Problems with MAC Rear Hub Motor , What did you do ?

[ScooterMan101]

There are a few problems with the MAC 500 Rear Hub Motor, and perhaps other Rear Hub Motors as well.

Problem :

1) The Rear Disc Brake Body Rubs on the Motor Hub, I bought a bike to convert that has the cheep mechanical disc brakes, and when I put in the MAC Hub Motor into the dropouts it would not go in , the Body of the Disc Brake is too wide ( 32mm from the innermost part of the Disc Caliper to where it bolts onto the frame .
So I went to my parts bin and pulled out a Avid BB7 Mechanical Disc Brake, tried to installed it , only to have the same problem it is also 34 mm wide . from the innermost part where the spokes are, or rather , where the hub motor body is .


What Rear Disc Caliper have you found that is 25mm or even 20mm inner body and Bracket width ?


Note that my bike has a all in one Shifter/Brake Lever, so a mechanical/cable disc brake is preferable over a Hydraulic Disc , but I would change out the Brake Lever/Shifter levers if I had to .

2) The Hub width is too wide to accept a 8 or 9 speed freewheel, First I bought a Sunrace MFEX9 9 speed freewheel, which by the way is what Sunrace says is made for electric bicycles, only to find out that the hub body interferes with the back of the Sunrace 9 speed freewheel, and I would have to use spacers so that the outermost/smallest cog does not rub on / have clearance with the frame .
I did get a 8 speed cog from Sunrace , but then bought a 8 speed bike to work , and came across the problem listed above with it having a combined
Shifter / Brake lever.

So have you found a 9 speed freewheel that works on the Mac 500 Rear Hub Motor ?

It seems like we need a thread on these two problems with Hub Motors .

 

[ScooterMan101]

This is the Back of the Sunrace MFEX9 9 speed Freewheel
You will see 3 black/grey rings inside of the gold part, the ring with the little holes ( 2nd out from center , one with holes for a tool for installation ) is coming into contact with the hub motor body, thereby not allowing the freewheel to do what it is supposed to , which is to, Freewheel !
The 8 speed freewheel from Sunrace is made differently, and does not have the same problem on the MAC 500 Rear Hub Motor. As it has only 2 rings, and the bearings located not right at the back of the freewheel body.

Who has experience with a different brand 9 speed freewheel ? have any pictures of the Back ?

At this time I do not know who's fault it is , the People that Make MAC hub motors ? or the People at Sunrace, that must have designed the MFEX 9 9 speed freewheel for a different hub ?

 

[gonespa]

Had the same problem with a Bafang BPM and had the urge to answer: The best solution (the cheapest and easiest I found) is to buy a brake caliper adaptor to install a larger (diameter) brake disc. That will move the caliper out (from the wheel axle) so it will avoid the interference with the hub cover. In my case, my bike had 160mm disc. I put a 203mm disc and caliper adaptor so it solved the problem. This means you only have to buy the mounting adaptor (which is really cheap) as well as a 203mm disc (which is cheap too if you go for something basic).

Regarding the 9 and 8 speeds. I had to put a 7 speed one. I was unable to use the others without significant fork spreading.

 

[ScooterMan101]

I just measured, and a 203 mm caliper adaptor would work, with just 1 mm to spare, I could make that space 2 mm by grinding down part of the caliper.

An Interesting note here, the stock , real cheep disc caliper that comes with the cheap bike, would work, however the much better Avid BB7 rear disc caliper , is still way too big and wide since it has a big red hand adjuster , for inner pad adjustment, Disappointing that a much better brake caliper would not work on electric hub motors . I think some of the higher end Disc Calipers are smaller, hoping someone here on E.S. has done that or has one on their non electric bike and can get me the measurements. Anyone ? ( will try to stay with a mechanical / cable disc brake caliper since my bike for this electric conversion has the brake lever and shifter combined, so I could , Not use a hydraulic one unless I bought a new shifter set also.

In regards to the 8 or 9 speed freewheel, the Sunrace 8 speed freewheel works on the MAC hub motor ( with a 2mm-2.5mm washer used as a spacer
, but even the Sunrace , 9 speed freewheel that is the same thickness, does not work because of the way Sunrace made the back of it ,with an extra ring that presses on the bearings when it is tighten on the hub
So is it Sunrace's fault or the MAC ? ?

