[Ekim]

So I just recently had my front tire replaced by my friend and local custom motorcycle shop owner. I remounted the wheel and just got around to take it for a spin this evening.

When coming to a stop using the front brake I noticed a strong pulsing and that the brake was very very grabby. I thought maybe there was some grease or contaminant on the rotor and figured I would just clean it up with some brake cleaner when I got home. Once home and under closer inspection I found the ABS ring had a dent in it:

So my questions are, Do you think this dent in the ring would cause the pulsing and grabby brake? Any idea how much a new ring will cost?? It looks like you can replace the ring without replacing the rotor...true? I checked both rotors and they are straight, so looks like just the ring will need replaced.

As for how it happened. I know it happened at my friends shop...I was there when the wheel fell over into the mounting machine. He nor I thought much of it at the time and didnt even think to look at it. It was a complete accident and is one of those unfortunate things. Hopefully it wont be one of those expensive unfortunate things!

 

[DavidTaylor]

First, did you check the weight rating on the Z6 to make sure it can handle the LT's loaded weight? AFAIK the ME880 is the only Metzler load rated for the LT. If not I would be VERY careful running that tire on the LT for fear of a severe front tire failure at speed.

As for the pulsing brake, I somewhat doubt the dent you showed in the pics would cause that. If the slots of the ring were damaged in some way I would think that could, but the dent appears to not affect to spacing or integrity of the rest of the ring.

 

[Ekim]

The picture really doesnt do the dent justice. The slot circled is quite a bit lower or dented in than the neighboring slots.

If the ring is not suspected...any idea's what may cause the brake to pulse and be grabby? It wasnt that way before I removed the wheel.

 

[PhantomK12LT]

If it's pulsing when applying the brakes, I would expect a bent or warped rotor as the culprit. If it's grabbing, check the brake pads for wear. Also check the rotor surface for gouging or scratch marks.

 

[HarvRead]

Brake Shake

Check the front disc(s) for lateral run-out (bent while changing your tire). This happens frequently when the tire changer doesn't know what he is doing.

 

[jzeiler]

Ekim,


Two things

1. Earlier post said you had battery issues. Did you just charge it or replace the battery. And I take it you are not getting any warning lights? Weak batteries can cause strange symptoms with this integral brake system.

2. When you removed the front calipers - did you disconnect the hydraulic lines? (It has happened before right here on this site). If you did you need to bleed the system.

I don't think that minor damage would cause the problem based on the fact that the front sensor does not have a gap setting like the rear. So I suspect there is a bigger tolerance for that sensor.

 

[Dick]

Ekim,


Two things

1. Earlier post said you had battery issues. Did you just charge it or replace the battery. And I take it you are not getting any warning lights? Weak batteries can cause strange symptoms with this integral brake system.

2. When you removed the front calipers - did you disconnect the hydraulic lines? (It has happened before right here on this site). If you did you need to bleed the system.

I don't think that minor damage would cause the problem based on the fact that the front sensor does not have a gap setting like the rear. So I suspect there is a bigger tolerance for that sensor.

Hi, John -

Would there be merit in swapping front wheels with another LT (Do you know if one can swap front wheels with any model year, or with an '05 only in this case)? So as to eliminate the *dented* ABS ring as the culprit? Just a thought. Gotta feeling y'all are gonna solve Ekim's problem - team effort does it every time! :thumb:

 

[Ekim]

Battery??

1. Earlier post said you had battery issues. Did you just charge it or replace the battery. And I take it you are not getting any warning lights? Weak batteries can cause strange symptoms with this integral brake system.

2. When you removed the front calipers - did you disconnect the hydraulic lines? (It has happened before right here on this site). If you did you need to bleed the system.

I did and still may have a battery issue. I had to jump start the bike before I took it out since the battery didn't have enough juice to turn it over (it was at 11.8 when I checked it). Once started the bike ran fine with no warning lights. I rode the bike for about an hour to charge the battery. While at speed I did not notice anything peculiar with the brakes. No pulsing or shaking or anything that would indicate a worped rotor. I only notice it at very low speed (less than 10mph)...very noticable, scary noticable. When I got home I checked the voltage on the battery and it was at 12.8Volts. When starting the bike it dropped down to around 10.5 to 11Volts and while running it was at 13.5-13.8Volts. Does that sound right?

Is it possible it could be that the battery isnt charging correctly and when at low speed when the bike is closer to idle and servo activated it could be causing a weird pulsing?

I did not remove the hydraulic line, so I dont think bleeding the brakes are necessary.

As for a worped rotor, I did jack the bike up so I could spin the front tire and placed a straight edge against the rotor. I slowly spun the wheel, while holding the straight edge to the rotor I did not see any obvious movement, it looked very true.

I think I may need to tackle the battery issue first and see if that makes a difference.

 

[jzeiler]

Ok - good on not removing the hydraulic lines. Like I said one person did do this so I had to eliminate it.


The weak battery usually throws a fault light on brake application that clears on restart. But like I said that is typical, there could be other modes related to weak batteries we haven't seen yet.

