Hello all,

I just replaced my handle bars with Santee 11" bagger apes. The front brake master cylinder resovoir was perfectly level with the ground on my old bars, so the brake fluid was an even 1/4" from the top all around. With the new bars, the angle on the front brake master cylinder resovoir is such that the back of the resovoir is lower than the front, so when I filled it with brake fluid, the level of the fluid was 1/4" from the top in the rear of the resovoir, and about 5/8" from the top in the front of the resovoir. Is that going to be an issue? I thought about loosening the mount and setting the resovoir even with the ground, filling it, putting the top on, then adjusting acordingly, but I'm concerned that if someone opens it for service, or if I forget, all the fluid will come spilling out.

What say you all on what I should do here?

Thanks in advance for your help.

 

It is fine just like it is, the reason to have a reservoir is to keep air out of the lines, keeping enough fluid over the piston to keep air out.

 

Your fine, ride on.

 

If the system is still dry and open you can do some measurements for peace of mind.

In principle, you need to make sure that the outlet port me between reservoir and master cylinder in always 100% flooded / covered.

A key function of the reservoir is to allow for variation of fluid volume in the system. As the brake is applied and the pistons push out, so the volume of fluid in the reservoir changes.

If you can take the following measurements:

Piston diameter and number of pistons

Pad thickness

Length, breadth and height of reservoir

Firstly you can then calculate the total volume change as the brake pads wear down. This would be:

Pi x (piston diam)^2 x (pad thickness + air gap)

Then calculate reservoir cross sectional area :

Area = length x breadth (if you wanted to get really clever you could calculate this as a function of reservoir angle but ignoring that for now)

Finally you can then calculate the change in reservoir height due to the full volume change

Height = volume (calc 1) / Area (calc 2)

That should give you a reasonable indication. If, at the worst case (ie pads worn down completely) you are only just covering the port then you should be careful as well. Sloshing of the fluid while riding and having a marginal flooding of the port will result in air ingression

 

Just to be clear, the volume calc above is for each piston so you would need to multiply this by the number of pistons to get total volume.

So, change the final calc to

Height = volume (calc 1) x no. of pistons / area (calc 2)

 

As someone wih a degree in mathematics, you just made my day...lol

While the above would work great, I'll just take comfort in knowing that the pickup from the resovoir to the piston is covered, so I should be good to go.

Thanks

 

My first bike with hydraulic brakes was a Harley with cowhorn bars. Before I opened the reservoir I turned the handlebars to the left, which while parked on the jiffy got it close to horizontal. Bleeding obvious really! Try that with yours.

 

Pun intended??

 

I cannot lie!

 

All the Math calculations "Really", Turn the bars to the left take off the cover slowly squeeze the brake if there is still fluid in the resivour you are good to go.