Bloody Brakes!!!

**The Stranger:Me** · 14th September 2007, 19:36

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** · 14th September 2007, 19:41

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

**Sparky Bills** · 14th September 2007, 19:44

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

**cowpoos** · 14th September 2007, 19:44

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:Me** · 14th September 2007, 19:49

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:Me** · 14th September 2007, 19:56

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** · 14th September 2007, 20:08

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** · 14th September 2007, 20:17

Originally Posted by riffer

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** · 14th September 2007, 20:29

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

Probably a red herring. As you were.

**The Stranger:Me** · 14th September 2007, 20:42

Originally Posted by riffer

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** · 14th September 2007, 20:45

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:Me** · 14th September 2007, 20:46

crank those bearings down

**Max Preload** · 14th September 2007, 20:48

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:Me** · 14th September 2007, 21:07

Originally Posted by FROSTY

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:Me** · 14th September 2007, 21:11

Originally Posted by riffer

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