MAC rear motor – what size disc to clear the motor?

[pschmatz]

I’m planning to upgrade my ride to a MAC motor (rear), and I’d like to install a larger rear disc (Avid BB7) , and I don’t want to add any shims/washers.

The Avid BB7 comes in 180/185/200/203mm rear rotor size, and I’d like to get smallest size for which the caliper clears the motor.
The largest 203mm clears it for sure but may have clearance issues with the frame.

Does anyone have a 185mm disc on a MAC motor in the rear, and can confirm that it clears the motor (also which brand)?

Thanks Peter

 

[migueralliart]

OMG just today I was having this same question and was going to post a new thread.

I know with the DD MXUS rear motor the max rotor to clear elixirs is a 203mm.

I was planning on buying a MAC rear motor but didn't know the rear disc size to have it fit.

 

[DAND214]

i am using a 203 rotor with spacing to clear the caliper.
Here is what is posted on line.

The available space for the disk is a little limited at 15mm between the side casing and the inner face of the disk, so some care when selecting a suitable caliper is required or some spacing of the disk away from the side cover and possibly modification of the caliper mounting may be required for some models of disk brake caliper.

You only need to do it once, unless you change brakes or frames.

Dan

 

[pschmatz]

Thanks - I just found this thread: http://endless-sphere.com/forums/viewtopic.php?f=3&t=41417

This shows that a 203mm disc with an Avid BB7 caliper just clears the motor on the rear. So I'll go with a 203 (and hope my frame does not get in the way).
I guess the concern is that the hub is not true, and a larger disc makes it even hard to avoid rubbing. I hope the MACs are better better in this respect than the Crystalytes...

Thanks
Peter

 

[DAND214]

Both of mine are almost perfect in straight or runout. Very little wobble at all. Could be the disc.

Dan

 

[migueralliart]

So a 180mm would not fit?

 

[kudos]

Thanks - I just found this thread: http://endless-sphere.com/forums/viewtopic.php?f=3&t=41417

This shows that a 203mm disc with an Avid BB7 caliper just clears the motor on the rear. So I'll go with a 203 (and hope my frame does not get in the way).
I guess the concern is that the hub is not true, and a larger disc makes it even hard to avoid rubbing. I hope the MACs are better better in this respect than the Crystalytes...

Thanks
Peter

I hear what you're saying Peter, I've had endless hours of frustration trying to align rear rotor brakes due the motors not running true. I can certainly say in my instance my mac motor is better than my xlyte but it certainly is not true either.

I've used Avid bb7 and bb5 brakes on a standard 180mm rotor with my mac but you do have to file down the inner adjustment metal key holder a couple of mm. It's simple to do and gives you a couple of mm clearance.

Kudos

 

[pschmatz]

Thanks Kudos for the details.

So a 180mm is ok, if you file down the this bolt/screw like this? (borrowing the pic from the other thread - sorry need to select the link to see the pic)

http://sdrv.ms/11dj8HC

Thanks Peter

 

[cal3thousand]

There's another thread on here that kudos answered as well.

My solution is to actually shave down the thickness of the caliper adapter, bringing the caliper away from the hub. Then you might need a spacer under the disc to move it in the same direction to give clearance. Some caliper adapters (Avids especially) are extra thick and square-ish (for simplicity in production I presume).