Front brake shudder

[Comfy Old Boots]

Hi,

2007 R1200Gs. I've got a shudder in the front brakes, very noticeable when braking at slow speeds. It's like the pads are loosing grip momentarily. It is not dangerous or unsafe (yet) but I'm just wondering what I can do about it.

Firstly, i had a disc lock on the bike about 18 months ago and went to take off. Bike went down. That was eighteen months ago. WOuld it take that long for an issue to show up?

What I'm considering doing today, is firstly, giving everything a really good clean and make sure the disks themselves don't have any buildup on them.

I'm going to give the calipers a good clean out with some brake cleaner and check if the pistons are moving freely.

The other thing I'm thinking of doing, if the above don't fix it, is to remove the disks one at a time and check them on a flat surface. I don't have one of those special tools for checking. Are the bolts that hold it locktited? Do I need a bit of heat on them and would anyone by chance have the torque setting needed to reattach them.

Lastly, I only noticed this after getting a new set of tyres. Could damage have possibly been done there? Anyway, just throwing this out there before I get stuck in.

 

[RigsVille]

I had a similar issue with a Triumph ST a number of years ago, turned out that one of the brake discs was warped and had to be replaced.

 

[D9lek]

So did I... the front wheel was very slightly buckled

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[Comfy Old Boots]

Yeah, I'm thinking one of the disks is warped. I guess I'll find out when I take it apart. Other than build up on the disk itself, is there anything else that could cause this?

How did the buckled front wheel give a pulse in the brakes?

 

[Andi_archer]

An overheated or excessively worn warped disc will give a noticeable issue with braking , there have been posts of people with fairly new brakes suffering the same issue.

 

[Blackal]

Wheel bearings could be shot

 

[milleplod]

My 1200ST was the same at about 25k miles. No need to take the disc off to check it - I just lifted the front wheel off the ground, then held the end of a steel rule so it was just touching the disc surface and spun the wheel....you'll soon see if its warped. The bolts are threadlocked with what I think is referred to as 'mechanical' stuff, which I took to mean 'very strong' - I heated the bolt-heads using my wife's hairdryer! It worked, they all came out easily enough. Some say to use new bolts, they come with pre-applied threadlock - I cleaned up the old ones and re-used them.

Pete

 

[Comfy Old Boots]

My 1200ST was the same at about 25k miles. No need to take the disc off to check it - I just lifted the front wheel off the ground, then held the end of a steel rule so it was just touching the disc surface and spun the wheel....you'll soon see if its warped. The bolts are threadlocked with what I think is referred to as 'mechanical' stuff, which I took to mean 'very strong' - I heated the bolt-heads using my wife's hairdryer! It worked, they all came out easily enough. Some say to use new bolts, they come with pre-applied threadlock - I cleaned up the old ones and re-used them.

Pete

Hi, thanks for that. I figured the bolts would be threadlocked. Thing is, I've just been down to the bike. Took the calipers off and cable tied them safely out of the way, just to take the friction off the disc itself. I used the screwdriver trick, holding it just touching the surface of disc. No noticeable warping on either side. I kept a steady hand, and whilst not scientific, the screw driver didn't move at all. Could a tiny warp cause a pulse in the breaks or would it be obvious to the eye?

 

[UturnTony]

Hi,

2007 R1200Gs. I've got a shudder in the front brakes, very noticeable when braking at slow speeds. It's like the pads are loosing grip momentarily. It is not dangerous or unsafe (yet) but I'm just wondering what I can do about it.

Firstly, i had a disc lock on the bike about 18 months ago and went to take off. Bike went down. That was eighteen months ago. WOuld it take that long for an issue to show up?

What I'm considering doing today, is firstly, giving everything a really good clean and make sure the disks themselves don't have any buildup on them.

I'm going to give the calipers a good clean out with some brake cleaner and check if the pistons are moving freely.

The other thing I'm thinking of doing, if the above don't fix it, is to remove the disks one at a time and check them on a flat surface. I don't have one of those special tools for checking. Are the bolts that hold it locktited? Do I need a bit of heat on them and would anyone by chance have the torque setting needed to reattach them.

Lastly, I only noticed this after getting a new set of tyres. Could damage have possibly been done there? Anyway, just throwing this out there before I get stuck in.

Likely to be a warped disc. I check them with a dial test indicator set up but lacking that any set up where you can spin the wheel and get an indication of the out of true will do.
The bolts, yes they are threadlocked and you need to make sure the tool to remove them fits very well, take care when undoing them as you can soon chew the heads up.
I have always re-used the bolts and no i haven't re-threadlocked them either.

