TIV wrote:Hi all.
I have had this rather annoying problem on my K75RT all the time I’ve had it. Front brakes are OK when brake pads are brand new. After a short time, maybe 1 or 2000 km, they begin to pulsate when applied. Worst at relatively low speed and when not braking hard. I seem to remember having heard that this problem is fairly common on these bikes. Anyone found a way to cure this?

My 1988 K100rs does the same.........

nobbylon wrote:Just because they were new doesn’t mean they were true. Get them checked and skimmed before anything else. Check the run after installation also.

Dai wrote:Just y'all bear in mind one thing: the caliper relies on minor imperfections in the disc to knock the pads back in. If the pads aren't pushed back properly i.e the disc is absolutely flat, you can get a build up of road shite behind the pads which will eventually cause them to make permanent contact with the discs. Mind you, depending on what country you're in, some of you will never suffer from that.

TIV wrote:I have sometimes considered running a line from the master cylender to a T-junction, and from there separate lines to each cylender. Anybody done this?

MartinW wrote:YG a dial gauge indicator complete with magnetic base can be had for around $20.00. The brackets to attach it to the top caliper bolt do require a bit of wrangling.
Regards Martin.

nobbylon wrote:

Dai wrote:Just y'all bear in mind one thing: the caliper relies on minor imperfections in the disc to knock the pads back in. If the pads aren't pushed back properly i.e the disc is absolutely flat, you can get a build up of road shite behind the pads which will eventually cause them to make permanent contact with the discs. Mind you, depending on what country you're in, some of you will never suffer from that.

This is not my understanding of how a disc set up works. The master cylinder is designed to pull fluid back in when pressure on lever is released thereby pulling the pistons slightly back to release pressure from the disc. This is probably the effect seen of fluid spurting in the master cylinder as pressure is released.  Using square edge seals helps this process thus no return springs required.
On the old airhead master cylinders it was necessary to set up with a feeler blade so that the relief hole lined up correctly with the piston. Failure to do this could result in wheel lock up as the calipers would not release. Discs should be true.

nobbylon wrote:

Dai wrote:Just y'all bear in mind one thing: the caliper relies on minor imperfections in the disc to knock the pads back in. If the pads aren't pushed back properly i.e the disc is absolutely flat, you can get a build up of road shite behind the pads which will eventually cause them to make permanent contact with the discs. Mind you, depending on what country you're in, some of you will never suffer from that.

This is not my understanding of how a disc set up works. The master cylinder is designed to pull fluid back in when pressure on lever is released thereby pulling the pistons slightly back to release pressure from the disc. This is probably the effect seen of fluid spurting in the master cylinder as pressure is released.  Using square edge seals helps this process thus no return springs required.
On the old airhead master cylinders it was necessary to set up with a feeler blade so that the relief hole lined up correctly with the piston. Failure to do this could result in wheel lock up as the calipers would not release. Discs should be true.

nobbylon wrote:I think we’ll have to agree to disagree on this one fellas.