My front brake started acting funny .....

[Scoots]

..... and now it's sporting a mustache and smoking a cigar!

Earlier this summer I changed out the brake fluid on my Brembo front brake. No problems, just like changing the fluid on my VW bugs and buses, and the pads looked very good. All worked very well, until now. Moderately applying the front brake, I get sort of a "pulsing" action on the brake. Light application or applying the front brake with some force and all is well. No "sponginess" in applying the brake.

Am I looking at a warped rotor? What should be my next step in evaluating this situation?

Oh, the brake says, "Outside of a dog, a book is man's best friend. Inside of a dog it's too dark to read."

[Duane Ausherman]

Yep, warped rotor. On the center stand, roll the front wheel and you can feel the warp.

[Scoots]

I was thinking if the dufus at the BMW dealership may have screwed up when he mounted a new front tire on the wheel a couple of weeks ago? Everything was working fine before then.

[Major Softie]

In that case, yes, they could be responsible. If they removed the disc for some reason, then it may be that taking it off and re-mounting it could fix it. There could be something under the carrier, or it could be that they changed its orientation on the hub and mounting it in a different position may fix it. It's also possible that they bent it, of course, but you'd be hard pressed to prove it now, so lets hope just remounting can fix it.

[Duane Ausherman]

During our first factory technical school in 74, we were warned to be very careful when changing a tire on the front wheel due to how easily the rotors would warp.

I predict that the rotor wasn't removed. If the tire changer just changed the tire on that wheel the same way one would on a /5 wheel then the person's full weight was on one side of the rotor.

If the pulsing goes away with heavy braking, then it isn't badly warped. They can be far worse. I always wondered if there was a way to true them. The can be ground flat again, but we never found anybody who was set up to do it. That was 37 years ago, so maybe a fix is available now.

[SteveD]

You might get lucky with some brake cleaner and some very fine wet & dry paper, doing light circular moves over all the disc surfaces. Road grime can build up and cause a very fine pulsation. It's sure worth bothering to do the clean as it just may be a simple solution.

[Ray from Indiana]

Why not just check for warp with a dial indicator first?

[Jean]

We had a similar issue on this forum a while back. SteveD's (and mine) suggestion was what "fixed" it.
Not everyone has a dial indicator or immediate access to one.
BUT...you can set-up a feeler of some sort and see if warpage is significant same as when you true a spoked wheel.
Try cleaning and lightly scuffing first. It's easy to do.

[chasbmw]

I had real problems with my 1070 bike, with brake pulsing, I had also changed MOT (annual safety check) garage and the new one refused to pass the bike. (they were right, heavy braking at slow speed in the wet would have been really dangerous)
I tried everything, even took the wheel down to Steve at Pistonbroke to get the Wheels machined straight. But on the cheapo dial guage I could not get the discs to run true. In the end I fitted a set of EBC floating rotors, kind of expensive.

[barryh]

.... and the pads looked very good.

Did you take the pads out and if so did they go back in the same sides ?