Brake Disc Problem

[leegriffiths128]

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?

[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.
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?

[Dangerous Dave]

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.

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.

[Stig]

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.

[Stig]

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.

[leegriffiths128]

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#-o) 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.

[Dangerous Dave]

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

...If you have a front paddock stand put the bike on that and spin the wheel, you will visibly see the disc is warped by doing this and looking at it head on.

[leegriffiths128]

Cheers Viney......Oh, woe is me.....please let it not be a warped disc[-o<

I might ask the garage to re-look at the disc as it has to go back in for its MOT.....can't check myself..haven't a front paddock, or a 12mm socket to get the front wheel off....but the real reason I won't remove the disc myself is through fear of rounding the bolts !

Would I feel any vibration from a warped disc or would that only be if the disc was severely warped ?

[Dangerous Dave]

A pulse through the brake lever is common, mainly on badly warped discs though. I would have thought the garage would have tested/check such an important safety feature of a bike first though.

[daveb]

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

Fair point, didn't think of that - however, I still would never only replace the one disc tho and I would still argue that braking would not be as good as if both discs and pads were replaced at the same time - this is why I would always replace as a set imho...

Dave

[Stig]

After all of your more detailed explanation I fail to think of anything other than a warped disk. As Viney said, check it, but also bear in mind if it has grooves that does not necessarily mean the disk is warped. The grooves would be even all the way round the disk though.

A pulse through the lever is a good indication but a pulse is not always felt. Depends on the severity of the warp, the age and condition of the brake lines.

[yorkie_chris]

I had a set of quite badly worn busa discs on a while back, could hardly feel the lever pulsing but there was serious front end shudder going on.

[leegriffiths128]

Just had a good look at the caliper again and can't spot anything obviously wrong.

Couldn't feel any 'pulsing' from the lever, but like I say, there is hardly any travel in the lever now anyway.....I'm gutted :(

Thanks for all the replies everyone....really appreciated, even if it wasn't what I wanted to hear.

[yorkie_chris]

Disc being warped will feel normal at standstill, but more lever travel when moving.

[leegriffiths128]

I've only got a rear paddock - no front.

Is it okay to jack up the front ? If so, what do I use as a safe jacking point ?

Thanks

[yorkie_chris]

Yes but do it on sidestand. Jack on engine just behind oil filter.

[daveb]

I would jack on downpipe at the join (bike on side stand) and make sure you use a folded cloth or similar between the jack cup and the downpipe - I have done this to take the front wheel out (as per manual instructions) most of the weight is transfered to the stand and assuming your jack is sound then its a fairly solid set-up.
Not meaning to critise yorkie chris's comment but I would avoid jacking on the bottom of the engine as the alloy is very soft here and could easily crack - not good!
As mentioned, the Suzuki owners manual says to jack on the downpipe while bike is on the stand so I think this is the safest option.

Dave

[leegriffiths128]

Ok, thanks for that....think we can all guess what I'll be doing tonight :)

[weecorey]

It was myself that sold Lee the disc, disc was removed from a crashed K6 I bought with 3700 miles on the clock. I changed the front end to GSXR, one disc was damaged this one looked 100% with no marks groves ect. My experince with warped discs would be the brakes binding on certin parts of wheel rotation and not constant, I can't understand the small amount of travel in the lever, that shouldn't happen even if the disc is severly warped, I would have thought pistons in the caliper not working as they should be would cause this. The guy who fitted the disc should have noticed the brake lever problem imediatley if he is any way compedant.

[leegriffiths128]

Hi Emmet, you are right, the guy who fitted it should have noticed.

Also, when I got the front end up on the jack earlier, the brake was binding at one area of rotation like you suggested. I then took the calliper off so I could spin the wheel freely to verify that it is indeed warped.

Thanks for being so good about it all.

[Stig]

Wasn't a witch hunt fella. Just passing of advice.

[leegriffiths128]

Just wanted to put down my thanks to WeeCorey.

He sold me the warped disc (not known to him at the time), but has given me a full refund, which I'm sure, if he had so wished, he could have flatly refused.

Nice to see, in this day and age, that there are some gents still around.

Cheers Emmet, and thanks to everyone else for their advice throughout the thread.