Front brakes are acting funny - GSXR 600

[Brett]

After a littl ebit of getting used to the gsxr, the only thing i can complain about is the front brakes. They seem to ever so slightly pulse, and when on hard braking they almost seem to have an ABS feeling to them, i.e. they grip and let go, grip and let go...but not the same as pulsing from warped rotors, much more subtle.
I know the brakes on my zxr were smooth as anything, and very consistent. These are not. Has anyone got any ideas on what could be going on? I have checked the bike over thoroughly, and it is mint, never even scratched let alone smashed, so i am guessing they have been heated up by a previous rider, maybe in stop start hi-speed traffic, and then they have stopped and sat with the brake lever under pressurse cauing a different cooling co-efficient thus warping the rotor. Any other guesses? new rotors will cost me nearly a grrand, so kinda keen to avoid that if possible!

Thanks in advance!

Brett

[Disco Dan]

bummer, try putting it on it's centre stand and rotate front wheel... see if there is any scraping sound. try applying brake ever so slighty and rotate again... will tell you if it is warped.

you could also try removing brake pad, blowing the caliper with some compressed air and re fitting.. may not be seated corectly or build up of gunk?

My ZZR behaves a little like that, but my front disc is scored and needs resurfacing...

[vifferman]

My VFR did that when I bought it, and a run-out check of the errant disk showed it was within spec. It disappeared when new pads were fitted, so I guess it had something to do with uneven wear.

If you don't have access to a dial gauge, you can check for wobble in the disk by raising the front of the bike, spinning the wheel and holding a permanent marker against the fork leg. Move it in slowly till it just barely touches the disk, and any high spots will leave marks where the marker touches. Using this method, I got rid of run-out on my VF500 which had fixed disks (rather than floating disks with carriers) by adding/removing paper shims under each mounting point. On many bikes you can tweak the disk with a large crescent spanner or put it on a perfectlyflat surface and bash it. If it's too bad, then replacement is the only option.

But I'm getting ahead of myself. First, check the condition of the pads, including checking that each pair is wearing evenly, check that the pad retaining pins aren't gunked up and preventing the calipers moving in and out easily, maybe check that the pistons aren't dirty and/or corroded, all those sorts of things.

[XP@]

Using this method, I got rid of run-out on my VF500 which had fixed disks (rather than floating disks with carriers) by adding/removing paper shims under each mounting point.

All that too and visa versa, I managed to end up with a bit of crud under the mount points of my CBR's disks. Then rotating the fork legs seemed to centre up the rotor between the pads a bit...

Is that $1000 for aftermarket rotors?

[imdying]

but not the same as pulsing from warped rotors, much more subtle.

They call that barely warped and only going to get worse Check all the usual stuff, including wheel bearings etc.

[Cajun]

Brett,
Throw some ebc HH pads, and flush the backfluid(personally the 600 and 1000 use ebc dot 4 also), then see if that fixes your problem.

[riffer]

God. You poor bastard. Welcome to my life. I get exactly the same thing, except its random and intermittent. You never know when it will happen.

So far I've:

1. Checked rotors for out-of-true
2. Completely stripped and cleaned, lubed, etc the calipers
3. Replaced pads
4. Replaced wheel bearings
5. Replaced bolts holding the caliper on (just in case)
6. Checked axle for out-of-round
7. Replaced one of the pad locating bolts (right side)
8. Used an easy-out and a drill to loosen the rivets which hold the rotors on.
9. Pulled the steering head apart, regreased and retorqued the steering.

The only thing left I can think of for me now is either the pad locating bolt on the left caliper or the actual caliper mounts on the forks.

Good luck. Try all the things I've mentioned. If you find anything else, let me know.

[aff-man]

Thigns to do in list of least expensive to most expensive.

Do a runout check on your rotors. Check that the bolts holding the rotors are all done up the same and to spec. (i.e correct torque) People are known to use rattle guns on them and it can over tighten them making then not straight but this would only be a minor pulse.

Check to see all your pistons in the callipers are working evenly. Easiest way to check this is to take out the brake pads and check for uneven wear pattern.

you sure the bike hasn't been raced?? people who ride these bikes really hard on stock rotors tend to heat them up quite a bit.

Bleed your brakes you might have an air bubble in one of the callipers. I had that problem on my cbr600 and it would kick the front to the left when brakes first applied hard and then shudder like mad.

Rplace brake pads. Maybe you just got a bung set or something.

Replace rotors. LAst resort really so don't jump into it, cause it'll cost a little more than a grand for new ones. (I think about $600 a side for genuine parts)

[Shaun]

If they are heat warped, they are buggered and will not ever stay true

I can get very good true ones with next to no miles on them for $ 500NZ

[R6_kid:Me]

or, you could take a day or two off work, ride down to shaun (i hear its a good ride anyway) get your brakes checked, and your suspension setup properly to your weight... and be all the better for the whole experience!