Interesting that it is only at low speeds. The bent rotor theory would cause a vibration at speed and could cause the grabbiness at low speed so I don't really suspect that. Really need to check with a dial indicator as run out of as little .005 inch can cause a problem. The manual does not specify a runout limit.

I do stand corrected on the front ABS senor - it does have a gap spec. 0.0039 to 0.0669 inches so check that as well. If your "dent" falls out side that range the system will most likely detect it but I am not sure if it will react to one missing pulse. I think it looks for a change in speed and one pulse may not be enough for it to detect and react to anything.

Also did you install the axle properly? Tighten the axle nut to spec and compress the forks several times before tightening the pinch bolts. I, for the life of me, don't see why this is important given the tight fit of the axle in the forks but BMW felt it was important to put in the manual. Also the torque on the calipers.

Other than that I guess you could try another wheel assy as Dick suggested or just replace the ring ($66.00 part). I looks like you could remove it and lay it face down on a hard surface and hammer it back out with a drift as it is just stamped steel. I would give that a shot.

 

[Ekim]

Thanks for all the info jzeiler! I will check the axel and and caliper again to make sure everything is tight. Having the specs for the gap and rotor will help, I'll check that as well. Worse case I take to Bob's and say...please fix!

 

[mtrevelino]

The abs ring does not have anything to do with the pulsating brakes. The ring is only there to send the impulse to the wheel sensor back to the abs unit. That would be like people with the smart tire system stating that it is causing pulsating brakes. The front brake on my LT has a slight pulsating, but it is not bad, I just know that it is there. I would check each rotor with a dial gauge as others have suggested. You may also check with the gauge the rim, but again only the rotors would make the pulsating.

 

[Ekim]

First...Thanks for all the advise..this forum is great (just wanted to state that )

So I have checked everything and all looks good with exception to the ABS Ring. I took the bike out again this evening and paid closer attention to what was going on. Pulsating may not be the correct word...maybe surging..no feedback in the lever, it feels just like ABS kicking in.

I got up to speed and slowed down using just the front brake lever. No pulsing in the lever or anything out of the ordinary. As I slowed I applied more and more pressure to just the front brake lever and the bike stopped great as usual (I was being careful not to dump it). As I slowed to just below 15 mph or so I noticed the ABS sensation. The level was solid and no movement or feedback but that feeling like the ABS was kicking in. I tried going very slow and and giving a good hearty pull of the lever to stop and the same sensation. Looking at the ring I can tell it is definitely out of spec. Thoughts?

I know it sounds like I am just wishing it was the ring...but I cant find anything else wrong and that is the only obvious change made after remounting the wheel.

I am going to order a new ABS ring because it needs to be replaced regardless. I checked Beemer Boneyard and they are sold out (too bad too..$15!). Where would be another good place to order one? Is it just as cheap to order it from the dealer?

BTW...the bike sat in the cold garage all day today and the battery read 12.55 Volts...just down from the 12.8 right after my ride yesterday, so I think the Battery is ok.

 

[mtrevelino]

Personally, I do not think that anything is wrong with the abs ring. If it was warped or out of spec, you would have the abs lights flashing at all times and the abs would not be working.
If you start the bike and start moving and the abs light goes out, there is nothing wrong with it.
Just my $.02

 

[jzeiler]

Ekim,

I may well be the ABS kicking in - how many miles have you put on that new (slick) front tire? The last time I put a new rear tire on the bike scared me for the first 30 miles. I thought I had a flat it was that squirrely until it got scuffed in.

I agree with Mike even though this is a different braking system than on his bike. The ring defect should not cause this type of behavior.

You can go to MAX BMW and use the online catalog to get the PN and order from them or try Chicago BMW on line as they give a 20% discount (but you may have to wait if it is not in stock).

 

[Ekim]

Well I ordered a new Ring from Bob's...$66 so not too bad. When I pull the wheel off to replace it I'll triple check everything again. I'll post an update on what, if anything, that I find.

 

[DaFlake]

Ekim,

Have you confirmed that the air gap between the sensor and the ring IS within specs? If so .. did the gap change when the sensor aligned with the "dent"? Some problems occur when the sensor is bumped out of alignment when installing the rim (with the new tire) back to the bike..... Sometimes the sensor also just need cleaning.....

JMTCW

Ramon

 

[Ekim]

I havent checked the gap or cleaned the sensor, but will be sure to do it when I pull the wheel off to replace the ABS ring.

 

[Ekim]

Fixed!

I just wanted to post a follow up on the problem I was having. I recieved the new ABS ring from Bob's this week and put it on tonight and all is good again.

Looking closer at the ring off the bike you can see the gaps are definitly at different levels and spaces. That apparently was enough to fake out the ABS sensor causing the ABS to kick in when coming to a stop.

Thanks again for all your guy's help!

 

[jzeiler]

Ekim,


Glad that fixed it, and thanks for the feed back. Now we know to be really careful with the ring or the Gremlins will get us!