Rear ABS engaging too often

[Larsf]

Hi,
  My rear ABS is  acting up on a 91 K75RT.  After the brakes are warmed up,  my rear ABS will release the brake when I'm getting close to stopping.  It's not all the time, but enough now where I can't really trust it.  I've done 2 brake bleeds, first through the module, and then the caliper.  The first bleed had some very old fluid come out, but very clean now.  I was gonna try swapping out the pads.  Maybe they're too grabby?

Cheers,
 Lars

[Martin]

How old are your brake hoses? Old hoses can degrade causing problems.
Regards Martin.

[frankenduck]

How old are your tires?

How much front/rear braking do you use? 80/20? 70/30?

[Laitch]

My rear ABS is  acting up on a 91 K75RT.  After the brakes are warmed up,  my rear ABS will release the brake when I'm getting close to stopping. 

I'm not understanding your description. ABS is only activated when wheels start slipping; that usually happens during panic braking or braking on slippery surfaces at excess speed for conditions. If you're riding on banana skins, lack of tread could cause frequent loss of traction, as frankenduck seems to be indicating.

[Larsf]

Hoses are probably original.  Maybe I'll replace those?  Tires have plenty of tread.   It's engaging / releasing the brakes almost at the end of stops at stop lights.

[Laitch]

Consider detaching the hoses from the calipers and determining if they're clogged or starting to clog. They may need to be flushed or replaced.

[frankenduck]

If you're riding on banana skins, lack of tread could cause frequent loss of traction, as frankenduck seems to be indicating.

Actually I was thinking more about age, not tread. As tires age they oxidize and harden resulting in reduced traction.

[The Mighty Gryphon]

If the ABS sensor on one wheel suddenly stops getting pulses the brain will momentarily release the brakes for that wheel.  This normally occurs when the wheel locks up when braking on a surface with poor traction.

It can also happen when the sensor is getting weak pulses from the toothed wheel.  You might want to check the gap between the sensor and the toothed wheel.  Check it in several spots to make sure there is no runout in the toothed wheel.

Also, you might want to clean the connectors in the ABS system, especially those for the wheel sensors.

[K1300S]

Hoses are probably original.  Maybe I'll replace those?  Tires have plenty of tread.   It's engaging / releasing the brakes almost at the end of stops at stop lights.

if hoses are original, they are WAY WAY beyond their replacement date.  get new ones.

tread on tires is only one factor.  just because they have tread doesn't mean they are good.  how old are they?  read the date codes on the side.

[Larsf]

I ended up putting a 4 hose spiegler brake line kit on the front and rear, cleaned the rear caliber good with brake cleaner, and swaped the rear pads from side to side.  Seems to be much better.  I haven't had it release on me prematurely, and no more squeal from the rear.   The new front line had a banjo on the caliber end,  so I ended having to buy a banjo bolt for it.  Not sure why speigler didn't do a direct screw in for that end.

[alabrew]

That is the same symptoms that I had on my K 12 LT when the sensor ring was dented during a tire change. It released both front and rear coming to a stop, since the system is linked. You didn’t say that you had, but check the sensor gap, and whether or not a tooth is missing from the ring.