[Brett]

Thanks all, yeah i have put the bike up on the stands, and checked the run out of the disks and rims and niether have warped enough for the eye to see, however i can definitely hear rubbing, and there is a *slightly* tighter spot.

CAJUN - Yeah i am thinking about that, will pull the pads out tomorrow and check for even wear, then get them bled well and replaced with new fluid. Cheers for that.

Thigns to do in list of least expensive to most expensive.

Do a runout check on your rotors. Check that the bolts holding the rotors are all done up the same and to spec. (i.e correct torque) People are known to use rattle guns on them and it can over tighten them making then not straight but this would only be a minor pulse.

you sure the bike hasn't been raced?? people who ride these bikes really hard on stock rotors tend to heat them up quite a bit.

Bleed your brakes you might have an air bubble in one of the callipers. I had that problem on my cbr600 and it would kick the front to the left when brakes first applied hard and then shudder like mad.

Rplace brake pads. Maybe you just got a bung set or something.

Replace rotors. LAst resort really so don't jump into it, cause it'll cost a little more than a grand for new ones. (I think about $600 a side for genuine parts)

I am very very certain that this bike has not been raced, it realy has no scratches or marks or any signs at all of being raced, a trackday maybe, but it does not have any of the typical race bike signs.

Colemans gave me a price of $465 each for the disks.

cheers for the input!

If they are heat warped, they are buggered and will not ever stay true

I can get very good true ones with next to no miles on them for $ 500NZ

Yes, so i have heard. Changes the disks forever. I was wanting to ride down to you anyway and get you to set the suspension up for me, so it might make sense to book it in with you and you can give me your expert opinion on the brakes too. How long would it take you to get the disks? If these are the problem, i will get you to grab a set for me. How long are you booked out for?

or, you could take a day or two off work, ride down to shaun (i hear its a good ride anyway) get your brakes checked, and your suspension setup properly to your weight... and be all the better for the whole experience!

I was just thinking that today. I played with the suspension quite a bit over the weekend, but it still isn't quite right. Need someone like shaun with the right experience to do it properly!

[Shaun]

I have 6 sets of discs arriving next week, all good! Give me a call if you want to discuss 027 2559143

[aff-man]

I am very very certain that this bike has not been raced, it realy has no scratches or marks or any signs at all of being raced, a trackday maybe, but it does not have any of the typical race bike signs.

!

Mate of mine came off a trackday session with his rotors literally glowing purple on his k3 600. All depends on how you riding the bike.

That price from colemans is pretty good.

[Brett]

Well after some deliberating and easement of the problem, i have managed to isolate the issue to two main faults.
1 - The steering bearing is a tad loose, thus getting a slight vibration under some braking conditions, will tighten and she will be sweet.
2 - I believe that at some point, someone has put something like silicon on the bike, and a little has made its way onto pat of the rotor and the pads, thus changing the braking co-efficient of the materials. I will fit some new pads, get them really really well worked, and that should hopefully burn off any residule material.

Failing that, I will be visiting Shaun for a set of new rotors...which i may get anyway just to have a spare set.

[botb]

Thigns to do in list of least expensive to most expensive.

Do a runout check on your rotors. Check that the bolts holding the rotors are all done up the same and to spec. (i.e correct torque) People are known to use rattle guns on them and it can over tighten them making then not straight but this would only be a minor pulse.

Check to see all your pistons in the callipers are working evenly. Easiest way to check this is to take out the brake pads and check for uneven wear pattern.

you sure the bike hasn't been raced?? people who ride these bikes really hard on stock rotors tend to heat them up quite a bit.

*****Bleed your brakes you might have an air bubble in one of the callipers. I had that problem on my cbr600 and it would kick the front to the left when brakes first applied hard and then shudder like mad.*****

Rplace brake pads. Maybe you just got a bung set or something.

Replace rotors. LAst resort really so don't jump into it, cause it'll cost a little more than a grand for new ones. (I think about $600 a side for genuine parts)

Wow thanks for that had this happen on my bike after having new tyre put on i am fairly new to riding and coming to corner applied both brakes and front kicked out and i thought *shit* gonna stop and see what the hell that was slowed, braked again and it either kicked out again or locked when i braked again and i came off i have tried explaining this to people i ride with and they all seemed a bit puzzled about it and i was starting to doubt myself too... and wondered wether i had done something horrifically wrong to cause it mmm i think i will be bleeding my brakes once my bloody broken leg heals LOL..... mutter mutter mutter