Rear Pressure Sensor Blew Out

[Bat-1]

Recently got a 2019 FTR S with just 540 miles on it. No mods but PO ran into something and I repaired some front end damage.

Went for a ride yesterday just to get gas when she started to feel sluggish. Right about the time I could pull over to check what was up, the rear brake pressure switch blew out (photo).

Seems some amount of brake was being applied and it overheated. I had the bike on stands and wheel spun with some resistance but not such that I thought anything of it. Rear brake had proper amount of fluid. I'm thinking the brake carrier is deformed slightly and causing friction but not sure.

 

[Charliemurphay]

Seems similar to what @ferraiolo1 experienced and why he changed to the ‘22 brake switch that is mounted to the master cylinder instead of the caliper.

 

[Bat-1]

I saw his post/video and checked to see if piston on the MC was 'adjusted.' Doesn't look like it as no tool marks on anything and the index paint marks still match.

Took off the wheel and all is good with axle and bearings. Brake carrier looks like it may be slightly distorted. Not sure, maybe the odd shape is normal. Ordered a used one to check.

Something was obviously rubbing lightly, though it may have just started once I applied some rear brake and the pads didn't move back. As I was driving the friction increased and things expanded. I'm not a fan of these pressure switches for the brake light but they do serve a good secondary purpose as a relief valve if you're boiling your brake fluid. In the scheme of things this cheap part blowing out beats a rear wheel lock-up or warped rotor.

I'll update this once I figure out what the issue.

 

[Bat-1]

To conclude this thread for someone's future reference:

Near as I can tell it's just the poorly designed rear Brembo caliper.

Ended up just buying the entire rear brake setup from the MC back. A salvager was selling the entire thing as one lot. Anyone need a rear speed sensor or brake carrier

After first taking off my existing caliper, replacing pads, bleeding twice, it still heated up the rotor more than it should (and rear rotors tend to run hot on most bikes anyway).

Then I installed the (actually much higher mileage) eBay caliper. I installed my new brake pads in it. It seem to me this is poorly designed. The pads are held in by a single pin held by a spring clamp that is super tight. So tight the pads can't 'relax' and move off the rotor after applying brake. You have to use a punch to knock the pin out and a punch to get it back in (which is a chore).

My bike had sat for a month or two in a dusty tow lot and since that pin faces straight up had lots of crud deposited on it. I think the pads just couldn't disengage at all after I applied brake because the pin holds them so tight and once crudded up allows no movement.

With my much higher mileage, but cleaned, eBay caliper, pin well lubricated, the pads now do retract a little. The rotor still gets very hot, but not to the point of boiling the brake fluid.

Give me a good old Nissin caliper any day.

 

[Max Kool]

Interestingly, this caliper is very commonly used, and not only on motorcycles.

 

[Bat-1]

I'm no engineer but I have changed dozens of brake pads and this caliper was the most difficult. You really have to put some downward pressure on that clamp while aligning that single push pin to reinstall it. With new pads it's near impossible to move the pads once it's all together.

Give me a couple of screw-in bolts any day over this setup. And why the 11mm bleeder bolt? That's a first for me as well.

Several things on this bike seem to have been done just to make maintenance difficult (like the tiny torque screws that hold the back of the switch housings).

Other factors in the system could have contributed to the locking but the bike had less than 600 miles on it when it happened so it was all basically new.

 

[ferraiolo1]

Yep. My helicopter uses almost the exact same brembo caliper.

 

[MacBayne]

My bike had sat for a month or two in a dusty tow lot and since that pin faces straight up had lots of crud deposited on it. I think the pads just couldn't disengage at all after I applied brake because the pin holds them so tight and once crudded up allows no movement.

And that is what I believe to be the centre of this issue. Given what info that you volunteered...

P34 Calipers are prolific. They are NOT "poorly designed."

Ducati, KTM, Moto Guzzi,, BMW, and Aprilia use them on most models. Race bikes, out-of-the-box.

Most of those brands use the cast version in lower models... Their higher-offerings used the machined version.

The Japanese "Big Four" use the cast versions... Look at the Honda Grom and the Kawi Z125... Beginner bikes...

You bought the machine from a junk yard after a PO crash and after sitting for months... Are the rearsets even OEM, or are they Chinese knockoffs? Is the spring, PN 7045293 present?

Give me a couple of screw-in bolts any day over this setup. And why the 11mm bleeder bolt? That's a first for me as well.

Several things on this bike seem to have been done just to make maintenance difficult (like the tiny torque screws that hold the back of the switch housings).

Torx fasteners are the "western" standard fastener, now. The Japanese still use JIS... Phillips fasteners are, and always were, junk.

Ask an American motorcycle mechanic what JIS, is. I'd bet 90% of them don't know... yet have wrenched on Japanese machines their whole career... stripping countless fasteners along the way...

KTM/Husky, BMW, Triumph, Ducati, Moto Guzzi, Aprillia, and every other brand of European machine uses Torx fasteners, and metric hex bolts. Indian isn't making maintenance more difficult, they are making it easier. Torx fasteners do not strip or "cam-out." Indian is keeping up with tech.

These machines are NOT a '72 C10 where you can disassemble one with a 7, 9, and 11/16ths wrench... hell,

11 mm is a standard size of bleeder bolt...

 

[ferraiolo1]

Um what?

1-there are no shims on the brake sensor. only the two banjo bolt copper crush washers
2- there is no way to clean it as its sealed in the brake line as a banjo bolt
3- its just a pressure sensor that sends signal to the abs unit that activates the brake lights.
4- they moved the sensor to the rear mc instead of the caliper in 22+ as this is a common issue.

 

[ferraiolo1]

The one attached to your rear caliper brake line at the banjo bolt. It’s what this thread is about.

 

[Max Kool]

If we clean up this topic and remove all assumptions and speculations we're stuck with a bike that spent 6 months in a junk yard, in a questionable state of repair.

Don't blame a caliper if you don't know how stuff's supposed to work.

 

[kungfoojesus]

If we clean up this topic and remove all assumptions and speculations we're stuck with a bike that spent 6 months in a junk yard, in a questionable state of repair.

Don't blame a caliper if you don't know how stuff's supposed to work.

My bad! I del my dumbversation for you fam!