Front brake MOT issue

[sideshow_bill]

Hi all, I have just taken my BMW R100GS in for its first MOT for 6 years as its been stuck in my garage pending getting time to ride it!
However, it got a fail on the front brake, as the brake pressure does not hold evenly.
Firstly Im not sure how one (the tester) can tell if they are maintaninng the same pressure on the lever.
Anyway the disk has only done some 200 or so miles and does not appear worn.
I can not measure any run-out, and there is no sign of juddery braking when on the road.
So what to do next?
There may be something spilled on the disk, but if so I can see it and have cleaned the disk with no change on the rolling road.
I suspect that the disk may need to bed in but with no tax I cant take the bike for a run.

Suggestions please?

 

[ianboydsnr]

I dont understand what your saying, I thought it just had to reach past a certain performance and not leak

 

[Redboots]

Hi all, I have just taken my BMW R100GS in for its first MOT for 6 years as its been stuck in my garage pending getting time to ride it!
However, it got a fail on the front brake, as the brake pressure does not hold evenly.

Suggestions please?

Bleed it.

John

 

[biggles12]

When you hold the brake on is it spongy? If so that can be the hoses expanding or old fluid etc and a failure.

Pete

 

[sideshow_bill]

When you hold the brake on is it spongy? If so that can be the hoses expanding or old fluid etc and a failure.

Pete

Not spongey, brakes will hold untill the bike jumps off the rolling road.

Its as if there is a fault on the disk, gripping more efficiently at one point than another. However I have looked for run-out, warpage, damage etc and can not find any.

 

[(RIP) Proff]

OK
stage one.
When on the rolling road the examiner holds the brake lever steadily increasing pressure till it locks
Stage two.
The examiner increases pressure to a fixed point and watches the dial register any fluctuations on the readings for a given pressure..EG warped brake disc same as in some cars you can feel pedal going up and down slightly usually means worn brake drum or disc....

I've only had one advisory on this problem, solved by giving the bike some beans and re bedding brakes in ..
Still on same disc and 4 MOTs later = very little variation on reading now

re reading your post it seems more than likely to be exactly where the disc and pads were together for such a long while whilst laid up..

 

[sideshow_bill]

OK
stage one.
When on the rolling road the examiner holds the brake lever steadily increasing pressure till it locks
Stage two.
The examiner increases pressure to a fixed point and watches the dial register any fluctuations on the readings for a given pressure..EG warped brake disc same as in some cars you can feel pedal going up and down slightly usually means worn brake drum or disc....

I've only had one advisory on this problem, solved by giving the bike some beans and re bedding brakes in ..
Still on same disc and 4 MOTs later = very little variation on reading now

re reading your post it seems more than likely to be exactly where the disc and pads were together for such a long while whilst laid up..

This seems likely, as the disk as only sone some 200 miles - unless (heaven forbid) BMW sold me a duff disk, and its never been any good! - only thing now, is what to do to get it road leagal?
Im thinking of going to a more sympathetic tester . . .

 

[(RIP) Proff]

This seems likely, as the disk as only sone some 200 miles - unless (heaven forbid) BMW sold me a duff disk, and its never been any good! - only thing now, is what to do to get it road leagal?
Im thinking of going to a more sympathetic tester . . .

So was I Book it in to one a bit further away so you can have a good bedding in ride
Pity you ain't in Devon, I'd put the trade plate on her and do it for you

 

[nick.ct]

Ther are still some bike MOT stations that have a static brake test for brakes, a piece of wire attached to a spring guage that is pulled to the required tension for the weight of the bike. Seems like one of these would sort out the problem and then you can bed the brakes in on the road. After all, when you fit new tyres they come with a warning to take it easy for 100 miles or so, so why not brakes

Nick

 

[brassmonkey001]

Go for a good ride and feather the front brake now and again once it's got warm. And then try a few emergency stops. That should bed it in nicely.
As Proff says, it's probably where the pads have been laying against the disc while standing.

edit: Ah, you can't take it for a run. Take the pads out and give them a good rub with some emery paper to take any shine off them. Give the discs a good rub down as well. If there is any point on the disc that looks different to the rest e.g. slightly more corroded/discoloured then give that particular attention with the emery.

 

[D6]

Ther are still some bike MOT stations that have a static brake test for brakes, a piece of wire attached to a spring guage that is pulled to the required tension for the weight of the bike.

Nick

yup 2 left in england, salters

 

[biggles12]

I still have one come and see me for a MOT

Pete

 

[(RIP) pastyman]

Shouldnt take more than a few miles to bed brakes in if as been suggested you work the brakes both lightly and firmly.
You are entitled to ride your bike to the mot station for a pre arranged test. so just go the long way round. If you are unlucky enough to get pulled, which would be pretty unlikely, you are covered. just dont go 100 miles in the wrong direction.
Personally though I dont think the brakes will need much bedding in its more likely after standing for a long time that a) they need bleeding or new fluid or b) you have a sticking piston.

 

[sideshow_bill]

Success! I took it to another test garage. I explained the problem before booking the test.
The tester had a good look at the brake prior to testing, and couldnt see any issue.
After the test he told me that the fluctuation should have been an advisory at most as the brake was sound.
So - lesson learned. I wont be going to Victor Motorcycles in Bristol for a future MOT! (or anything else for that matter!)