Rear Caliper - Big drag - New pads

98 R1100RT

It was time for me to put new pads on the rear again, however this time when I went to do it the new pads create massive drag on the rotor. I can get them to ease off by pushing the caliper a little, manually forcing the pistons back in, but as soon as I brake, they drag really badly again.

I have cleaned the caliper 3 time already to no avail. When I put the old pads back on, I dont have the issue, but they are at the very very end of there life.

Also my rotor needs to be repalced, its @ 4.3mm (min is 4.5).

I was thinking about new rotor, new pads and rebuild the caliper. Any thoughts?

Also does anyone have a link to the caliper blown up, so I can see all the components?

Thanks in advance!

(Note: I had a front right caliper stick once, Its also documented on this forum, cleaning resolved that issue.)

https://shop.maxbmw.com/fiche/PartsFiche.aspx

98 R1100RT

 

It was time for me to put new pads on the rear again, however this time when I went to do it the new pads create massive drag on the rotor. I can get them to ease off by pushing the caliper a little, manually forcing the pistons back in, but as soon as I brake, they drag really badly again.

 

I have cleaned the caliper 3 time already to no avail. When I put the old pads back on, I dont have the issue, but they are at the very very end of there life.

)

Are the new pads, OEM or from a different vendor?

Do the two halves of the caliper move easily on the guide pins? If you don't know what I mean by that, I can describe it in detail or point you to a PDF that describes taking the caliper apart.

Don't split the caliper .

Don't split the caliper.

When was the last time the brake lines were replaced? Could very well be a clogged line that the fluid is able to traverse but then due to the clog it doesn't allow the pressure to back out of the line. Check out Chris Harris youtube vid selection, he has a video directly talking about this. Not saying that is the problem but it could be an additional area of consideration prior to revamping your caliper...

98 R1100RT

 

It was time for me to put new pads on the rear again, however this time when I went to do it the new pads create massive drag on the rotor. I can get them to ease off by pushing the caliper a little, manually forcing the pistons back in, but as soon as I brake, they drag really badly again.

 

I have cleaned the caliper 3 time already to no avail. When I put the old pads back on, I dont have the issue, but they are at the very very end of there life.

 

Also my rotor needs to be repalced, its @ 4.3mm (min is 4.5).

 

I was thinking about new rotor, new pads and rebuild the caliper. Any thoughts?

Also does anyone have a link to the caliper blown up, so I can see all the components?

 

Thanks in advance!

 

(Note: I had a front right caliper stick once, Its also documented on this forum, cleaning resolved that issue.)

Morning McDuugle

Usually 2 things cause a dragging problem like you are seeing. (assuming the caliper isn't all gummed up inside)

First, is that the master cylinder reservoir is overfull so forces the caliper pistons back out once they are retracted. (if you still have the new pads installed be careful opening the reservoir cover or you could end up with brake fluid all over the bike). There is a rubber bladder inside the rear master cylinder reservoir that can trap fluid pressure under it if overfull.

Second, some aftermarket rear brake pads are just a little to thick so won't allow proper brake rotor clearance when released. Back in the 1100 days I had a couple of occasions of too-thick rear brake pads so just installed one new pad & the thickest of the old pads. Then rode the bike a couple of thousand miles, then I reinstalled the other new brake pad without any further issues.

If you are careful you can live with the thinner rear brake rotor, one of the reasons of a minimum brake rotor thickness is so the caliper pistons won't extend too far out & cock with very worn brake pads. If you replace the rear pads before max wear then you can easily live with a slightly thinner rear brake rotor. The other reason is for a minimum thickness measurement is rotor warping but this usually isn't a problem on BMW boxer bike rear rotors. Plus if it would ever warp you would feel that in the braking so can replace it if that ever happens.

I like the brake line hypothesis. Re new rotor, when I replaced the rear rotor on my R1100RT, I decided to take a chance and source a Chinese rotor from eBay. It was indistinguishable from OEM, 20,000 miles later performs flawlessly.

Don't split the caliper .

Don't split the caliper.

 

Tri750, the rear caliper on the R1100RT separates into two pieces at the guide pins. Completely different than the front caliper. No seals or o-rings are involved.

Usually 2 things cause a dragging problem like you are seeing. (assuming the caliper isn't all gummed up inside)

.............

Second, some aftermarket rear brake pads are just a little to thick so won't allow proper brake rotor clearance when released. Back in the 1100 days I had a couple of occasions of too-thick rear brake pads so just installed one new pad & the thickest of the old pads. Then rode the bike a couple of thousand miles, then I reinstalled the other new brake pad without any further issues.

.......................

