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Rear disc warped

 
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Bazsm
Big Brick Rider


Joined: 09 Aug 2021
Posts: 52
Location: Hayling Island, UK

PostPosted: Wed Jul 27, 2022 8:46 am    Post subject: Rear disc warped Reply with quote

My bike just failed it's MOT with a warped rear disc which was news to me!

I can get a new EBC disc without the ABS ring so can anyone tell me if the ABS ring is an easy home removal job or is it one of those things it's easier to get the garage to do? I'm hoping it just unboolts but in the back of my mind I'm thinking it might be an interference fit.

TIA
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Flying Duck
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Joined: 27 Jan 2005
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PostPosted: Wed Jul 27, 2022 11:14 am    Post subject: Reply with quote

It's kind of a pain to get ABS ring off of the rear rotor but it is doable at home. You need to work your way around it slowly backing it off.

It can also be tough just to get the rear rotor off of the final drive.
http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/rear.rotor/rear.rotor.htm
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Bazsm
Big Brick Rider


Joined: 09 Aug 2021
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Location: Hayling Island, UK

PostPosted: Wed Jul 27, 2022 3:00 pm    Post subject: Reply with quote

Great advice as always so much appreciated Smile

I have some Facom bits that will work with a T bar so will start there and the wheel still on the bike as you suggest, is an impact driver worth a try?

Is the ABS ring just held by those 3 bolts and very tight - I read somewhere that putting the disc and ring in the freezer might help but I usually go with the heat method if I can!
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Flying Duck
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PostPosted: Wed Jul 27, 2022 7:33 pm    Post subject: Reply with quote

I don't have any really good hex bits so have never tried using an impact driver. It might help though.

When I've removed rear ABS rings I've done it at room temperature. Never tried heating or cooling.
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93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
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Grunter
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Joined: 30 Sep 2015
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Location: North East England

PostPosted: Thu Jul 28, 2022 2:53 am    Post subject: Reply with quote

Flying Duck wrote:
I don't have any really good hex bits so have never tried using an impact driver. It might help though.

When I've removed rear ABS rings I've done it at room temperature. Never tried heating or cooling.


As you are in UK, try Halfords (Yes I know some people think they are more of a toy shop) but ask to see their range of professional tools. I recently bought a rack of 3/8" drive hex bits which range from 2mm up to 10mm.
The quality is really impressive. They fit all the Allen screws I come across without any 'wobble' or loose fitting.
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Bazsm
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Joined: 09 Aug 2021
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Location: Hayling Island, UK

PostPosted: Thu Jul 28, 2022 8:50 am    Post subject: Reply with quote

Grunter wrote:
As you are in UK, try Halfords (Yes I know some people think they are more of a toy shop) but ask to see their range of professional tools.


Halfrauds have their place Smile, in fact I do have 2 of their Pro sets and agreed they're good quality but I have a couple of 1/4" Facom sets which are really innovative and ideal for getting into nooks and crannies on bikes and cars.

I won't be using the 1/4" drive on the back wheel of course and will report back.
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Bazsm
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PostPosted: Sat Jul 30, 2022 11:26 am    Post subject: Reply with quote

Good news, the 2 bigger allen bolts loosened with a good quality allen key on the end of a breaker bar, tried the impact driver but it didn't seem to help which tbh is very unusual. Old and new disc both in the freezer in the hope the ABS ring comes off much easier (I didn't attempt to remove yet).

Cleaned up the area behind the disc, should new disc be fitted dry or put some kind of anti seize between disc and hub? I guess the brown ring is just a tad rusted:



New EBC disc looks very nice quality and cost £160 Sad



New pads also ordered!
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Grunter
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PostPosted: Sat Jul 30, 2022 2:12 pm    Post subject: Reply with quote

These are usually held on with a thread lock that breaks down if you use a bit of heat before trying to unscrew them.

