disc brake fitting question

r3hxn

when some one gave me advice on swapping out my gear onto a new frame they said
"most of it may fit, or none of it may fit"

the latter is turning out to be more true! but nevertheless its a learning experience I appreciate.

My next stumbling block is the rear disc brake.
photo of it here:


everything I had read so far, made me believe this would be a straight forward swap. mount point on the frame was in the same place and same type, my guide suggested adjusting the positioning using the Shims, fine all good.

However if you see the picture below ( sorry for poor quality)

the issue I have is the distance between the disc and the frame, is not even enough for the disc brake to fit.

So I am guessing that black bit on the disc brake is what I need to replace with an appropriate size? if that is the case, could you guys please tell me what this is called, and what information I need in order to buy an appropriate one? otherwise any advice is appreciated. thanks

nicklouse

Looks like wrong adaptor.

Read this? viewtopic.php?f=40073&t=1590919

Front and rear are not the same.

Ouija

I think the problem he has isn't that the adaptor is wrong for the diameter of the rotor so much as the adapter is too fat to physically fit between the rotor and the frame (hard to tell from the photo).

nicklouse

If that is the case then the hub has a fault.

Or the disc is incorrectly mounted.

nicklouse

But again trying to fit the caliper with the wheel in place is not a good starting point.

Wheel out. Mount caliper. Slaken caliper bolts. Insert wheel do up qr lightly. Place bike on ground press on saddle undo Qr so you can seat wheel correctly. Do up Qr correctly. Then back in stand. And set up caliper.

r3hxn

Ouija is right in that the problem is it's too fat.
I had the wheel on just for the photo, but had I i initially done it as you say (minus the sitting on saddle, as there is none at this point). It fits fine on my other frame, which is a caad5 cannandale I think. And I litterly just moved it over to this fre leaving the wheels / hub as is.

Any other thoughts?

if it helps, heres a photo of the distance between disc and mount points



unfortunately My lbs is a pile of poo & very unhelpful , a recent conversation
"Can u help remove the bottom bracket from a bare frame I don't have the tool"
Lbs: "£20"

Me: "That's a bit much for 2 min job

Lbs "We will service it and install again"

Me:"But I only want it removed nothing else"

Lbs "Sorry we don't do that...only full service"

The Rookie

Some adaptors can be on the thick side, you just need to try and find a thinner one as it looks like your wheel puts the disc that little bit closer to the frame.

cobba

Try a different method.

1) Remove the rear wheel from the frame.
2) Remove the disc rotor from the hub, flip it around 180 degrees so it's facing the right way around and put it back on the hub.
3) Remove the brake caliper from the brake adapter (the black mounting bracket).
4) Attach the brake adapter to the frame.
5) Put the wheel back on the frame, if the rotor rubs on the adapter the brake mounts on the frame will need facing.
6) Attach the brake caliper to the brake adapter.

* A 1mm gap between the rotor and the adapter is fine.
* Sometimes the brake mounts on the frame can be out and will need facing.
* Adapters are front and rear specific.
* The adapter size needs to match the rotor size.
* Rotors are only meant to rotate one way.

BB7 Setup & Installation Guide: http://cdn.sram.com/sites/default/files/techdocs/2006_BB5and7_English.pdf

* You look to be missing some of the CPS washers between the brake caliper and the brake adapter, without those washers the brake might rub on the rotor, you should get some more washers.

r3hxn

thanks for an extensive answer, I will give this a try on the weekend.

just to clear up a few things.


2) Remove the disc rotor from the hub, flip it around 180 degrees so it's facing the right way around and put it back on the hub.
what did you mean by flip it around 180 ( i.e do you mean flip it so the right side face is now the left side face?)


* The adapter size needs to match the rotor size.

is there a standard way of identifying this, i.e what do I measure? thanks

TJ20862

The adapter may be fr the front only check you have them the right way round?

The Rookie

No adaptor would be front only......

Don't turn the disc round unless it's fitted the wrong way to start with.

Check the disc for dishing, it doesn't look dished in the photo but worth checking

cobba

r3hxn wrote:

thanks for an extensive answer, I will give this a try on the weekend.

just to clear up a few things.


2) Remove the disc rotor from the hub, flip it around 180 degrees so it's facing the right way around and put it back on the hub.
what did you mean by flip it around 180 ( i.e do you mean flip it so the right side face is now the left side face?)


