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-   -   Front wheel shudders uner braking (http://www.horizonsunlimited.com/hubb/bmw-tech/front-wheel-shudders-uner-braking-52896)

Lonesome George 25 Sep 2010 04:40

Front wheel shudders uner braking
 
Riding along today (on a awesome stretch of coast road in Oregon by the way!) and the front brake felt a little shuddery. When I stoped I took the pads out to see if they were OK and there's plenty of life left in them. I then squeezed the front brake with the pads out. Only the top two disks on the brake system moved inwards. I assume all 4 are supposed to move thus pushing the pads against the front rotor.

Am I missing something? I guess this could explain the shuddering if only the top half of the brake pad is being squeezed agains the rotor. Is there anything I can do apart from take it to a BMW shop and get ripped off?

Thanks

oothef 25 Sep 2010 12:07

With the pads out only the pistons with the least resistance will be pushed out, push them back in and put something(wood is best),screwdriver,spanner between the piston and disc to hold the ones that are moving in the caliper then try again, the others should be pressed out. Make sure the discs are clean and are not buckled/warped.
Don't push the pistons out too far or they'll pop out and you'll loose fluid and have to sweardoh

illustratedman 25 Sep 2010 17:40

Brakes
 
Sounds like a warped disc/s also on some beemers where the disc mounts can wear oval causing the same feeling.

dajg 27 Sep 2010 10:03

what speeds does it shudder? you said under braking so you are thinking brakes.

i've done 2 steering head bearings on my 650 twin. first time noticed shudder at 40-60kmh. 2nd one, vibration in the cruise. strangely more vibration in the right grip than left.

put the bike on the centre stand, weight on the back so the front is off the ground. spin it, tilt left - right. is it balanced? tyre wear? pretty hard to damage a disc.

good luck
d

Steve Pickford 28 Sep 2010 00:06

Quote:

Originally Posted by Lonesome George (Post 306734)
Riding along today (on a awesome stretch of coast road in Oregon by the way!) and the front brake felt a little shuddery. When I stoped I took the pads out to see if they were OK and there's plenty of life left in them. I then squeezed the front brake with the pads out. Only the top two disks on the brake system moved inwards. I assume all 4 are supposed to move thus pushing the pads against the front rotor.

Am I missing something? I guess this could explain the shuddering if only the top half of the brake pad is being squeezed agains the rotor. Is there anything I can do apart from take it to a BMW shop and get ripped off?

Thanks

The "disks" you refer to are called pistons. If they're not moving, it just means that there's a bit of dirt etc that's seizing or holding them in place & preventing them from moving.

1. Unbolt the caliper from the bike, stick something (small piece of wood is good) between two opposing pistons.
2. With the two remaining pistons, use a G-clamp to hold one in place. Very gently squeeze the brake lever, the unsecured piston should now start to move as it's receiving all of the hydraulic pressure.
3. Once it's moved out a few millimetres, squirt a bit of WD40 around the piston & clean it well as possible with an old toothbrush or a Scotchbrite pad - nothing too abrasive.
4. Once clean, dry with tissue paper & then smear a little brake fluid around the piston before very slowly pushing the piston back in to place. Ensure that you push it in square to the caliper body & don't push it all the way in, leave it protruding a few milimetres.
5. Repeat for all pistons on both calipers.
6. If a piston refuses to budge, you'll need to remove the caliper & blow it out - I use a compressor blowing through an airline fitting welded to a brake banjo bolt. Works 99% of the time. Obviously you'll need to bleed the whole brake system.

Mickey D 28 Sep 2010 23:42

All good procedures proposed by Steve!
Could be the Caliper pistons are hanging up due to dirt/corrosion. Check out the rubber seals that surround the pistons.
This can have several affects. When was the last time they were cleaned? Fluid flushed?

Generally a quick clean and new fluid every 10,000 miles should keep them working well. I do it at least once a year, regardless of mileage. I add anti-seize on the caliper guide pins as well.

If the front wheel was put on improperly ... and if your caliper pistons are hanging up a bit ... it could be ... your front brake was dragging, thus over heating your brake Rotor (disc) and Warping it. And there is your "shudder'. This is worst case scenario. Generally they can't be trued ... and you have to buy another. $$$$$$$$ doh

Good luck!

djorob 1 Oct 2010 13:59

Warp speed.
 
[quote=Steve Pickford;307014]The "disks" you refer to are called pistons. If they're not moving, it just means that there's a bit of dirt etc that's seizing or holding them in place & preventing them from moving.


Hi.
If you remove the wheel and squeeze the brake lever it is normal to see only one piston work.
As mentioned above it's because only the one with least resistance will move.

I have had 4 sets of disks on my 05 200 GS due to disc warping! BMW told me it isn't a problem but a friend who works for BMW has told me that they have had lots of issues with this!

It's most noticeable when braking hard from speed and shows itself as a judder from the front.

BMW may consider offering a replacement if the bike is still in warranty ect!
All the best.
Dave.

motoreiter 1 Oct 2010 15:07

you don't say what kind of BMW you have, but on the GS12s warped discs are pretty common and cause similar symptons. Although technically a wear item and not covered by warranty in my experience BMW has been pretty good about replacing them for free. Guess it depends how many miles are on the bike and how hard the dealer will fight for you.

dc lindberg 2 Oct 2010 08:05

Quote:

Originally Posted by Lonesome George (Post 306734)
Riding along today (on a awesome stretch of coast road in Oregon by the way!) and the front brake felt a little shuddery. When I stoped I took the pads out to see if they were OK and there's plenty of life left in them. I then squeezed the front brake with the pads out. Only the top two disks on the brake system moved inwards. I assume all 4 are supposed to move thus pushing the pads against the front rotor.

Am I missing something? I guess this could explain the shuddering if only the top half of the brake pad is being squeezed agains the rotor. Is there anything I can do apart from take it to a BMW shop and get ripped off?

Thanks

Yes you did.
Which vehicle?
Which brake system?

Lonesome George 5 Oct 2010 04:17

It WAS warped rotor blades. All fixed now and I'm poorer for it but back on the road.

Thanks for the help


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