The last one I did was on an R1100RT - not much different from a K1100 as far as the brakes go. If you don't like the idea of using a naked flame on the heads of the bolts I have used the highest setting on an electric paint stripper you need it hot enough so if you spit on it there is a distinct hiss.
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Bazsm
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PostPosted: Sat Jul 30, 2022 6:30 pm    Post subject: Reply with quote

Removing the ABS ring was relatively easy but did make a lot of noise! I don't think the trim removal tool I used is gonna be quite so useful in the future but it was ideal for this (along with a big hammer):



I'll clean up the inner edge of the ABS ring which looks a bit crusty and possibly use some fairy liquid as a lube to help it slide onto the new disc
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Last edited by Bazsm on Sun Jul 31, 2022 1:24 am; edited 1 time in total
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Flying Duck
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PostPosted: Sun Jul 31, 2022 12:36 am    Post subject: Reply with quote

Just don't put the ABS ring on backwards on the EBC rotor. (joke)

I'm envious that you got the rear rotor off so easily. I've only had such luck a few times.


no need to worry about ant-seize or whatever when installing the new rotor.
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93 LT (x2)
94 RS
86-97 K75F(K75/100/1100 Frankenbrick)
86 K75C w/paralever, hi perf cams,TURBO!
91 & 92 K75Ss
91 K1
86 custom K100
14 WR250R
IBA #17739 (SS1K, BBG, 50CC)
Buy parts HERE
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Bazsm
Big Brick Rider


Joined: 09 Aug 2021
Posts: 52
Location: Hayling Island, UK

PostPosted: Sun Jul 31, 2022 1:29 am    Post subject: Reply with quote

Flying Duck wrote:
Just don't put the ABS ring on backwards on the EBC rotor. (joke)

I'm envious that you got the rear rotor off so easily. I've only had such luck a few times.

no need to worry about ant-seize or whatever when installing the new rotor.


I did look at whether the ring is reversible but have been very careful to keep it in the same orientation it came off as that is the kind of thing I might do!

I'm not planning to do this job again so first time lucky makes a change for me, and thanks for confirming the disc goes back without any kind of grease etc Smile
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Bazsm
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Location: Hayling Island, UK

PostPosted: Sun Jul 31, 2022 4:09 am    Post subject: Reply with quote

Just popped out to the garage, wire wooled the inside of the ABS ring as there was mild corrosion in places.

Removed the new disc from the freezer and the ABS ring literally dropped into place and within 5mins of getting back to temp was tight. I'd left the disc in the freezer overnight which might be overkill but it made the aluminium carrier shrink enough to make this a doddle - hope that helps someone in the future.
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Bazsm
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PostPosted: Sun Jul 31, 2022 5:59 pm    Post subject: Reply with quote

All back together but disc was pretty hot after a short ride Sad

I did think the new pads & disc were a bit snug but there's no scope to push them further back into the caliper, brake fluid is midway between high & low and the brake pedal has some slack so I'm out of ideas how to reduce friction:



I might re-fit the old pads that were minimally worn but would introduce a bit of free space between disc & pads!
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Scott_Anderson
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PostPosted: Sun Jul 31, 2022 9:36 pm    Post subject: Reply with quote

the "free" space will only be there until the 1st time you apply the brakes. If they are not retracting, it's possible you need new seals in the caliper, or you need to clean the master cylinder to help release fluid pressure when the pedal is released.
The seals are what "retract" the pads when not braking. The pads will normally "touch" the disk but they should not cause "drag" on the disk.
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Bazsm
Big Brick Rider


Joined: 09 Aug 2021
Posts: 52
Location: Hayling Island, UK

PostPosted: Mon Aug 01, 2022 1:25 am    Post subject: Reply with quote

Scott_Anderson wrote:
The pads will normally "touch" the disk but they should not cause "drag" on the disk.


I agree the pads should be very close to the pad but not touching to the point that they're generating a lot of heat. Never come across this before where I couldn't retract the pistons any more to create some genuine free play before first application, so will keep an eye on it for the first couple of rides
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