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Bike brake bobbins.

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Now I've been riding since I was 14 and had loads of bikes but just when you think you know it all along comes something you never even thought of, I watch quite a lot of "how to" videos on youtube and particularly like a guy called Delboys garage, makes me laugh anyway, but I have never thought about why the front discs are called "floating discs" and had no idea that the floating part was an actual moving item, I'm sure some of you did but I was brought up using brake shoes and drums and just assumed that discs on a bike were the same or similar to a car DOH! If you know this good for you if you don't then it could save you having to buy new discs with just a few minutes effort and a squirt of brake cleaner. Just done the FJR this morning and believe it or not quite a few were less than optimal, so when you think you know it all and there's nothing that can catch you out look again. Watch this link if your interested https://youtu.be/1qoPqN2GBdw

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Great tip! I wonder how many people have changed their discs in that situation because they didn't know that

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I knew what floating disks were, but never thought to ensure they needed to be kept clean.

 

what was he using in the spray, carb cleaner?

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I was about to buy a new disc!
Definitely doing this first, cheers!!

I assume he was using chain and brake disc cleaner.

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Yeah wurth brake and chain cleaner is good stuff

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I used brake cleaner, it's great cos it evaporates and is easy to clean up afterwards, glad it's not just me that thinks this is a good idea, think I will do it once a year in with the service.

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I can get brake cleaner for a £1 from the local Polksi shop

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3 hours ago, drewpy said:

I can get brake cleaner for a £1 from the local Polksi shop

Really?

Im in the motor trade and I pay about £1.30 a litre for the stuff! Cheap as chips if it's a quid!! 

 

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26 minutes ago, Harrywr65 said:

Really?

Im in the motor trade and I pay about £1.30 a litre for the stuff! Cheap as chips if it's a quid!! 

 

its only 330ml so cheaper for trade

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If you ever get a close look at a race bike you'll see the discs on some are held onto the disc centre by a single slip ring (like a large circlip) , if you grab the disc outer and give it a shake it'll rattle like buggery . The disc'll usually be cast iron and the clearance tightens up (a bit ) when the disc is properly warmed up .

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Found this on another site, explains it quite nicely.

Fixed and Floating Brake Discs

There are three principal types of motorcycle brake discs: fixed, fully floating & semi floating.

A fixed brake disc is a one piece brake disc. That is, its brake pad contact face and wheel mounting face are all part of the same piece of metal. They are relatively cheap to produce and they perform perfectly well within certain parameters, but if they are subjected to serious heat then they are unable to dilate or expand because they are not floating.

Both fully_floating_brake_discs and semi-floating_brake_discs are constructed in two parts. An aluminium centre part which is fixed to the motorcycle wheel and a stainless rotor part which the brake pads push on.

When the rotor is subjected to serious heat it expands. By allowing it to float separately from the mounting face it is free to expand and shrink again at will without being constrained by its mounting. When this expansion takes place is does so in all directions at once and it will not be constrained. If you prevent this from happening in one direction (by fixing it on its mounting face) it has no choice but to warp, so floating_discs and semi-floating_discs are made in two parts to allow the discs to expand and prevent them from warping. This is mainly a high performance type brake disc.

Bikes of more moderate performance can use fixed brake discs perfectly happily and you will also see that most rear brake discs are fixed. This is because they don’t get used as hard and therefore subjected to as much heat. Even so, most rear brake discs are thicker than front brake discs and this is a compromise because the cooling is not as good as the front discs. They don’t get as hot but don’t cool as well either, so the thicker material helps prevent them from warping.

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Watched this exact video a few days ago, great channel, been subscribed for a while now. I was in the same situation, I'd never even though about that before, great thing to know that will actually save money in the future

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Tried this earlier today, worked a treat! I did cheat though, used my battery drill haha. Great trick!

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Great tip, having grown up with crappy drum brakes I thought disc brakes were all basically the same, guess what they say about never being too old to learn is true - even for an old fart like me :mellow:

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12 hours ago, meatloaf said:

Great tip, having grown up with crappy drum brakes I thought disc brakes were all basically the same, guess what they say about never being too old to learn is true - even for an old fart like me :mellow:

Right on Meatloaf ! We never needed poncy Anti-lock brakes ! 

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Must admit, this thread made me look at mine on the fazer. Cleaned up and all working ok anyway, but now on the regular checlist

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When the FJ developed a pulsing front brake action after changing pads last year the bobbins was my first port of call.

It was really annoying because at slow speed/coming to a stop I had the feeling the discs were warped by an inch or so and the whole front end was juddering.

Sprayed the bobbins and gave them a turn and felt they needed doing but that but that was not the solution.

Opened up the calipers but there is only so much you can see : little oil ring & 4 pistons.  Fook me .... at the price those pistons go for it would cost a bomb to do both sides.

A £25 quid pair of calipers from ebay was the solution.

I think that an uneven action from the pistons must have caused the pads to engage at wrong angles but I will never know unless I spend best part of 250 quid and refurb my old ones.

 

 

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Christ Dutch that's a lot of money, I did the FJR set for £30 a corner, just replaced the seals, are you talking about removing and replacing the pistons as well mate? Mine polished up a treat with a trick that I got from somewhere, take a cloth, spread on some Autosol and rub till the shit vanishes off of them, easy and cheap to do, plus you can't damage the pistons with Autosol cos it's so fine. Just a thought.

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Just bought a rebuild set, for the rear caliper, on eBay. Full set of pistons, seals, new bleed nipples for £27. Company called powerhouse I think

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3 hours ago, slice said:

Christ Dutch that's a lot of money, I did the FJR set for £30 a corner, just replaced the seals, are you talking about removing and replacing the pistons as well mate? Mine polished up a treat with a trick that I got from somewhere, take a cloth, spread on some Autosol and rub till the shit vanishes off of them, easy and cheap to do, plus you can't damage the pistons with Autosol cos it's so fine. Just a thought.

Yeah, that was seals & pistons, the lot.

Now sorted anyway but may refurb my old ones, new seals only, if I want to get away from SWMBO for a bit :-)

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