Moving the brake caliper inwards

I just put a rear hub onto a fat bike, but I have a problem... The existing caliper needs to move inwards (closer to the hub) by about 2 centimeters. Is there an adapter that will allow for this?

Dumsterdave said:

Is there an adapter that will allow for this?

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I've been in similar situation (not a fat bike and not a two centimeters, though). I've decided not to search for adapter but use a right amount of washers instead:

you can use a chunk of 3/4x3/4 aluminum bar or square tube, cut to length and drill 2 holes. you can machine aluminum with a skill saw and carbide blade. so if you have a chunk of aluminum, a drill and a skill saw and a belt sander, you can machine, plane, sand any shape you want

Sometimes it's better to move the rotor out with a spacer, but you may need slightly longer bolts too. Don't use a plastic spacer that comes with some motors.. That's just to keep the bolts from going in too far to the motor case while no rotor is mounted... It's too mushy for actual spacer-ing.

Edit...I just reread 2cm... Maybe some of both... Spacer the caliper in and the rotor out?

Moving the caliper away from the frame with washers means repeated shear loading on the bolts. Depending on the bolts, etc., the repeated bending back and forth has the potential to break them and leave you unable to brake (or to have the caliper get tangled up in the rotor and lockup the wheel).


Spacing the rotor away from the motor, with the right kind of spacer and sufficient bolt pressure, has a different kind of loading on that extension, which is unlikely to fail in the same way. Spacers for this purpose specifically are commonly available, as are longer bolts.


So if I were doing it, I'd put the spacers on the rotor, not the caliper, though 2cm is quite a distance.

In my experince 1cm spacing on both rotor and caliper works fine on a back disc brake.

Voltron said:

Sometimes it's better to move the rotor out with a spacer, but you may need slightly longer bolts too. Don't use a plastic spacer that comes with some motors.. That's just to keep the bolts from going in too far to the motor case while no rotor is mounted... It's too mushy for actual spacer-ing.s-l300.jpg

Edit...I just reread 2cm... Maybe some of both... Spacer the caliper in and the rotor out?

Click to expand...

Where can I find that 7mm spacer

That was some random Google image... I've never needed to order one that big.

Dumsterdave said:

Where can I find that 7mm spacer

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I would note that some rotors (when adequately cut down) make excellent spacers.

Fiddly, but stacks of washers (preferably taped together) will work. I'd rather use a spacer of some kind though.

Dumsterdave said:

Voltron said:

Sometimes it's better to move the rotor out with a spacer, but you may need slightly longer bolts too. Don't use a plastic spacer that comes with some motors.. That's just to keep the bolts from going in too far to the motor case while no rotor is mounted... It's too mushy for actual spacer-ing.s-l300.jpg

Edit...I just reread 2cm... Maybe some of both... Spacer the caliper in and the rotor out?

Click to expand...

Where can I find that 7mm spacer

Click to expand...

Disc rotor spacers here : https://mbrebel.com/bike-parts/