Front end judder when braking

[AMCQ46]

Over the winter I have fitted taper brgs to the headstock, and fitted CBR600 calipers and master cylinder, and yesterday was my first outing on the bike.

Took it gentle to bed the brakes in but they felt powerfull right from the start, which was a good sign, but after 30 miles and some harder braking I started to get a wobble through the bars when I was braking above 60mph.
It is not comming through the brake lever, it is a high frequency weave on the bars, it is worse the harder I brake, and below 40/50mph it is gone even if I brake hard.

Looking at the discs they did not look to be marking up evenly, with what looked like hot spots [or high spots] about 6mm diam in places.
At this time I still had the standard Honda / Nissin pads fitted, which came with the calipers. So these were already used, but not with these discs, so I took the out and fitted the new EBC HH pads and gave the discs a good dressing with sand paper.
With this set up I went out and started to bed in the new pads, and after 30 miles of gentle braking cycles I gave them a go to test for the judder.........Good news is the judder was not so bad, but the bad news is the braking performace was poor [so that may be why I didnt get Judder].
The initial bite was weak, and the retardation vs lever effort was also poor.........just as bad as the standard Storm set up, and miles from the bite and feel I was getting with the Nissin Pads.

SO the questions are:
a) Any Idea why I was getting Judder with the 2nd hand pads, as I want the performance they offered over the EBC's?
-was it because I didnt sand the disks and pads before I ran them?
-how should I prep them before I refit?

b) what else can I do to bed in the EBC's, as they are normally a well rated pad?

c) what else could be causing the judder?
-I checked the head bearings and increasing the tension didnt make any improvement, and there was no clunk when braking, could over tightening cause a judder?
-Calipers were cleaned and rebuilt before fitting, so they are not sticking, but am I missing a trick on fitting the old pads, do they need to be in the same position that they ran in on the doner bike?
- are the fork bushes worn? bike has low mlilage and had Roger rebuild the forks last winter, so I am hoping that is not the issue........and anyway, bushes would not be the cause of the judder, they would just be allowing it to move more.

Anyone had similar problems>?

[benny hedges]

just had frightening fork judder myself racing a gixxer (on a private road), coming upto a roundabout - sh1t meself lol.
id say head bearings are loose???
pissed on the gsx btw

[tony.mon]

Sounds like warped discs.
Try taking them off and cleaning the mounting surfaces.

[sirch345]

AMqC,
It sounds like warped disc's to me too.

Did you service the CBR600 brake calipers before fitting them as if you didn't you could have a sticking piston or two.

Chris.

[AMCQ46]

Tony,
I had considered warped discs, and will have a check with a DTI later in the week, but I had no problems with the standard brakes last year, and the discs have not been touched. So if they are warped, it was when bedding in the new pads!
Is there a spec for runout or flatness?

the wear / hot spots on the disc were my main worry, looked like there was localised overheating, but in small spots, not big enough to suggest warping?
The marks cleaned off with sanding, and have not returned with the EBC pads, but as i said, they are not doing enough braking either

Benny, loose bearings were my 1st thought, but no change when I tightened them.

[AMCQ46]

AMqC,
It sounds like warped disc's to me too.

Did you service the CBR600 brake calipers before fitting them as if you didn't you could have a sticking piston or two.

Chris.

calipers were stripped and cleaned, took all the seals out, went through it all with a tooth brush and an airline, then rebuilt with lots of fresh fluid.......I will confess that I reused the seals, but all 8 pistons moved freely.

As for the warped discs, I will have to go ride again with the EBC to see if I have "no" Judder or just "much less" judder, that and the DTI may tell me something about the discs.

I am not sure if the difference between the 2 sets of pads is big clue, what are teh EBCs better? did the Nissin pads hot spot the discs. If it was hot spots, I dont think the sanding would fix it, as it would change the local material properties.

Dont you just hate it when a plan falls apart!

[AMCQ46]

ok, I got the Dail indicator out and checked the discs for runout, and the result is 0.005" at the outer edge of the disc [converts to 0.127mm], and the spec is 0.3mm.

So does that rule out warped discs, or is runout not a good measure of this, or is the spec value in haynes manual jut too big?

I think I will dress the Nissin pads on a flat plate with emery cloth, sand the disc surfaces again, and try them again.........as I want the bite they offered.

[sirch345]

AMqC,
It sounds like warped disc's to me too.

Did you service the CBR600 brake calipers before fitting them as if you didn't you could have a sticking piston or two.

Chris.

calipers were stripped and cleaned, took all the seals out, went through it all with a tooth brush and an airline, then rebuilt with lots of fresh fluid.......I will confess that I reused the seals, but all 8 pistons moved freely.

As for the warped discs, I will have to go ride again with the EBC to see if I have "no" Judder or just "much less" judder, that and the DTI may tell me something about the discs.

