Possible Modified Front brakes?

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2003 ST1300
Hi All
Need some help in regards to the left front brake caliper parts. I cannot identify the rubber block that is fitted to my 2003 ST1300 non ABS.
Been a member for some years, but not overly active.

This being my second 2003 model, first one went, when getting married....Anyway replaced it with an different bike same year, but from a braking point of view it never felt the same.

Today noticed there is a rubber block that appears that it would alter the action of the Dual braking system.
Left Front.jpg

Hopefully the picture comes through OK.

Is it meant to be there? The previous owner did do some neat little mods elsewhere....

Cheers for any help.

Steve
 
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That block should not be there. Looks like an attempt to defeat the linked brake system by prohibiting the Secondary Master Cylinder, located at the top of your left caliper, from actuating. Would probably be a good idea to flush the old fluid and give the entire system a good service. Links to how the brake system works can be found in the ST1300 technical sub-forum. Pay particular attention to what Igofar, Ann's Dad, and Jheath have to say... they are very knowledgeable about the ST1300 braking system.
 
OP
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Thanks Vinny
Confirmed my thoughts, but I know how some of the Parts listings leave things out.

Time to buy a brake bleed tool and start from there, after removing the block...

Cheers

PS
Have always loved DCBS. I rode the press bike in Australia before most of the magazines even got to have a look at it when it came out on the CBR1000 way back then.
Oh how time flies.
 
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ST Gui

240Robert
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Looks like an attempt to defeat the linked brake system by prohibiting the Secondary Master Cylinder, located at the top of your left caliper, from actuating.
I'd say that's exactly right. There'd be no need for it with a properly maintained SMC. So either it's some 'preventative' measure or the PO was having trouble with the SMC and instead of fixing it decided to just take it out of the equation. Proper servicing might help or it could be too late.
 
OP
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I'd say that's exactly right. There'd be no need for it with a properly maintained SMC. So either it's some 'preventative' measure or the PO was having trouble with the SMC and instead of fixing it decided to just take it out of the equation. Proper servicing might help or it could be too late.
That's what I was really afraid of! Is it covering an issue or did the Previous Owner simply not like the DCBS...

Time will tell.

Just got to find the brake system test procedure.

Any chance it is in the "Service Manual"?
Found trouble shooting for "improper operation", but nothing, so far, to show how to test for correct operation.

Time to hit the forums a bit harder.

Cheers
 
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That block should not be there. Looks like an attempt to defeat the linked brake system by prohibiting the Secondary Master Cylinder, located at the top of your left caliper, from actuating. Would probably be a good idea to flush the old fluid and give the entire system a good service. Links to how the brake system works can be found in the ST1300 technical sub-forum. Pay particular attention to what Igofar, Ann's Dad, and Jheath have to say... they are very knowledgeable about the ST1300 braking system.
I don't think the block is there to defeat or prevent the SMC from actuating. As the wheel turns and the SMC grabs the disk, the arm it is mounted on pivots toward the front compressing that block. There would be considerable force placed against the rubber - look at that lever arm's length. If the SMC piston stuck in its bore, then this little rubber block would help push the arm back (toward the rear) and unlock the rear wheel.

Regardless, it doesn't belong there. You may end up replacing the SMC.
 
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Danger,, Will Robinson,, Danger !!!

The only reason to put that rubber there is to try to deal with a failing SMC. It is a band-aid at best,,, and likely to let you down, perhaps at a critical moment. It should not have passed it's safety check when you purchased it,, however, there are lots of un-knowledgeable certifier's out there,, granted. Buy a new SMC,, and ensure that the methods for R&R on this site are followed. Then ride with some peace of mind,,, Cat'

22049905_770080223177388_7374121542120330882_n.jpg
 

jfheath

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I don't think the block is there to defeat or prevent the SMC from actuating. As the wheel turns and the SMC grabs the disk, the arm it is mounted on pivots toward the front compressing that block. There would be considerable force placed against the rubber - look at that lever arm's length. If the SMC piston stuck in its bore, then this little rubber block would help push the arm back (toward the rear) and unlock the rear wheel.

