Brake Disc Problem

Morning everyone.

Had the garage change one of the front brake discs the weekend.
Is it ok to change just one side or should I have done both ?
I know I should also have changed the brake pads at the same time but was trying to save money so didn't.

The new disc is now dragging. Stripped both calipers last night and regreased / bled the system. Unfortunately, still dragging on the ride in to work this morning. There is also no travel (or hardly any) at the brake lever....more like an on/off switch !

When I stripped the caliper, noticed that one of the pads (on the new disc side) is only making contact with disc at the centre opf the pad.

My question is, if I change the pads, should everything then be ok ?

Thanks everyone

[yorkie_chris]

Too much fluid in reservoir?

You should never change a disc without also replacing the pads - I personally would never just fit a single front disc either as this may unballance the front braking.
My advise would be get a new disc for the other side and fit new pads all round - I should think this will solve the dragging issue as well.

Dave

[yorkie_chris]

Dragging isn't usually caused by the discs. Unbalance front braking? Lots of bikes work fine with only 1 disc.

Gotta wonder why it's dragging rather than just throwing money at it. You got forks in line right? Calipers properly bolted on? Sliding pins free?

Originally Posted by daveb

You should never change a disc without also replacing the pads - I personally would never just fit a single front disc either as this may unballance the front braking.

I can be done, it is mostly a brake disc manufacturers recommendation but it is not entirely neccessary as the wear it would create is minimal and the pad and disc will soon bed in together.

Originally Posted by yorkie_chris

Too much fluid in reservoir?

+ 1, have a look and check the sliding pins like Chris also suggested.

[yorkie_chris]

Yes recommended for safety, by someone trying to sell you something.

The reason you put new pads in with new discs is because old pads will be worn into the contours of the old disc.

Thus when braking it wont be as effective as the whole of the pad will not be in contact with the disc. This can lead to excessive pressure on the pad to the disc which in turn will cause excessive heat which in turn could cause the disc to warp.

If you put new pads in with new discs you have ideally two flat surfaces together so the bedding in period will be far less.

Regarding your sticking brake pads. I would hazard a guess that it was already doing this prior to having your disc replaced, hence only needing one disc replacing. You say you have serviced the callipers so will assume you have done a complete dismantle and rebuild. What condition were the seals in? Did you use new ones. If you did, what condition are the pots in? If they are pitted it could well be this that is causing the issue against the seals. If the pitting is extensive it could well be pulling the seals out of position which would also give you sticking pistons and thus binding pads.

Oh and another one for checking the pins. Uneven wear can cause the pads to not move freely. But also check the hole the pin goes through in the calliper as that can get elongated and cause the same effect.

Thanks for the replies guys......think I maybe didn't go into enough detail in my original post......rushing to get it posted at work.

I had to replace the brake disc as the brake rotor had become loose as the washers behind the rivets appeared to have perished ?

The disc I replaced was not brand new, but was purchased second hand from the org. It seemed in very, very good cond.

The brakes definitely were not binding before the new disc was fitted (although I take Big Apes point that something could well have been amiss).

After the new disc was fitted, I immediately noticed a problem........it is not huge (for example, the bike can still be fairly easily manouvered by hand), but the bike would not pick up speed or would actually decelerate when going down an incline (with clutch pulled in to test).

Tried to get away with giving the calipers, pots and pins a good clean on Monday but the problem was still there. So last night I took out the pistons, seals, pins etc and gave everything a good old clean then copper greased pins/bolts, rubber greased pistons and seals. Hoped that would cure the problem but no....checked the actual disc tonight after my ride home, and the new one is fairly hot due to it sticking.

The pistons do have the odd mark on them (where some amateur, on his first ever attempt at the job, used kitchen paper and mole grips to pull them out......yes it was me) but I did my best to smooth em out with wet and dry and this has been a few years ago and hadn't had a problem since. Anyway, the marks on the pistons are towards the top edge which are past the dust seals now anyway as the pads are'nt that new.

Have I brought a warped disc ??? Is there an easy way to tell ?

Thanks again......sorry for the ramble.

P.S, I don't think for a second that the guy who sold me it knew if it was warped (if indeed it is)...seemed a really nice bloke.

[Viney]

Sounds like a warped disc to be honest. take the disc off and get a ruler and a set of feeler guages. Its a crude way of checking to see if its warped. Lay the disc down put the ruler on its edge from the centre of the disc to the outer edge, then 1st see if you cen see light between the ruler and the disc. Try this around aevery quarter or more just to be on the safe side. If not, try with a thin feeler guage. If all is well, then i would check that the disc is correct for the SV. Take the otehr one off and check that the disc itself is spaced correctly.

I would also check that you havent, like i did once, got both pads on one side of the caliper (It was raining, it was dark, and i was rushing ok) and that the caliper is seated correctly.

agian, it could be the caliper sticking ever so slightly. Its not un common at all.

As for unbalancing breaking, im sorry but i fail to see how this could happen where both discs are attached to the same wheel. In a car yes, but not on a bike. So, 1 disc will be fine to change.