Anyone here use a Shimano 9 speed freewheel or other brand that is good enough quality for the torque of hub motors on the MAC 500-1000 Hub Motor ?


gonespa wrote :

Had the same problem with a Bafang BPM and had the urge to answer: The best solution (the cheapest and easiest I found) is to buy a brake caliper adaptor to install a larger (diameter) brake disc. That will move the caliper out (from the wheel axle) so it will avoid the interference with the hub cover. In my case, my bike had 160mm disc. I put a 203mm disc and caliper adaptor so it solved the problem. This means you only have to buy the mounting adaptor (which is really cheap) as well as a 203mm disc (which is cheap too if you go for something basic).

Regarding the 9 and 8 speeds. I had to put a 7 speed one. I was unable to use the others without significant fork spreading.
Last edited by gonespa on Mon Nov 10, 2014 12:43 pm, edited 1 time in total. View post history.
gonespa
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Joined: Wed Aug 14, 2013 7:07 am

 

[gonespa]

I just measured, and a 203 mm caliper adaptor would work, with just 1 mm to spare, I could make that space 2 mm by grinding down part of the caliper.

An Interesting note here, the stock , real cheep disc caliper that comes with the cheap bike, would work, however the much better Avid BB7 rear disc caliper , is still way too big and wide since it has a big red hand adjuster , for inner pad adjustment, Disappointing that a much better brake caliper would not work on electric hub motors . I think some of the higher end Disc Calipers are smaller, hoping someone here on E.S. has done that or has one on their non electric bike and can get me the measurements. Anyone ? ( will try to stay with a mechanical / cable disc brake caliper since my bike for this electric conversion has the brake lever and shifter combined, so I could , Not use a hydraulic one unless I bought a new shifter set also.

In regards to the 8 or 9 speed freewheel, the Sunrace 8 speed freewheel works on the MAC hub motor ( with a 2mm-2.5mm washer used as a spacer
, but even the Sunrace , 9 speed freewheel that is the same thickness, does not work because of the way Sunrace made the back of it ,with an extra ring that presses on the bearings when it is tighten on the hub
So is it Sunrace's fault or the MAC ? ?

Anyone here use a Shimano 9 speed freewheel or other brand that is good enough quality for the torque of hub motors on the MAC 500-1000 Hub Motor ?


gonespa wrote :

Had the same problem with a Bafang BPM and had the urge to answer: The best solution (the cheapest and easiest I found) is to buy a brake caliper adaptor to install a larger (diameter) brake disc. That will move the caliper out (from the wheel axle) so it will avoid the interference with the hub cover. In my case, my bike had 160mm disc. I put a 203mm disc and caliper adaptor so it solved the problem. This means you only have to buy the mounting adaptor (which is really cheap) as well as a 203mm disc (which is cheap too if you go for something basic).

Regarding the 9 and 8 speeds. I had to put a 7 speed one. I was unable to use the others without significant fork spreading.
Last edited by gonespa on Mon Nov 10, 2014 12:43 pm, edited 1 time in total. View post history.
gonespa
1 µW
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Posts: 2
Joined: Wed Aug 14, 2013 7:07 am

I think hidraulic brakes calipers are generally wider than mechanical ones (I am not really sure why, but I think I read it somewhere).
MAC motor casing must be wider or something than my Bafang because moving to 203mm gave me a lot of clearance, so much that I think even a 180mm disc would do. My calipers are hidraulics (Tektro Draco), like the ones shown in the link:

http://bicycles.stackexchange.com/q...g-the-rotor-because-piston-is-not-moving-back

 

[cal3thousand]

If you have room (ie if your chainstays don't narrow too much) just use a combination of rotor spacers and a larger rotor.

 

[dancliff]

I have a MAC motor, and I had nearly the same experience as gonespa:

1) I put on a 203 mm caliper adapter (i.s. to p.m) and a new 203 mm rotor, and it took care of the clearance issue. The rotor just barely clears the chainstay, and I see scratches on the frame next to the rotor edge, but I don't hear anything rubbing.

2) Replaced the 8 speed cassette with 7 speed freewheel and adjusted the rear derailleur. With a motor, I don't even notice the missing gear.

