Not warped discs; what could it be??

I have noticed something when using the brakes on my GSX-R K5.

As I come to a stop at a set of lights, I can feel a faint juddering through the bars coming from the front brakes; a bit like runing a wet finger down glass. But I can't feel the vibes through the brake lever. I have had the bike up on a stand and checked the discs for warpiness (is that a word?) and they are well within the tolerances specified by Suzuki themselves.

Then I went over the discs with some wet'n'dry paper and also went over the pads with a fine file as they did look a bit glazed.There are NOT any backing plates on the pads like there are with EBC ones; guess they're OEM ones. Cleaned the calipers up with some brake cleaner, and reassembled the whole lot (with copper grease on the pins and back of pads) following the procedure in the manual (not Haynes BOL) Better; but it's still there, albeit very faint.

Any ideas what I may have missed? I am going to slap some new pads in there at the weekend; whilst looking back through the SH, a fork seal was replaced so maybe one of the pads got contaminated with fork oil. A few people on the GSXR forums have said its the forks and its a design fault, but other owners I know/have contacted have said their bike doesn't suffer from the above symptoms and I am talking bo**ocks

 

I've heard of some bikes suffering from brake chatter at low speeds, I have heard that bikes with a steep steering angle can suffer from this more. If there is no pulsing through the lever then I would assume this is what it is. A change or pads may help the issue but you may find it could be something you have to live with. You could try a couple of heavy stops on the bike 100mph>5mph but do not come to a complete stop, to see if this cleans up the disc faces at all.

My bmw actually has some brake chatter at low speeds too.

 

Have you had the wheel off lately??

did you bounce the suspension before tightening up the pinch bolts?

 

Pull your pads out, check all the pistons move freely. A uneven pressure across the pad could cause pulsing as you describe and you'll not feel it in the lever because the pressure between caliper and lever is even, it's the pad to disc that's not.

A contaminated pad would give poor braking but not inconsistency.

A design fault?! That's a new one "yeah they're meant to do that mate, Michio Suzuki thought it'd be a laugh".

Other possiblity could be an airlock in the caliper, give em a quick bleed to eliminate that.

 

I had this on my cbr, I tightened the nut in the middle of the handle bars (I think it's call the yolk?) and hey presto it stopped !

 

Not had the wheel out, no. But I read up on it, and loosened the calipers, undid the RHS fork pinch bolts, loosened the axle; then did up the caliper bolts, did up the axle, and bounced the front before doing up the pinch bolts. All to the right torques. It helped...

Skortchio, all the pistons bar one moved easily. One was a bit sticky, but a good clean soon had it moving the same as the others. At least there was only 4 pistons; the old ZX9R had 6 per caliper and they were right buggers to get all the pistons moving the same. I'll try the bleeding tomorrow lunchtime at work.

 

Off to the garage to check that one!! Didn't even ocur to me...

 

When i recently replaced the front discs on my harley i forgot to remove the tin anti - rattle plates from the old discs and fit them to the new ones, there role is to prevent vibration. Every time i now pull the front, i feel a small amount of chattering and vibration, no big thing but i notice it all the same .. could be that.... ?

 

Hmmm... the Gixer steering angle is definitely steeper that the ZX9R I had..very twitchy. Another thing to try...

Cheers lads; if this gets sorted the coffees are on me

 

The other thing you could do... Is not use your front brake for low speed braking!

 

Is the front tyre badly worn/near limit?

 

Its getting low. Probably got a couple of months before it need replacing.

 

Could well be a cause, IMHO and experience

 

I agree with Mikey, could be head bearings.

 

You should be able to tell any play in the headstock by popping the front wheel off the floor, turning the bar to full lock and giving it a bit of wiggle. Be gentle and you should be able to feel any free motion there.

If you can then it could be as simple as whipping the top yoke off and nipping up the locking collars beneath.

 

I had more of a pulsing/judder through the lever so I cleaned the callipers etc, better but still there, measured the disks, no obvious sign of warping, changed the hoses, even better but still there. It showed to be worse at heavy braking (really noticed it on the track day) but the brakes did have more power! So took the plunge and stuck on new disks, hey presto! All gone! I have a GSXR600 0n a 98 plate by the way.

 

So the discs were warping when they got hot on the trackday and then nearly straightening up on the road? Just swapped mine for some used EBCs, will report back after Snetterton.

 

If the lever pulses/judders then that's a sure sign the discs are usually warped and replacement is needed.

 

Seems to have vanished

I cleaned the discs up with some wire wool and brake cleaner, did a quick bleed (Scortchio), nipped up the headset locking rings and the big gold nut (lots of people), undid the front axle and did the 'bounce thing' again (ducky). Am going to replace the front tyre (but not at £135 for a BT-016...)

Looks like I might have a big coffee bill looming guys

 

At least it,s sorted mate. When you out on it?