Front brake problem

[PJD]

In the summer I replaced all three discs on the Girly. Stripped, cleaned and rebuilt the calipers and reassembled with new seals. Recently I have been getting a strange grabbing in the front brakes when braking gently. It is less noticeable when braking hard. As I apply the brakes they seem to grab and release, grab and release, so I get very uneven braking. At first I thought it was a warped or poorly seated disc but there is no run-out and I am not getting feedback through the brake lever.

[metalguru]

When you replaced the disc rotors were they the cheepies or not and were the pads replaced with quality ones?

Why I ask is that if, like me you ride all year then with all the c**p on the road is highly corrosive at this time of year and can lead to many brake problems. As long as the caliper pistons are free to move and retract and the pads free to move in the caliper body, then the usual thing is corrosion on the rotor working face. This is never even and can lead to a very slight high spot on the face, sometimes where the bike is left after use the rotors corrode between the pads and rotor. It can be so slight that it would not be felt through the lever.
Have a look at cast iron discs on a car and see how quick a layer of rust forms after washing them!
The cheepie rotors have a higher ratio of cast iron in the recipie than the dearer ones that have more chrome in the stainless mix.

[Loops]

What Metalguru said.

I used cheap Stealth discs for a while and they warped within 10k on my 885i.

Now got EBC discs and they seem ok, so far (about 5k)

One other thing to check is if you have any play between the fork sliders and the fork tubes (like mine!) that causes an odd juddering at low speed while braking.

Mine needs new bushes really so maybe I'll fit a 955i set of forks.

Cheers

Loops

[PJD]

Thanks for the replies metalguru and loops. Rather than buying the Triumph parts (which cost a fortune) I got discs from All Bike Engineering in Greenwich. They had been recommended to me. They sent pads along with the discs. I am pretty sure that the discs aren't warped, because I would get some feedback through the lever if they were. Also, I have checked for run-out but they seem to be true.
I don't think it's corrosion either. I use the bike every day and the discs look clean. I know what you mean about the cast iron discs though. I used to have a 1986 Harris Bonneville with cast iron discs and they would go orange in front of your eyes when a spot of water got on them!
The fork idea is interesting. My Girly was registered in 2001, I bought it in 2005 and I have put 50,000 miles on it since then without ever touching the forks. Also, there is a bit of play in the steering head bearing. But surely these problems would have shown up before I changed the discs?

[metalguru]

In that case check the wheel bearings too.

[ChazzyB]

I'd be looking at my head bearings.

[Bixxer Bob]

I had what turned out to be warped discs even though I couldn't feel it through the lever and there was no discernable runout.

I fitted EBC floating discs and matching pads and the problem went away.  Just be aware though that the floating discs can give a slight feeling of flutter as you're easing off the brake as you come to a stop.   It's a bit alarming until you get used to it, but doesn't affect the braking force.

[Chris Canning]

I have put 50,000 miles on it since then without ever touching the forks.

Blimey  :shock: ,I suggest a peg on your nose if ever you change the sludge inside  :D

[ChazzyB]

I have put 50,000 miles on it since then without ever touching the forks.

Blimey  :shock: ,I suggest a peg on your nose if ever you change the sludge inside  :D

I changed the oil in the forks of an SV650 I owned (oil I'd replaced a year or so before): one leg had reasonably clean oil, the other leg's fill was thin, jet black and stank really, really bad! I thought an internal seal must have disintegrated and dissolved. It hadn't, but clearly the hydraulics were so different that one leg really put the oil through it.

[JonRoss]

I had a similar sounding issue. Brakes would pulse, but not on hard braking, just on soft braking. Run out checked out fine. I was about to replace the rotors when I stumbled upon someone talking about pad residue on the rotors. I took steel wool to the rotors, and hey presto, pulsing disappeared. Worth a try.
JR

[PJD]

At the weekend I took the front wheel off and found this on the speedo side of the wheel. Any thoughts as to why it might have broken? I put the 2 Euro coin and the caliper bolt in the photo to show the size.

[delecti]

the problem is the speedo drive has been fitted incorrectly into the wheel hub and cracks the magnetic disc. buy a new one $165us + postage and make sure it is aligned before placing the axle.

the disk vibration could be caused, as it was on mine 06 by the brake pad I fitted a set of EBC organic pad fixed the problem.

Mark

[ChazzyB]

I fitted EBC floating discs and matching pads and the problem went away.  Just be aware though that the floating discs can give a slight feeling of flutter as you're easing off the brake as you come to a stop.   It's a bit alarming until you get used to it, but doesn't affect the braking force.

I came to the conclusion this 'fluttering' only happens with HH pads. I had a set of cheap organic pads fitted for a while and the fluttering didn't happen. In the end I binned the organic pads and went back to EBC HH, as the organic pads were total shite when wet. The fluttering returned. I think it starts as the pads wear.

[metalguru]

I fitted EBC floating discs and matching pads and the problem went away.  Just be aware though that the floating discs can give a slight feeling of flutter as you're easing off the brake as you come to a stop.   It's a bit alarming until you get used to it, but doesn't affect the braking force.

I came to the conclusion this 'fluttering' only happens with HH pads. I had a set of cheap organic pads fitted for a while and the fluttering didn't happen. In the end I binned the organic pads and went back to EBC HH, as the organic pads were total shite when wet. The fluttering returned. I think it starts as the pads wear.

Would concur with what Chazzy is saying here as the EBC Gold pads seem to give trouble, ie hanging on, when they get down to about 2:5mm. (Wear limit is 1mm). Found the best are the standard black EBC pads.

[Bixxer Bob]

Mine are standard EBC and have done it since I fitted them and the discs.  :roll:

Frightened the hell out of me first time it happened. I wasn't overly careful scrubbing the new discs and pads in, but wasn't hard on them either. Must say though, the discs felt slightly glazed even from new and took a long time to bed in.