Hi all, could do with some advice reference front disc brake bobbins. I’m a relative newbie to motorbikes compared to most, apologies If this has been covered before. I have had a look through previous posts and google and have ended up confusing myself. After a ride today and a check over of the bike on return I noticed that the front discs when physically pulled with force move back and forwards. firstly can someone confirm that this is normal? I’m aware they are semi floating so allow flex side to side as such just not certain they should have movement move back and forth. if the bobbin is circular and sits in a circular hole then there should be space to move in all directions? I will take a further look tomorrow in the daylight. Both left and right discs have forward and backward movement the right side more than left. Secondly - if forward and backward play is acceptable should the play be equal on both sides? being my first road bike I’m as good as clueless on bobbins. Braking system works fine. Thanks in advance, Stew.
Morning Stew, the last line says all you need to know, the brakes work fine so no worries. It’s good that you can feel that bit of movement as that says the bobbins are clean and doing their job properly. If neglected they stick in position and this can lead to the disc warping which shows up as a pulsing feeling at the lever and sometimes a wobble from the front if braking hard. You’ve already searched the net about this so you may be aware that one way to keep them freed up is to use a large flat blade screwdriver jammed into the bobbin so you can rotate it to clear out any crap that can lead to it sticking, that and a bit of aerosol brake cleaner (nothing else) sprayed on them, is all you need to do, say every thousand miles.
If you think about it, the force the bobbins need to resist is tangential and generated by the friction between pad and disc. Lateral movement accommodates any slight axial variations in the brake assembly. Yanking them applies a radial force they will barely experience! See how you get on rotating them......
Thanks gents.... the internet is fantastic for finding out information. too much looking and you can end up as confused as you start have a great weekend everyone. happy and safe riding
