Front Brake pulsing

[silverstripes]

Hi Guys

I know the issue over front disc (rotors) warping has been done before. However I thought I had warped front discs, as when riding slow I had pulsing which was getting worse.

I checked disc run out and they were fine. So I set about looking at the bobbins. These are the little round things between the disc and the mounting. Well they were all solid, no rotational movement nor let the disc float. So I put a bolt through the bobbin hole and locked it off with a nut. When I turned it with a ratchet and socket it was very stiff an gritty from wet riding and brake dust. I started squirting brake cleaner on and the were getting better but it was taking ages. So I got to thinking and used my air wheel gun to rotate them. You could also use a rechargeable drill. This spun them and as they were spinning I sprayed more cleaner and the black crap just poured out.

Each one now turns by hand and you can pull the disc in and out from the fork leg a few mm, so it now floats.

Result no pulsing. Not a thing, the brakes are like new. The bike is easier to push out of the garage as I think they must have been binding and the bike rolls better so I guess my MPG will be better but not been far enough to tell yet.

So this will now be a part of regular maintenance. The bike had done 8k miles and the bobbins had not been touched in that time. The bike had also done a lot of wet miles.

Worth checking Yours

[Zebraranger]

Thanks for the reminder. I have no pulsing, but I do need to check (inspect) my brakes.

[RocketSteve]

  Adrian!

I'm going to put a wide blade screwdriver to all my bobbins today - now you've mentioned it 

UPDATE: Yep, mine were also gritty but all free to move, done about the same mileage so I'll get some Gunk on them soon.

[GarminDave]

 , thanks for sharing.

Later

Dave

[KaliforniaKook]

Sorry, guys, I'm not a Brit. What is a "bobbin"? I looked it up in the dictionary and the parts list. The former discussed sewing machine and topics related to spools, and the latter didn't show. Can someone post a picture?

[r1pete]

Round rivet like objects between the disk or rotor and the frame/bracket that attaches to the wheel in 6,8,10,12 places and each place is a hole made of 1/2 in the bracket and the other 1/2 hole is in the rotor in each place where there is a button, bobbin etc.
These hold the rotors loosely enough that they float and deal with expansion/contraction of the rotor caused by use and resulting heat etc...

[KaliforniaKook]

Holy crap. I had no idea. I saw the thing about "floating rotors" and assumed someone had no idea what they were talking about. Comes of being an old fool. First time I've recognized that bike rotors could be lighter than the calipers.

Thanks! $4.49 for brake cleaner - I'll try it first thing tomorrow morning! A lot cheaper than $900 if it works.

[Stelyn]

Hi KaliforniaKook,  easy process,; ie ,  small bolt through bobbing with washer on rear,  pinch tight, spray with brake cleaner, initially just  ease/turn  gently,  once moving  you can use hand drill to expedite process whilst spraying more cleaner, and watch the `crud' come out....  
Click on photo to expand view.  ( `red tape'   was to help me remember what ones I'd cleaned )
Regards,
Steve 

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