Avid BB7 Rotor-Motor Clearance?

[Punx0r]

I was just looking at ordering an Avid BB7 rear calliper when it suddenly occurred to me that I ought to check it will fit first...

Can anyone with one of these brakes please tell me how much clearance it needs between the back of the rotor and the motor casing? I can't seem to find this dimension online.

Thanks

 

[ambroseliao]

With my Tidalforce S-750 frame and Crystalyte HS3540, the Avid BB5 brake I have the gap between the adjustment screw and the side cover of the motor is very small indeed. I would guess <3mm.

 

[MAGICPIE3FOCUSPOWER]

I am using BB7 with HS3540 motor.
Yes the clearance between rotor and adjustment screw is small.
But when I am doing a adjustment I am using the red knob instead of using the screw.

 

[Kingfish]

For the 9C, I had to use disc rotor spacers to move the rotor out away from the hub cover about 1-2 mm, plus I filed down the nut facing the cover. I also used a thin washer on both sides – front and back for 2WD – to further increase the clearance. It’s real tight and a PITA to sort out brake adjustment without incurring ringing. I posted an article on this last year – about ¾ the way down the page.

~KF

 

[Punx0r]

Thanks for the replies guys, it looks like it might fit my bike based on the photos (I already made a ~3mm spacer to clear the original calliper). Would anyone mind offering a vernier or ruler to theirs to provide me with an actual measurement of the space? It doesn't need to be super accurate, just so I know I'd be in the ballpark and could shim a millimetre or two if required.

Imperial measurements also accepted

 

[vfxmorley]

Hi there. No answers for you, but Im pretty keen to know this as well. Im in the same boat. Trying to fit my smart pie today lead me to a dead end with my avid juicy brakes. These ones are about 4-5mm in the foul.

A measurement on this would be great. The pictures of the bb7s look promising. No one local sells them so I cant just go try them out.

Without being to precise on the measuring, Ive got about 12-13mm of room to fit something without washers. Im happy to add washers, but I dont have any easy way of grinding off some of the mounting plate to compensate for the shifted disc.

 

[teklektik]

Without being to precise on the measuring, Ive got about 12-13mm of room to fit something without washers.

Measuring a virgin out-of-box BB7 with new pads shows 16.66mm from the surface of the inner pad (near the inner rotor face) to the butt of the Torx inner adjuster stem. This has to be measured with new pads since the Torx adjuster stem (visible in the middle of the inner adjuster knob) screws in and out and is a fixed distance from the rear of the pad backing plate, so thick pad = sticks out more. You will need a bit more for pad/rotor clearance, etc.

 

[vfxmorley]

thanks mate.

sound almost identical in size to my current juicys. So unfortunately not worth the risk to test

I amazed that manufacturers dont show any form of measurement for brakes online. Seems like it is something people do sometimes want/need to know

cheers

 

[migueralliart]

I just installed BB7's on a 9C clone with 180mm rotors like a month ago. You don't need a spacer for the disc.

All you need to do is remove the red adjustment knob and trim the nut/bolt down. It is harder to adjust but it fits without additional parts such as spacers etc.

 

[vfxmorley]

interesting. So how wide do you think your setup would be now? Do you know the width of the 9C motor? maybe that will help me?

How do you adjust it now then?

thanks

 

[teklektik]

The inner adjuster knob also provides adjustment detents and serves as a cover for the threaded adjuster to keep out dirt and debris. I think that adjustment may become slightly more problematic without the knob in place as the fine threads fill with poo - although gumming up somewhat may partially offset the loss of the detents...

Seriously, though - the BB7 is so cleverly designed that it seems a shame to modify it... adjusting the brakes for normal wear (including centering the rotor) takes less than two minutes and requires no tools. It's a personal call, but I'd rather add a spacer and file away the adapter once rather than lose the recurring benefit of quickie adjustments. On the other hand, if you need a full 6mm, you may be stuck unless you can spring the stays enough to get in some axle spacers to get more clearance.

 

[migueralliart]

The part that adjusts the pad in the hub side doesn't move freely. The knob is there JUST to provide steps in the adjustment. I've gone hundred of miles and no issue. Once you adjust your breaks just check it every 300-500miles and be done with it.

I just hate to see people buying disc adapters for 5$'s and then paying 10$ for shipping only to find that now they have to spread their frame a bit more.

To each its own choose the easiest method for you!

 

[Punx0r]

Ah, I'd forgotten about this thread so will update for future reference should anyone stumble across it.

I already had a 3mm spacer between th motor and threaded brake disc adapter and ended up spacing the disc away from the adapter by another ~2.5mm, which have me just enough clearance between the motor and calliper on a 160mm disc.

I had to use about 10mm of spacers (washers) between the BB7 calliper bracket and the ISO mounting tab on the frame. That could be due to me having an oddball frame, though.

The biggest headache was the brake disc. The BB7 requires a 160mm minimum disc and my old one was 140mm. The brake disc adapater (this is a goldenmotor 901 kit) is not 6-bolt ISO size! It's about 3mm larger PCD, so the avid disc wouldn't fit. You can order a different adapater online from a few specialist suppliers, but I didn't have the time. So I filed the adapter flat (removing the centre bore lip) so the disc would sit flat on it, then ground/filed the holes in the disc into slots so they'd line up with the threads in the adapter. That was hard work, made only slightly easier by crudely annealing the disc hole area with a propane torch. I would prefered to drill and tap new holes in the adapater but there wasn't enough meat on it