Rear brake system

Joined
Jul 7, 2014
Messages
77
Location
California
Bike
2004 ST1300
So on the way home last week and stopped at the only stop sign till I get there. I heard and felt what I thought was a wheel dragging. It was the rear disc being ground. 22 miles from home, no cell service and 0310. Yup, I rode it home. So now I'm wondering why, and can I get a used rotor?
 

Trapperdog

R.I.P. - 2022/10/14
Rest In Peace
Joined
Oct 2, 2016
Messages
304
Location
Los altos Ca
Bike
09 ST1300 PA
Yes, I’ll bet your SMC is frozen as well. I was lucky in that one of my ST’s SMC was frozen in the open position but I’ve seen a drawer for of them Locked In the closed position over at Larry’s. I’d address that and a good bleed first.
 

SupraSabre

48 Years of SoCal Lane Splitting/Commuting-Retired
Site Supporter
Joined
Nov 20, 2005
Messages
9,499
Location
Cedar City, Utah
Bike
12/04 ST 1300s
2024 Miles
000145
STOC #
5901
So on the way home last week and stopped at the only stop sign till I get there. I heard and felt what I thought was a wheel dragging. It was the rear disc being ground. 22 miles from home, no cell service and 0310. Yup, I rode it home. So now I'm wondering why, and can I get a used rotor?
I know where you might be able to pick up a rear rotor....cheap....:rolleyes:

I'll have to check the specs to make sure those I have are within specs.
 
OP
OP
Joined
Jul 7, 2014
Messages
77
Location
California
Bike
2004 ST1300
Thanks to all that responded and yes, SupraSabre, I'd be VERY interested in a good used rear rotor. Hard to imagine the prices commanded for a new one. My next question is....what's an SMC? What do they do and how much are they? Based on the price of the rotor, I'm sure they are not inexpensive.
 
Joined
Feb 25, 2016
Messages
4,759
Location
Northumberland UK
Bike
VStrom 650
Raybonz, check in the technicals re SMC, they take up about 90% of the posts. Well maybe not 90%. I've told myself a million times not to exaggerate.
But, the SMC is strapped on your front caliper and when it detects braking force on the front it distributes braking force to the rear, if it sticks then you can get constant braking force onto the rear, hence a sticking brake. Don't think the prices are too had but the expertise and knowledge required to fit and bleed may be an issue. The SMC is what makes your CBS work, or NOT.
Hope it helps.
Upt'North.
 

technotony007

Marvellous !
Joined
Oct 30, 2016
Messages
146
Location
durham ,uk
Bike
2005 Pan Euro ST1300
Plus one for the SMC , i had exactly the same episode.... A good flush through with New Quality brake Fluid. Make sure you follow the bled sequence also.

It took me around 5 months to sort mine out , with a visit to Mr Heath as well.

regards

tony
 

jfheath

John Heath
Site Supporter
Joined
Mar 18, 2006
Messages
2,786
Age
69
Location
Ilkley, W Yorkshire, UK
Bike
2013 ST1300 A9
2024 Miles
000679
STOC #
2570
You say the rear rotor was being 'ground' ? Do you mean metal on metal contact ? Or do you mean that the brakes were not releasing and the friction material on the pads was in constant contact with the brake disc / rotor ?

You managed to ride it home, so the wheel wasn't completely locked up.

Before solving a problem with the rear brakes, it helps to know what all of the symptoms are. It is true that an SMC that isn't functioning as it should will cause problems on the rear brake, but there are many other things that will cause problems without the SMC being the culprit. And some of these are easy to check and fix.

A few examples:

  • Stuck caliper pistons
  • Incorrect location of, or damage to pad spring (very possible).
  • Caliper sliders not allowing movement when brakes are applied and released (common)
  • Too much grease in caliper slider pins (yes, really).
  • Rusty / pitted / bent pad spring - preventing movement of pads (common).
  • Riding with new boots (and inadvertently applying pressure to rear brake pedal)
  • Collapsed rear wheel or rear flange bearings (putting rear wheel and rotor at an angle in relation to the caliper)
  • Both pads fitted to the same side of the disc rotor. (Yes, really).
  • Pads not seated in the clip at the deep end of the caliper (and resting / scraping on the wheel hub).
  • Spacing collar not put on axle (yikes)
  • New wheel bearings not inserted in the correct manner (displaces the centre line of the wheel and may cause the disc rotor to scrape on the caliper bracket).
  • Caliper bracket stopper bolt not located correctly (unlikely, but possible)
  • Front brake pads not releasing properly (thereby applying SMC and applying rear brake - So check pad pins, pad springs, caliper able to move on slider pins)
  • Front wheel not inserted correctly - check axle end and clearance between rotor and caliper bracket; also distance collars on each side are correctly installed.
  • Front pads are new and too thick, or have a heat shield fitted (there isn't enough room when pads are fairly new - the brakes drag and apply the SMC).
  • Compensation port in front brake lever master cylinder blocked.

