Newbee (to BMW) brake question - need help

[thestumper]

Hi all,

Spent the who season enjoying my 2016 1200RS.  New TPMS sensors and rear brake pads were my big ticket items.  I do have a question about the brakes.  The front lever has what I consider to be almost free play, until there is a "click" that you can feel and hear?  Is that normal?  Its mostly noticeable at low speeds and does not seem to impact braking performance.  

I also notice that, while the front brakes grab and top just fine, at the point of complete stop, I feel a slight "clunk"/tiny "dive".  I can ride all day and there is no such sensation - braking performance is generally very good.  Its just the complete stop - at the very end of the travel is get that sensation.  

Is any of this normal?  I don't even know what to search on.  All is get is "check mounting hardware for rotors and calipers" but that all seems solid.  It doesn't seem like a bleed issue - pressure is progressive and firm after that initial little click.

Its almost like in the second scenario, they just grab hard in the last inch or so as I'm pulling to complete the stop and I get the little dive.  

I should also mention that the bike had aftermarket levers when I bought them - they are gold and were supposedly very good, but I also stumbled across that video with the grub screws that adjust the pull/piston activation - what is the correct feel?  Smooth all the way through?  How much play should there be.  Again, they feel good to the very end of the stop.  

Anyone here that might know what I'm talking about?  I apologize in advance for my ignorance, but I've been a "rice" guy for a LONG save for two Triumphs and I don't remember either sensation above.  

Thx!

[Ray]

1. ...The front lever has what I consider to be almost free play, until there is a "click" that you can feel and hear?  Is that normal?  

2. ...the front brakes grab and top just fine, at the point of complete stop, I feel a slight "clunk"/tiny "dive".  Its just the complete stop - at the very end of the travel is get that sensation.  

1. Nope. Though see number 2. 

2. Probably not. The rotors have a little play on the inner carrier, but not as much as wheels folks use on the track.  That said, if you've never experienced semi-floating rotors, and you're a sensitve guy, then that might be what you're feeling. 

You might wiggle the rotor to see if the buttons are loose on the carrier. 

For efficiency, and since we can't experience what you do, recommend you have one of the shop techs, who do this for a living, evaluate the cause.  When it comes to brakes on a 125 hp bike, I tend to get a little anxious.

[thestumper]

1. Nope. Though see number 2. 

2. Probably not. The rotors have a little play on the inner carrier, but not as much as wheels folks use on the track.  That said, if you've never experienced semi-floating rotors, and you're a sensitve guy, then that might be what you're feeling. 

You might wiggle the rotor to see if the buttons are loose on the carrier. 

For efficiency, and since we can't experience what you do, recommend you have one of the shop techs, who do this for a living, evaluate the cause.  When it comes to brakes on a 125 hp bike, I tend to get a little anxious.

Do you happen to know the torque specs for those rotor buttons/bolts?  I've seen anywhere between 12Nm and 19Nm - not sure I can trust AI on this one

[thestumper]

Upon further inspection, the noise seems to be coming from the caliper itself. The sound and feel are not normal - I was able to test on a friends identical bike. Will keep this updated as we go, but we're going to be doing a thorough cleaning and inspection of calipers and possibly replacing pads.

[Grumpy Goat]

Upon further inspection, the noise seems to be coming from the caliper itself.  The sound and feel are not normal - I was able to test on a friends identical bike.  Will keep this updated as we go, but we're going to be doing a thorough cleaning and inspection of calipers and possibly replacing pads.

Reading the thread so far, that was my suspicion. You did not mention if / when the brakes - specifically the calipers - were last serviced. Also not mentioned was when the front suspension (forks) were serviced and how many miles were on the bike.

The sensation of slight clunk *and dive* in the last part of a complete stop after riding the bike for a while without such issues, is indeed a strange one, and nothing that I have ever experienced with my 2016 which now has 65k miles on it. My bike's maintenance events are all on my YouTube channel. Brakes have never been re-built and I have replaced them once at 48k miles. Forks were just serviced for the second time, first was at about 36k miles.

I have not cracked open my service manual (PITA as it is on CD-ROM) but 19 Nm seems to be right. These screws are loaded in shear and have to be installed with thread locker to help assure that they do not back out. They need to be installed evenly to further ensure that axial overload is minimized and that all screws share the load as evenly as possible.

[thestumper]

Upon further inspection, the noise seems to be coming from the caliper itself.  The sound and feel are not normal - I was able to test on a friends identical bike.  Will keep this updated as we go, but we're going to be doing a thorough cleaning and inspection of calipers and possibly replacing pads.

Reading the thread so far, that was my suspicion. You did not mention if / when the brakes - specifically the calipers - were last serviced. Also not mentioned was when the front suspension (forks) were serviced and how many miles were on the bike.

The sensation of slight clunk *and dive* in the last part of a complete stop after riding the bike for a while without such issues, is indeed a strange one, and nothing that I have ever experienced with my 2016 which now has 65k miles on it. My bike's maintenance events are all on my YouTube channel. Brakes have never been re-built and I have replaced them once at 48k miles. Forks were just serviced for the second time, first was at about 36k miles.

I have not cracked open my service manual (PITA as it is on CD-ROM) but 19 Nm seems to be right. These screws are loaded in shear and have to be installed with thread locker to help assure that they do not back out. They need to be installed evenly to further ensure that axial overload is minimized and that all screws share the load as evenly as possible.

Yeah, I had the 24K service done but I see no evidence that they touched the brakes.  They just said they were "good" so minor inspection I suspect.  I honestly think the calipers are likely filthy after watching you video, and if a pad was loose/damaged/moving around, that could account for the odd "end of stop" behavior because that makes the same sound and you can almost 'feel' it in the lever.  Maybe even a stuck/sticky piston.  24+K on the bike right now - I put 6k of those on this season, and I'm more of a sport rider, so they weren't easy miles.  I'm going to do pads while I'm in there regardless - Amazon accidentally sent me the fronts when I ordered the rears, so I kept them assuming I'd need them at some point and ordered another set yesterday.  Work commences on Saturday and will keep this thread up to date.