Regardless, it doesn't belong there. You may end up replacing the SMC.
That would be my guess too - When the SMC fails it is often due to a lack of 'proper' servicing. This can result in crud and corrosion forming at the top end of the SMC - located inside the cylinder behind the securing plate and circlip. This is located behind the rubber boot - up at the top end of the bracket where the caliper bracket attaches to the fork leg.

This prevents the plunger from returning to its proper resting position when the brakes have been released - the result being that the back brake (which is activated by the movement of the SMC) remains on, and drags.

I would guess that the block of rubber was a crude attempt to stop the SMC from activating in the first place - by stopping the caliper from rocking forward when the front brake is applied. But the notion that a bit of rubber is enough to stop the massive forces created when those brake pads grab hold of the front disc rotor seems ridiculous. As SMSW said - it might be that it worked by giving the SMC a bit of a shove back once the brakes had been released.

Whatever - it is an indication of quite a serious problem which was developing when the rubber was put in. Who knows how bad the problem has now become - doubtless you would find out if it ever fell out, or disintegrated under the braking forces - but a rear wheel lock up is really not something that you want to happen.

When this problem first starts, the rear brake drags, and you may not notice it as the power of the engine will overcome the brake drag. But the disc gets hotter, and so does the caliper and the brake fluid. The SMC is not able to return to its resting state, so the pressure in the rear brake line is not able to be released, as it would be normally. The heat causes the pressure to build up and all of a sudden, the back wheel stops turning. The ABS cannot help you in this situation.

It would seem that the solution would be a new SMC (do not get the service kit as a cheaper alternative - often the problem is in the cylinder bore itself, and the service kit simply replaces the piston in the old cylinder bore). The job is relatively painless, but you need to know how to replace the brake fluid and bleed it through. You need the left caliper bracket assembly, a handful of copper / aluminium crush washers for the banjo bolts (4 I think), and the upper and lower mounting bolts.

But before you do any of that, a few tests that you can carry out to convince yourself of the problem.

With the rubber not in place, put the bike in neutral, and on its centre stand. Rotate the rear wheel by hand. Any sign of dragging ? A good yank on the rear wheel should result in 1-2 revolutions I suppose, but its not an exact science.
Then lie down on the left of the bike so that you can turn the back wheel with your foot, and get your hands on the front left brake caliper. The caliper should move a mm or two, and when it does, it should prevent you from turning the back wheel. More importantly, when you release the bracket, it should turn as freely as it did before.
A word about how to move the caliper. I can activate it rather like a brake lever with my fingers around the fork leg and my thumb around the back of the caliper. A firm squeeze is all that is needed to move it.

If you feel that you can ride it after doing these tests, then go out without the panniers on, and go out on the flat, or better still up a hill near to home. Check the temperature of the rear disc. Then ride a little way and apply the front brake to bring the bike to a stop. Check the temperature again. The back disc should be hotter. Then ride for a while and come to a stop without touching the brakes. The rear disc should have cooled down.

The reason it is a good idea to go uphill (if you have the choice) is purely practical. Its easier to come to a stop without touching your brakes, going uphill, and it's easier to get a bike back home if you encounter problems.

I put a full brake test procedure of this nature in the back of 'Avoiding the Pitfalls' - which may be of use.

But beware - that front brake caliper has got a bodge job on it, and it is masking a problem that has not been addressed by the previous owner.

Well done for looking over the bike and spotting something that looked odd.
 
