front discs and servo question, and comment.

[Den]

Just failed its MOT because the one of the front discs is warped.

Very surprised ... and more than a bit annoyed, because there was no evidence of any warpage while braking.

Now, after arguing with the tester, who refused to take it out to try it on the road. I had to accept the evidence of the brake test machine.

I tried it several times on the way down the road. Perfect. No pulsing, no judder.

Until I tried it whilst coasting with the engine ... and the servo switched off.
I could then feel it pulsing a little.

So .... how dont I feel it with the servo engaged ?

I'm more annoyed with myself for disputing the blokes knowledge than anything else. And the fact that Im going to have to return with my tail between my legs.

So the moral of the story is, ( apart from keeping ones mouth closed) Before you take your servo equiped GS to the testers, try your brakes with the servo turned off. It may save you some embarassment.

 

[Stewart H]

Is it actually warped, ie how much run out is there ? or is it just an area displaying different friction characteristics?

Stewart

 

[Den]

Is it actually warped, ie how much run out is there ? or is it just an area displaying different friction characteristics?

Stewart

Different friction characteristics. The needle on the tester is moving through 5 of its little divisions.
New pads 300 miles ago, so they are well bedded. Bike well used, so no sticky areas on discs.

I cant measure any warping (flat ruler between fork and disc, just clear of disc).
Ive not got a dial gauge for more accuracy.

 

[Stewart H]

There was a thread over on ADV rider where the guy got rid of that type of problem by aggressively cleaning the disc, I think wet or dry, what have you got to lose?
Stewart

 

[Steptoe]

Those brake testing machines are so so sensitive.

You can't feel the "pulsing" at the lever because the "pulse" is only reaching as far back as the servo unit, where the fluid is seperated from the fluid at the lever, so isolating any domino effect to the bars.

 

[Den]

Got any good or new discs laying around Neil ... best pal