons. I then removed the spacer and pressed the lever slightly to move the pistons slightly further in. It appears this effectively resets the pistons using the mineral oil in the reservoir. Once the wheel was inserted the levers had little play before biting. Result.

 

[Theoldfm]

I’ve just done the same - although I just removed the wheel and used a piece of cardboard as a spacer - pumped the brakes a few times, put the wheels back in and hey presto! Perfect brake feel at last 👍