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I remember a few years back that a forum member tried to make a rubber wedge to stop his failing SMC from actuating, I hope you didn't purchase his bike.
Roll the bike forward on level ground, and apply both brakes, then release them, get off the bike, and then roll the bike backwards. Is it hard to roll backwards? This is the easiest way to "feel" the SMC dragging.
Do as Jfheath said and test the SMC to see if its releasing after being applied.
I'll bet you a pint that the SMC failed, and that the piston is stuck halfway down inside the bore*, and it was rattling back and forth, and the rubber was put there to stop the noise :rolleyes:
On a bike that old, with a bandaid fix on it, I would remove/replace the entire SMC and replace it with a new one, then bleed the entire system correctly.
The part number for the SMC you need is (BRACKET SUB-ASSY., L. FR.06454-MCS-G03, you'll also need 4 crush washers (WASHER, OIL BOLT 90545-300-000).
Get 4 small bottles of DOT 4 brake fluid, and a motion pro brake bleeding tool (Part # 08-0143).
After bleeding the entire system, strap both the hand lever, and the foot lever down over night.
You'll find alot of good information on how to do this with Jheaths write up.
Good luck.
Igofar

*Note: The piston can be stuck towards the end of the forward end of the bore and keep the brakes from working, or towards the rear of the bore (deep) and cause the brakes to drag and lock up without warning!
This position could change at any moment without warning, do not attempt to ride the bike without correcting this situation first.
 
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Great information gentlemen! The more I read posts and the replies, the more I understand the system and what to watch for prior to any fails in the systems. Great knowledge on here.
 

ST Gui

240Robert
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Igofar said:
I remember a few years back that a forum member tried to make a rubber wedge to stop his failing SMC from actuating
Exactly. Same/different thread someone mentioned using a wedge to relieve pressure on the back brake if it started dragging while you were out on the road. A band aid to get home again trying to take the SMC out of the equation.

Whether it did or didn't work the intention was the same. Didn't someone else want to weld some kind of spring assembly in the same place?



But the notion that a bit of rubber is enough to stop the massive forces created when those brake pads grab hold of the front disc rotor seems.
Nobody said the PO was an engineer! :rofl1: Besides if he knew that the rear wheel contains rubber bits and considering its radius— as the old saw goes... A little bit of knowledge... And add a shady tree...


Well done for looking over the bike and spotting something that looked odd.
+1!
 
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Exactly. Same/different thread someone mentioned using a wedge to relieve pressure on the back brake if it started dragging while you were out on the road. A band aid to get home again trying to take the SMC out of the equation.

Whether it did or didn't work the intention was the same. Didn't someone else want to weld some kind of spring assembly in the same place?





Nobody said the PO was an engineer! :rofl1: Besides if he knew that the rear wheel contains rubber bits and considering its radius— as the old saw goes... A little bit of knowledge... And add a shady tree...




+1![/QUOTE

Thread: My solution to left brake clunking on bumps
 
OP
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2003 ST1300
I remember a few years back that a forum member tried to make a rubber wedge to stop his failing SMC from actuating, I hope you didn't purchase his bike.
Roll the bike forward on level ground, and apply both brakes, then release them, get off the bike, and then roll the bike backwards. Is it hard to roll backwards? This is the easiest way to "feel" the SMC dragging.
Do as Jfheath said and test the SMC to see if its releasing after being applied.
I'll bet you a pint that the SMC failed, and that the piston is stuck halfway down inside the bore*, and it was rattling back and forth, and the rubber was put there to stop the noise :rolleyes:
On a bike that old, with a bandaid fix on it, I would remove/replace the entire SMC and replace it with a new one, then bleed the entire system correctly.
The part number for the SMC you need is (BRACKET SUB-ASSY., L. FR.06454-MCS-G03, you'll also need 4 crush washers (WASHER, OIL BOLT 90545-300-000).
Get 4 small bottles of DOT 4 brake fluid, and a motion pro brake bleeding tool (Part # 08-0143).
After bleeding the entire system, strap both the hand lever, and the foot lever down over night.
You'll find alot of good information on how to do this with Jheaths write up.
Good luck.
Igofar

*Note: The piston can be stuck towards the end of the forward end of the bore and keep the brakes from working, or towards the rear of the bore (deep) and cause the brakes to drag and lock up without warning!
This position could change at any moment without warning, do not attempt to ride the bike without correcting this situation first.
What sort of dollars are we talking about for the above parts? Labour is cheap, my time.
I understand it would only be a guide as most of you are US based, but will ease the hurt a little, or at least the initial shock.