I am not sure if the difference between the 2 sets of pads is big clue, what are teh EBCs better? did the Nissin pads hot spot the discs. If it was hot spots, I dont think the sanding would fix it, as it would change the local material properties.

Dont you just hate it when a plan falls apart!

AMcQ,
I should have known you would have serviced the calipers first, and if I read your first post properly I would have seen that you had. Interesting about the amount of run out you found when you checked the disc's, it would appear not to be that according to the manual. I wonder if the run out would be more when hot.

One thing I did think about was now that you've fitted new steering head bearings I assume you had the front wheel stripped out from the forks. Did you follow the correct procedure (as described in the Haynes manual) for tightening up the lefthand (clutch lever side) fork leg on the wheel spindle. It has to be tightened up with the leg in line with the stanchion. To make sure it is you need to operate the forks up and down a few times to center the fork leg before tightening it up. You do that after tightening up the righthand side first. Only a suggestion, but it could be out of alignment.

Chris.

[Silver twin]

Also those EBC pads will need a few miles before thay have bedded in to your discs properly. Once done you should have that bite back again, coupled with the lovely "ssssssssshhhhhhhhhh" noise fron the sintered pads rubbing metal off the disc.

[AMCQ46]

Chris, thanks for the suggestion, I will slacken everything off and realign, cant hurt!

[AMCQ46]

Ok, I am back from other distractions like visiting Barcalona with the Mrs, and then Sking with mates, and what with the sun being out I got a few more miles done, and can report.

1) I passed the MOT
2) The EBC pads are getting much better.
3) as the EBC pads get better, the judder is now noticable with them, just not as violent as with the Nissin pads.

Tried realigning the forks as Cris suggested, but no help......was worth a try

It looks like the CBR caliper / pads set up sweeps more of the disc than the standard ones, so is now using a bit more of the inner diameter of the disk, so not sure if that is the issue, but I am still investigating.

Only good news is that it is better braking than stock, and the judder is not effecting the handleing [it was so violent on the Nissins it felt like it could get frightening], but I know its there and it shouldnt be!

so next step will be to recheck the calipers for any sticking pistons, as there is more pad rubbing friction than I would expect for a set of calipers that were just fully stripped & cleaned, and if not that then I will replace the front disks.

Anybody got any good or bad reccomedations for aftermarket discs?

[benny hedges]

it is better braking than stock, and the judder is not effecting the handleing [it was so violent on the Nissins it felt like it could get frightening], but I know its there and it shouldnt be!

?

i feel judder on mine a bit, sometimes a lot - had the discs off and on a sheet of glass and they're true as a die, calipers ok etc, headstock fine.
i put it down to the front suspension being too soft and hitting the bottom when braking hard, with minute bouncing.
had a few scary moments cos of it so hoping to get it right with a bit of fork tweaking, otherwise new front end is going on

[AMCQ46]

Benny,
soft forks are a problem with the standard bike, and the reccomendation is that we shouldnt fit better barkes or drop the forks for faster steering till these are fixed.

I already had Roger at Revolution Racing re spring and valve my forks, so they dont dive and the front end is good. The braking judder is new with my new calipers and just so frustrating when I know it should work better.

I did read in the USA form that if the fork bushes are worn, the braking forces can set them off, but my bike is low milage and as I said, had the forks rebuilt 1 year ago.

I do reccomend the Roger treatment on the forks if you can afford it, you will see lots of comments on here, and he sure knows what it takes to get a firestorm to work well on the road as well as the track.

[benny hedges]

don't know if this is a possible cause, but definately is a fault that needs fixing - took my front wheel off to spray the rim and fork legs and guess what i saw.............. spindle bent!
just out of curiosity rolled it on my glass table (don't ask!) and it most definately is not straight.
not like a dogleg, but not sraight either - don't know if this was from my droppage or an earlier crash?

was a swine to get out lol need to get on fleabay and get another methinks.
think i'll do the wheel bearings as well if it's took a knock, just in case there's a slight flat spot?

*ed - got a new spindle, spacers and nut for £7.00

[MarkHunt]

Hi AMcQ,

I'm running a new brake set up that is CBR600R 2004 calipers, SP1 Master Cylinder, EBC HH pads and HEL lines and can report no juddering noted, even under heavy braking, so I'm not sure if the problem lines with the disc area or somewhere else. My bike has standard discs and I have had the front suspension done by K-TECH married up to a Hyperpro progressive spring set. The braking power is extremely good now and I even have to treat them with respect as opposed to pulling hard and hoping with the standard set up

Just wanted you to know in case you are running the same set up, that it does work ok.

One question, did you have to machine the calipers and if so, are the mounting holes 100% in alignment, just a thought...

All the best.

regards

Mark