Nearly finished a custom GMAC DIY

penserv

Member
Region
Canada
City
Calgary, AB
This Ebike has been my COVID-19 mental health project and it proves that I am now certifiable, but who cares, it's almost done. I've been following Linklemming's build and I didn't go for a custom frame. I had traded an indoor trainer to my son in law for a Specialized Curve bike and then found that the triangle in the frame was too small to fit the battery into. So, just before Christmas, I bought a used mountain bike. In Calgary, in December, the pickings are rather slim, so the bike I got was a GT Karakorum. It's a reasonable aluminum frame and it met my 2 criteria - large size and big enough triangle to fit the battery onto the lower tube. I discarded everything else on the frame except the handlebars and the front fork. It's a Suntour suspension fork and it's not great quality but the bike head is not tapered. It's just a straight 1 1/8" tube and the RockShox fork from the Specialized bike wouldn't fit. That's about the only component I might upgrade at this point. The bike is a bit dirty because i was able to ride it a couple of days ago and it was really wet with all the melting snow. I had to go with a 220 mm brake rotor on the rear wheel to get clearance between the edge of the GMAC hub motor and the caliper of the hydraulic brake. I also went to Magura MT5 brakes which are about 2 mm thinner than Hope brakes. I actually wanted MT7 brakes, but the LBS only had MT5 and even ChainReactionCycle was backordered till spring. Riding this thing is awesome. I averaged 27 km/hr on a long uphill climb of about 2 km from the bottom of the Bow Valley to the top of the ridge. I still have to fine tune the PAS sensor, because right now the power cuts in at max. I've got the Baserunner controller, which is incorporated into the battery cradle and just makes the battery look bigger (52V, 20 AH). The Baserunner is just as configurable as the Phaserunner, so I have the electronic freewheeling set up on 1.5 amps I also found a nice USB adapter so I can charge my cell phone or Garmin on longer rides. This is the same adapter that Grin sells (they're out of stock till spring). I got this one from Golden Motor. I also added the SPL-01 headlight from Grin (again, out of stock). I got that one at Hilleater. Wonderful headlight. May never need it, but you never know, one evening at the golf course, after a few pints, it might be nice to have a good headlight. This hasn't been a cheap project. I haven't tabulated everything the way Linklemming did, but I figure I have about $4K Cdn in this build. That's equivalent to the $3K US Linklemming had. But everything is quality components and built the way I want it. I've got a handlebar bottle holder and bell coming this week and if I have to, I'll put the handlebar extender back on for all the accessories. Another cool thing I put on this bike is the N-Lock head piece. You have to ride with the key in, but when you lock it, the handlebars move independently of the front fork.
 

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Deacon Blues

Well-Known Member
I've been itching to do a build like yours, but I've already got an awesome e-gravel bike and I've got another ebike (commuter) coming in May, so putting out even more money for another ebike is hard to justify.
I do have a nice bike for the conversion (a 1990 Rocky Mountain commuter), but it has rim brakes, which might be inadequate for the GMAC's power and much higher speeds.
 

penserv

Member
Region
Canada
City
Calgary, AB
Building a custom Ebike is not a trivial pursuit, but with COVID, what else can you spend your money on? This is my travel budget, cuz I can't go to Spain. It's also been a lot of fun, except for the day I fried my cell phone, when I discovered that not all bike USB adapters are created equal.
 

JRA

Well-Known Member
There really is a certain amount of satisfaction gained with any DIY process. There may be some frustrations along the way and not for everyone but when you view the final result and it's just as you imagined that is the reward.

Nice bike and I don't often read run on reviews without paragraphing but I managed to make it through yours....
 

penserv

Member
Region
Canada
City
Calgary, AB
Being able to post on a forum is the fun part of this build, so i tend to get a bit excited about it. I'll try to observe better grammar and structure in future posts.😊
 
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penserv

Member
Region
Canada
City
Calgary, AB
Just had an interesting experience with this bike. Locked it up and parked it outside a pharmacy while I went in to get my 2nd vaccination and when I came out and started to ride away, man, was it tough pedaling. There was no pedal assist at all. I had to get home just on throttle with some pedaling. Threw it up on the workstand when I got home and it was a simple fix. The PAS connector had separated. Works great when there is power there. So, just another thing to keep an eye on. Don't know if someone was messing with the bike or if it just happened over time. I've got almost 500 km on this bike now.
 

creativepart

Active Member
Region
USA
Looks GREAT!. At the end of December I built my DIY eBike from a Dillenger Kit - the "Premium Rear {Geared Drive} Off-Road kit." It's been super. I started riding it in January have have just under 700 miles on it already. That's 1,100 km's In your neck of the woods isn't it?

