Rear Braking Issue

Big_Willy

Registered
Lately I’ve noticed I have to press the rear brake pedal a bit harder. I replaced the rear pads......braking not much better. So I suppose the master cylinder is going out. I saw a new one on bike bandits for almost $200. Master cylinder rebuild kits are under $40. I’m not sure which route I want to take. Also, who makes quality rebuild kits for Rear master cylinders?
 
1) Gen 1 or 2?
2) How many miles on it?
3) When was the last time (miles) the brake pads and brake fluid was changed?
4) What brand and type ( organic or sintered material? ) are the pads?
5) Is the rotor OEM or aftermarket (brand?)
6) Condition of the rotor and pads?
7) Have you tried bleeding the air from the caliper?
8) Have you checked the caliper pistons' ease of movement? free or stiff/seized?
9) Does it have a standard rubber hose or is it stainless braided hose?
10) Is the fluid level low or dirty?

. . . . This is information you need to divulge when asking the forum about why your brake has a problem . . . just assuming the master cylinder is "going out" is totally the wrong approach to diagnosing a perceived fault in the braking performance.... there are many many reasons why braking performance suffers loss, let's get to the bottom of this . . .
 
@Big_Willy

clean deep the rear caliper - i guess he´s producing your issue.

see here what i found in ´99 tokico front calipers

terrifying i guess :shocked: :banghead: :eek:

and i suppose your rear one is in similar condition.
To answer the questions Kiwi asked:
Gen 1
15k miles.
New EBC sintered pads.
Never changed flu
OEM rotors.
Did not try bleeding the system since I hadn’t done anything to introduce air.
Fluid is topped off.
caliper pistons move freely.
stainless Steel lines.

To Berlin.....I cleaned the calipers when I installed the new pads 2 weeks ago.

Willy
 
To answer the questions Kiwi asked:
Gen 1
15k miles.
New EBC sintered pads.
Never changed flu
OEM rotors.
Did not try bleeding the system since I hadn’t done anything to introduce air.
Fluid is topped off.
caliper pistons move freely.
stainless Steel lines.

To Berlin.....I cleaned the calipers when I installed the new pads 2 weeks ago.

Willy
The rear brakes generally suck on these bikes...

Your pads could have become glazed as sometimes people's feet accidentally ride the rear brake slightly without knowing it...
 
To answer the questions Kiwi asked:
Gen 1
15k miles.
New EBC sintered pads.
Never changed flu
OEM rotors.
Did not try bleeding the system since I hadn’t done anything to introduce air.
Fluid is topped off.
caliper pistons move freely.
stainless Steel lines.

To Berlin.....I cleaned the calipers when I installed the new pads 2 weeks ago.

Willy
Ok, try changing the fluid and flushing it thoroughly.
My rear brake was very poor UNTIL I replaced the brake hose on my ‘99, ....and I’d already done EBC HH sintered pads, new fluid, cleaned out the caliper etc, and the braking was soft and lousy, UNTIL I fitted that new stainless braided hose... man what a difference that made!
If the fluid is old it may very well have a high moisture content... when heated with braking the fluid will boil due to the water/moisture and will cause cavitation causing air bubbles to form.
It happened to me on a bike I’d just bought and the rear brake faded and went spongey on hard braking... air was introduced into the system because of that.
 
Ok, try changing the fluid and flushing it thoroughly.
My rear brake was very poor UNTIL I replaced the brake hose on my ‘99, ....and I’d already done EBC HH sintered pads, new fluid, cleaned out the caliper etc, and the braking was soft and lousy, UNTIL I fitted that new stainless braided hose... man what a difference that made!
If the fluid is old it may very well have a high moisture content... when heated with braking the fluid will boil due to the water/moisture and will cause cavitation causing air bubbles to form.
It happened to me on a bike I’d just bought and the rear brake faded and went spongey on hard braking... air was introduced into the system because of that.
My rear brake sucks even with HH pads and a steel line...I generally use it to scrub a little speed off while entering an apex....it kind of works for that..
 
Ok, try changing the fluid and flushing it thoroughly.
My rear brake was very poor UNTIL I replaced the brake hose on my ‘99, ....and I’d already done EBC HH sintered pads, new fluid, cleaned out the caliper etc, and the braking was soft and lousy, UNTIL I fitted that new stainless braided hose... man what a difference that made!
If the fluid is old it may very well have a high moisture content... when heated with braking the fluid will boil due to the water/moisture and will cause cavitation causing air bubbles to form.
It happened to me on a bike I’d just bought and the rear brake faded and went spongey on hard braking... air was introduced into the system because of that.
Thanks Kiwi. I will try all of your recommendations.

Willy
 
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