Standby for a multi pager on the merits de merits of re-using not re-using re- threadlocking not re-threadlocking (your life is worth more than the price of new bolts etc etc) the bolts

Edit; just seen the above, the last one i did was a rear and there was a pronounced pulse at low speed but the warp couldn't be detected by (my) eye but warped it was to about iirc 20 odd thou.

 

[Comfy Old Boots]

Wheel bearings could be shot

Well, it's got 88000 miles on it and i'm not sure if they have been replaced. The wheel spins freely. No grinding or duff spots when rotating it. I guess that does not mean anything though does it? Bearings are not under load when it's up on the stand.

 

[Comfy Old Boots]

Likely to be a warped disc. I check them with a dial test indicator set up but lacking that any set up where you can spin the wheel and get an indication of the out of true will do.
The bolts, yes they are threadlocked and you need to make sure the tool to remove them fits very well, take care when undoing them as you can soon chew the heads up.
I have always re-used the bolts and no i haven't re-threadlocked them either.

Standby for a multi pager on the merits de merits of re-using not re-using re- threadlocking not re-threadlocking (your life is worth more than the price of new bolts etc etc) the bolts

Thanks Tony. Think I'll bring the bike to a local guy. He changed the tyres, I'm sure he has the kit to check the discs.

I'm not that mad on threadlock myself. I'm more likely to reuse the bolts and tension them correctly.

 

[Andi_archer]

Another alternative is head stock bearing wear, I was going to say you could lift the front off the ground to check but if its going into a garage have them check.

 

[Comfy Old Boots]

Yeah, the thing is though, it feels like the pads are gripping and momentarily not gripping. There is a definite thrump thrump thrump feel in the lever as the bike does a full rotation. The sensation slows as the speed of the wheel rotation slows. I've checked for a build up of brake pad material on the disks themselves and there is nothing there. The calipers and pads seem fine.

I hope it's a warped disk. Expensive to replace but at least that would be that. The abs sensor took a knock when the disk lock mistake happened. Bmw kindly bent it back to shape for me and all was fine, no error codes and it kicks in when it should.

I'm not expecting anyone to solve this for me on the internet, just teasing out home remedies. Anyway, I'm heading to get the disks checked at eleven. If they are warped I'll change them, if they are not, it's obviously something else!

 

[squibb34]

I've been there on several occasions - always turned out to be a run-out on one or both of the discs.

A DTI should pick it up, if you have a fixed disc, but with floating discs it is notoriously difficult. However, careful examination of the disc surface may give you a clue.

Another option is to get the bike on the rollers at an MoT bay - this soon shows up a warped disc, even when slight in the case of my HD.

 

[Comfy Old Boots]

They are fixed disks, not floating. Not sure what kit this lad has but with luck he can tell me the disks have a run out or not. I'm getting the impression that the run out does not need to be big to have an effect... Anyway, quick cuppa and I'm down to refit the calipers and see what the story is.

 

[Bendy toy]

My steering head bearing (sealed double row thingy) in the steering top yoke was replaced at 50K miles. It would be well worn at 80K miles.

 

[Deleted account 191119001]

They are fixed disks, not floating. Not sure what kit this lad has but with luck he can tell me the disks have a run out or not. I'm getting the impression that the run out does not need to be big to have an effect... Anyway, quick cuppa and I'm down to refit the calipers and see what the story is.

This is what he will probably do to look at the disks, however, I remember years ago I had a shudder on my old Triumph and blew compressed air somewhere in the disk, but bloody alzeimer cannot remember exactly what I done.

 

[JJH]

How were tyers fitted? Wheel on ground and tyer levers? Disk could be warped from the floor. JJH

 

[Pukmeister]

Disks are semi floating not rigidly mounted, the bolt holes are slotted radially to allow for expansion outwards, the disks run on washers beneath the bolt heads.

It is possible that you have corrosion to the alloy of the disk mounting lugs of the wheel hub which requires heating the loctite and removing the disks to clean up then remount. You can also measure runout with a dti then rotate the disk to put high spots where low are and vice-versa to see if it improves.


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[Comfy Old Boots]

I might look into that Pukmeister. Thanks.

Well, just back from the mechanic. Firstly, I do have a warped disk. Secondly, it's not the one that had the misadventure with the disk lock! The lads were saying it's very very small. I think I'm going to put up with it for the moment. It's not unsafe and more a concern about the feel. If it gets worse I'll investigate your option Pukmeister. Mind you, it's bloody annoying, so I think I'll be looking at it sooner rather than later. The lads in the shop seemed to think there was a tiny bow inwards on the disk itself at one spot, so I'm not sure changing the washers will help. Certainly a cheaper option to buying two new disks. I'll have to take the disk off to see exactly what you mean by the washers etc.

Thanks gang.