Front Brake Issues - advice please

[axis 26]

Hi all - I'm hoping for some advice please. First real issue I've had on the bike in over 4 years !

I set off to work this morning and noticed a pulsing from the front when applying the front brake. I stopped and had a look, nothing obvious, a quick check of the caliper bolts etc and all seemed OK. Disc looked/felt OK. However I was pushed for time so headed back home and set off on one of my other bikes. I did appear to get worse the more I used the front brake on the way back. If I slowed right down, it's clear that the pulsing is from one revolution of the front wheel/disc.

 

For reference, there's no pulsing from the front when free-wheeling, only when the front brake is applied. Pads are relatively new and looked OK (changed around 1500-2000 miles ago). It's a 750 so no linked brakes.

 

I can take more of a look this evening when I get home.

 

Thanks all

 

[KingJames 1,262]

Brake fluid above the line in the reservoir? When brakes applied and when not?

 

Plus check your front tyre pressure as any slip could trigger the ABS which feels like you have described.

[Grumpy old man 4,673]

For it just appear sounds odd. Could it be a sticking pad? Or wheel bearings?  Is the ABS light working as it should?  Warped disc? Good luck. 

[DaveM59 1,604]

For the pulse to be in time with wheel rotation would eliminate ABS as the pulse from that is rapid regardless of wheel rotation speed.

It sounds more like a problem with the disc/wheel/pad or even the tyre. Is anything touching the pad backing plate when the brakes are applied such as some debris in one of the disc drillings. Check the tyre tread for splits or embeded screws!

[axis 26]

Thanks for the responses Guys. No ABS or other warning lights came up on the dash.

[trisaki 2,029]

 With front wheel  off the ground  does it spin freely  , pump front brake , now does it still move freely  , if not , Pull caliper off and clean and regrease the slider pins but not with copper grease , take pads out clean with brake cleaner  and apply a smear of copper grease to the backs and also a little  on the small piece of metal that one end of the pad sits on after cleaning that , pump the piston  out a little  , clean with a toothbrush  and brake cleaner then push piston  most of the way in ,enough  to get the pads in ,reassemble , cleaning the disc  with brake cleaner  and take for a spin  

[steelhorseuk 1,690]

Everything Mark (trisaki) says above but before you go to all that trouble (you say you recently changed the pads) you can try the power clean with a hose.

 

Have a look at the rotor and see if there is any marking in one place but all around the disc. It will be evidence of something trapped that should not be there!  

 

A nice hose wash at medium pressure (not blasted) directed into the pads from above.

Provided you have a centre stand or someone to elevate the front wheel for you.

Give it a good soak and spin the wheel freely.

It may just be debris trapped in there which will work loose and out.

 

 

Worked for me in the past. Hope you sort it!

[axis 26]

Thanks for the additional responses all - this is where my dislike of centre stands works against me!

I'd like to be able to do what Mark has described but no way of getting the front wheel off the ground - any suggestions here ?

 

BTW Mark - why not copper grease on the slider pin ? I've must admit I've done this in the past.

[Andy m 23,505]

What do you have in the way of service stand or trolley jack? The trolley under the sump will lift but the service stand makes it more stable.

 

Copper grease goes gunky after a while and is poor if it gets on the seals. It's an anti-seize not a lubricant. Putting it on the backs of the pads can be controversial, but does no harm.

 

When was the fluid last changed? This sounds mechanical because its constant, but old fluid can do odd  things.

 

Andy 

[Herr Flick 85]

Surely this is a warped disc? No pulsing when 'freewheeling' i.e. no brake applied, only when the brake is used. It only needs a few thousandths of an inch to give the symptoms. Replacement is the only cure for the majority of modern discs.

[MikeBike 5,005]

Useful recent info in the thread linked below, including run out tolerances and recommended source of non OEM brake disk.

 

I had advisories on my MOT last year for front and rear. Before this year's MOT I sanded the discs with emery paper, cleaned with wheel cleaner (Valet PRO Bilberry Wheel Cleaner) and went out and gave it some serious (mostly front) braking also practicing my emergency stops in case it helped.

 

Don't know if it was a fix but this year I just got the advisory on the rear. I can feel it pulsing on the rear if I use it from speed, but only ever use it lightly for manoevres at slow speed.

 

 

Edited March 5, 2019 by MikeBike

[arengle 449]

Just push the bike around, slightly apply the brake and have a fill if it pulse again. Have a look at disk in that position. The brakes are floating, taken the caliper and move it inward and outward to see if they "float". If you do this hit the brakes a few time to get the pressure back on the pads before riding. 

