Braking problem on the Triple

[Mr Hammers]

When braking it feels like it's pulsating... as if the discs were warped. But, i've checked the discs, and they seem to be pretty straight (see vids). I've checked the wheel bearings and headstock bearings (by manually pulling/pushing the wheel and forks) and they seem to be ok too.

Some history that may or may not be relevent: When i first bought it i found one the brembo discs was slightly warped. Having never had ABS before i had assumed it was that, but when i realised it was a disc i changed them both for brand new ones.

That was fine, and all was good. Then, after going to Wales fairly recently, the welsh claylike mud got in all the vent holes and hardened into a sort of cement. It made braking horrible, all grindy and harsh. I poked it all out of the holes and put new pads in.

https://i.imgur.com/ykti3en.jpg

It was a lot better, the grinding had gone, but still there was this sort of pulsating (don't know how best to describe it). Then i checked the bobbins, which all of them seemed to be stuck fast, again i'm guessing the welsh clay mud got in there.

Cleaned them all off with carb cleaner, and spun them all round with a nut and bolt so they were free. Then jetwashed them all, making sure to get right on them as close as i could with the nozzle. The discs still didn't seem to move though, usually the discs will have *some* amount of play, and while it seemed to be slightly better (although it could be my imagination) it's still there... this.... vibration... when braking.

I took a new street triple out for a test ride (and a new Speed Triple... man... what a bike that was!) and realised how silky smooth the braking was, and how mine should be at least something close to that.

So... the fact that the discs don't appear to be free in the bobbins are most likely the cause, but if so, how else can i free them up so there is some play, and, if it's not that, what else could it be?

Look forward to some suggestions! Cheers!

https://youtu.be/TtrRxUzlsAs
https://youtu.be/LY2mUbd1LpI
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A Guide To Powerbands

[stinkwheel]

So what, maximum runout 0.3mm on your videos? Which is top-end of acceptable.

Set up a pointer and check vertical runout too, I had a CB500 which had somehow slightly "egged" the disc so it was shimmying vertically. May also be worth dismounting the discs and checking for corrosion under the mounting points.

Maybe mark the high and low spots. If they are both at maximim runout and it's clocked at the same point on both discs, it could be adding.

Any odd tyre wear? I find a badly feathered tyre can feel like it's pulsing under braking.
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“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.

[Mr Hammers]

Thanks, stinkwheel. Checked the vertical runout, no egginess there. Forgot to check each high spot to see if they were the same, but there's no odd wear on the tyre... though i suspect if i left it as it is it wouldn't be long before there was. I didn't have time to take the discs off, but these have only been on for less than a year so i think they should be ok.

Gave the bobbins another clean though, and wiggled the bolt on each one to check it could move freely (ish). They all do, but i'm still not entirely convinced they are in fact as loose as they should be, but i could be wrong and they're fine.

If it's no better, i might just take the whole front braking system apart at some point, and rebuild it... new pistons, fluid, pads, pins etc and see if that cures it.

It's frustrating because you can't get good feedback and really feel what the tyre's doing because of all the noise. They do still stop very well though.
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A Guide To Powerbands