dual front brakes - jackal

Jackal dual front brakes (not linked brakes)

A couple of things, not sure if they are related.

When applying front brakes, more so at over 30 mph there is a buzzing noise like a bee in a jar from somewhere. It’s audible whether a minute amount of pressure is applied (barely slowing down) or hard braking.

I noticed today that one disc is hot and the other cold. New pads, bled system to no available. Pistons move okay. no crud or dirt in there that I can see.

I’m guessing maybe a bit of air still in the system causing the difference in temperature, but the buzzing?

Any ideas welcome.

If there was air in the systyem, wouldn’t both calipers be spongy?

Guessing buzzing is something vibrating. When you put in new pads you must allow them to bed in to the disc AND the pistons adjust up behind them, then the lever / pedal feel should go harder and often with a shorter travel. Diff in temps likely due to one caliper’s pistons and pads not fully bedded in yet compared to the other. Or, another way of lookng at it, most of your braking is being done with one disc until the other catches up.

Appendix ~ that buzzing noise (just remembered) is by the sounds of it what I get sometimes by just rotating a wheel wih rusty disc, the rust rubs past the pads and causes them vibrate to make that noise. Could be worse, when I first got it my R80 its fr discs used to squeal. Fingernails down a blackboard style. Quite amusing in high streets watching pedestrians clap their hands over their ears and grit their teeth.

It was buzzing before the pads were changed. Stainless rotors, so no rust involved

One set was worn a lot more than the other. I haven’t had the bike long and I assumed that was due to the dual disc kit being fitted at a later stage.

To be honest the braking feels fine, but there again it probably would with one calliper working properly, as one disc is standard.

I only noticed the difference in rotor temperatures when looking for a cause of the buzzing. Anyway bled the system again, will test out in the morning.

Sounds like one set of pistons are not retracting into the calliper, causing additional wear to the pads, and heating up the disc. Whether that could also cause the noise, I don’t know.

or that the cold one is seized solid ?

buzzing / vibrating could be rust on disks/warped disk / stuck pads / one piston seized

prob best to stop riding and get the calipers off and check the pistons are moving and pad free in the guides

if one disc is standard and yors has been fitted with 2 discs have you checked to see if the additional one has the same size piston as the original
i also tend to put a very light /light smear of copperslip on the face of the piston where it pushes on the pads it cuts the squeal down (think you can actually get antisqueal paste)

I would drop one caliper off the bike and put a spanner inbetwenn the disc pads and operate the brake then see if the one on the bike is gripping the disc and also releasing etc , then swop them over and try again
as mentioned any air in the system will affect both calipers not just one

happy hunting

If one set of pads were worn much more than the other then those pistons are not retracting, was that the disc which was hot too?Pistons not retracting could be that they are partially seized, but could possibly be some blockage in the pipe feeding that calliper which is acting as a one way valve. Not likely, but possible.Simple test, much as Ray suggests above. Remove one calliper, put a bit of plywood between the pads, then operate the brake and check that the wheel is locked, releas the brake and see if the wheel then turns freely. Put calliper back and do the same with the other one off.While each calliper is off, just, as Ray says, put a screwdriver between the pads and lever them back. Make sure that both move the same, and compare the effort you have to use on each calliper. If one is more stiff than the other, that is the problem one.

Brian UK2013-06-09 09:50:24

Understand what you’re saying Brian. All the pistons seem to push back in by hand fairly easily.

I would have expected both discs to be hot after a spirited ride? I assumed the cold one was the the problem?

Test rode this morning after bleeding again last night. One rotor hot (same as before) the other warm (as opposed to cold before)

Still buzzing (and so are the brakes )

Ex-smoker, good idea. I’ll give that a whirl when I get a chance.gooseontheloose2013-06-09 10:39:57

Again, wait until all pads have bedded in and worn off the high spots, then there’s a better chance of getting a more realistic 100% contact area. Also, by pushing the pistons back you ‘destroy’ the position they are automatically trying to adjust themselves to which is normally just the gnat’s wotsits worth needed to push the pads up the the disc. So they have to ‘start all over again’. This initial loose distance can account for quite a bit of lever / pedal play. Last year the car had new discs and pads on the rear, took quite a few miles for the pedal to eventually return to ‘hard’. Hell I’m still waiting for the R80’s ‘new’ rear shoes, (‘new’ as in 10 years ago!) to bed in fully and show signs wear over their entire surfaces

Following ex-smokers advice, I tried each caliper in turn. The side that was hottest was dragging slightly (as suggested by Brian). Not enough to stop the wheel, but more than the other one. I pumped the pistons out a bit and gave them a clean. That seemed to help. On the last run both rotors were about the same temperature, hot, but not excessively so.

Still have the buzzing. Having googled the symptoms, this seems to be quite common especially with the ebc organic pads, which I have fitted. I’m sure it did the same with the previous pads (brembo), but I may have imagined this The only way I’ll know for sure is to put the old ones back.

Thanks for the sound advice chaps

Glad you’re getting somewhere.In normal use, discs don’t usually get that hot, unless you are going down the Stelvio. Thus if one disc is getting quite hot, the chances are the pads are dragging.

Ah right! Have I told you the story …? No, OK then Many years ago coming home from work one late afternoon on me Triumph T140, which had hydraulic rear disc, I turned it off then tried to wheel it in but couldn’t move it at all by pushing / pulling. As though a brake was on. It was. The main road I’d just come up to get home had just been resurfaced with tar and chippings and one had jumped up and lodged in front of the master cylinder, jamming it on. The tar meant it was glued in there so wouldn’t fall out when brake was applied normally. Disc were flippin’ 'ot it was…

one thought
is the one that is dragging the original or added one ? and are the calipers spaced exactly central over the discs

Had the buzzing and one hot disc on a LM3, found that one piston was not fully retracting and ended up with the rear end of the pad still touching the disc, the buzzing was the edge of the pad running over the disc holes. Solution was a rebuild of the calipers with new seals.Cheers, Gerry

can any one recommend someone to skim guzzi disks as all 3 of mine need doing

Just a bijou note by-the-way, I noticed today printed on my tube of copper grease: “Prevents disc brake squeal!” This refers to putting a layer of it on the back of the pads I believe.

Because? Sorry

Does the bike have floating discs?
Could be the play between the disc, the disc hanger and the retaining pins. Just a thought.