Grind or Vibration in Rear Brake Pedal?

[Ryan_B]

Hello All,
I bought new 2016 and now have about 250 miles on it. As I get more comfortable riding this one, I noticed that I get a "grind" or a rough vibration when I lift off the gas and touch the rear brake. As an example - pulling back into my neighborhood, I am normally driving at 20mph in 2nd or 3rd gear. I can release the throttle without issue, but if I barely touch the rear brake I get a rough engagement that almost feels/sounds like lightly grinding a gear (you can feel it in the seat if you are waiting for it). It is just for a very brief instant and goes away as soon as the brake pads touch the rotor. No noise/issues at all from the front brake. Doesn't seem to matter if clutch is in or out.

My question is, is this possibly something wrong with the shaft drive that I should be concerned with? Basically, this is so new that I am questioning if it was assembled correctly, fluids topped off, etc.. Anything I should look at immediately? I am just worried that I may be damaging something due to an assembly or adjustment oversight that can be easily fixed.

If not, I will change the fluids at the 600 mile mark and just enjoy it!

Thank you!
Ryan

 

[Igofar]

Standing by the white courtesy phone ...

 

[Ryan_B]

Thank you Igofar for the call and explanation of what is going on!

For everyone else - I have been a member of several different forums over the years (4x4 off road, miatas, general mechanic repair). I am blown away and somewhat in disbelief that an expert that can describe every single part in detail (using simple words in my case), reaches out to a brand new member to troubleshoot an explain what is happening. Glancing through his review page I can see that I am not alone. I can tell you, there are some nice people on other forums - but this level of knowledge and service does not exist. Or maybe on the other forums they are just too busy making a fortune with that knowledge!

Alright, now to some homework. I somehow missed the "articles" page, which should probably be mandatory reading before posting. ;-)

Thanks again!
Ryan

 

[jfheath]

Thank you for the very clear description of the symptoms. I know where I would look to find this and I could list a few suspicions, but nothing that Larry would not have covered or that you can't find out from the articles.

Let us know what you find, please. There is something about the fact that it doesn't happen when the front lever is applied that intrigues me.

The last time I had a noise like this - I had just started going down the Furka Pass in the Alps - famous for a scene in the film Goldfinger. It was throwing it down, the roads were mirror smooth with the surface water and it was very thick fog - visibility less than 10m

The first time I used my brake pedal for a long time at the top, I got a noise similar to your description - but mine was from the front right caliper. Thereafter it did it every time I used the front brake lever. I decided that I knew what it was, but it was an 'exciting' descent, hoping that my diagnosis was correct. If I was wrong, well those hairpins emerged out of the fog very quickly. I was able to fix it at the hotel, my diagnosis was correct and I learned another quirk about the ST1300 brakes. The answer to this particular issue is in one of the articles that you will probably read for 'homework'.

 

[Oldbikefixr]

Just a habit of mine here. I ride through the neighborhoods and city streets at between 2500 and 3000 rpm....a practical low speed power band. If I'm lugging the bike along and get into a situation that requires me to accelerate out of trouble, I'm just a good target.

 

[caldercay]

. I was able to fix it at the hotel, my diagnosis was correct and I learned another quirk about the ST1300 brakes.

oooooooh, the suspense!

 

[Slydynbye]

Was it a loose nut on the Handle bars?

 

[jfheath]

Was it a loose nut on the Handle bars?

A loose nut holding the handlebars, maybe !

 

[Al st1100]

a loose nut between the handle bars and the seat

 

[Ryan_B]

Hello jfheath,
I only made it through a few of your articles last night. I did have a car to work on this morning, but now I am settling in for some more homework! I must say, your articles are incredible. I start to skim through a page and have to restart and actually read it because there is so much information and 'watch-outs' packed into each one.

I did test drive mine for about a mile this morning (I didn't pass 20mph). Off the start nothing, but after about two blocks of driving and braking I can get it to start. Clutch in or out doesn't matter, throttle on or off doesn't matter (it is easier to feel and hear with no throttle though), you get a slight grind almost a little "honk" sound when you barely touch the rear brake pedal. I noticed it makes it both engaging and releasing, I can extended the noise if I just find the perfect spot with the brake and keep my speed between 15-20mph. The best way to describe it - it feels like you are barely engaging a parking brake on a large vehicle with drum brakes. After that initial little "honk" it engages smoothly, firmly and without fuss.

