unusual brake problem

tswisher21

Joined
May 6, 2012
Messages
4
Location
exeter nh
I have a 05 st1300a.It has 15,000 mileson it. I don't think my rear brakes are working. When i
step on the pedal, the front of the bike will dive but the bike really doesen't want to stop.Yea it stops but not the way it should!!!!!!!I can stand on the pedal. If i did this on my bmw the abs would kick in and the bike would stop. Help please. Tim
 
The front breaks hold 2/3 of the breaking power. You will need to check the system. It could be anywhere. rear brake cylinders, blocked brake fluid, air, smc. Laying on the ground hold the SMC closed and spin the rear wheel with your foot. It you can stop it with the SMC in your left hand it will give you a clue where the problem is.
Ron
 
Well yeah if all you are doing is stepping on the foot brake?

That engages only 2 of the 6 pistons in the front BRAKES. The front brakes give perhaps 75 to 80% of braking power. On BMW linked brakes the pedal engages all of the front pistons IIRC. Honda's linked brake system on the ST1300 is not the same as BMW's. Don't you normally use mostly the front brake to stop?
 
You should be able to lock the rear standing on the pedal. I'd begin by flushing the entire system.
 
I had a weak foot brake when I was bleeding the lines. I had to continue bleeding to get the last bit of air out. Have you been working on any of the brake system lately? Also, how are the brake pads?
Ron
 
jfheath said:
Its also possible that someone at some time has used inappropriate grease when the wheel has been out. If so, when it gets thin (as it will with heat build up from the brakes and exhaust) it throws itself out and forms feint streaks on the disk surface, the wheels and tyres. And of course this ends up on the pads. You can tell by running your fingers over the hub closest to the axle. If it is smeared, you need to clear out the old grease and put in smears of General Purpose Lithium based High Melting point stuff. I use Castrol LM. But its only to keep the seal lubricated, and it helps to keep the water out. The sealed bearing contains the grease that does the real work.
Click to expand...

:plus1:
 
tswisher21 said:
I don't think my rear brakes are working. When i step on the pedal, the front of the bike will dive
Click to expand...
Hmm.. If the front end dives when applying the rear brake, then something is working.

The Honda linked brake system is a clever bit of engineering, however it is sensitive to regular maintenance.
Leave off on the maintenance, and the brake system will most likely not perform as well as it was intended to.

Here is a sketch I made to aid in my understanding of how the Honda Dual Combined Brake System works, perhaps it will help you in resolving your braking issue.
 
Bleed the system correctly, lube the pivot point on the lower left caliper, grease the pivot bearings, then do the SMC test again.
After you bleed the system, strap the levers open over night, this will also help vent air bubbles you can't see out of the system.
.02
 
I am most likely to believe that the rotor and pads are contaminated with improper grease or grease from a tire change. So now what, sand the rotors and the pads? There is no reason for air to be in the system, it has not been bleed sence i bought the bike,last spring. thanks for the ideas keep them coming. Tim
 
tswisher21 said:
I am most likely to believe that the rotor and pads are contaminated with improper grease or grease from a tire change. So now what, sand the rotors and the pads? There is no reason for air to be in the system, it has not been bleed sence i bought the bike,last spring. thanks for the ideas keep them coming. Tim
Click to expand...

1. Remove all the pads and clean them with break cleaner and industrial scotchbright pad.
2. Bleed the system CORRECTLY
3. Lube pivot points in left front caliper

Air does not "get into the system", more than likely what your feeling is the fluid starting to break down and degrading.
Search the threads for brake bleeding info.
Milehigh has a great artical on the subject.

.02
 
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Igofar said:
1. Remove all the pads and clean them with break cleaner and industrial scotchbright pad.
2. Bleed the system CORRECTLY
3. Lube pivot points in left front caliper

Air does not "get into the system", more than likely what your feeling is the fluid starting to break down and degrading.
Search the threads for brake bleeding info.
Milehigh has a great artical on the subject.

.02
Click to expand...
Air indeed gets into brake systems because of the nature of common DOT 3 & 4 brake fluid. It is hygroscopic - it attracts tiny amounts of moisture through permeable rubber lines and gaskets under reservoir caps. When fluid is heated during brake use or from proximity to hot engines or exhaust pipes this moisture separates into very small bubbles and eventually these bubbles accumulate together into quantities large enough to create sponginess in pedals and levers. This is well known science. In many hydraulic systems the accumulated air works its way up and out of the critical parts of the system but on the ST1300 the design and placing of components does not allow this to happen. Moisture and air tends to accumulate in the bore of the secondary master cylinder and near the proportional control valve. Honda recognized this and recommends regular changing. This service can be ignored only at the risk of the problems that regularly pop up on this bike.
 
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Fred D said:
That being the case, it would seem that exercising the piston in the secondary master would be all the more critical, to ensure the moisture and air is expelled both from the secondary master cylinder and the proportional control valve.

https://www.st-owners.com/forums/showthread.php?120665-Brake-bleed-experience&highlight=
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The stroke of the SMC does not include enough travel to displace the entire volume of the bore. Because the SMC is oriented downward from inlet to outlet, air accumulates at the upper front end and is not pushed out of the bore in use. Exercising the SMC at bleed doesn't change the angle and position of the bore inlets and outlets and can't clear old fluid and air completely. Honda knew this and wrote the step of removing and tilting the SMC 15 degrees so air/moisture would travel upwards and be in position to leave the SMC when bled.
 
dduelin said:
The stroke of the SMC does not include enough travel to displace the entire volume of the bore. Because the SMC is oriented downward from inlet to outlet, air accumulates at the upper front end and is not pushed out of the bore in use. Exercising the SMC at bleed doesn't change the angle and position of the bore inlets and outlets and can't clear old fluid and air completely. Honda knew this and wrote the step of removing and tilting the SMC 15 degrees so air/moisture would travel upwards and be in position to leave the SMC when bled.
Click to expand...

So do it several times, tilted at 15 degrees.
 
Fred D said:
So do it several times, tilted at 15 degrees.
Click to expand...
Yes, I do probably two or three reservoir fills of new fluid through from rear master cylinder reservoir to bleed nipple on the circuit that runs thru the SMC. I know that the Motion Pro bleeder works well but I still use a vacuum pump and it just can't pull fluid through the very long circuits to the rear caliper so I help it by pumping the brake pedal while vacuum is present. I do about 10 strokes of the pedal and check the master cylinder level as it cannot run dry and pull air in.
 
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