Disk bobbins, should they turn freely?

[Martin#30]

Morning all,

I have started getting that warped disk, pulsing type of brake symptom. I have checked the spinning disks against a fixed reference point, and there is no runout, so I thought I would have a look at the bobbins.

I have attacked them with brake cleaner, and I can rotate them with a spanner if I tighten a nut & bolt through the bobbin for leverage/purchase.

There is no way on earth I could turn them by hand.

Is this normal behaviour? Braking symptoms certainly seem much reduced after doing this spanner based freeing-up.

Martin.

[yorkshirepud]

Thats correct.  They should be fairly stiff, but with a nut/bolt through then they should turn.

If the disc has warped already, then freeing the bobbins off won't help much now I'm afraid.

[Kwikasfuki]

A 10mm allen socket fits fine as well.

If they've warped though not sure you can do much other than replace the discs

[Martin#30]

Thanks guys. I don't think the disks have warped, there is certainly zero side to side runout on the disks when I spin the front wheel.

I was just wondering how freely those buttons should be. On my Arashi disks that I took off as I did not really trust them, the buttons are very easy to turn by hand - they rattle, you could call them loose even.

Martin

[Kwikasfuki]

Mine don't turn by hand alone. I use a 10mm allen socket and then spray liberal amounts of brake cleaner

[Andy]

They are pretty tight don't think they are designed to turn by hand or by any other method . Disc type have been changed twice since this model. I had mine checked yesterday and they are 0.9mm out.

Fully floating discs have shims rather than maybe a spring arrangement on semi's.