deacon mark

I am a bike mechanic although I work for myself mostly not in LBS. I got a road bike with full Shimano 7920 Hydraulic brakes. I find the front rear shifter is not spongy but requires more throw back to the bars that I like. First of all, I have the set for the lever stroke all the way back for the biggest gap. That is adjustable. But the free stroke before the brakes bite all the way is not. The brakes work but I wish the would fully engage before almost get to the bar. I have tried everything. I did full bleed and in fact have done it twice along with some tweaking and getting out any air in system. That did not do a lot of good really.. The rear brake is better and I can live with it but the front is the stopping brake I want it to perform correct or at least like my rim brakes. On my rim brake Shimano 6800 the brake is fully locked up before I get anywhere near the bar.

My question is those of you who are riding on 105 hydraulics how much brake squeeze do have. Does the lever almost hit the bar or is it close, not close. Frankly I went down to the LBS to check some and I find these too were a bit more lever throw for sure. I take any feedback or suggestions this is driving me crazy. I am not putting in the mechanics section until I get some feedback here. One person in the mechanic section suggested I pull the wheel and lightly pump brake to have the pistons extend more and then see. I tried this a some improvement but I really frustrated.

Elvo

Sounds like you need a two way bleed? Or worn discs? I have 7020 and I can lock up the wheel a few mm before the shift paddle hits the bars.

deacon mark

I did a full bleed including what I believe is a two way bleed by pushing the brake fluid back up and out the cup. Does not seem like any air in line. The bike is new with 1700 miles the rotors are perfect.

genejockey 

I had this issue with a bike with the same STIs. It had been fine when I bought it, but after a year it felt like the free stroke had gotten really long. I wondered if it was pad wear, but people reassured me that the system is self adjusting. I lived with it. Then I replaced the pads with new pads, and guess what? The free stroke is back to what it was like when new.

Take home lesson: road bike disc brakes are NOT self-adjusting, because there's a spring to push the pads back off the rotor. If this bike is new, I'm not sure what you can do, but if it's used, check the amount of pad left and consider replacing them.

deacon mark

Well now I have figured out I have a small leak in the bladder cavity on the inboard side of the shifter. I clean all the oil and then notice and can actually see a bit seep out at around thiis area. Still under warranty so have to see if I go to Shimano or Habanero bikes. I don't care just get it fixed. I can even buy and new one for speed and in warranty get another which I can deal with.

SoSmellyAir

Do you mind taking and posting a photo of the above, so that others (especially a hydraulic disc brake noob like me) would know what to look for? Thank you.

deacon mark

Ok update figure this out. I had the bladder in the shifter get a tear. I had to remove the 3 screws and then see the rubber bladder had small tear. This is not a replacement part as such. It can be replaced but you have to go through a dealer and then they have to go to warranty department. I actually bought a set of them on ebay coming from China. The deal is that workers in factories take them home and then sell them on ebay. So now just need to replace this and add and bleed brakes, hopefully this will resolve all the issues. An remember when pushing piston back into caliper open the top bleed port of the shifter so you don't create too much pressure.