Braking issues

[krist0ph3r]

After last month's ride, I noticed my ST1100 was noticeably difficult to wheel around. Since I'm not heavy/strong enough to put it on the main stand, I didn't end up checking which wheel was the culprit. When I had it looked at (preparing for the annual MOT) the mechanic said the brakes were binding due to grit/muck and cleaned them. Can now wheel the bike easily, but on firm braking, there seems to be a strange judder that I feel through the front fork. Braking doesn't seem significantly affected, although I'm concerned it may be the start of something that might get worse. I asked the mechanic who cleaned the brakes, and he said it might be a warped disc. He said I probably didn't notice it earlier as the brakes were dragging all the while. I find that hard to believe though, as I purchased the bike with brand new discs fitted (all 3 discs had absolutely no sign of wear when purchased, they do have very slight scratches now) and the previous owner claimed he only ordered parts from Honda directly.

I asked the mechanic how I can verify it's a warped disc, but the only way he suggested is to take them off with the wheels and get them checked. Is there a more practical way to rule out the possibility of warped discs, or are there more likely/easier to eliminate possibilities?

 

[Larry Fine]

I would think you can check it in place, with a dial gauge if not visually, by spinning it.

 

[Whooshka]

What Larry said. Use a dial guage and check the run out. An easier thing to do... since your pistons were gritty enough to stick you might want to clean the bobbins on the rotors. Spraying them down with some brake cleaner and rotating the bobbins so they can move freely will help.

 

[CYYJ]

What is a bobbin?

Michael

 

[John OoSTerhuis]

you might want to clean the bobbins on the rotors. Spraying them down with some brake cleaner and rotating the bobbins

I assume you mean the brake caliper pistons. Do not spray brake cleaner on the pistons’ rubber seals! It is basically acetone which will swell the seals and keep the pistons from retracting. Brake cleaner is used to remove grease, oil and other contaminants from metallic surfaces, like brake rotors (before reinstalling the wheel, NOT in situ where you might accidentally contaminate the caliper seals) and pads.

John

 

[Uncle Phil]

If you don't have gauge, clamp a ruler to the forks close to the discs and slowly rotate the wheel while you watch the gap.
If the disc is warped significantly, you'll see it.

 

[Whooshka]

What is a bobbin?

Michael

they are the little round disks that hold the outer steel rim of a brake rotor to the disk hub.

Do a search on YouTube for how to clean rotor bobbins. Delboy has a good video. ---->

EDIT: I typed this last night but never hit the send button. And no John Ooster, I meant the bobbins.

 

[John OoSTerhuis]

they are the little round disks that hold the outer steel rim of a brake rotor to the disk hub.

Aha. Thanks. No wonder I didn’t know what bobbins are... the OP and I have ST1100s, which don’t have any.

John

 

[Whooshka]

Aha. Thanks. No wonder I didn’t know what bobbins are... the OP and I have ST1100s, which don’t have any.

John

Solid 1 piece rotors? I'm surprised at Honda.

 

[CYYJ]

The ST 1300 bikes have the "bobbins" mentioned above, but they are very solidly mounted to the disc around the perimeter and the smaller attachment ring on the inside - no rotation of the bobbin is possible.

Michasel

 

[John OoSTerhuis]

Solid 1 piece rotors? I'm surprised at Honda.

Shows what I (don’t) know about ST1300s... and vice versa.

 

[krist0ph3r]

If you don't have gauge, clamp a ruler to the forks close to the discs and slowly rotate the wheel while you watch the gap.
If the disc is warped significantly, you'll see it.

Brilliant! I'm going to try this

Aha. Thanks. No wonder I didn’t know what bobbins are... the OP and I have ST1100s, which don’t have any.

John

Thanks for clearing that up for me... I had no idea as I've never owned a bike that had bobbins - always discs mounted straight on the wheel.

Anyway, bike failed MOT today because of something completely unrelated - the right exhaust was loose! Need to fix that and pass the MOT before I continue investigating the brakes :/

 

[Whooshka]

The ST 1300 bikes have the "bobbins" mentioned above, but they are very solidly mounted to the disc around the perimeter and the smaller attachment ring on the inside - no rotation of the bobbin is possible.

Michasel

Rotation is very possible. I can move mine by grasping them between by thumb and forefinger. Their very function is to move freely so the part of the rotor that makes contact with the brake pads can stay centered between the pads when the brakes are applied. This is what a semi-floating rotor is. It's a good idea to clean them as a regular maintenance item. Did you watch the video?

