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From: Joerg <news@analogconsultants.com>
Newsgroups: rec.bicycles.tech
Subject: Re: Disc Compatibility?
Date: Tue, 4 Mar 2025 15:49:26 -0800
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On 3/4/25 2:29 PM, Mark J cleary wrote:
> On 3/4/2025 2:16 PM, cyclintom wrote:
>> Andrew, I have GRX levers and Ultegra  actuators. It acts as if these 
>> are not compatible. The levers on both front and rear will not "pump" 
>> the brake pades close enough to the discs so that they actuate with 
>> almost no pull. Instead they pull almost all of the way to the bar.
>>
>> The pads are hardly worn and there are no leaks from the connections.
> This is a common problem if I understand it correct from you. The travel 
> of the brake levers hits the bars before the pads fully engage or stop. 
> The first thing to do is take of the bleed nipple in the shifter and 
> pump it lightly with the wheel in lace. You likely have air in the 
> system that is not fully out. Just pump a little at a time no all the 
> way down to allow air to come up out of the top. Might need to do it 
> twice. It can be that you need to even add bit of fluid to the brakes 
> but see how this goes and report back.
> 

Tom, look at the brake pads closely while pulling the handle very 
slowly. If they travel the whole time while pulling they might be 
incompatible. But that would be really odd.

If they engage the rotor and stop there but you can pull the handle 
farther without the pads moving, that indicates air in the system like 
Mark said. Very dangerous and it needs to be bled off.

When the pads hit the rotor there should instantly be a hard-stop 
feeling in the brake lever. There should also never be a need to "pump" 
bike disc brakes except during the bleeding process.

-- 
Regards, Joerg

http://www.analogconsultants.com/