* The adapter size needs to match the rotor size.

is there a standard way of identifying this, i.e what do I measure? thanks

Yep flip it so the left face is on the right side.

In the following photo go from the left side and go clockwise, the adapters in the photo are:
Rear 203mm IS to PM,
Front 203mm IS to PM or Rear 185mm IS to PM
Rear 160mm IS to PM,
Front 185mm IS to PM,
Front 160mm/Rear 140mm IS to PM,
Front 185mm PM to PM,
Front 203mm PM to PM.

Old Avid Adapter Photo

Not sure if those old Avid adapters had directional arrows on them but it looks like the way they are in the photo is how they go onto the bike if you're looking at it from the left side. * The 160mm Rear IS to PM adapter in that photo might be around the wrong way.

Page 3 of the BB7 Setup & Installation Guide shows the different adapters.

cobba

The Rookie wrote:

No adaptor would be front only......

Don't turn the disc round unless it's fitted the wrong way to start with.

Most of the old Avid adapters were front and rear specific because of the 185mm & 203mm sizes.

185mm front = 165mm rear
203mm front = 183mm rear
185mm rear = 205mm front
203mm rear = 223mm front

The first photo in this thread shows the rotor is on the wrong way, the way the 'arms' of the rotor are sloping shows this.

cobba

The distance between the inside surface of the IS brake mount and the inner face of the rotor should be about 15mm.
The distance between the inside surface of the IS brake mount and the outer face of the rotor should be about 13mm.

http://www.hayesdiscbrake.com/wp-content/themes/hdb/pdf/Rear%20installation%20drawing%20160mm.pdf

r3hxn

once again, I appreciate the time you took for those detailed suggestions. will let you know how it goes.

Kind regards!

Ouija

Can also just buy an axle washer that sits between the endcap of the hub and the frame and move it out 1mm. Have some (think they're made by Hope). Don't be tempted to use ordinary style washers as spacers unless you can get one that's very, very thin (most washers for DIY type stuff are pretty thick at the size you'd need to fit round the hub axle and skewers).

r3hxn

thats a good suggestion! thanks.

I followed all the suggested steps last night. The disc is definitely the right way already, it became obvious by the design shape.
The Brake caliper mount is also the correct orientation, it wasn't physically possible to put it on wrong, without it looking wrong.
There was indeed a small arrow on it, ( one that pointed in the direction of the disc moving) and on the other side of it was a small "R" . Not sure what the R meant, as there wasn't really a left/right.
You were correct about the missing cps washers. So I will order some of these.
By following your suggestion of removing the caliper mount from the caliper and attach directly to frame first, it was much easier to see where the problem was, and it indeed was a matter of a mm or 2 making contact. The above suggestion should work so will give it a try and order some.

Kind regards

The Rookie

In the first pic the disc is on the wrong way round, the legs should go forwards to the braking surface, not trail back, it may not look 'right' but it is, not that it will change your issue.

r3hxn

The Rookie wrote:

In the first pic the disc is on the wrong way round, the legs should go forwards to the braking surface, not trail back, it may not look 'right' but it is, not that it will change your issue.

oh thats interesting! gotcha, will make the change. strange, I took the bike out of storage after several years, it was my brothers old bike, who was a keen biker.I didn't touch the wheels, If he had them on wrong, what hope do I have!

cobba

The 'R' on the adapter means rear, if it had 'F' it would be for the front.

r3hxn

Ouija wrote:

Can also just buy an axle washer that sits between the endcap of the hub and the frame and move it out 1mm. Have some (think they're made by Hope). Don't be tempted to use ordinary style washers as spacers unless you can get one that's very, very thin (most washers for DIY type stuff are pretty thick at the size you'd need to fit round the hub axle and skewers).

I can't seem to find an appropriate axle washer as you described, ( searched various bike sites and ebay). Even standard washers at the required diameter are wider then 1mm any help linking to something appropriate would be appreciated! thanks.

Ouija

Was a while ago. Think i got them on ebay. Something like this might be helpful... Just select the thickness (better off buying 1mm as you could always stack two together to get 2mm, rather than going for a larger size and finding it's too wide).

r3hxn

ahh perfect! your a star.