Steve

Don't worry, found a local site, and didn't fall down at the price. $260 AU for the Bracket assy.

BTW the bike has 66,100 km or approx 41,000 miles on it.

Thinking will do the test and flush before ordering the parts.
Your thoughts would be appreciated.

S
 
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jfheath

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I'll bet you a pint that the SMC failed, and that the piston is stuck halfway down inside the bore*, and it was rattling back and forth, and the rubber was put there to stop the noise
In that case, it was an ingenious solution. Most people that don't know better will just fit earplugs !


BTW the bike has 66,100 km or approx 41,000 miles on it.

Thinking will do the test and flush before ordering the parts.
Your thoughts would be appreciated.
That isn't a lot of miles, but it is a lot of time - 15 years since the 2002 came out. 3000 miles per year. Fluid should be changed every 12,000 miles or 18 months, whichever comes sooner because it absorbs moisture - even in the closed environment of the hydraulic system. Moisture causes corrosion. If I were a betting man, I would guess that the figure used between services would have been at least 12,000 miles - that is about every 4 years, which might imply that the bike has spent much of its life with moisture rich fluid in its system. Pure guesswork - but given that the PO has chosen to put a rubber stopper on his brakes......

If the SMC doesn't need replacing now, it will do before too long, and we are not sure how long the supply of these parts will last. From 2008 a new version of SMC was installed - so it is already 10 years since the last bike with your variety of SMC was built. I'd switch it out anyway, it is worth the peace of mind.

You'll find lots of info about bleeding the brakes on these forums, but I'll point you to Getting the Air out of the System anyway - not least because the video about the behaviour of bubbles in a tube is quite a good image to have in your head when bleeding the brakes. Download the pdf in post#1 - it has more information than the images in the post. (nb others have included the link in replies, but the document has had some changes and their links are now invalid. The link in post #1 points to the updated pdf file).
 
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OP
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In that case, it was an ingenious solution. Most people that don't know better will just fit earplugs !




That isn't a lot of miles, but it is a lot of time - 15 years since the 2002 came out. 3000 miles per year. Fluid should be changed every 12,000 miles or 18 months - whichever comes sooner - because it absorbs moisture - even in the closed environment of the hydraulic system. Moisture causes corrosion. If I were a betting man, I would guess that the figure used would be 12,000 miles - every 4 years - suggesting that the bike has spent much of its life with moisture rich fluid in its system.

If it doesn't need replacing now, it will do before too long, and we are not sure how long the supply of these parts will last. I'd switch it out anyway, it is worth the peace of mind.

You'll find lots of info about bleeding the brakes on these forums, but I'll point you to Getting the Air out of the System anyway - not least because the video about the behaviour of bubbles in a tube is quite a good image to have in your head when bleeding the brakes. Download the pdf in post#1 - it has more information than the images in the post. (nb others have included the link in replies, but the document has had some changes and their links are now invalid. The link in post #1 points to the updated pdf file).
Good point on parts availability.
"Getting Air out" pdf looks great and easy to follow.
Time to shop then.

Steve
 
OP
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Update
Did test, confirmed rear brake drag after manually activating the SMC.

Parts on order, Ex Japan for Bracket assy 2 weeks...

Thanks again for your help so far.

Steve
 

Blrfl

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Who knew the Wonder Foam in the toolkit could be put to such good use? :D

Really, if there's any give at all in that foam, the braking forces would compress it without difficulty. I wonder if the PO had the SMC rattle and put it in there to damp it.

--Mark
 
OP
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Who knew the Wonder Foam in the toolkit could be put to such good use? :D

Really, if there's any give at all in that foam, the braking forces would compress it without difficulty. I wonder if the PO had the SMC rattle and put it in there to damp it.

--Mark
I'd say it was the rattle as even with the block in place I was still able to activate it by hand, did take a pretty good one hand squeeze, more than I had expected it to take.
 

Trapperdog

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Although not applicacable here, as a note many seasoned Police Motor competitors make and put those in for competitions to defeat the linked system.
 
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