Disc Brake Clearance Issues

[joshseitz]

I am about to lace my Amped (bafang) internally geared brushless front hub motor onto a new wheel which will be affixed to a new fork with disc brakes (Avid BB5).

Right off the bat, it appears that the motor housing will rub on the back of the brake caliper. Does anyone know of an easy remedy to disc brake clearance issues? I am considering going to a 203mm rotor, so the bracket will likely stand the caliper off of the fork far enough to clear the motor housing. 203mm should add braking power too. I also plan to replace the BB5s with hyrdaulics(Hayes Stroker?), so maybe different brakes have different caliper depths?

Any wisdom on this subject is appreciated as always - thanks!

 

[biohazardman]

Don't have a front motor but have done the 203mm rotor upgrade on my Hayes MX4 cable disk units and it is well worth the time and funds. Never found the need for hydraulics after the upgrade as these stop me on a dime. You can use better brakes anyway now that you have a motor so if it will fix things feel good about doing it. Just be confident that your forks and frame are up to the task.

 

[neptronix]

BTW, your amped geared motor is not a bafang, it's a MXUS motor. This is important to know so that you don't get advice from people with bafangs..

Good luck finding a proper caliper. This is always a problem with hub motors.
203mm will get the caliper farther away from the hub motor cover. however, i hope you have a fork that is capable of dealing with those braking forces.

 

[joshseitz]

Good to know! Any notable difference b/w MXUS and Bafang? For what it's worth, my Amped motor is a hair over 2 years old. Not sure if they have changed suppliers since then.

 

[Sacman]

I am about to lace my Amped (bafang) internally geared brushless front hub motor onto a new wheel which will be affixed to a new fork with disc brakes (Avid BB5).

Right off the bat, it appears that the motor housing will rub on the back of the brake caliper. Does anyone know of an easy remedy to disc brake clearance issues? I am considering going to a 203mm rotor, so the bracket will likely stand the caliper off of the fork far enough to clear the motor housing. 203mm should add braking power too. I also plan to replace the BB5s with hyrdaulics(Hayes Stroker?), so maybe different brakes have different caliper depths?

Any wisdom on this subject is appreciated as always - thanks!

How much distance do you need for the caliper to clear the motor housing? If you're only talking about 2-3 milimeters then you can use a spacer or stack washers between the disc and motor housing. You can also use a different (more shallow) mechanical brake caliper.

You can find both the 2.5mm disc brake spacer and the Alhonga (shallow) Mechanical Caliper at Ebikes.ca
Look in the motors section.

If you do plan to upgrade to hydraulic brakes just know that most hydraulic calipers require even more disc-to-motor housing clearance than mechanical brake calipers.

 

[motomech]

I am about to lace my Amped (bafang) internally geared brushless front hub motor onto a new wheel which will be affixed to a new fork with disc brakes (Avid BB5).

Right off the bat, it appears that the motor housing will rub on the back of the brake caliper. Does anyone know of an easy remedy to disc brake clearance issues? I am considering going to a 203mm rotor, so the bracket will likely stand the caliper off of the fork far enough to clear the motor housing. 203mm should add braking power too. I also plan to replace the BB5s with hyrdaulics(Hayes Stroker?), so maybe different brakes have different caliper depths?

Any wisdom on this subject is appreciated as always - thanks!

MXUS frt. motor

Fork Brand & Model Marzocchi DJ 2, 130mm travel
Fork Material Aluminum/magnesium, single crown

Shimano Deore M525 hydraulic disc brakes.

I had clearance issues as well, but nothing some judicious grinding with a Dremel tool couldn't fix.

 

[dogman dan]

Very often you can make adjustments by spreading the frame a few mm, and using spacer washers. Another spacer under the disk may or may not then be needed.

 

[Russell]

I am about to lace my Amped (bafang) internally geared brushless front hub motor onto a new wheel which will be affixed to a new fork with disc brakes (Avid BB5).

Right off the bat, it appears that the motor housing will rub on the back of the brake caliper. Does anyone know of an easy remedy to disc brake clearance issues? I am considering going to a 203mm rotor, so the bracket will likely stand the caliper off of the fork far enough to clear the motor housing. 203mm should add braking power too. I also plan to replace the BB5s with hyrdaulics(Hayes Stroker?), so maybe different brakes have different caliper depths?

Any wisdom on this subject is appreciated as always - thanks!

I have a Bafang front motor which has a diameter nearly identical to the Amped (MXUS) geared motor. I thought since it's such a small motor upgrading to a disc brake would be easy but the motor is also wide which places the spokes out further. I tried the stock 160mm rotor that came with my new bike but the caliper would strike the spokes, and this was with a caliper with a fairly narrow body. I ordered a 180mm rotor and adapter but the spokes still hit...so I ordered a 203mm rotor and adapter and that finally cleared.



One thing I did notice was it was the spokes with the heads FACING IN which struck the caliper. I originally laced the wheel with a 2X alternating pattern just because that seemed natural and it of course was never an issue with rim brakes however I could have saved money on brake parts if I had relaced the wheel with all of the heads FACING OUT. Since you are starting from scratch it's something to consider and will provide a few precious mm's of extra clearance. You'll still want a narrow caliper for maximum clearance however. My cheap-o "Radius" brand and a no-name disc brake set I bought from BMSBattery are two such narrow body designs.

-R

 

[dogman dan]

Duhh, I didn't read good enough to catch on that this was a front install. No quick easy fixes like bend the frame for that problem.

 

[Sacman]

Duhh, I didn't read good enough to catch on that this was a front install. No quick easy fixes like bend the frame for that problem.

Heh... didn't want to point it out. Glad you caught it yourself.

