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F800GT front brakes

LuciferMutt

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These brakes are weird to my eye. Four piston brembo calipers on each side that are rigidly, axially mounted

But the discs are rigidly mounted to the wheel too -- just bolted right on to the hub This confuses me -- I've never seen anything like this before. I've had a Ducati with a radial-mount brembo caliper but the disc floated on bobbins so it could compensate for slight misalignments between the disc and calipers.

How does the braking system on the F800 account for misalignments? Surely if one set of pistons in the caliper is slightly dragging and doesn't push out as far as the opposing set, you're going to have issues with the brakes?

The reason I ask is that my new-to-me F800GT has pulsating front brakes....the first thing I wanted to do was clean and lube the caliper slider pins, only to find out there are none. Then I wanted to clean and lube the bobbins -- only to find there are none! The pulsating has improved a bit after using the brakes really hard a few times, but it seems worse when the bike is cold. Other suggestions? Bike has 24K miles on it and the pads look newish, but I think they are the original discs.
 

kickstandsup

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The calipers are fixed, but the disks are actually floating...BMW does it differently than Ducati (and most others). The bolts that hold the disk to the wheel have thrust washers and spring washers that allow the disk to move slightly. BMW recommends replacing them when the disk is removed.

In my experience, front disks can easily get bent if someone is not careful changing a tire, or just taking off a wheel and laying on the ground.

A suggestion: First, loosen all the disk retaining bolts in a criss/cross pattern, then re-torque to specs, again in a criss/cross pattern. 19 Nm. See if that fixes it. If not, then I'd try replacing all the washers before replacing the disks.

If you've got measurement equipment, the minimum thickness is 4.0 mm, and the maximum runout is 0.15 mm.
 

LuciferMutt

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Thanks for the tips. Ive been looking at parts fiches and am more confused. There seems to have been an update that BMW calls the "rivet pack" for the front disc. I was thinking about maybe replacing just the disc mounting hardware -- the screws and wavy washers, for example, but I can't seem to find them in parts fiches, just a "rivet pack" which is the whol brake disc, with what appear to be different bobbins where the screws go. Now I'm really confused. Was trying to avoid it but this might require a visit to the dealer. Ah the joys of sorting out a used motorcycle...
 

kickstandsup

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Thanks for the tips. Ive been looking at parts fiches and am more confused. There seems to have been an update that BMW calls the "rivet pack" for the front disc. I was thinking about maybe replacing just the disc mounting hardware -- the screws and wavy washers, for example, but I can't seem to find them in parts fiches, just a "rivet pack" which is the whol brake disc, with what appear to be different bobbins where the screws go. Now I'm really confused. Was trying to avoid it but this might require a visit to the dealer. Ah the joys of sorting out a used motorcycle...

Wondering if you've solved the brake issue?

Wunderlich sells replacement front rotors if you decide you need to go that route.

 

LuciferMutt

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Wondering if you've solved the brake issue?

Wunderlich sells replacement front rotors if you decide you need to go that route.

I sure haven't, but I haven't put a ton of time in it yet -- just cleaning and checking the discs and bobbins, which all seem to be "fine." I haven't put a dial indicator on the rotors yet, but I did a visual comparison with a fixed object and I can't see any variation. The pulsing at slow speeds makes coming to a smooth stop with the front brake very difficult. The forks actually bob up and down. At high speeds, I feel rapid vibrating when I use the brakes hard.

The problem is much worse when the bike is cold and the brakes haven't been used in a few days, but it never goes away. I've read a ton of posts on F800riders.org about people with similar problems who eventually gave up and just replaced the rotors with aftermarket and didn't have any more problems.

I did see those Wunderlich Lucas rotors, but it's not clear to me if they come with the necessary mounting hardware, which I believe should also be replaced.
 

LuciferMutt

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Looks like Galfer has a full stock on GT brake parts. I think I'm going to give their wavy rotors a try -- same price as the round version, and at least appear to come with new bushings. $165-195/ea depending where you look. Supposedly part# DF707W is the correct part per Galfer's own website here https://galferusa.com/moto/product/96943/DF707W, but Denis Kirk says the DF707W they sell is NOT compatible with the F800GT. I hate this shit. I should probably call Galfer and make absolutely certain.
I see this same part # on Ebay for $165 but that makes a bit nervous. One review says it comes with all the hardware.
 

kickstandsup

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Looks like Galfer has a full stock on GT brake parts. I think I'm going to give their wavy rotors a try -- same price as the round version, and at least appear to come with new bushings. $165-195/ea depending where you look. Supposedly part# DF707W is the correct part per Galfer's own website here https://galferusa.com/moto/product/96943/DF707W, but Denis Kirk says the DF707W they sell is NOT compatible with the F800GT. I hate this shit. I should probably call Galfer and make absolutely certain.
I see this same part # on Ebay for $165 but that makes a bit nervous. One review says it comes with all the hardware.

How does that compare to the stock BMW parts?

FWIW, if you replace the rotors you might consider replacing the pads at the same time so if there is any issue with the old pads they won't contaminate the new disks, which then starts the cycle again. Or at the least, sand the old pads down a bit and perhaps chamfer the leading edges.
 
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LuciferMutt

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How does that compare to the stock BMW parts?

FWIW, if you replace the rotors you might consider replacing the pads at the same time so if there is any issue with the old pads they won't contaminate the new disks, which then starts the cycle again. Or at the least, sand the old pads down a bit and perhaps chamfer the leading edges.
OEM discs from BMW are $390 EACH!

Yeah, I'll probably do the pads too just to make sure everything is fresh.
 

kickstandsup

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OEM discs from BMW are $390 EACH!

Yeah, I'll probably do the pads too just to make sure everything is fresh.

Ouch.

The GT is very popular in Europe, as is the whole F800 series. Might check the Euro Galfer and other sites for parts numbers and compatibility. I would not trust Dennis Kirk, YMMV.
 

kickstandsup

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Wunderlich also as a different cut front rotor


As you can see from their web address, it is the same rotor as the R1200 and R9T, FWIW.

In my experience, they get the parts right.

Edit...and others like the RS and RT. They also sell an "install kit" that has the correct bolts, washers, bobbins...
 

18415

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Somewhere on ADVrider there is a site that is out of Italy that sells Brembo components at a really affordable price. I thought I had saved the site but I can’t find it. Im trying to dig for you. Maybe that will jog someone’s memory on here.
 

LuciferMutt

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Well, after more wasted time cleaning, sanding, and checking my stock discs, as well as checking the front wheel bearings and calipers, etc, yesterday to no improvement, I just pulled the trigger on Ebay this morning for a set of 2 Galfer DF707V discs which include new bobbins, wavy washers, and flat washers, shipped from the UK for ~$350USD. There is a seller on there (calsport-1) with a huge listing of Galfer discs for many BMWs. The DF707 is shared among a large number of BMWs from the F800 to the K1600 to the R1200R. The DF707V is the standard round rotor -- I decided to not try the wavy rotors, since Galfer's website said the 707V is a "seamless replacement" for the stock items.

Should be here in the first couple of weeks of April, I'll update then.
 

LuciferMutt

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Woah...guess what arrived yesterday! Those folks in the UK got those brake discs shipped to me faster than a lot of places in the US ship stuff. Ordered Sunday, arrived Wednesday. I was NOT expecting to get these so fast...they are here so soon I haven't even decided on what new brake pads to use with the new discs. I want something as close to OEM as possible to ensure zero squeal and long rotor life (organic I think?) but it seems Galfer no longer has an organic pad. The OEM BMW pads are, of course, three times more expensive than other options, so what are the BMW guys running for brake pads these days?
 

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