Brake specs

[backlander]

Here's an article explaining master cylinders, its on cars but the same principle applies.


https://markwilliams.com/braketech.aspx

 

[slabghost]

Good article.

 

[brianinpa]

backlander » Thu Oct 20, 2016 9:59 pm[/url]":fp5na6wi]
I edited my post and you might not of seen where I ask about the possibility of out of spec wear on the mc bore and/ or piston. Did you rebuild the m/c?

I had this problem when I first installed the donor bike 84 brake caliper onto the 81 MC and brake line, so I rebuilt the caliper, MC and replaced the brake line. I still had the same problem. So I took the MC off of the 84 Standard but that didn't change anything, so the MC has been rebuilt (and everything was within tolerances), a new SS brake line, and the caliper is known to have worked for me when I had the bike in Texas back in August.

I have the push rod adjustment on the MC so far out that I know I am getting full travel of the piston which is why I think it is lack of fluid volume being moved.

I am still at basic hydraulics here. While I agree you might not have enough to get a good push on the rotors with the smaller MC, but it should still fill the lines and pistons with fluid and take good pressure. Pumping up only proves air in the system.

I hear what you are saying (or rather see what you are typing) but if there is still air in that system, I am at a loss as to how to get it out of there.

I have been searching (without any luck) for something that shows what kind of pressure the different model master cylinders put out or what the calipers need so I could match up parts but I cannot seem to find anything. I am just about to the point of putting the 81 caliper back on just to confirm my suspicion that the caliper isn't putting out enough fluid for the 84 caliper - the problem with that, there is no way to easily adapt the 81 brake caliper bracket to the 84 swingarm.

 

[brianinpa]

backlander » Fri Oct 21, 2016 1:23 am[/url]":3q6lylj9]
Here's an article explaining master cylinders, its on cars but the same principle applies.


https://markwilliams.com/braketech.aspx

Ooooo!

After reading that, I have a few things to look at...

Spongy Pedal:

1) Air in system. Bleed brakes, making sure that the bleed valve is the highest point.
2) Disc warped (saucer shaped). Replace or surface rotors
3) Calipers not square with disc. Check housing end alignment, both concentricity and squareness.
4) Linings worn on taper. Make sure that caliper is centered over the rotor and the caliper bracket is not deflecting.
5) Master cylinder bore too small creating excessive high line pressure. Match master cylinder to system.
6) Master cylinder deflection. Stiffen master cylinder mounts

 

[Tom_Charlton]

Since you have already tried the 84 MC, the prime candidate remaining is air in the lines.

 

[brianinpa]

PurpleGL1200I » Fri Oct 21, 2016 2:18 pm[/url]":jr28y803]
Since you have already tried the 84 MC, the prime candidate remaining is air in the lines.

Let me correct something in a previous post...

So I took the MC off of the 84 Standard but that didn't change anything.

That should be caliper. I haven't changed the Master Cylinder with the 84 yet.

 

[slabghost]

84 master might just do the trick nicely.

 

[backlander]

84 Rear Master cylinder is linked so the front port will have to be blocked off.

 

[joedrum]

i personally dont think there is a mismatch in the parts .....they should work together

 

[backlander]

They should work together, maybe not as well as if they matched but they should work. Putting a larger bore master on it will increase volume of fluid moved but gives a harder pedal. The smaller master increases pressure in the line. Since all these other things have been tried, might not hurt to check the new ss brake line, I've read about cases where people have found partial or total blockage in a new line especially in the rubber flex part

 

[brianinpa]

THis morning I awoke to some of that frozen stuff on the ground so today was the day to try something with the brakes. I pulled the 1200 caliper off and put the 1100 caliper on. I bled the brake with the vacuum bleeder just like I did the 1200 caliper, and I had a stiff pedal.

I know there are those that think it was air in the system, but I cannot see that I had any air in the system with the 1200 caliper. The bore of MC on the 1100 is 1 MM smaller than the MC of the 1200... Could that 1 MM be enough? It looks like it to me.

Now I need to tear the rear end apart again and figure out how I am going to get the 1100 caliper/mount to work with the 1200 rotor and Swingarm.

 

[slabghost]

Pretty sure Joe is using the 1200 caliper because the mounts are that different.

 

[brianinpa]

The 1200 mount will not hold the 1100 caliper. The thing I need to figure out is holding the 1100 mount in place on the 1200 Swingarm since the anchor point for the 1200 is not the same. I have a few ideas, I just need to see what works best.

 

[Denver]

Think the 1100's use a metal bar to brace the caliper not the bolt set up on the 1200's, if memory serves. :headscratch:

 

[brianinpa]

Correct, but the 1200 SA does not have the anchor point for the bar, so I need to find/make an anchor point

 

[brianinpa]

I have the 1100 caliper mount on with the 1200 swing arm and wheel. I had to change the rotor to an 1100 rotor since the brake pads are a different size. When putting everything together, I am finding that the caliper mounts are a different thickness.

The only way to get everyone to fit is to use an 1100 axle and install the wheel just like an 1100 wheel... anyone see a reason it won't work? The axle bolts are the same diameter, just a different length.

 

[kerryb]

You're going to a great deal of trouble for a goal that seems unclear to me. Before trying to make a carrier for an '84 caliper to a '81 swingarm, how about trying an '82 or '83 caliper which might be plug and play? You just want brakes that work right? I've struggled with air in the lines many times, clamping down the Mc and leaving it to let the air find its way out overnight has usually solved my problem.

 

[brianinpa]

I am working with the parts that I have and I am not buying any more. In addition, the 82/83 master cylinder is a different part number from the 81 master cylinder, so I am not sure that a 82/83 caliper it is plug and play with the 81 MC or will I be in the same situation as I was with the 1200 MC. :Awe:

I had all the air out of the system when I had the 1200 caliper on the bike. I tried every trick that I know and I could not get a stiff brake pedal. As soon as I put the 1100 caliper on with the 1100 master cylinder, I was able to get a stiff brake pedal on the first pump of the pedal after using the vacuum bleeder.

I have everything is place and ready to finish it tomorrow.

 

[joedrum]

good deal

 

[julimike54]

Finished? no pics, didn't happen