Front brake 'pulsing'

Champ's post about his car brakes reminded me of something, when I
brake hard on the GSXR, I get a kind of 'pulsing' from the front. At
it's most extreme when braking very hard it feels like the front wheel
is juddering off the road. I've had a good look over and can't see
anything loose or wrong looking. Spinning the wheel the discs appear
to run true.

Any ideas? Maybe I should get it into the men who know prior to my
Silverstone trackday.

 

Get a rag with brake cleaner on it and clean your discs down. Might
just be a build up of brake dust on the discs themselves.


--
Lozzo
Versys 650 Inter-Continental Hyperbolistic Missile , CBR600F-W racebike
in the making, TS250C, RD400F (somewhere)
BMW E46 318iSE (it's a car, not one of those 2-wheeled pieces of shite
they churn out)

 

What he said.

 

Thirded.

 

And if that doesn't work you can check them quite simply by taping or
elastic banding a biro to the fork leg with the end just quite not
touching the disc, then spinning the wheel to see if the gap changes
at all.

 

completely different bike, but when I (waaay back in December 2002)
collected the R65 from WUN, it felt like what you described. Just
cleaning the discs (with Fuxitorf, IIRC) and riding and braking like a
twat sorted it out. The problem just "went away".

 

I've seen it many times where you'd swear the disks were warped but it
was something embedded in the disks and a few minutes rubbing them down
with coarse sandpaper while spinning the wheel sorted it out. You can
get as fancy as you like, clamping the sandpaper between two pieces of
lath, or whatever, but I simply used my fingers and nobody died.

 

Very often caused by material transfer from the pads to the disk which
is usually mis-diagnosed as a warped disk.
This is caused by clamping the brakes onto a very hot disk.
When coming to a stop from high speed or other heavy braking always
release the brake as soon as you come to a stop and preferably
take a gentle pootle to cool the disks.

This generally happens when the disk is very hot, the transferred
material migrates into the disk surface and can only be removed
by slightly skimming the disk.

 

If its a floating disc then its also worth checking that the bobbins
aren't seized. You should be able to turn them by gripping between finger
and thumb on either side and twisting or by inserting a flat-bladed
screwdriver in the bobbin hole so that it tightens on the taper of the
blade then turning the screwdriver. If any bobbins appear seized then you
need to free them off. A drop of WD40 or penetrating fluid will usually do
the trick but you will need to scrupulously clean the disc afterwards so
its best to remove the disc before you start.

If disc cleaning doesn't work and there is no evidence of disc warping
the check your head bearings.

 

Or doing as Loz says or using a bit of emery paper you fucking twat.

 

I have some brake cleaner so will give that a go.

 

Hmm, I've tried riding like a twat and that makes the problem appear.

Riding like a granny, it doesn't show up.

 

try "cleaning" the disks with a bit of emery paper[1] anyway and see
how you get on - I really doubt you've actually got warped disks if
the effect doesn't manifest at slow speeds.

[1] or, as I once did, try using sugar soap and a "green" kitchen
scouring cloth - worked a treat that did, on similar (though I think
milder) symptoms on my old TRX.

 

That's exactly what it was with my Zed, a build up of crap, but not brake
dust, it was the crap that the discs were coated with from the - after
market - factory. (Black to make them look "cool") I also took the pads out
too and gave them a few seconds abuse with a sheet of 320grip paper and for
my troubles I was rewarded with instant pulse free braking and a better
initial feel too.

 

message

Or you could get a dial gauge and know how much they're warped by if they
*are* warped.

I think the brake cleaning thing is the best route to take though.

 

Mine started doing it Sunday, after a quick run, i let them cool & got the
brake cleaner out, the muck & shit that came off was unreal.

Gave them a light rub over with some wet & dry, took it out & it was fine.

Nige

 

Take it to a bike shop with a dial gauge. It could be a warped disk.
Not a big job to check.

Fraser

 

I gave the discs a good scrubbing down with brake cleaner on Sunday
and took it out for a thrash. Still happens when braking really hard,
but not as much as before. It's a bit like the pads grip, then slip,
then grip, then slip.

I'll scrub them a bit more this weekend.

Didn't take the pads out because they're radial calipers and I
couldn't for the life of me work out how to get them out without
actually taking the calipers off the fork legs, which seemed a little
odd. Will do some googling on that.

But first I've got to take the centre console out of my Focus to fix
an electrical gremlin which is turning the stereo off.

 

My 07 GSX-R 1000 was bought as a wreck and it had a bent disk even
though it was unmarked. Might be soft disk material that caused it.
Pulling the calipers off isn't a big job only 2 bolts per side. Just
don't attempt it on a ZX-10R where the caliper bolts are made of silver
cheese.

Fraser

 

I've had the same ZX10R caliper bolts on and off my mate's race bike
about 5 times every weekend we raced, which was once a month, for four
years and never chewed one of them. Buy decent tools

--
Lozzo
Versys 650 Inter-Continental Hyperbolistic Missile , CBR600F-W racebike
in the making, TS250C, RD400F (somewhere)
BMW E46 318iSE (it's a car, not one of those 2-wheeled pieces of shite
they churn out)