OP's issue is caliper clearance because there is not enough distance between brake disc and face of motor housing.
He says caliper scrubs on the face of the motor housing.
He can increase that distance by:
1) using ring spacers sold by ebikes.ca (look in motor section)
2) using washers between disc and motor (same idea as spacer rings)

He can also use a thinner/shallower brake caliper (also sold at ebikes.ca) so caliper clears the motor housing.

 

[joshseitz]

Thanks for all of the helpful advice. It sounds like 203mm rotor and caliper spacer is the path of least resistance (and better braking). It will b going onto a Cannondale Headshok DLR80 "Super Fatty Ultra", which is pretty substantial (and one-piece), so I think it should handle the braking forces fine.

 

[d8veh]

It's always worth putting a bit of sealant on the threads or behind the disc or spacer because water can enter up the threads.

 

[shock]

I just went through the same isseues with my 9c hub and in the end, the best solution is just to upgrade to a 203mm rotor and all clearance issues are solved, along with upgrading the braking capacity.

 

[joshseitz]

So I just got my new custom wheels (amped geared front hub, shimano Alfine 8 rear, 13/14 gauge single-butted spokes, sun 33mm downhill rims). I upgraded to a 203mm front rotor and the requisite caliper adapter as advised to clear the front hub. The caliper clears the hub, but the red adjuster knob on my avid bb7 caliper is hitting the spokes.

Does anyone know of any tricks to add clearance to a setup like this? Worst case, I'll need to go to another caliper. Does anyone know of a quality low-profile caliper (preferably cable-actuated)?

Thanks again.

 

[Sacman]

So I just got my new custom wheels (amped geared front hub, shimano Alfine 8 rear, 13/14 gauge single-butted spokes, sun 33mm downhill rims). I upgraded to a 203mm front rotor and the requisite caliper adapter as advised to clear the front hub. The caliper clears the hub, but the red adjuster knob on my avid bb7 caliper is hitting the spokes.

Does anyone know of any tricks to add clearance to a setup like this? Worst case, I'll need to go to another caliper. Does anyone know of a quality low-profile caliper (preferably cable-actuated)?

Thanks again.

Same advice as stated before... use a 2.5mm disc brake spacer to increase the distance between your rotor and the rest of the wheel or use the shallower Alhonga Mechanical Caliper at Ebikes.ca
Look in the motors section.

 

[Drunkskunk]

I had the same issue with a BB7 on mine. I lased the spoke heads all facing out, added a washer under the disk at each bolt, and pried off the red adjustment knob. Its a close fit but it works. I've got a 160mm. a 185-203 would have fit better, but I had a box of these 160mm disks....

 

[joshseitz]

I just ordered the 2.5mm spacer from Justin, though I'm not sure that will buy me enough clearance. I will also have to add an additional washer on the axle to space the forks wider. Otherwise, I don't believe that the caliper has enough lateral adjustment to get it far enough away from the spokes. I suppose I could also face the caliper adapter to make it a but shallower.

The AVID BB7 doesn't appear to lend itself to filing and other modificationl. The actual red adjuster knob isn't so much the culprit as the torx-head bolt that secures it.

Thanks again for the suggestions.

 

[Sacman]

I don't believe that the caliper has enough lateral adjustment to get it far enough away from the spokes. I suppose I could also face the caliper adapter to make it a but shallower.

The AVID BB7 doesn't appear to lend itself to filing and other modificationl. The actual red adjuster knob isn't so much the culprit as the torx-head bolt that secures it.

Thanks again for the suggestions.

The mechanic at my LBS showed me a little trick with the BB7's. You can reverse the order of the cup & ball washers (one set is shorter than the other) on both sides of the caliper to get more lateral adjustment.

 

[joshseitz]

So when I look at my BB7s, it looks like the cup and ball washer on the bolt side is larger than on the bracket side of the caliper. Are you saying to swap them - put hte larger washer set b/w the caliper and adapter bracket?

 

[Sacman]

So when I look at my BB7s, it looks like the cup and ball washer on the bolt side is larger than on the bracket side of the caliper. Are you saying to swap them - put hte larger washer set b/w the caliper and adapter bracket?

Yes you got the jist of the idea... one set of those ball & cup washers are thicker than the other side. You can swap them, or file their flat sides down to make them thinner, or stack more flat washers along the bolt to make them thicker, but only if it helps you move your caliper's red adjuster knob and torx-head farther away from your spokes.

 

[GMUseless]

You can also replace that torx screw with a lower profile bolt. Or just grind it down some. The Torx is there so you can adjust the pad clearance easier than using the red knob. You could grind it flush and make you're self a tool like Teklektick's: http://endless-sphere.com/forums/viewtopic.php?f=2&t=37423

 

[teklektik]

You can also replace that torx screw with a lower profile bolt. Or just grind it down some.

This adjuster screws in and out according to pad wear and certainly could be shortened a bit - not a bad plan I think. It's not really a bolt, but a big mushroom shaped thing, so grinding is really the only option. Pop the cap and unscrew the adjuster from the barrel.

BTW - Avid sells an inner+outer plastic cap replacement kit for $5 bucks, so if you mess those up, it's a cheap fix.

You can also fab quickie spacers from old discs if you don't want to wait for the mail (a trick from Methods)

The Avid CPS alignment system is very forgiving, allowing all sorts of adapter and caliper misalignments. You could thin the adapter somewhat where it bolts to the fork mounts to pick up some clearance. If you can't do this yourself, an auto machine shop will do it in a day or so pretty cheap (probably $25-$30). Otherwise, you can have at it with a file and rely on the CPS to take up any 3D skew you introduce.