Front Brake Judder

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Pete.
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Re: Front Brake Judder

Postby Pete. » Sun May 19, 2019 11:43 pm

Humbug wrote:Well, after a new wheel, new seals and bearings and new Brembo pads, the judder remains! Discs within permissible run out, wheel straight and true. Next will need to be the callipers. Seem a bit sticky on the inside pistons and the ceramic inserts are cracked although mechanic said that cracked inserts wouldn't affect the braking.
Not sure whether to go down the Motorworks calliper repair kit, second hand callipers at £100 each with 6 months guarantee from Motorworks or rebuild of my old callipers at up to £180 each calliper.
To top it all, neutral light not indicating unless I put light pressure on the gear lever meaning bike won't start without this light pressure. Too much and 1st gear selected!!!
Another option of course to scrap the bike and get something with less miles


Clamp off the front brake lines one at a time. That will tell you if it's a disc. Make sure you press the pistons back slightly on the one you clamp off or it'll bind the pad after a short bit of riding as the caliper (and thus the oil) heats up with friction.

My friend had this problem after fitting new pattern discs just last month. Turned out that one of the discs was not even thickness all the way round. Badly ground from new. I measured the thickness of both with my micrometer and one was good, the other varied - not by much but enough to cause huge juddering. I clamped off the braided line with a tiny G-clamp and braking was smooth as silk on the one good disc. He got a pair of replacements from the supplier FOC.

Pics of the disc as measured attached. As you can see the variation was only 0.06mm but it cause massive juddering.

disk1.jpg
disk1.jpg (117.85 KiB) Viewed 9155 times


disk2.jpg
disk2.jpg (122.74 KiB) Viewed 9155 times


disk3.jpg
disk3.jpg (122.78 KiB) Viewed 9155 times

Humbug
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Re: Front Brake Judder

Postby Humbug » Mon May 20, 2019 4:18 pm

Thanks for the suggestions chaps, I have changed the discs to no avail, Armstrong and Brembo. I have ordered replacement callipers from Motorworks as mine are definitely sticking on the inside pistons with both callipers for some reason. I'll try changing them first. I have braided lines on mine so can't try the clamping of a calliper although that would be a great method of trying each calliper. I had thought about removing one calliper and sealing off the line as an alternative to clamping but am running out of time as due to tour Spain and France in 6 weeks. I will post the results and hopefully get a conclusion as I hate to leave a post unresolved.
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Pete.
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Re: Front Brake Judder

Postby Pete. » Mon May 20, 2019 5:29 pm

You can so clamp a braided brake line just like you would any other. It does them no harm and they return to shape readily. I have done it many times. The bike in the pics above was fitted with them.

Humbug
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Re: Front Brake Judder

Postby Humbug » Mon May 20, 2019 6:23 pm

Thanks Pete, that is my next move then to see if I can at least identify the dodgy side.
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Humbug
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Re: Front Brake Judder

Postby Humbug » Wed May 22, 2019 7:04 pm

Great idea Pete, tried the g clamp and it showed that the left hand calliper/disc is the issue. With that side clamped, braking was fine, albeit a bit reduced as a single disc. Clamped the other side and judder was evident. Replacement calliper arrives tomorrow from Motorworks.
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Pete.
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Re: Front Brake Judder

Postby Pete. » Wed May 22, 2019 8:34 pm

I hope it is the caliper now you have bought one. I would have swapped the discs over first to see if the problem swaps with it.

Humbug
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Re: Front Brake Judder

Postby Humbug » Wed May 22, 2019 9:32 pm

I have had the discs checked for runout and have tried other discs so have gone for the next option although had I tried your clamping suggestion first I would have gone for discs next. Thanks for the help anyway, I'll post if I am successful with the calliper.
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Humbug
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Re: Front Brake Judder

Postby Humbug » Thu May 23, 2019 4:47 pm

Does anyone know if the ABS sensor ring has washers behind, in front or not at all on the 12S. I can't seem to find details on the microfiche
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Humbug
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Re: Front Brake Judder

Postby Humbug » Sat Jun 01, 2019 6:53 pm

Replacement callipers and discs has sorted the issue. Jammed piston in the calliper was causing the discs to heat up and warp. Thanks to Petefor the clamping tip which helped to identify the side.
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Humbug
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Re: Front Brake Judder

Postby Humbug » Wed Aug 07, 2019 4:41 pm

aaargh, its back again!!! Can't believe new wheel, discs, callipers, bearings, seals and tyre worked for a short time and now its back with a vengeance. Could it be forks, ball joints, telelever bearings and how would I check? It got an MOT two weeks ago and although he felt a little resistance on the brake tester, nothing to raise an advisory on. No ABS light on so don't think the pump is the culprit but can't work out what is causing the discs to warp. Any more ideas of thoughts welcome. Trackday at Cadwell booked for Monday next week :shock:
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dave the german
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Re: Front Brake Judder

Postby dave the german » Thu Aug 08, 2019 3:09 am

could be the telelever bearings - they sit in the same position and don't rotate so do not wear evenly. Dismantling, I think would be the only way to check
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slparry
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Re: Front Brake Judder

Postby slparry » Thu Aug 08, 2019 8:37 am

Humbug wrote:aaargh, its back again!!! Can't believe new wheel, discs, callipers, bearings, seals and tyre worked for a short time and now its back with a vengeance. Could it be forks, ball joints, telelever bearings and how would I check? It got an MOT two weeks ago and although he felt a little resistance on the brake tester, nothing to raise an advisory on. No ABS light on so don't think the pump is the culprit but can't work out what is causing the discs to warp. Any more ideas of thoughts welcome. Trackday at Cadwell booked for Monday next week :shock:



I had a dealership fit new disk bolts to my K12GT once and a few weeks later noticed some disk warp pulsing. I rode around the issue for a few months until pennies allowed me to buy new disks. Upon fitting the problem was when the dealership had fitted one of the new bolts in they'd trapped one of the wave washers which effectively locked that bobbin solid, which resulted in the warp.

Not sure if it helps but worth a check?
--
Steve Parry


Current fleet: '14 F800GS, '87 R80RS, '03 R1100S BoxerCup, '15 R1200RT LE Dynamic, '90 K1

Humbug
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Re: Front Brake Judder

Postby Humbug » Thu Aug 08, 2019 12:52 pm

Thanks chaps, all suggestions welcome
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boxerscott
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Re: Front Brake Judder

Postby boxerscott » Thu Aug 08, 2019 10:13 pm

Humbug wrote:Thanks for the ideas chaps
I'm wondering if I might be looking in the wrong places and should I consider the upper and lower ball joints? Anyone had experience of changing these? Cost and difficulty?
aye you may be looking in wrong place, after eliminating pads, discs and bearings. Is the wheel true? Ball joints possibly not both of them but one may be going wonky. I have removed these from my boxer cup and followed clymer instructions. Did not have any issues.

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Humbug
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Re: Front Brake Judder

Postby Humbug » Fri Aug 09, 2019 1:59 pm

Thanks Chris
Bought a replacement wheel from one of our illustrious members and had the wheel checked and straightened by ST motorcycles near Newark so I'm sure this is ok.
I think you may be right with a ball joint but thought there would be some other signs if they were failing. I think there is increased vibration at the bars, my fingers now go white and numb in 6 minutes rather than eight!
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