Also serves as a handy guide on what to do if the head of a hex bolt etc… is worn away. Hopefully this is pretty similar for changing the rear discs for most bikes.
First of all the tools you will need to do the job will be a decent ratchet handle/ socket set, with standard metric (maybe imperial depending on bike) square, hex and 6 spline torque sockets. You’ll need sizes ranging from 6 to 12mm generally along with a couple of larger ones for the rear wheel spindle. You’ll also need a couple of breaker bars – a small one, say 8 inch, and a larger one, either 18 or 24 inch. to go with these you’ll also probably need a couple of converters for the sockets: 1/2 inch to 1/4 inch probably. You’ll need the larger bar for the rear wheel and the smaller is in case of stiff bolts. Finally you’ll need a rubber headed mallet – just in case you’re reading this and the bolt head is worn, more explained later on. You may also need a flat headed screwdriver or something to open the brake calipers up a bit to fit the new disc – or you can take the caliper apart to do this.
Parts wise, well you’ll need a replacement disc and some blue Loctite Threadlocker (or something similar) and thats it.
I’d also recommend doing this in a nice cosy garage and not out in the icy streets of London because what was meant to be a 30 minute job took longer than anticipated and it was really fucking cold! Also having 2 people doing this is much easier – especially for when you want to refit the wheel.
Here’s my step by step guide:
Stage One: Remove the rear brake caliper
Firstly get your bike on the centre stand or if on paddock stands if your bike doesnt have one. You can see why the disc needs refitting, its rusty and warped, if you look close enough you can see just how worn it it. To remove the caliper just undo the bolts holding it in place and you can leave the caliper to dangle off the swingarm. You may need to wiggle and tease it a bit to get it off of the disc.
Stage Two: Remove the rear axle
You’ll need a 18-24 inch breaker bar probably to get enough leverage to loosen the bolt and its handy having a second person to hold the nut in place on the other side and to support the rear wheel.
Stage Three: Remove the rear wheel
With the axle remove you can begin to ease the rear wheel out, look out for the spacers either side of the wheel that may drop off. They’ll be different sizes so remember their position – take a photo to remind you if unsure. The caliper plate/ holder will also probably fall out as well as depending on how its fixed. In the case of this bike its held in place by the same bolts that hold the caliper on which also bolt it to the swingarm. Remove the sprocket from the chain and sit the wheel down on an old blanket with the disc brake facing up.
Stage Four: Remove the disc
Slacken off the bolts holding the rear disc in place and remove them.
Stage Four still: Oh shit this one wont come out
The bolt head has worn away too much to get a good grip to loosen the bolt. To get around this using a rubber headed mallet, get a slightly larger socket and hammer this in to the socket. Rotate the wheel around periodically to ensure the socket is hammered in equally to avoid it being wonky. The bolts on this brake are hex, so using a 6 splined socket works well, hammering it in won’t damage the socket as the bolt is a softer metal. It will take at least 20 minutes to hammer it in well enough for it to get a grip, if you don’t hammer it in enough you’ll wreck the bolt and cause more hassle. Tap it in all the way to the depth of the original hole to be sure.
Stage Four: The socket hammered in
Stage Four: Remove the pesky bolt
Using a smaller breaker bar try to ease the bolt out, you should find that it will shift now that the socket has grip. If you use a large bar, it’ll probably wreck the bolt head.
Stage Five: Fit the new disc
Place on the new disc and apply Loctite blue Threadlock to the threads of the bolts – not the base, just the thread. tighten the bolts until you feel resistance. Then work around each bolt as per your manual to tighten them to the correct setting – or just until it feels right I guess.
Stage Six: Refit the rear wheel
Now fit the rear wheel, its really handy having a second person to help support the wheel. First fit the chain on the sprocket, then attach the spacers and the caliper holder. The next trick is to get everything inline as you push the rear axle through and it may take a while!
After this then you’ll need to refit the caliper, this may be a struggle as was in this case as the disc had worn away so the caliper needed to be opened up more accommodate a thicker disc. You can take the caliper apart or force the plates apart using something flat.
The old disc
Check it out, no wonder the rear brake didn’t work to well. You can’t see it but the brake disc is also warped as well as heavily worn away.
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