Bloody Brakes!!!

[The Stranger]

The Bike.
K3 GSXR 1000

The problem.
There is a significant and rather disconcerting shudder under firm braking.

The History.
Bike had done 30,000 very hard km when I got it and a small shudder was present at that time. It got progressively worse so at around 36,000 I rebuilt the front end. Robert Taylor did some work on springing and forks, Head bearings and wheel beearings have been replaced. As rotors were below wear limit I replaced these with second hand units with plenty of wear left. I stripped and cleaned the calipers and replaced the pads. Thanks to Poos I also replaced the steering damper.

Ok the shudder was much much better and only present a little bit under very heavy braking once all this was done.

It has progressively got worse again to the point that it is not pleasent to ride the bike.

The checks so far.
The disks appear to be fine - LHS=.19mm run out and RHS=.15mm, limit is .30mm. Front wheel run out (axial) is .71mm, limit is 2.0mm.
Picking the bike up and shaking the shit out of the lower end of the forks - there is no movement apparent in the steering head or slider bushes. The head bearings are smooth and reasonably firm to turn (not too tight though)
Front wheel bearings feel good.

So where to look now?

[klyong82]

Are your rotors straight? If it is warped I know you get shuddering or pulsing

[Sparky Bills]

Sorry to say dude, but Shuddering brakes means warped rotors.

[cowpoos]

warpped disks...I found with stock pads I would blue the disk's easily and then they would warp after a while...that could be a solution...I'ld PM gav [htdboy] and get him to have a look for you...and check the head bearings are tight enough aswell!

[The Stranger]

But the run out is well within limits as is wear, they aint warped.

Possible epiphany though, could it be caused by the front tyre?
Just recalled that I was running a Viper sport last time I had this shit, then went to an M3 and it now has a Viper sport on it again and at about the same state of wear as last time.

[FROSTY]

Mate work the process of elimination.
Try cranking your steering bearings down untill the front doesn't flop to one side easily-Not restricted just not an easy flop.
One step at a time bro

[riffer]

You're running a Viper front?

Those suckers are reaaaaaally sensitive to wheel balance.

When was the last time you did a full clean of the brakes also?

You said the rotors aren't warped. Have you actually had them checked professionally?

Although having re-read what you've posted, I'm picking you may just have a bit of a dodgy set of steering head bearings, or they're just a bit loose.

The shuddering - is it rhythmic? Does the brake lever pulse?

Usually brake lever pulsing indicates rotors. No pulsing, but shuddering around the 80-100 mark indicates worn steering head bearings. And I've discovered that you can do them up reasonably tight too but if they're worn they'll still shudder.

[cowpoos]

You're running a Viper front?

Those suckers are reaaaaaally sensitive to wheel balance.



you would notice a unbalenced front wheel alot of the time...not just under heavy braking!

[riffer]

Yeah, I would have imagined that would be correct. I have no problems with my Viper front.

Probably a red herring. As you were. :mellow:

[The Stranger]

When was the last time you did a full clean of the brakes also?


The shuddering - is it rhythmic? Does the brake lever pulse?



The last time I really cleaned the front brakes was about 20,000km ago, but I keep a can of brake cleen handy and give them a good blast frequently.

Good point. No the brake lever doesn't pulse. Which tends point to something other than rotors doesn't it?

[riffer]

Yeah.

Like Frosty, my money's on the steering head bearings.

Another thing you could look into is the forks.

When was the last time the oil was replaced? It's possible its not damping properly and you're getting a bit of a shudder going on there.

But I'm still picking the head bearings.

[FROSTY]

crank those bearings down

[Max Preload]

Worse cold or hot?

Aren't they full floating? Have they been checked on an engineers surface plate for runout or just using a DTI?

Could be a the hub, even if full floating.

[The Stranger]

crank those bearings down

Ok, ok I get the message.
First thing in the morning now.
Will call in and let you know how it goes.

[FROSTY]

Another thing you could look into is the forks.

When was the last time the oil was replaced? It's possible its not damping properly and you're getting a bit of a shudder going on there.

But I'm still picking the head bearings.
Gee bro How could it POSSIBLY be the forks--- after all robert Taylor sorted them out recently

[The Stranger]

Worse cold or hot?

