Soft rear brake after recall

Here's a crazy thought: Has anyone noticed the hill hold function having an effect on rear brake softness? Might be total coincidence, but I had great rear brakes until the week after the first time I tried Hill Hold. Took a long ride yesterday after pumping up the rear brakes and they went soft again after using hill hold.

I know correlation isn't causation, but Hill Hold does manipulate the rear brakes, right? For the owners who have had great luck with the warranty brake fix, do you use hill hold?
 
The online service manual has it, as does the searchable PDF download of the service manual on this website under Resources. It's first mentioned on page 1,075 of the PDF.
 
I had the recall lager module put in and was fine for about a year or better but now it is returning. It does pump up with one push of the pedal but it’s still not right.
 
...good point...after reading what you have said i have disabled the hill hold to see if it helps....air is getting into the brake line from somewhere ...could be there..
 
The air does seem to collect at the abs modulator. I'm not sure it comes from there or is just naturally occurring air that is released from the brake fluid collecting at the high point. Seems like a leak big enough to allow air into the system would also leak brake fluid out when under pressure of braking pressure. Using the procedure of "replacing the abs modulator" to push the air back to the master cylinder before bleeding to the caliper seems to be the best way of getting the air out. Most bikes accomplish that through regular geometry, bubbles rising to the master cylinder to be released. Our air gets trapped in the system until forced out. Seems to be a design flaw.
 
Given there really is no way to actually bleed the high point of the system (abs modulator), I think you've hit the nail on the head. The procedure in the service manual just relies on flushing fluid through the system from low point to low point, which will always leave some air at the high point. Couple that with the fact that there are SO MANY hot points in the rear brake lines (more than other bikes), and it's really just a bad design. I just wonder what differentiates the bikes with problems from the the ones without problems?
 
Probably coincidence. Hill hold only temporarily holds pressure at the rear. It doesn't manipulate the brake, it only keeps the pressure supplied to the rear when you squeeze the front brake when certain requirements are met. Plenty of us use it with no rear brake softness. Though if the rear brake is soft, the hill hold would be made less effective.
Dr.D said:
I had the recall lager module put in and was fine for about a year or better but now it is returning. It does pump up with one push of the pedal but it’s still not right.
Click to expand...
A larger slave increases how "firm" it feels at the expense of reduced clamping force. If something else is letting air into the system, it won't address that.
 
I did a thorough rear brake bleed last night and there were ZERO bubbles of air at either end of the system. Usually, with a soft pedal, you'd expect expect air bubbles at one end or the other, or else the fluid is just old and has a high moisture content, so I also tested the moisture content of the fluid at each end and the fluid was as good as fresh from the bottle at both ends. This is NOT a bleeding issue. It is most definitely an issue with the ABS modulator or system high point. Given that I do not think Triumph is stupid, I'm guessing they know they have an issue with the Modulator, but that fix is too expensive, hence the band-aides with the bigger master cylinder. I would guess it's also an intermittent, or tolerance issue, hence why not everyone has the problem. They've probably fixed the issue in production for later model bikes, which is why there's no new part number.

All just engineer best guesses on my part, but this one really angers me. I take brake performance seriously and "you just have to pump the rear brakes to get them to work" is something from 1925, not 2025.
 
I think my rear is 30% of my breaking and I just have to double hit it first thing or after a stop. Mine is tolerable but not ideal. I’ve seen less than perfection in many bikes but I do love both my Rockets.
 
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