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shim out rear brake disc - what can go wrong?

Posted: Tue Sep 08, 2009 7:29 pm
Author: 02GF74
righty ho, did some measurements on my rear disc (Z1000 A1) and run out is 0.5 mm (Haynes say 0.3 mm max) and it is dished, gotta be close to 1 mm between inner and outer surface :shock:

anyways, got a replacement, run out is 0.18 mm and no dishing to note ..... but when fitted, the disc is not central in the brake caliper slot - it is too close to the inner side. (original disc was too close to the outer :?? )

To get round this, I can put in a 0.5 or 0.7 mm shim between the hub and disc. I cannot see any issues with this as the disc carrier will still have lots of overlap over the raised hub section to be centralised plus the disc will be clamped up tight as before.

So what do the Z1 owners collective brain think?

The alternatvie is to true the rear caliper or replace it in the hope that a replacement fits.

Any other suggestions????

Posted: Tue Sep 08, 2009 7:31 pm
Author: 02GF74
.. oh, forgot - one of the pistons appear to be seized argghhhh so looks like I'm gonna have to take it apart AGAIN!!!!!

What paint to people use - satin black? not looking for 100% originality but don't want it to look wank either.

Posted: Tue Sep 08, 2009 7:48 pm
Author: tlc
Always used the PJ1 satin VHT before.

Good colour :D

Posted: Tue Sep 08, 2009 9:11 pm
Author: Pigford
OK.. so my first choice would be to remove the offending item & bin it :!:

But, a nice little shim is just the job for this sort of adjustment. As long as it fits nice & snug to ensure heat transfer is good :wink:

Dished disc

Posted: Tue Sep 08, 2009 9:53 pm
Author: DAVE LEWIS
Hi All I had a front brake disc on my A4 that was so concaved it was obviously scrap, but a friend of mine said he could fix it as he worked for a shot peening company.

Well he hit it with ball bearings and the disc is perfectly true and has been now for 6 years so there are ways round these things so don't just chuck them in the bin.

(Although dose help if you have a mate who works for a shot peening company)

Dave L

Posted: Wed Sep 09, 2009 8:26 am
Author: Taffus
Pigford wrote:OK.. so my first choice would be to remove the offending item & bin it :!:

But, a nice little shim is just the job for this sort of adjustment. As long as it fits nice & snug to ensure heat transfer is good :wink:

Only one brake on the back, so if you remove that.......... Don't think you'll get spanners for that solution :D

Posted: Wed Sep 09, 2009 12:35 pm
Author: 02GF74
Pigford wrote:OK.. so my first choice would be to remove the offending item & bin it :!:

But, a nice little shim is just the job for this sort of adjustment. As long as it fits nice & snug to ensure heat transfer is good :wink:


yeah, but it is not as if you can buy rear calipers readily, certainly don't have them in my local Tescos ... and then there is the price.

good point about heat trasnfer although rear disc isn't gonna get as hot as front but using aluminium and a smear of thermal past should sort it.

I will have a go at hitting the caliper to see if I can persuade it a bit over but suspect tht isn't gonna get me far.

Posted: Wed Sep 09, 2009 7:47 pm
Author: 02GF74
02GF74 wrote:
I will have a go at hitting the caliper to see if I can persuade it a bit over but suspect tht isn't gonna get me far.


... surprisingly that did help; block of wood, big hammer a big few whacks has mooved it in maybe 1 mm at most. Not sure if alloy has a "memory" but will see in a couple of days if it sprtings back.

Posted: Thu Sep 10, 2009 9:00 am
Author: paul doran
Pigford wrote:OK.. so my first choice would be to remove the offending item & bin it :!:

But, a nice little shim is just the job for this sort of adjustment. As long as it fits nice & snug to ensure heat transfer is good :wink:



yeah well We have all seen Your effort's when it comes to brakes :lol: :lol: :lol: :lol: :lol: :lol: :lol:

Posted: Thu Sep 10, 2009 6:09 pm
Author: Rich
Isn't it twin opposing piston on the back? 0.5mm off centre shouldn't make that much difference. If it does shim / skim the spacer / check the bearings are located correctly.

Posted: Sat Sep 12, 2009 10:44 am
Author: 02GF74
yes it is.

all back together and all is good, no drag like before. :lol:

charging up the battery as I write to fire it up ....... :arrow: