Are disc brake rotor screw mounting patterns universal?

[RMW]

There are typically 6 screws near the axle that attach the brake disc to the motor housing. Is thread size and hole spacing interchangeable among virtually all brands of motors and brands of brakes?
I ask because I am making plans to add front wheel drive electric to my road/touring 18 speed bike. The original bike has rim grabbing "V" brakes, and I suspect that motorized front wheel rims are not made to work with "V" brakes. The conversion kits I have looked at do not come with a brake disc so I would need to buy and install calipers and a disc separately. That is why I wonder if any brake disk can attach to any motor.

 

[harryS]

Some high end wheels use proprietary fasteners, but hub motors use the cheap universal mount. I never thought about a wheel kit not working with rim brakes, You would think they cater to the lowest end application.

 

[JRA]

It does seem that the bike industry, known for setting incompatible "standards" does agree with the 6 bolt spacing for brake discs. However I have found that not all e front hubs have the same relative width to the disc face so that getting a caliper that fits can be an issue. Caveat is that Shimano makes a disc that fits their hubs via what they call a Centerlock system but you won't run into that probably.

There is no reason that rim brakes won't work on most of the kits unless they are labeled disc specific which only means they lack the proper width and surfacing necessary for rim brake pads.

If your bikes fork doesn't have the mounts for a caliper that can be your biggest obstacle to setting up disc brakes on your bike. If is does it should be relatively easy to do with either a mechanical or hydraulic disc setup and preferred actually by most over rim brakes. But be aware that there are several different types of caliper mount styles too.

 

[indianajo]

There is no reason that rim brakes won't work on most of the kits unless they are labeled disc specific which only means they lack the proper width and surfacing necessary for rim brake pads.

I've run into the side of a car in the rain with rim brakes, after I stopped at the 4 way sign. She didn't stop. Rim brakes are about 1/3 as powerful in the rain. That was a pedal pushed 3 speed, not exactly a high end bike. Upgrade at least one wheel to disk if you can, unless you never will ride in the rain, or ride through a puddle.

 

[RMW]

Some high end wheels use proprietary fasteners, but hub motors use the cheap universal mount. I never thought about a wheel kit not working with rim brakes, You would think they cater to the lowest end application.

I made a quick leap to a wrong conclusion about rim V brakes not working. One of the conversion kits* I looked at said to not use rim brakes and I assumed all would be that way.

*(probably because their rims are soft cheap aluminum, easily scratched or gouged by debris on the brake pads.)

 

[Sierratim]

JRA has hit the nail on the head. If you want disc brakes, which many of us would recommend for any ebike, you need to a kit that specifically references disc brakes. Otherwise it will come setup for rim brakes (no disc rotor mounting holes and a rim reinforced and surfaced for rim brakes).

Mounting disc brake calipers on your bike is an entirely different topic. Again, as JRA mentioned, the bike needs to be setup to accept calipers. Otherwise you're looking at changing out the front fork. The rear brake would also require a compatible wheel hub and an adapter kit for the caliper.

 

[ki11a]

JRA has hit the nail on the head. If you want disc brakes, which many of us would recommend for any ebike, you need to a kit that specifically references disc brakes. Otherwise it will come setup for rim brakes (no disc rotor mounting holes and a rim reinforced and surfaced for rim brakes).

Mounting disc brake calipers on your bike is an entirely different topic. Again, as JRA mentioned, the bike needs to be setup to accept calipers. Otherwise you're looking at changing out the front fork. The rear brake would also require a compatible wheel hub and an adapter kit for the caliper.

Never really considered it but yeah the sizing and specs would need to be within a good margin of error to have a good fitment and placement.