ST1100 1997 ABSII Rear Brake Pad Wear

[Uncle Phil]

One of my girls is 'eating' rear brake pads a lot quicker (4,000-5,000) miles than I think she should.
Is there an easy 'test' to see if it is the SMC or the rear caliper?
It is curious that the 'worn out' pad is always the one on the opposite side of the caliper pistons so I am thinking SMC at this point.

 

[Obo]

Swap the caliper with one of the other girls?

 

[Uncle Phil]

Swap the caliper with one of the other girls?

I have 'spares' but before I do parts change I was hoping someone might confirm yes or no if it was probably the SMC.
Bleeding the ABSII brakes is a bit of work that I hope I don't have to do twice.
I definitely do not swap parts off one of my other 'runners' as then I would have two that aren't working.

 

[Larry Fine]

It is curious that the 'worn out' pad is always the one on the opposite side of the caliper pistons so I am thinking SMC at this point.

That suggests to me that the caliper is not sliding easily on the rails.

 

[Firstpeke]

I would recommend giving the caliper a right good strip and clean....

When I had my ST's I was a bit OCD regarding brakes as I had been told they could be problematic if not looked after.

Cleaned the calipers every tyre change and service, used ACF50 after cleaning to coat the exposed piston and used copper grease on the back of the pads....
Pins and sliders were cleaned and lubed with required product, I used to coat the hanger pins lightly in moly paste as it seemed to work better.

If the pistons were not going back in correctly, that would involve a piston pull to clean everything more thoroughly, especially the seal grooves.
Red rubber grease used on re-assembly on the seals...
I even cleaned the brake pads with an old toothbrush and brake cleaner.....

As you say, bleeding the brakes is tediously frustrating on the ABS/CBS bikes.... and keeping the SMC working properly can be too....

Never had a brake problem.

Hope this isn't a lesson in sucking eggs, you have had your ST's longer than I ever did!

 

[Bmacleod]

ST 1100 has linked brakes?? I thought that was only 1300. I would agree with @Larry Fine , sounds like the caliper is sticking.

 

[Andrew Shadow]

If the pad wear is more pronounced on the side of the caliper opposite the pistons, that is because that side of the caliper is no longer moving away from the disc once the hydraulic pressure has been released. This indicates that the caliper is no longer moving freely on the slider pins.

An SMC maintaining un-commanded hydraulic pressure would manifest itself by the pads being worn very similarly on both sides of the caliper if the caliper is moving freely on the slider pins. If the caliper is sticking on the slider pins at the same time that there is a defective SMC, this would result in more wear of the pads on the piston side as these pads are being pressed against the disc while the pads on the opposite side have less force applied to them because the caliper is not moving freely on the slider pins.

Manually pivoting the SMC while checking to see if it prevents wheel rotation, and that it allows the wheel to rotate freely when it is released, gives an indication of the condition of the SMC.

 

[ToddC]

What they said...!! Caliper isn't releasing evenly.
T

 

[Uncle Phil]

ST 1100 has linked brakes?? I thought that was only 1300. I would agree with @Larry Fine , sounds like the caliper is sticking.

Yeppers, the ST1100 ABS had linked brakes (or at least the ABSII did).

 

[Bmacleod]

Yeppers, the ST1100 ABS had linked brakes (or at least the ABSII did).

Learned something new

 

[Uncle Phil]

Took the rear caliper off and what I found was that the pads on the other side of the disc (not the piston side) were worn at an angle -
thin at the top but reasonable at the bottom.
So I pulled the mounting bracket off the caliper, cleaned up the two sliders (yes they were nasty!), lubed them up and put on new pads.
I plan on a little 'test' ride tomorrow to see if that solves the problem.
Thanks again for all of your input.

 

[IndyRob]

Clean brakes are happy brakes.

 

[Ron]

In case you're wondering, the pin is the same fronts and back on the ABS II model.

 

[Al st1100]

Took the rear caliper off and what I found was that the pads on the other side of the disc (not the piston side) were worn at an angle -
thin at the top but reasonable at the bottom.
So I pulled the mounting bracket off the caliper, cleaned up the two sliders (yes they were nasty!), lubed them up and put on new pads.
I plan on a little 'test' ride tomorrow to see if that solves the problem.
Thanks again for all of your input.

are there seals/dust covers to keep the slides from getting water or grime in there?

 

[Uncle Phil]

are there seals/dust covers to keep the slides from getting water or grime in there?

There are some rubber 'grommets' but obviously they do not do a really good job over time.

 

[Uncle Phil]

Just got back from a test ride and the wheel spins freely and the pads are fine.
Sure beats having to replace/repair a SMC.
New rear tire change procedure addition - clean and lube the caliper pins!

 

[bdalameda]

I do know that if the SMC has issues with the small vent hole in the small plastic check valve (puck on the side) being plugged or partially plugged you will eat rear brake pads as the brakes will be slow to release completely causing rapid pad wear. Does the rear disk show any signs of overheating or wear??

 

[Uncle Phil]

I do know that if the SMC has issues with the small vent hole in the small plastic check valve (puck on the side) being plugged or partially plugged you will eat rear brake pads as the brakes will be slow to release completely causing rapid pad wear. Does the rear disk show any signs of overheating or wear??

Nope, I think it was just cruddy slider pins.
The rear wheel spins freely now - which is a pretty good sign the SMC is not sticking.

 

[Larry Fine]

So I guessed correctly?

 

[jfheath]

Well done for getting it sorted. The other thing that can cause this behaviour is a damaged or incorrectly located pad spring.

ST 1100 has linked brakes?? I thought that was only 1300.

The 1300 adopted the same logical layout of the brake system from the ST1100 ABS II models . All of the individual components were re-designed of course, but there are a lot of similarities.

The 1100 has an SMC which - like the rear master cylinder - faces downwards so that any water near the rubber boot will never pool - now there's a good idea ! But the linkage between SMC, caliper and front forks is a 3-pivot arrangement with needle roller bearings, and it is more of a suspect for rear brake drag than is SMC failure. Its a good idea to take a look behind the shroud and see if it needs cleaning it up - every now and then - especially if you frequently ride wet roads. My first rear brake drag issue was due to this linkage become clogged / rusted and the parts were not free to move as they should. I cleaned it up twice in 50,000 miles, first out of necessity - the bike was second hand and had been sitting a while. Second time was just routine maintenance now that I had identified it as a potential problem.