I could go on (and usually do, but I'll stop there), but you get the idea ? - There are too many scenarios to work out what could be going wrong. Some photos of the damage and of the rear wheel / caliper might help. It might be something simple.

A useful check for the SMC is to check that the rear wheel isn't dragging, and then lie on the floor alongside the left side of the bike, with the bike on centre stand and gear in neutral. Turn the rear wheel with your foot. Apply the SMC with your hand - push it towards the fork to compress the plunger. It moves only a small fraction 1mm or 2, and shouldn't require force (I use the fork leg to squeeze it in my hand like a brake lever). If the rear wheel cannot be turned, then the SMC is applying the rear brake OK. Release the SMC and the rear wheel should turn OK. Do it a few times. If the wheel releases each time, then the SMC isn't the primary culprit. It isn't completely off the hook, but there must be something else causing the drag.
 
Joined
Feb 2, 2014
Messages
1,857
Location
houston, tx
So on the way home last week and stopped at the only stop sign till I get there. I heard and felt what I thought was a wheel dragging. It was the rear disc being ground. 22 miles from home, no cell service and 0310. Yup, I rode it home. So now I'm wondering why, and can I get a used rotor?
At your starting point, did you move the bike forward / backward using your legs, prior to riding away under the bike's power?

I ask, because if the answer is "yes", did you notice if it was more difficult to push the bike around? If the rear was locked up then, then i assume it's not as easy to move it around.
 
Joined
Feb 2, 2014
Messages
1,857
Location
houston, tx
So on the way home last week and stopped at the only stop sign till I get there. I heard and felt what I thought was a wheel dragging. It was the rear disc being ground. 22 miles from home, no cell service and 0310. Yup, I rode it home. So now I'm wondering why, and can I get a used rotor?
At your starting point, did you move the bike forward / backward using your legs, prior to riding away under the bike's power?

I ask, because if the answer is "yes", did you notice if it was more difficult to push the bike around? If the rear was locked up then, then i assume it's not as easy to move it around.
 

paulcb

- - - Tetelestai - - - R.I.P. - 2022/05/26
Rest In Peace
Joined
Jun 4, 2013
Messages
4,652
Location
Celina, TX
Bike
'97/'01 ST1100 ABSII
STOC #
8735
FWIW, I'm always conscious of how my bike rolls. I check it when I roll out of the garage and when I'm at a stop light, especially after hard braking, which I try to do every once in a while to push the pistons out to their limit, as the pads wear. If I'm on a slight incline at a light, I try to let it roll backward a bit to make sure my brakes are always free. I rode my bothers '07 ST1300 for a few weeks and was checking this every chance I got, considering their history. When I change pads, I always push the pistons out a little and clean them really well with a toothbrush. I think I'm a little OCD about this, even on my ST1100 which doesn't have a history of SMC failures. Heck, I even do the same thing with my truck... pay attention to how easy it rolls and feel the metal wheels every once in a while when I park for excessive temps.
 
Joined
Sep 25, 2017
Messages
5
Location
Washington
Bike
1991 st1100
STOC #
8979
Always got a kick out of this pic...this is probably not your problem...just noted as things that can happen...

19225986_10154864738825186_8261034556284421520_n.jpg
You say the rear rotor was being 'ground' ? Do you mean metal on metal contact ? Or do you mean that the brakes were not releasing and the friction material on the pads was in constant contact with the brake disc / rotor ?

You managed to ride it home, so the wheel wasn't completely locked up.

Before solving a problem with the rear brakes, it helps to know what all of the symptoms are. It is true that an SMC that isn't functioning as it should will cause problems on the rear brake, but there are many other things that will cause problems without the SMC being the culprit. And some of these are easy to check and fix.

