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Newer Shimano disk brakes replacing older Avid brakes

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Newer Shimano disk brakes replacing older Avid brakes

Old 06-01-21, 01:19 PM
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black_box 
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Newer Shimano disk brakes replacing older Avid brakes

I've got a 2010 Gary Fisher x-caliber (just before Trek bought them) that came with Avid Juicy 3 brakes and 185mm rotors up front, I think 160mm in the rear. I replaced the rear brake with Deore M6000 brakes (lever/caliper) and 160mm Avid rotor with seemingly no issues, using the hardware that came with the Deore brakes.

The front brake doesn't seem to line up nicely and I've read that there have been some changes to the geometry of the calipers and post mount adapters... I have it working using some spacers from the Avids (and their longer bolts) and the original post mount adapter with new 185mm rotor, but the caliper is a few millimeters too far from the rotor. (This is short term, I know it's very bad when the pads wear down and contact each other)

Also, the caliper doesn't seem to want to sit flush on the post mount, do I need a new post mount? Or can I just use spacers somehow?
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Old 06-01-21, 01:52 PM
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Trek bought Fisher in 1994. As for your brakes it's impossible to say w/o seeing the bike. Do you have the ability to post photos?
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Old 06-01-21, 02:20 PM
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I guess it was the branding changeover I was thinking of. Pics attached, spacers are just the reused conical washers from the Avids. Hopefully you can see the wear pattern on the rotors (rears have a few rides, fronts have one ride).


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Old 06-01-21, 02:40 PM
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Originally Posted by black_box View Post

.... I've read that there have been some changes to the geometry of the calipers and post mount adapters...
Apart from Flat-Mount (for road bikes), I’m not aware of any geometry changes. Where did you read that?
Originally Posted by black_box View Post

The front brake doesn't seem to line up nicely ... I have it working using some spacers from the Avids (and their longer bolts) and the original post mount adapter with new 185mm rotor, but the caliper is a few millimeters too far from the rotor.
Shimano rotor size is 180 mm, not 185. That may well explain some of your issues.
Originally Posted by black_box View Post

Also, the caliper doesn't seem to want to sit flush on the post mount, do I need a new post mount?
Once upon a time, Avid calipers used what they called ”Tri-Align washers” between the Post Mount and the caliper. I don’t know when they stopped. If your bike had those, transferring them to Shimano calipers is another way of messing up alignment.

Is this the fixed PM surfaces on the fork/frame you’re talking about, or is it the surfaces of an adapter?
Needing to touch up PM surfaces on fork/frame does happen.
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Old 06-01-21, 04:31 PM
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Remove the concave/convex washers from the front...you've installed the inner ones backwards anyway. The rear looks damn close to being correct.
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Old 06-01-21, 05:49 PM
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Originally Posted by black_box View Post
Also, the caliper doesn't seem to want to sit flush on the post mount, do I need a new post mount? Or can I just use spacers somehow?
The mounting surfaces on the 185mm post mount adapter aren't even, this adapter is only made to be used with Avid CPS calipers which have the spherical washers below it and allow the it to be mounted on an uneven surface.

Shimano calipers are not made to have any extra washers between the caliper and adapter or caliper and post mounts





Solutions....

1) Get rid of the 185mm adapter/rotor and buy a 180mm adapter/rotor
or
2) Get a Shimano 180mm adapter and put a 2.5mm washer/shim under each side of the caliper to evenly space it over the 180mm adapter, an extra 2.5mm of spacing will equate to 5mm increase of rotor size.

If you space out a 180mm adapter and use Shimano bolts, check that they screw into enough thread, if you use the Avid bolts, make sure that they don't bottom out in the post mounts.

https://si.shimano.com/pdfs/si/SI-8170A-001-ENG.pdf

.

Last edited by cobba; 06-01-21 at 06:18 PM.
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Old 06-01-21, 07:11 PM
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Thank you, cobba, that's the bit I've been missing. I'll grab a new 180mm adapter and see where the bolts are at with some spacers.
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Old 06-02-21, 09:55 AM
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Originally Posted by dabac View Post
Apart from Flat-Mount (for road bikes), I’m not aware of any geometry changes. Where did you read that?
There hasn't been any since Post Mount became a standard, for the MTB world, there are 2 common standards, IS (older less used now) and Post Mount (pretty much the current standard for everything MTB now), anything else is so obsolete, if you ever came across it, you would already be very deep into that part of the retro world.

All the issues that you (black_box) seem to be facing are self inflicted, you're mixing rotor sizes, bolts and mounts which were never intended to be mixed from brands which have minimal to no compatibility, stick with parts from one brand when working with brakes and you won't have any issues.
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