Second Question; Centering the rotor in caliper.

[suecanada]

The right side Brembo caliper was not centered over the rotor on Little Red Baron, a 1983 R65LS. I could see and hear a slight rubbing sound. SO I took the washers off the caliper mounting bolts (they are thin ones) and put them on the back of the mounting bolts so the caliper moved slightly outwards and so the rotor was more centred.
Question: Is this the the kosher way to achieve a centered rotor? OR.....?? I do not sense there is a warped rotor and it is within thickness spec.

During this covid-19 period, it seems an ideal time to get these jobs done. I emboldened myself by taking on a rebuild of the Nissin caliper on the 1988 Honda NX250 and have now bought myself a Mityvac brake bleeder. I am still not happy with the honda's lever pressure. IF and only if these jobs go well and not cause too much extra stress, I think I enjoy working on the bikes more than riding at times. This work can be hard on my back if I don't organize my work space well though... at 73 yrs. of age!

[Bob_Roller]

From the factory the 'hat' spacer or flanged spacer that aligns the caliper, sits in the threaded hole to center the bolt .
The hole is larger than the bolt, thus the need for something to fill in the gap between the fork leg and the bolt .

[suecanada]

Hi there Bob! Well, try as I might, I cannot for the life of me understand your reply. That's never happened before   
I see no top hat spacer on the caliper, caliper mounting bolts and none show on the illustrated diagram of the front caliper Type B. The only top hat spacer I can think of is on the front wheel axle assembly!?

I must be losin' it??!  :-[Can you think of any reason that putting washers on the back of the 2 caliper mounting bolts as a way to move the caliper body away from the rotor a bit is not recommended? :-?

[georgesgiralt]

Hello,
I've no time to explain much. But see the picture of RealOem site.
The spacer we are referring to is part #4 in the picture. It exist various hat thicknesses to center the caliper on the rotor.
On the other side, the caliper position is fixed. You have to adjust the rotor by putting some spacers under the rotor bowl on the wheel.

[georgesgiralt]

Hum, missed...

[Luca]

I must be losin' it??!  Can you think of any reason that putting washers on the back of the 2 caliper mounting bolts as a way to move the caliper body away from the rotor a bit is not recommended?

the spacers for the RH caliper are nicely machined.  They fit inside the caliper mounting holes and the flanges space the caliper away from the fork.  If those spacers are missing and you were to use plain old washers to space the caliper you will have two issues

1) Plain washers are not nicely machined, so the fitment of the parts will not be as good and the caliper will be more prone to coming loose

2) those spacers also align the caliper fore/aft up/down by filling the larger holes of the RH caliper.  A plain washer will not do that.  Now you're relying solely on the clamping force of the bolts to keep the caliper from moving with the rotor when the brakes are applied: not good.

If the brakes were fine, you took them apart, and now there is an issue, I'd try to retrace your steps and see if you dropped something.  Those little spacers often stick in the caliper for a little while and then fall out when you aren't looking!

[suecanada]

Wow...ya learn something everyday! Little did I know anything about a top hat sleeve needed for only the right hand side Brembo caliper mounting bolt holes. These bolt holes are much bigger than the left hand side caliper mounting bolt holes!!! Who'da thunk it??!
In the 17 years I have owned LRB I have never noticed this or seen these or this top hat spacer... I gather there are 2 of them needed?? Correct?

Maybe my first winter (2004) working on the bike I missed them??? Thinking about how I usually work and try to pay attention, I really doubt they have gone missing in recent years. So....to be clear these spacers serve not only to fill up this big, oversized, mounting bolt hole properly BUT also to space the caliper over the rotor.? Thus, to make the flange (rim) part of this spacer work to space the caliper over the rotor, I would need the thickness of this flange to move the caliper outwards in my case...so I'd be putting it into the mounting bolt hole from the inside of the caliper to the outside?? Correct?
To choose a size of top hat spacer I will need,  I would guess I should measure any washer thickness that centers the caliper to my satisfaction...correct?

Boy, do I feel pretty dumb! :-? :-? :-?

[Kelvin]

No need to feel dumb: I wasn't aware of the spacers until I started reading this forum, and I've been removing the caliper since 1986! 

The spacers are of fairly soft metal, on my LS they've moulded to the caliper mount and don't fall out. Are you sure they're not still in place?

To check, ID on LHS is 10mm, ID on RHS is 12mm.

My RHS caliper is slightly off centre, 1.5mm clearance on the outside, 4mm on the inside (clearance rotor to caliper). I don't see this as a problem.

[suecanada]

So I measured the ID on the RHS mounting hole, Kelvin and it is 12mm like you say. Too big for the bolt not to slop around. So what spacer top hat do I need then? There are 4 to choose from. Like you, my the caliper was offset but just not enough as there was no clearance.from the rotor...kissing it a tad! That is not right.

[Kelvin]

From RealOEM it looks like they have 5 spacers:

https://www.realoem.com/bmw/enUS/showparts?id=0365-USA-08-1983-248-BMW-R65LS&diagId=34_0600

12      Sleeve      1,2      X                  34111238079      $8.25            
12      Sleeve      2,35      X                  34111238080      $8.25            
12      Sleeve      3,5      X                  34111238081      $8.25            
12      Sleeve      1,7      X                  34112301735      $4.60            
12      Sleeve      2,9      X                  34112301736      $4.60      

If it's kissing the rotor on the outside and there is 5.5mm free space on the inside then I'd go for 2.35mm, 34111238080.

[georgesgiralt]

Also, keep in mind that clearance is tight here. triple check that the disc rivet head are not grabbing the fork stanchion because they will cut metal on the stanchion which is aluminum...
Check the other side for the rotor to be centered too. If it is not, you have to remove the rotor from the wheel and check/change the fine "washer" put under it between the rim and rotor bowl. These are NLA so you may be forced to devise something if you need another.
Lastly, it is important before checking this centering thing that the wheel itself sit on it's perfect position. Check the two hat on the axe (the two tubes the lip seal rides on) for they state.  If someone, one day, over tightened the axe nut they could have split and/or be a little shorter than required (do not ask me how I know) and, thus, the wheel won't be centered in the stanchions...
A lot of tolerances pile up on this assembly and BMW took pride to have proper alignment on these part of the bike. Hence the parts for adjusting.
Nothing on a BMW bike (at least of that era) is done by accident. They are very well engineered with solutions which are either brilliant or elegant or both.

[suecanada]

No need to feel dumb: I wasn't aware of the spacers until I started reading this forum, and I've been removing the caliper since 1986! 

The spacers are of fairly soft metal, on my LS they've moulded to the caliper mount and don't fall out. Are you sure they're not still in place?

To check, ID on LHS is 10mm, ID on RHS is 12mm.

My RHS caliper is slightly off centre, 1.5mm clearance on the outside, 4mm on the inside (clearance rotor to caliper). I don't see this as a problem.

Just to be absolutely clear Kelvin. When you say to check that the ID on the RHS is 12mm do you mean this is how it should be? OR as it measures without the required top hat space/bushing which will take up the extra 2mm?? Right now the ID of the RHS hole IS 12mm...too big for the mounting bolt not to slop around.....so I need the spacer/top hat, I am concluding.

[georgesgiralt]

Yes you do. The NAKED caliper has 12 mm holes to accommodate the special spacer which reduce the hole size to the 10 mm the bolts are.
So if you caliper holes measure 12 mm dia, you miss the top hat special spacer... Is that clear ? 

[suecanada]

As a bell!!!!