A few examples:

  • Stuck caliper pistons
  • Incorrect location of, or damage to pad spring (very possible).
  • Caliper sliders not allowing movement when brakes are applied and released (common)
  • Too much grease in caliper slider pins (yes, really).
  • Rusty / pitted / bent pad spring - preventing movement of pads (common).
  • Riding with new boots (and inadvertently applying pressure to rear brake pedal)
  • Collapsed rear wheel or rear flange bearings (putting rear wheel and rotor at an angle in relation to the caliper)
  • Both pads fitted to the same side of the disc rotor. (Yes, really).
  • Pads not seated in the clip at the deep end of the caliper (and resting / scraping on the wheel hub).
  • Spacing collar not put on axle (yikes)
  • New wheel bearings not inserted in the correct manner (displaces the centre line of the wheel and may cause the disc rotor to scrape on the caliper bracket).
  • Caliper bracket stopper bolt not located correctly (unlikely, but possible)
  • Front brake pads not releasing properly (thereby applying SMC and applying rear brake - So check pad pins, pad springs, caliper able to move on slider pins)
  • Front wheel not inserted correctly - check axle end and clearance between rotor and caliper bracket; also distance collars on each side are correctly installed.
  • Front pads are new and too thick, or have a heat shield fitted (there isn't enough room when pads are fairly new - the brakes drag and apply the SMC).
  • Compensation port in front brake lever master cylinder blocked.

I could go on (and usually do, but I'll stop there), but you get the idea ? - There are too many scenarios to work out what could be going wrong. Some photos of the damage and of the rear wheel / caliper might help. It might be something simple.

A useful check for the SMC is to check that the rear wheel isn't dragging, and then lie on the floor alongside the left side of the bike, with the bike on centre stand and gear in neutral. Turn the rear wheel with your foot. Apply the SMC with your hand - push it towards the fork to compress the plunger. It moves only a small fraction 1mm or 2, and shouldn't require force (I use the fork leg to squeeze it in my hand like a brake lever). If the rear wheel cannot be turned, then the SMC is applying the rear brake OK. Release the SMC and the rear wheel should turn OK. Do it a few times. If the wheel releases each time, then the SMC isn't the primary culprit. It isn't completely off the hook, but there must be something else causing the drag.
 
OP
OP
Joined
Jul 7, 2014
Messages
77
Location
California
Bike
2004 ST1300
Wow. Lots more ideas than I thought possible.... I was able to ride it home that morning and when I got there, ran my finger over the rotor. It felt like a very fine threaded bolt. I would say the deepest groove to be 1/16. I've not had the time to do anything to it yet but it will be started on Sunday morning. Prior to having to stop that night, absolutely no sign of any problem with the rear brake at all. Original pads still on and the only time the caliper was moved was to have a new tire put on. I remove the wheels, have new tires mounted then put the wheels on myself. Never had any problems with the caliper while installing the wheel back on. I was able to move the bike using just leg power but to be honest, I was pretty upset and it was 0300. As Upt North said, there are lots of SMC posts here and Iv'e been reading most of them.
 

ST Gui

240Robert
Site Supporter
Joined
Sep 12, 2011
Messages
9,262
Location
SF-Oakland CA
Bike
ST1300, 2010


Pro Tip: Always check your work

Given the wear on the left side of the caliper someone put a mile or two on that rig. I'd have never believed it without the pic!
 
OP
OP
Joined
Jul 7, 2014
Messages
77
Location
California
Bike
2004 ST1300
I'm finally down the home stretch with my brake system rebuild. SMC is rebuilt, rear caliper is cleaned and all new seals are in, even found some silicon grease. Then I took one more look at the manual and noticed that I should be replacing bolts. Lots of them. Along with sealing washers. I'm not cheap but when all was totaled, it came to over 100 bucks!!! So my question is, who among all that have done this stuff has replaced these bolts? The washers I understand but the bolts are hard for me to swallow.
 

SupraSabre

48 Years of SoCal Lane Splitting/Commuting-Retired
Site Supporter
Joined
Nov 20, 2005
Messages
9,499
Location
Cedar City, Utah
Bike
12/04 ST 1300s
2024 Miles
000145
STOC #
5901
I'm finally down the home stretch with my brake system rebuild. SMC is rebuilt, rear caliper is cleaned and all new seals are in, even found some silicon grease. Then I took one more look at the manual and noticed that I should be replacing bolts. Lots of them. Along with sealing washers. I'm not cheap but when all was totaled, it came to over 100 bucks!!! So my question is, who among all that have done this stuff has replaced these bolts? The washers I understand but the bolts are hard for me to swallow.
I'm assuming your are talking about the brake line bolts.

When I did mine, maybe Byron can remind me, but I know I didn't replace any of the bolts, but I'm thinking that I may have not replaced the washers either. I just can't remember.
 
OP
OP
Joined
Jul 7, 2014
Messages
77
Location
California
Bike
2004 ST1300
Yes Bob, as well as the rear caliper body bolts (3) and the SMC joint and pivot bolts.
 
Top Bottom