Greggers
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Well, you know what I mean!I decided it was time to replace the rear pads as I'd noticed that they were down to their last micron...
For anyone who's not done it, the job itself is fairly straightforward - requiring the rear wheel to be dropped to get good access to the caliper. I must apologise in advance for not taking pictures of the pad replacement itself (yet anyway) cos I've only just decided to try and do a write-up for it, so hopefully it'll be clear enough as explained! I can post a step by step guide with pictures next week if anyone thinks it's worth it ...
Tools needed - 24mm socket for the axle bolt, T30 torx bit for the ABS sensor bolt, needle-nose pliers for the 'R' clip, blind punch, small hammer and some copper grease.
Ok - while the wheel's out check the wheel bearings for roughness or any other nastiness, and don't lose the spacers or the axle nut/washer. For safety's sake I decided to remove the ABS sensor, and taped it up out of the way. The first 'problem' you're likely to encounter will be pressing the pad retaining pin out. As the pads were being replaced I wasn't too worried about oil contamination, so I squirted the area generously with penetrating oil, obviously DON'T DO THIS IF YOU ARE RE-USING YOUR PADS!!
You'll need to remove the retaining 'R' clip first, but once it's out you can push the pin through the caliper from the outside (from the disc side towards the hub) with a blind punch (that's one without a point on it) and small and gentle hammer tapping. If you haven't got a punch, then grind the point off a masonry nail ... Once the pin's out, the pads will fall down out of the caliper - look at the heels of the pads to see how they locate in the caliper. It's really easy when you look at it. Find the pin then take a few minutes to clean the crud off it and give it a light smear of copper grease
Now, use a tyre lever or similar to push the caliper piston back into the cylinder, you can use a G-clamp too if you're careful, to give you enough room to install the new pads - they will be a lot thicker than the ones you're replacing! Once the piston is retracted you can clean up the caliper if needed (mine was dusty but clean enough so I didn't do anything) and install the new pads. Get them oriented properly and smear a little copper grease on the back of the pads - KEEP YOUR GREASY FINGERS OFF THE PAD SURFACE - this is supposed to help prevent brake squeal, but the BMW piston has a plastic cover on it so I don't really know if greasing will prevent any noise... With the pads properly oriented slip them into the caliper, making sure the heel of the pad locates properly in the caliper. Don't loose the little steel slipper on the caliper, it should be a tightish fit, but can sometimes get unhooked and fall out. Once they're in re-install the pad retaining pin and gently tap it home. Use your tyre lever again to make sure the pads are fully pushed back into the caliper as it can be a bit of an arse getting the disc between them otherwise. Take this time to clean off the caliper retaining lug on the swing arm and the corresponding slot in the caliper arm, as well as the inside faces of the swing-arm. A smear of copper grease in all these places will keep things moving smoothly.
Before refitting the wheel, give the axle a wipe over to clean off any shite, then smear lightly with copper grease. This will assist future removal and minimise the risk of the axle seizing in the bearings which has been seen before...
Refitting the wheel can be a bit of a juggle - the sprocket plate can tip over and unless you have the spacer properly seated and square its top edge can snag on the axle hole on the swingarm making it difficult to get it all properly square. Start with installing the axle enough to hold the caliper arm in place. Then lift the wheel into place, making sure the disc slips between the pads and at the same time trying to keep the sprocket carrier square on the wheel. Push the axle into the wheel - this will let you play with the sprocket side to get everything aligned. DON'T PUSH THE AXLE ALL THE WAY IN YET as you need some slack in the chain to be able to slip it back onto the sprocket. Once the chain's on, pull the wheel backwards so that the adjustment plates sit on the adjuster screws again then gently tap the axle into place. Re-fit the sprocket side adjuster plate, jiggle the wheel until it's right then tighten the axle nut to 90 Nm torque.
We're nearly there now! Refit the ABS sensor and tighten gently - spin the wheel a couple of times to make sure its rotating freely and there are no odd noises. Pump the rear brake lever a couple of times to seat the pads and you're finished.
I have a couple of observations from my job this afternoon….
1) My old pads were properly fukked, I’m embarrassed to say that I know I should have done them a while ago, but just kept putting it off – don’t make the same mistake, it could be costly!
2) Check the routing and condition of the ABS sensor wires –
I found that mine are in perilous condition having been resting against the caliper which has got so hot at some time in the past that the cables and sheathing have melted – I will have to replace these in the not too distant future, and will use a heatproof sheath where the cable passes over the caliper to protect it and prevent it happening again. I might also pass this onto BMW as well. It might be wise to check yours too.
3) I saw that the axle spindle appeared too long! Unless I’ve done something cataclysmically stupid (it doesn’t happen often!) I can’t see why or where I’ve gone wrong. I hope the pics will show what I mean… At the threaded end of the axle there is a chamfered section, but this section protrudes through the swingarm and prevents the adjustment plate from sitting flat.
I’ve never noticed this before and in the past have just tightened the nut up … But this time I thought I’d do something about it. I whipped the plate off again, and using a die grinder chamfered the inside face of the adjuster plate
to accommodate the chamfer on the axle. It seems to work, and everything sits nice and flat now.
I tightened everything up and spun the wheel before seating the pads – all was free and ok, so I donl;t think there’s a problem … it would be interesting to see if anyone else had a ‘long’ axle !
Thats it for now - I'm riding tomorrow!
Let me know if you want a proper picture post!
Happy Spannering!!
Greg