Aren't they full floating? Have they been checked on an engineers surface plate for runout or just using a DTI?

Could be a the hub, even if full floating.

With a dial indicator, which is the method shown in the manual.

It is getting progressively worse, so I would tend to think it is wear related. The hub being out of true would imply an event wouldn't it?

[FROSTY]

Mate another though given the bikes history --Im concerned about the condition of the calipers.Just wonder if anything is a bit dicky die maybee only showing up when the pads are worn past a certain point.
maybe the pad hangers or one sticky piston

[riffer]

You haven't taken the shims off the brake pads at the last change and forgot to put them back on have you?

[Robert Taylor]

Mate another though given the bikes history --Im concerned about the condition of the calipers.Just wonder if anything is a bit dicky die maybee only showing up when the pads are worn past a certain point.
maybe the pad hangers or one sticky piston

The calipers may well be causing issue and should be stripped and checked. Even though the disc runout is within factory tolerance 0.15mm runout IS a LOT and will cause either all or contribute significantly to this problem. This is just the sort of bike that is sensitive to such issues, its not a GN250, for example.

Back in the late 70s I had to fix a traffic department XS650 which had a frightening high speed weave at speeds in excess of 130km/h. In a less enlightened age ( maybe ? ) they werent too careful where they put weight on these bikes ( emulated by todays packracks ) so they were rear end heavy, much of that weight behind the rear axle centreline.

Riding this bike was frightening as it used ALL of the road at elevated speeds. I went through all the usuals, alignment, suspension set up ( what there was then ) tyre balance, pressures, head race condition and correct tension etc, totally to no avail. Disc runout was 7 one- hundreths of a millimetre. When replaced the problem was fixed.

The message here is that hyper performance bikes such as the GSXR1000 are very sensitive to such issues.

[Coldrider]

I had these issues a few months ago, I replaced a disc that had 0.12mm warp, problem fixed. I had previously replaced the head bearings so these weren't the issue, replaced the front wheel bearings prior to biffing the disc.
I know this is not what you want to hear, I had totally forgotten what good brakes were.

[imdying]

The disks appear to be fine - LHS=.19mm run out and RHS=.15mm, limit is .30mm. Front wheel run out (axial) is .71mm, limit is 2.0mm.In tolerance or not, that's pretty ghey.... 0.3mm is massive. Something else to check, measure the thickness of the disc at say 6-10 points around the disc, it might have some thickness variation.

[Nicksta]

Mr Taylor's on to it dude.. and man, if its worse than when we took it on Taupo, thats a very, very scary thing indeed.... Bruce said the disks were warped then and needed replacing.... poor 66 :)

[The Stranger]

Mr Taylor's on to it dude.. and man, if its worse than when we took it on Taupo, thats a very, very scary thing indeed.... Bruce said the disks were warped then and needed replacing.... poor 66 :)

I have replaced the disks sinse then, but they have been blue quite a few times now also.
I stripped and rebuilt the calipers last weekend, replaced the pads and tightened the head bearing a little.
Haven't had a chance yet to give the brakes hell, but it is certainly a LOT better.

Don't worry, still looking after it mate.

[Kwaka14]

Try the brake pads, I think the K3 runs the same radial brakes as in the zx12 and I have had problems when the pads are low with the bike shuddering, totally clkeared up on new pads - checked the runout with no issues (using a straight edge which was a bit dodgy). so tried pads and sweet as.

Should have read your previous post huh...

[MVnut]

reckon it's warped discs mate, maybe the old owner tried to keep up with an MV:clap::clap:

[Nicksta]

Haven't had a chance yet to give the brakes hell, but it is certainly a LOT better.

Don't worry, still looking after it mate.

:)

10 chars......

[The Pastor]

Bent rim or axel? (front AND rear)

Could be bent frame?

Did you change the rear wheel bearing?

I don't know much about these things, this is just what ixion told me when i had the problem with the gpz, he said shuddering can be caused by the wheels being out of alignment eg underbraking the rear wants to go in a differnt direction to the front?

Good luck, there are so many causes. (i never did fix my bike, but i think it was bent forks)