Shows what I (don’t) know about ST1300s... and vice versa.

I'm gonna say this straight up... you're a bit snarky John so here's something to think about. Neither has a turbo but I know what they are.

 

[Larry Fine]

Rotation is very possible. I can move mine by grasping them between by thumb and forefinger. Their very function is to move freely so the part of the rotor that makes contact with the brake pads can stay centered between the pads when the brakes are applied. This is what a semi-floating rotor is. It's a good idea to clean them as a regular maintenance item.

I read that it also helps with resistance to warping from heat.

 

[CYYJ]

Hello @Whooshka

That's a fascinating video, thanks for posting it.

My guess is that the bobbins on the front discs of my ST 1300 are not rotating at the moment because the bike is in a cold garage (winter storage) and the temperatures of the disc, the bobbins, and the disc carrier are equal. I suspect that when riding, the disc warms up a bit, expands a wee bit, and that creates enough free space for the disc to "float" on the bobbin.

That notwithstanding, I will follow Delboy's advice and clean & rotate the bobbins before riding season starts. The technique he suggests (with the bolt and large flat nut) is clever and it should not be too difficult to carry out this work.

Michael

 

[ST Gui]

No wonder I didn’t know what bobbins are...

These came to mind but I thought 'Nahhhh....'

There is Brit slang for bobbins but it didn't fit either. I knew it wasn't boffins. I know what those are and they don't like to be sprayed with brake cleaner either.

 

[Andrew Shadow]

Important to note in the video that the nut was not tightened to the bolt using tools. It was only snugged up finger-tight. When the bolt is rotated with the ratchet the nut will tighten up some more on its own. However, it will only tighten to the point where the static friction of the bobbin is overcome and the entire assembly then rotates. Using this method there is very little chance of damaging the bobbins.

I have seen examples of people who performed this procedure without actually understanding what they were doing. They tightened the nut to the bolt using tools believing that they had to be tightly fastened together to accomplish this. They over-tightened it and ended up compressing the bobbins to the point where they altered the disc from a free-floating one to a fixed one.

 

[John OoSTerhuis]

These came to mind....

Yeah, me too, I sew... have a parachute rigger license. Then I somehow conflated bobbin into thimble, which is somewhat like a caliper piston. DOH! And not at all familiar with floating rotors (or that they are on ST1300s); hence, my ‘embarrassed’ emoticon.

OK... back to your regularly scheduled program.

John

 

[krist0ph3r]

In my experience, slight warping does not normally create a judder sensation unless the brake pads are brand new. (Or someone has fitted the thicker but part worn rear pads to the front caliper) Normally, the warp is taken up by the calipers being able to slide freely. When the pads are brand new, the amount of caliper movement available is limited and you can feel it through the lever or pedal.

My discs and pads are at least 2000 miles old, and I didn't notice this before, so it's probably not the case.

That being the case, the judder may be due to something else related to the caliper / pad fittings. Which is why I asked whether your bike was an ABS with 3 piston calipers, or non ABS with two pistons.

Mine's the non ABS, so 2 pistons.

nb If you ride your back wheel onto a plank of wood, it makes putting the bike onto the centre stand so much easier. Not too thick though - it needs to be thinner than the clearance between wheel and ground when the bike is on the stand. Someone may be able to help with that figure. I am thinking maybe half inch to 1 inch, but I dont have an 1100 to check. Too thick and the wheel will not lift off the plank, and it may lean too far on the side stand.

Good idea! However, since I need to spin the wheels once on the stand, I'd need to drag the plank out. Won't it be pretty difficult?

 

[Andrew Shadow]

...... I'd need to drag the plank out. Won't it be pretty difficult?

Only if the thickness of the plank is equal to or greater than the space between the tire and the ground when the bike is on the centre-stand with its weight resting on the front tire.
On a fully stock ST1300 on a straight surface with the stock tire sizes fitted this gap is about one (1) inch.
Many here have stated that using a spacer of either 1/2" or 3/4" thick makes it a lot easier to get the bike up on to the centre-stand without any danger of the stand not touching the surface with the rear tire sitting on the spacer. Just be aware that the bike will lean farther over on the side-stand and will be harder to upright so you may want to start with a 1/2" spacer first if you are concerned about this.