I played with just the front brake and couldn't hear/feel anything at all until just as I pulled into the garage, I then heard it echo off the garage wall. It is still there, but it was much subdued and I could not feel it.

Igofar has pointed me to the SMC, which is definitely sticking, so it needs attention (we will see if it needs replaced). But I am curious what your issue was now. I will report back after I get through all your brake articles.

Ride safe!
Ryan

 

[jfheath]

Thanks for the feedback.

My issue was to do with the fact that the pad spring in the front caliper of the 2008+ ST1300s can rock when putting brand new pads in - so that the spring tag is snagged by the centre piston. It doesn't happen with old pads, cos the pistons are further out. My first application of the brake pedal caused the centre front piston to catch the tag on the spring, and thereafter the front right caliper was complaining, making noises and getting very hot.

It's possible for the rear caliper spring to do something similar if the inner pad hasn't been located behind the tag on the spring, but there are a whole load of other things that could cause the pads to be mis-aligned and/or create a noise like that you describe - most (but not all) of which are in the Avoiding the Pitfalls article, with photos. If you need clarification on any of them, post on here or PM me.

 

[SMSW]

Igofar has pointed me to the SMC, which is definitely sticking, so it needs attention (we will see if it needs replaced).

Larry has recommended replacement rather than attempting to rebuild the SMC in the past. If a good thorough flush does not clear up the problem, you might be headed in that direction.

 

[RaYzerman]

How much pad material is left on the rear brake pads? First place I'd look, and of course the source of any 'sticking'. I'm sure all your consultants have steered you well in that regard.

 

[Ryan_B]

Thank you jfheath, I did read that in your "pitfalls" article. I will make sure those clips are seated correctly.

Rayzerman - I assume there is a lot of material left, I think I am at 240 miles on the odometer. But I guess if they were dragging badly the pads may be gone. I am planning on dissembling today. I will report back!

Ryan

 

[Limshady88]

Just curious. Your initial post said you bought new 2016 and now has 250 miles. New as in within the past 12 months? Would there be any manufacture warranty left on it?

 

[Ryan_B]

Yes, full warranty (36 month). Honestly, it was such a minor sound that I don't know if a tech would even have heard it. I have a hard time trusting anyone with repairs too, so I guess the warranty is only good to me if the engine grenades for no reason.

I do owe an update on this though. With Igofar's direction this is nearly fixed, I basically disassembled and double checked the the front and rear brake and wheel assemblies. Everything seems to be functioning correctly now. I am going to full flush and bleed the brakes and probably the clutch. I will definitely be doing it once a year to hopefully prolong the life of the secondary master cylinder.

Issues found:
SMC bearing was not well lubed (nearly dry), which was causing it to bind when applied.
Front axle was not installed correctly and one of the forks was up too high which caused a bind and the handlebars slightly turned. Thanks to jfheath for his fancy animation! That was very helpful.
Rear caliper was slightly tweaked by tightening the rear axle before the caliper stop pin (I assume). Disassembling and reassembly stopped my noise (yay!).

Once again, credit goes to Igofar! I am comfortable turning wrenches, but I lack the knowledge and experience seeing a problem when it is right in front of me. Unfortunately for him this will probably not be the last time I ask for help. Lol

Thanks all,
Ryan

 

[Limshady88]

Great to hear that you found the source and was able to correct it. Unlike you, I am some what comfortable turning wrenches but after reading @jfheath articles AND speaking to @Igofar, it wasn’t too hard. Larry was also available by phone all day when I redid my brakes, installed new SMC and bled all brake lines. I wish him well in his recovery from dental surgery.

 

[jfheath]

Glad it is all sorted - well done ! Thanks for the comments and for the feedback !

SMC bearing was not well lubed (nearly dry), which was causing it to bind when applied

Something that is easily overlooked, I think.

Disassembling and reassembly stopped my noise

Yes. Funny how that works isn't it ? Take it all off, put it all back again. With only a slightly increased awareness of what needs to be done, and what needs to be avoided, everything slots into place and it all works just as it should.

 

[Ryan_B]

Okay - final update on this one. I received my Motion Pro bleeder and just flushed the brake system, paying close attention to the SMC. When I lie down and spin the back wheel and actuate the SMC it is a much more 'crisp' action than before. Previously it was a progressive slow stop that would work cleanly every 3rd or 4th try. Just from listening while bleeding the line I think there may have been air in there. I think this one is officially fixed!

Thank you again,
Ryan