On 3/2/2025 11:16 AM, cyclintom wrote:

I have no leaks anywhere but the rear GRX in particualr will not bleed correctly. I will try tilting the bike in the stand so that any air in the system will find its way to the lever. The Tektro set of brakes I had had this problem but leaving it lay

overnight allowed air bubbles to work their way out of it and it worked fine after that.

Remove the rear caliper so it hangs well below the rest of
the system. Rap the caliper lightly while you're pushing
fluid through, up to the lever. The way the rear caliper is
mounted, the line dips down from the caliper before rising
up to the lever. Air in the caliper won't move without some
encouragement

--
Andrew Muzi
am@yellowjersey.org
Open every day since 1 April, 1971

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On Sun Mar 2 11:20:56 2025 AMuzi wrote:

On 3/2/2025 11:16 AM, cyclintom wrote:

I have no leaks anywhere but the rear GRX in particualr will not bleed correctly. I will try tilting the bike in the stand so that any air in the system will find its way to the lever. The Tektro set of brakes I had had this problem but leaving it

lay overnight allowed air bubbles to work their way out of it and it worked fine after that.

Remove the rear caliper so it hangs well below the rest of
the system. Rap the caliper lightly while you're pushing
fluid through, up to the lever. The way the rear caliper is
mounted, the line dips down from the caliper before rising
up to the lever. Air in the caliper won't move without some
encouragement

After thinking about it I realized that on all of my previous disc bikes that the line ran up the \seat stay and down the top tube to the nevers and the actuators were mounted on the back of the seat stay. This gave pretty much an alway "up" route for
the brake fluid making it easy to flush air out of the system. The Idol has internal brake hoses making a lot of ups and down and making it difficult to flush air out of the system. I did try using the rear actuator port for pumping air out of the system
and that pulled out a lot of air. But the brake still would not pump the brake pads in very colose to the discs and it took full pull to get brakes though they were pretty strong.. Now I have to figure out how to eliminate all of the lever travel.

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On Mon Mar 3 16:57:58 2025 cyclintom wrote:

On Sun Mar 2 11:20:56 2025 AMuzi wrote:

On 3/2/2025 11:16 AM, cyclintom wrote:

I have no leaks anywhere but the rear GRX in particualr will not bleed correctly. I will try tilting the bike in the stand so that any air in the system will find its way to the lever. The Tektro set of brakes I had had this problem but leaving it

lay overnight allowed air bubbles to work their way out of it and it worked fine after that.

Remove the rear caliper so it hangs well below the rest of
the system. Rap the caliper lightly while you're pushing
fluid through, up to the lever. The way the rear caliper is
mounted, the line dips down from the caliper before rising
up to the lever. Air in the caliper won't move without some
encouragement

After thinking about it I realized that on all of my previous disc bikes that the line ran up the \seat stay and down the top tube to the nevers and the actuators were mounted on the back of the seat stay. This gave pretty much an alway "up" route for

the brake fluid making it easy to flush air out of the system. The Idol has internal brake hoses making a lot of ups and down and making it difficult to flush air out of the system. I did try using the rear actuator port for pumping air out of the system
and that pulled out a lot of air. But the brake still would not pump the brake pads in very colose to the discs and it took full pull to get brakes though they were pretty strong.. Now I have to figure out how to eliminate all of the lever travel.




And considering the Tekitro system - it uses regular brake fluid which is a LOT less viscus so that would make air bubbloes move more freely upwards which is why leaving it overnight allowed the brakes to work fine the next day. Shimano's mineral oil has
a high viscosity in comparison which is prolematic.

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On 3/3/2025 11:10 AM, cyclintom wrote:

On Mon Mar 3 16:57:58 2025 cyclintom wrote:

On Sun Mar 2 11:20:56 2025 AMuzi wrote:

On 3/2/2025 11:16 AM, cyclintom wrote:

I have no leaks anywhere but the rear GRX in particualr will not bleed correctly. I will try tilting the bike in the stand so that any air in the system will find its way to the lever. The Tektro set of brakes I had had this problem but leaving it

lay overnight allowed air bubbles to work their way out of it and it worked fine after that.

Remove the rear caliper so it hangs well below the rest of
the system. Rap the caliper lightly while you're pushing
fluid through, up to the lever. The way the rear caliper is
mounted, the line dips down from the caliper before rising
up to the lever. Air in the caliper won't move without some
encouragement

After thinking about it I realized that on all of my previous disc bikes that the line ran up the \seat stay and down the top tube to the nevers and the actuators were mounted on the back of the seat stay. This gave pretty much an alway "up" route for

the brake fluid making it easy to flush air out of the system. The Idol has internal brake hoses making a lot of ups and down and making it difficult to flush air out of the system. I did try using the rear actuator port for pumping air out of the system
and that pulled out a lot of air. But the brake still would not pump the brake pads in very colose to the discs and it took full pull to get brakes though they were pretty strong.. Now I have to figure out how to eliminate all of the lever travel.

And considering the Tekitro system - it uses regular brake fluid which is a LOT less viscus so that would make air bubbloes move more freely upwards which is why leaving it overnight allowed the brakes to work fine the next day. Shimano's mineral oil

has a high viscosity in comparison which is prolematic.

Well, yes.

More significantly, in all our bicycle hydraulic systems the
internal area of the lines is smallish relative to the fluid
viscosity and so air bubbles will not migrate up without
assistance in most cases. In practice, that's very different
from automotive brake lines.

--
Andrew Muzi
am@yellowjersey.org
Open every day since 1 April, 1971

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* Origin: fsxNet Usenet Gateway (21:1/5)

On Mon Mar 3 11:41:38 2025 AMuzi wrote:

On 3/3/2025 11:10 AM, cyclintom wrote:

After thinking about it I realized that on all of my previous disc bikes that the line ran up the seat stay and down the top tube to the levers and the actuators were mounted on the back of the seat stay. This gave pretty much an alway "up" route

for the brake fluid making it easy to flush air out of the system. The Idol has internal brake hoses making a lot of ups and down and making it difficult to flush air out of the system. I did try using the rear actuator port for pumping air out of the
system and that pulled out a lot of air. But the brake still would not pump the brake pads in very colose to the discs and it took full pull to get brakes though they were pretty strong.. Now I have to figure out how to eliminate all of the lever travel.

And considering the Tekitro system - it uses regular brake fluid which is a LOT less viscus so that would make air bubbl es move more freely upwards which is why leaving it overnight allowed the brakes to work fine the next day. Shimano's mineral oil

has a high viscosity in comparison which is prolematic.

Well, yes.

More significantly, in all our bicycle hydraulic systems the
internal area of the lines is smallish relative to the fluid
viscosity and so air bubbles will not migrate up without
assistance in most cases. In practice, that's very different
from automotive brake lines.

There was one video that showed how to bleed brakes only using gravity. I thinlk that if you have a work stand that can rotate the bike enough that might be a ood way to accomplish it.

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