The EBC equivalent pads for the R1100RT has a known issue. The backing plate is just slightly larger at the top near the hole. When installed, this larger backing plate interferes with the caliper housing and the pad is stuck and will not move at all. It requires that the backing plate get filed down a little. Not a big deal, but a PITA considering that EBC sells these as replacement pads for the RT rear. I suppose there may be a variance among calipers and some folks can install EBC rear pads with no modification. The OP has not yet said what brand rear pads he used.

Thanks everyone for your input.

I usually buy GoldFren - Ceramic. This time I bought some other brand organic pads... Already ordered some GoldFren again....

Michaelr11 - The two halves move very well on the guide pins. The PDF on how to take the caliper apart would still be of use to me though

Selden - Will also get a "china" Rotor for the rear eventually. BTW have you found any economic alternatives for the front rotors?

jelake - Lines were replaced less than 15k mile ago with Galfer Braided SS lines.

dirtrider - 1- Took fluid out of reservoir to make room for the new pads.

2 - The pads do look thick, will try to replace one first and see if there is still drag.

Will report back once I have tested this.

Didnt work. Massive drag with both new pads, semi massive drag with one new one new one old, and slight drag with both old pads.

Bled the system, no change.

McDuugle,

You may have some crud from the OEM brake lines still in the caliper passages. This is what locked up my front wheel a year ago. Lots of black rubber pieces in the passage between the halves of the caliper acted like a check valve, letting DOT4 in but not out of the caliper. Also, bleeding and/or replacing the brake fluid in either front or rear brake system will NOT clear the caliper passages or pistons, neither will removing the pistons clear the passage between the caliper halves. The passages and pistons are on a dead-end in the bleeding circuit - the bleed nipple is connected directly to the brake line next to it.

EDIT: Try pushing the pistons back into the calipers until they are flush with the inside face of the calipers with the brake pads removed. Wood wedges (like door frame shims) work well. If one piston pushes OUT when you push the one beside it IN, you may have a plug in the passage between the halves. If you can't wedge all four pistons back in (the reservoir may overflow), there may be a blockage in the line or in the caliper.

I completely disassembled all three calipers (front and rear) before replacing the OEM lines with Spiegler Teflon/SS lines. Yes, I know the BMW lawyers say "do not disassemble", but they are MY calipers and I'll do it if I want to. These calipers are much less complicated than a manual can opener, so, DO NOT ATTEMPT this if you cannot operate a can opener.

All of my piston seals and the O-ring were as-new and reinstalled, no problem. The O-ring is a square section, about 1/4" dia that sits in a recess in one of the caliper halves. It is the easiest O-ring you will ever do. There are two pistons in each caliper half on the front brakes. Each piston is a different diameter and there are two rubber seals for each piston, an inner and an outer (with a groove). Disassemble each caliper half one at a time, clean and reassemble before moving to the next. I just left the cyl seals in place, blew out the passages and wiped the pistons and calipers thoroughly. See pics. Front caliper disassembly R1100S

If you need Brembo parts, try Munich Motorcycles and Centric Parts.

The only issue I had was trying to find the torque values for the four caliper bolts. Ended up using values for M8 bolts in aluminum for other parts, don't remember what they were.

This is the crud locking up my front wheel, stuck in the passage between the caliper halves:

Didnt work. Massive drag with both new pads, semi massive drag with one new one new one old, and slight drag with both old pads.

 

Bled the system, no change.

Afternoon McDuugle

That is sort of pointing to a brake pad problem like pads just a bit too thick or pad backing plates not fitting perfectly.

As long as the rear master cylinder take-up port is open then bleeding should have no effect on your problem either.

It really doesn't sound like a line blockage or caliper blockage either as both of those would give you a massive drag even with the worn pads reinstalled & then only after applying rear brake pedal.

Do your new brake pads have a thick anti squeal coating on the rear of pad backing plate? If so the maybe it will take a lot of brake pressure & possibly a little riding to seat the anti-squeal material into the caliper piston (especially if your caliper pistons have the center filled with a filler cover). Or scrape some of the anti-squeal material off before installing (assuming your pads have that on them)

I really don't have much to give you but if it were my bike I would probably just install one new pad, & one old pad then ride the bike a very short ways to see if riding will free it up & seat the new pad enough to allow a lower spinning wheel brake drag.

After riding a short ways allow brakes to totally cool then ride it again a short ways WITHOUT using rear brake then stop to see how hot the rear rotor is getting. If not too hot then you can probably ride it enough to seat the pads then work OK. If way too hot then you will have to go back in & reevaluate.

Update!!!

No solution yet.

Installed new pads and rotor. The pads are the ones I have used in the past and have never had issues with.

Drag is still pretty strong... heat seams to be most prevalent on the pad on the piston side. Don't know if that normal.

I have ss braided lines, it looks like the back tire was rubbing on it... but damages looks like it's isolated to the ear plastic outside of the line.