[Tex 36,817]

30 minutes ago, Herr Flick said:

Surely this is a warped disc? No pulsing when 'freewheeling' i.e. no brake applied, only when the brake is used. It only needs a few thousandths of an inch to give the symptoms. Replacement is the only cure for the majority of modern discs.

 

I tend to agree. But it’s very odd if it’s come on suddenly? I mean, discs don’t warp in the garage overnight..

[Grumpy old man 4,673]

8 minutes ago, Tex said:

 

I tend to agree. But it’s very odd if it’s come on suddenly? I mean, discs don’t warp in the garage overnight..

Just a thought, if the bike has been parked for a few days after riding in the salt and damp the pads do tend to stick, so if you have uneven pressure, due to sticking pads, could it warp the disk?

Edited March 5, 2019 by Grumpy old man

[Tonyj 6,907]

Look to the obvious first my friend . You need to elevate the front wheel , even if it's by getting some one to lean against the stand and spin the wheel to see if the disc runs true after that check for movement in the bearing then calliper and pads . Pulsing would normally indicate disc bent which you would know if you done it so look to sticking calliper . That's what I would start with.

[Wedgepilot 727]

It does sound very much like a warped disk

[DaveM59 1,604]

Do you use a disc lock or any sort of chain that may have been put round the disc, if so it may have moved the disc on it's floating clasps or burred a hole if you put the disc lock through one. Has to be something simple to come on suddenly but not having the centre stand is a bigger problem initially.

[trisaki 2,029]

If a trolley jake is available  ,put bike in gear  push bike forward  till wont move turn handle bars full to the left put Jack under the fat part of exhaust  and gently lift front wheel  in the air , only needs to be just of the ground now you  can turn wheel , if moves freely  pump front brake  and see if it still moves  if not caliper strip down time 

Edited March 6, 2019 by trisaki

[axis 26]

Quote

 

Hi all - I pulled the caliper off last night. All looks good, pads are pretty new and I cleaned and lubed when fitted recently. Pads/pistons are definitely not sticking. I had a good look/feel of the disk and anything else that might account for this. Nothing obvious other than the fact that at 38k miles there is wear of the disk. There's a fair lip around the edge but it's even. I don't have a micrometer to measure min thickness unfortunately. Took it for a short run and still the same but seems to be getting progressively worse. The inability to get the front wheel off the ground is now preventing any further investigations.

 

Any recommendations for a reasonably priced stand that I could buy ?

 

Others points raised:

- Brake fluid level is OK

- I don't use a disk lock or anything else that might account for any damage

- The bike is used most days, has not been left standing

- I don't have access to a trolley jack

[Andy m 23,505]

Jungle run out test:

 

Fasten a pencil to the forks with blu-tak, point touching the disc. Spin the wheel, clean the mark off then spin again. If the pencil line is a solid circle its fine. If the line is dotted move it round to opposite the darkest marks and measure pencil point to disk there. 

 

You will see daylight or get a fag paper in the 0.3mm typically allowed but can measure half a mm which isn't. 

 

Andy

[Tex 36,817]

18 minutes ago, Andy m said:

Jungle run out test:

 

Fasten a pencil to the forks with blu-tak, point touching the disc. Spin the wheel, clean the mark off then spin again. If the pencil line is a solid circle its fine. If the line is dotted move it round to opposite the darkest marks and measure pencil point to disk there. 

 

You will see daylight or get a fag paper in the 0.3mm typically allowed but can measure half a mm which isn't. 

 

Andy

 

The posh way is to cable tie the pencil and use a marker pen.. Tough to do if he can’t get the wheel in the air, though. @axis, my home workshop is at your disposal at the weekend if it helps? Sussex coast. 

[steelhorseuk 1,690]

Also, another quickie.

check for bearing wear on the front wheel axle.

There should be no 'play' (movement) when manipulating the wheel from side to side. Really best to check with the wheel elevated if possible though.  

If the bearing is worn to any significant amount, load under braking will effect its rotation.

 

Edited March 6, 2019 by Steel Horse UK

[Tex 36,817]

Good point, Mark. I’m puzzled by how a disc can warp so suddenly, and it’s well worth a check of the bearings at 38K miles. 

[axis 26]

Thanks again for the responses folks, and Tex really appreciate the offer but am not keen to use the bike in this condition. Good point regarding wheel bearings Mark. I've asked some of my biking mates for help with a jack/lift and will check wheel movement and disk run-out shortly. And yep agree that the suddenness is odd. All was well to/from work on Monday, but Tuesday morning started to feel the pulsing, which has worsened in the short distance I've since travelled since then.

[makman 975]

If it is getting worse, then definitely do not ride the bike.  Bearings are a possibility, disc another. Brembo disc on that auction place site is £95 delivered.  Way less than OEM and decent quality. Bearings, I've no idea, but they are fairly straight forward to fit.