BMW K bikes (Bricks)

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purkolator

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So, on the way home tonight, I notice that the rear brake is dragging a bit and the pedal feels stiff. Pull over, up on center stand, spin rear wheel... Plenty of resistance but not locked, bit of a burny smell :/ Call wife... Rearrange child pick up, let brake cool... And release... Ride 5 miles with only front brake (glad it wasn't the other way around). Swear a bit...

So... $30 or so for rebuild kit for caliper and $60 or so for master cylinder rebuild kit. Should I spring for both right away or is the caliper likely the culprit. As i'm writing this I'm thinking $90 isn't such a dear cost to be sure that the rear brake will work, but I suppose I'll leave the question open for scholarly purposes.

Any other advice for a rear brake rebuild?

Thanks in advance...
Brad

    

purkolator

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I'll spring for new pads as well, obviously.

B

    

Guest

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I had a similar issue last week. First I bled the system until the new brake fluid came out clear and free of any sign of bubbles. Then I unbolted the caliper from the final drive and pressed the pistons back into their bores, then slipped some new pads in as the old ones were a bit thin, though not entirely worn out. I reckon the pistons had reached that point where the 'crust' that builds up in the bores was hanging them up. Now with the new pads, the pistons further back in their bores, and a good old fashioned bleed, she's back spinning freely and I've covered at least a thousand kilometres over that time (a week) and all's well.

What did it cost? A new set of Ferodo pads for a bit over $20, and a 500ml bottle of brake fluid from the auto parts store for about $12. Cheap and effective. Give it a go before you start taking things apart. Oh, I did locate a used K1100 rear caliper on eBay (same design, removed the ABS bracket) and grabbed it for under $29 including postage from Melbourne. I've cleaned it up and it's ready to go should it turn out to be that the original caliper is stuffed. The rear master cylinder seemed to be working fine, not hanging up at all.

    

purkolator

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OK, followed your advice TWB... went out and got some DOT4 and a set of pads. Bled the crap out of the system (nearly 2 resevoirs pumped through) and then installed the new pads. Found I had to prop the final drive and partially remove the bottom shock mount to get the 2nd pin out (progressive shock so maybe bigger than stock?), but all worked out fine and seems to be working well so far. I'll take a bit longer test drive this weekend to be sure it doesn't bind any more, but it seems to be sorted.

thanks!
B

    

Guest

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I'm glad that it seems to have worked for you too. Keep an eye on it so you don't cook your rear brake disc, which are expensive if you also have to buy seal kits later on for the master cylinder and caliper. Mine's not playing up at all any more after two weeks now. I have to say that the two small pieces of stone with road tar that I pulled out after I'd unbolted the caliper probably had a bit to do with the dragging. It sounds to me like you slipped the pads in without removing your caliper? I hope you were able to push the pistons all of the way back in and that you got any debris out of the way.
Cheers.

    

purkolator

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I did pull the caliper off, then slid the old pads in and used a little wedge of wood in between to move the pistons back in. Have to be careful to push evenly on all sides so the piston doesn't get bound. Wiped the inside of the caliper out as best I could, the blew it out with air, then cleaned up the mess of brake dust with a towel, used a bit of brake cleaner on the disc and put her all back together.

Like I said, I've yet to take ride more than a few blocks or so to test, but I hope to be able to do that tomorrow and will be keeping a close eye (and the occasional hand) on that rear disc.

thanks again,
Brad

    

Guest

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LOL...mine was so hot when I stopped that the centre of it had turned blue! I didn't have to get my gloved fingers too far from it to feel the intensity of the heat. But I reckon I caught it in time. There's the slightest of scores in the centre of the disc all the way round, but with the things I've done (just as you have) she stops like she should once again. Hope she's a goer for you. Good onya, mate!

    

walker

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Pistons were sticking when mine did this. A lot of BrakeCleen and then some simple green with a toothbrush did it.

    

Agerbundsen

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It's your behind on the line, so I would make sure it was a complete fix.

    

walker

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Sound advice Ager.

Thanks

walker

    

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