A lesson in brakes

[Claviger]

Setup: In preparing my Daytona 955i for RAA West, the one thing I absolutely couldn’t get to work right was the front brakes. I was forced to ride RAA with some seriously horrid front brakes. I tried everything except throwing money at it, here is the final resolution.

SKIP TO TLDR if it’s too long.

Deciding I wanted to isolate where the problem was I mentally separated it into two systems: hydraulic pumping, eg mastercylinder and fluid, and mechanical force eg calipers, pistons, pads, rotors.

Yes I know technically that’s wrong thanks.

That mental separation led to: swap the Rocket 3 front calipers in to remove the older but identical Daytona Calipers as a possibility since I was confident I had no air in the system. Saved the HH pads that were already bedded in and kept them in the same spots as originally located on the Daytona.

Sure enough a quick bleed later, brakes are BEASTLY. Sharper than on the R3, which is weird, because the R3 has a 5/8 MC and the Daytona has a 14mm.

TLDR: if your lever travels more than 1/2 range before engagement, you have good pads, good fluid, good rotors, and no reason to suspect the MC: rebuild your calipers!!

 

[1olbull]

Rob,
You're going to have to break down your acronyms for us who do not know them.

 

[Claviger]

TLDR-Too Long Didn’t Read
MC-Master Cylinder

 

[warp9.9]

CCQ

 

[Claviger]

CCQ

Lol

 

[rash_powder]

My 03 Sprint ST had some soft front brakes as well. I read to pump them up and band the lever to the handlebar to dissolve any air in the system, so I gave that a go. I bled them. No dice. Still soft. Feeling that the brake system was a rather simple system, being rather confident it the problem was in the calipers, and throw in some general overally confident 'I thought my way through this' I disassembled the front brake calipers.

Surprise! The calipers can split in half! Didn't consider that when I thought, but no matter; drive on. Pistons came out and I found a ring of hard scuzz right about where the rubber seal rides. I carefully polished that off and the caliper bores, cleaned everything up real nice and reassembled with probably a little more silicone disc brake grease than necessary. That stuff went every where a leak of air or brake fluid could possibly be. Figured it would help seal things up. Anyway, it all went back together and bled out splendidly. After that, I quite litterally had a set of one finger brakes!! Two fingers would nearly toss me!!!

Anywho, you may just need to tear them down and clean them up real nice. That scuzz ring, I don't know what it was but definitely did not belong.

 

[Claviger]

My 03 Sprint ST had some soft front brakes as well. I read to pump them up and band the lever to the handlebar to dissolve any air in the system, so I gave that a go. I bled them. No dice. Still soft. Feeling that the brake system was a rather simple system, being rather confident it the problem was in the calipers, and throw in some general overally confident 'I thought my way through this' I disassembled the front brake calipers.

Surprise! The calipers can split in half! Didn't consider that when I thought, but no matter; drive on. Pistons came out and I found a ring of hard scuzz right about where the rubber seal rides. I carefully polished that off and the caliper bores, cleaned everything up real nice and reassembled with probably a little more silicone disc brake grease than necessary. That stuff went every where a leak of air or brake fluid could possibly be. Figured it would help seal things up. Anyway, it all went back together and bled out splendidly. After that, I quite litterally had a set of one finger brakes!! Two fingers would nearly toss me!!!

Anywho, you may just need to tear them down and clean them up real nice. That scuzz ring, I don't know what it was but definitely did not belong.

Yep, that’s sounds about right.

A close look at the Rocket pistons revealed the 30mm (smaller) pistons are gold, while the 34mm pistons are silver. Thought maybe it was heat somehow.

I did find some interesting things looking through various parts drawings. Triumph sell a piston set that’s either like mine, with the two smaller ones coated or a set with full coating for all four pistons.

Think I’m going to order a set of full coating ones. The TiN coating they use is slicker and harder than the underlying steel pistons.

Very curious to see what the different pistons feel like back to back on the same bike!

 

[1olbull]

CCQ

EMS?

 

[mr hunt]

EMS?

WTF?

 

[barbagris]

WTF?

PMS!