Front brake help, please!

[RickTaff]

Fitted brand new discs and pads to my CB500S, took it to MOT passed fine, no advisory's at all. Checked brakes they were fine, spun front wheel while on a jack and it spun ok.

What I have noticed though, and it was noticeable even on way to MOT, is the rear brake works perfectly fine, but the front one is puzzling me.

If I am travelling say 30, 40, 50 etc mph and pull the front brake to slow down due to the car in front turning or braking etc it seems fine, but when rolling to a dead stop at a traffic light or say junction with front brake lever engaged; You can feel a sort of "jerky" feeling in the stopping motion, like the front wheel has abit of drag to it.

Discs aren't warped, theyre brand new and he checked it all in MOT, pushed pistons back in before fitting new pads, too

Could it be

1 - The front brakes need bleeding again, as i maybe still have air in system. (lever feels ever so slightly spongy, doesn't travel all the way to the bar when pressed, but i'd say at most halfway or so)

*I did query the air theory with a garage earlier and they seemed to think it could be, their opinion was because the lever has to travel maybe a little further than normal to engage the brakes, it's causing the pads to grab/bite the disc harder than maybe usual -due to the lever being further in-, thus causing the "non-smooth" stopping motion*

2 - There is maybe some shit on the disc/pads and brake cleaner and scotch pad is needed.

3. They still aren't quite worn in or bedded in. Have done about 90 miles on them
Cheers.

[Nobby the Bastard]

Check the run out of the new disks.

It's not unknown for supposedly new disks to be warped. I think it was paddy who had the problem last.
____________________
trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[RickTaff]

[Islander]

Did you clean the mounting surface thoroughly before you fitted the new discs?

[A100man]

[Robby]

Another vote for cleaning the mounting points. I had exactly this problem on a CB500 years ago.

The mounting point for the disc on the wheel looked fine, but the disc had too much runout. When I sanded back the mounting points to get to clean metal, I had a layer of loose paint or powder coat on top, then a thick layer of aluminium corrosion under that. Once I sanded back to clean metal the disc sat flat and the brakes worked properly.

Japanese aluminium alloy from the 80s and 90s seems to really like to corrode, particularly if it's anywhere near brakes.

[stinkwheel]

The ones with the brembos can be really bad for pulsing. I had a nighmare with Mrs stinkwheels one. Even landed up dial gauging and shimming the disc. Some of the pattern discs had a vertical runout straight out of the box!

You can buy floating discs for them now. Much better.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Robby]

However, if you do have the Brembo calipers, the genuine Honda brake pads are incredible.

[Polarbear]

If your brake lever is travelling halfway back to the bars I'd say you have an issue there. Saying that I can't see how that would have the effect you are saying but it is something you should rectify.

You would expect that to be an air problem but if something is not lined up properly it could mean the caliper is flexing.
____________________
Triumph Trophy Launch Edition

[RickTaff]

Thanks for all the replies guys, I definitely do have a spongey brake lever which I am bleeding today (havent used the bike since i posted this)

Have my suspicions the brake pads are constantly slightly rubbing the disc, whether it be the disc on the bike now is slightly thicker than the standard Honda OEM ones, I dont know.... -Ones i bought are not oem-

It's a total guess on my part, but i think it could explain why the "jerky" stopping motion only happens at very slow speeds, approaching a dead stop. And not at high speed. ????

Might turn out to be a case of the pads needing to wear down a slight bit more. I will check for run-out, too

[Robby]

Probably worth giving it a full brake service, including removing the pistons to clean and corrosion off them, and pulling the seals out of the caliper to scrape out any corrosion from behind the seal.

The CB500 brakes have the potential to be surprisingly good, but they also suffer from just about every annoying thing that happens to brakes. Corrosion around/behind anything that is meant to move, rusted/notched pad pins, rusted pistons, discs that won't sit flat on the wheel, old brake lines, ancient brake fluid and worn out master cylinder seals (particularly on high milers with ancient brake fluid).

Luckily, they are very easy to work on and parts are available.