Go Back  Bike Forums > Bike Forums > Bicycle Mechanics
Reload this Page >

GRX levers br-785 callipers problem

Notices
Bicycle Mechanics Broken bottom bracket? Tacoed wheel? If you're having problems with your bicycle, or just need help fixing a flat, drop in here for the latest on bicycle mechanics & bicycle maintenance.

GRX levers br-785 callipers problem

Old 03-04-20, 06:39 PM
  #1  
Paper Pixels
Newbie
Thread Starter
 
Join Date: Sep 2019
Posts: 3
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
GRX levers br-785 callipers problem

Is anyone else running Shimano BR-RS785 post mount callipers and grx 400/600 levers? I can get them working but they feel so spongy and touch the bars when being applied. There is no air trapped in the system. The hoses came with the GRX levers: sm-bk90-jk-SS. On the Shimano compatibility chart it says the br-rs785 callipers should use the SM-BH90 Hose, I thought the hose should match the lever? Itís really confusing me. Any help would be greatly appreciated. Thanks.
Paper Pixels is offline  
Old 03-04-20, 08:16 PM
  #2  
dsbrantjr
Senior Member
 
dsbrantjr's Avatar
 
Join Date: Sep 2010
Location: Roswell, GA
Posts: 7,560

Bikes: '93 Trek 750, '92 Schwinn Crisscross, '93 Mongoose Alta

Mentioned: 22 Post(s)
Tagged: 0 Thread(s)
Quoted: 1155 Post(s)
Liked 541 Times in 392 Posts
I am not familiar with that caliper/lever combination's compatibility, but I suspect that the combination,not the hoses, is the problem. The hoses merely transmit the hydraulic pressure from the levers to the calipers, regardless of their length or diameter. In the absence of air it is a hydrostatic system, and only the relative areas/diameters of the pistons determines the "leverage" of the system. I suspect that the levers' pistons are too small relative to the calipers' pistons. You should be checking the compatibility of the levers and calipers, not the levers and hoses.
Edit: There is a reach adjustment, which if set too close, can allow the lever to hit the bars before providing full power. Perhaps yours is set this way.
https://road.cc/content/review/11497...ydraulic-discs

Last edited by dsbrantjr; 03-04-20 at 09:35 PM.
dsbrantjr is offline  
Old 03-05-20, 12:02 AM
  #3  
Paper Pixels
Newbie
Thread Starter
 
Join Date: Sep 2019
Posts: 3
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
Thanks for getting back to me. As far as I know they are compatible as both are road components and Shimano doesnít make another post mount calliper. As for the reach adjustment, it is set to be as far out as possible, so canít be that. The levers are GRX 400 which donít have any free stroke adjustment, maybe that is the problem? Whatever it is, I canít use them as they are.
Paper Pixels is offline  
Old 03-05-20, 09:06 AM
  #4  
redlude97
Senior Member
 
Join Date: Sep 2011
Posts: 4,656
Mentioned: 28 Post(s)
Tagged: 0 Thread(s)
Quoted: 1924 Post(s)
Liked 178 Times in 130 Posts
Can you describe your bleed procedure? How many times have you tried?
redlude97 is offline  
Old 03-05-20, 09:39 AM
  #5  
Paper Pixels
Newbie
Thread Starter
 
Join Date: Sep 2019
Posts: 3
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times in 0 Posts
My best mate, who has been a bike mechanic for 30 years, spent a whole day trying and failed with both callipers. I am going to give it one last go and work through the official Shimano bleed procedure from the manual step by step before I try other options. But if you have any bleeding tips that would be great!
Paper Pixels is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service - Do Not Sell My Personal Information -

Copyright © 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.