 

[motomech]

Where did you buy the motor? Paul at EM3ev covers most of your issues at his web site.
You shouldn't be wasting your time with a Sundance freewheel. You will need an 11T sm. gear and that means a DNP freewheel.
As to whether or not you can fir an 8 or 9-speed freewheel depends on a few things. Lot's pf MAC installs here. It's a little difficult to search as the dumb search engine won't read 3 letters, Try searching geared motor or EM3ev.

 

[ScooterMan101]

I did not know about DNP freewheels, so I bought Sunrace, the 9 speed does not work , but with the right 2 or 2.5 mm spacer on the back side of the Freewheel, where it comes into contact with the hub, I might work, but then I would have to use more spacers on the axle near the dropout , so I will put that on hold and try the 8 speed freewheel the 8 speed freewheel does work on the Mac Hub, and it clears the frame with a 2mm-2.5mm washer from the hardware store that I use as a spacer on the axle.
the Sunrace 8 speed freewheel has a 13 tooth as the smallest, where as the 9 had an 11 tooth, I will just use it, I have to spin the cranks faster than most people because of pain in the knees. so I don't know what the deal is with 11 tooth cog on hub motors anyway not owning a e-bike before.

As far as the Caliper goes, I just late today , ordered a 203mm rotor and a 203mm adaptor which will be here in just over a week. as one part was on back order. I Will just have to wait a little longer to get it built up.

 

[kudos]

I've done a few Mac builds now and so have run into the usual issues you mention.

Like most others I ended up using a 7 speed DNP freewheel:

http://em3ev.com/store/index.php?route=product/product&path=41&product_id=63

(I actually never change gears on my ebikes and have been considering moving to single speed and removing rear gear change all together)

I notice you say you have brifters (brake and shifters combined). My first ebike had these too, but I ended up replacing them with separates.

Regarding the disk brake side, I too have a 203mm rotor on one build and this does help raise the brake up away from the side of the motor, but it doesn't always completely cure the issue depending on the bike itself.

I would always use disk brake spacers to move the disk away from the side of the motor, this allows you to more easily set the brake calipers in the right postion:

http://em3ev.com/store/index.php?route=product/product&path=41&product_id=89

I used as much as 7mm spacing on one build.

It is CRITICAL you use at least one disc spacer. If you don't and you just screw the disc onto the motor with the screws that come with the disc, due to their length they will push through the casing and push pieces of metal into the gears.

Even after reading about someone else who did this, I ended up doing the exact same thing, but managed to pick all the bits of metal out and was fine.

Just my thoughts....


Kudos

 

[ScooterMan101]

Thank You Kudos !

I did not even think that the designers of the MAC , did not make the holes for the bolts for the disc longer, or supply shorter bolts with the motor

I will after my build with the spokes I will measure the bolt length and depth of the disc mounting holes .

B.T.W. what spokes did you use on your MAC builds ?

 

[gonespa]

Are you sure no disc brake bolts are suplied with your motor? Mine came with them. They are shorter than the ones suplied with any disc you might buy.

By the way, in the Bafang you can use the supplied shorter bolts without the spacer (I have my disc with no spacer although I don´t know if that is the MAC case)

Thank You Kudos !

I did not even think that the designers of the MAC , did not make the holes for the bolts for the disc longer, or supply shorter bolts with the motor

I will after my build with the spokes I will measure the bolt length and depth of the disc mounting holes .

B.T.W. what spokes did you use on your MAC builds ?

 

[ScooterMan101]

No, disc brake rotor mounting bolts came with my MAC, I did buy it locally though.

I did some measurements and sure enough, the bolts supplied with my brake, and even with my new 203 rotor are 10mm at the threads, and the Mac Hub thread area is 7.2 mm deep
and the rotor is a little less than 2mm so I will need spacers,, I have found them on the internet, but the problem is that they are only .02 mm thick,
so now I am going to look around for a used disc rotor and just grind off the unneeded area, or, go to the hardware store and see if they have the same bolts that are shorter , then get the expensive blue locktite .

 

[gm6046]

I run a MAC rear hub motor with a BB7 caliper. I just machined up a spacer. Could you do something similar?

Here are a few pics....

http://endless-sphere.com/forums/viewtopic.php?f=6&t=33290&start=15