I thought it would be a lengthy process and take up some of my retirement time - but it took no time at all. It helps that I was working with a 2018 Specialized Crosstrail Disc that I purchased and had never put any miles on it. It's a cross between a road bike and a mountain bike but more of a mountain bike. It took 1/2 a day to strip it for the install, a full-ish day to install everything and 1/2 a day to dial in everything. Thank goodness for zip ties. The kit I purchased was all complete so, my build was $750 for the kit plus the "free" bike in my garage (it cost $850 new in 2018)

Be careful you don't get the bug after awhile to build another. I've been watching the used bike classifieds to pick up a good hard tail candidate to start a new build with a mid-drive kit.

SpCT-eBike-Rockport.jpeg
 

JES2020

Active Member
This Ebike has been my COVID-19 mental health project and it proves that I am now certifiable, but who cares, it's almost done. I've been following Linklemming's build and I didn't go for a custom frame. I had traded an indoor trainer to my son in law for a Specialized Curve bike and then found that the triangle in the frame was too small to fit the battery into. So, just before Christmas, I bought a used mountain bike. In Calgary, in December, the pickings are rather slim, so the bike I got was a GT Karakorum. It's a reasonable aluminum frame and it met my 2 criteria - large size and big enough triangle to fit the battery onto the lower tube. I discarded everything else on the frame except the handlebars and the front fork. It's a Suntour suspension fork and it's not great quality but the bike head is not tapered. It's just a straight 1 1/8" tube and the RockShox fork from the Specialized bike wouldn't fit. That's about the only component I might upgrade at this point. The bike is a bit dirty because i was able to ride it a couple of days ago and it was really wet with all the melting snow. I had to go with a 220 mm brake rotor on the rear wheel to get clearance between the edge of the GMAC hub motor and the caliper of the hydraulic brake. I also went to Magura MT5 brakes which are about 2 mm thinner than Hope brakes. I actually wanted MT7 brakes, but the LBS only had MT5 and even ChainReactionCycle was backordered till spring. Riding this thing is awesome. I averaged 27 km/hr on a long uphill climb of about 2 km from the bottom of the Bow Valley to the top of the ridge. I still have to fine tune the PAS sensor, because right now the power cuts in at max. I've got the Baserunner controller, which is incorporated into the battery cradle and just makes the battery look bigger (52V, 20 AH). The Baserunner is just as configurable as the Phaserunner, so I have the electronic freewheeling set up on 1.5 amps I also found a nice USB adapter so I can charge my cell phone or Garmin on longer rides. This is the same adapter that Grin sells (they're out of stock till spring). I got this one from Golden Motor. I also added the SPL-01 headlight from Grin (again, out of stock). I got that one at Hilleater. Wonderful headlight. May never need it, but you never know, one evening at the golf course, after a few pints, it might be nice to have a good headlight. This hasn't been a cheap project. I haven't tabulated everything the way Linklemming did, but I figure I have about $4K Cdn in this build. That's equivalent to the $3K US Linklemming had. But everything is quality components and built the way I want it. I've got a handlebar bottle holder and bell coming this week and if I have to, I'll put the handlebar extender back on for all the accessories. Another cool thing I put on this bike is the N-Lock head piece. You have to ride with the key in, but when you lock it, the handlebars move independently of the front fork.
Hey , looks like you need a longer chain, your derailleur is really sticking down.
I just ordered a new one for my 42 to 48t chain ring conversion installed today.
 

penserv

Member
Region
Canada
City
Calgary, AB
I've got almost 1200 km on this bike since March, mostly just back and forth to the golf course. At 25 km per trip, that's almost 48 rounds of golf, though there was some practice time in there too. So far no complaints about the bike, BUT, I got another flat tire, on the back, of course, for the second time. So this time I removed the rubber tube and installed the Tubolito tube. The only thing I don't like about the Tubolito is the valve stem is not threaded, which means you have to fiddle with the tube to get the valve stem straight in the hole in the rim.
TubolitoStem.jpg
As you can see from this photo, I didn't fiddle enough. It was straight with a little bit of air, but went crooked once fully inflated. I'm sure that the tire will tell me if there is a problem with a crooked stem.

Sometimes though, a flat tire can be a good thing, because it gets you to look at things again. My rear wheel axle has never seated all the way down into the cutout. When I installed the tire this time, I noticed that the torque arm on the GMAC motor was rubbing on the frame. Out with the grinder and problem solved, right?
TorqueArm.jpg


Well, not quite. The difference in the axle when fully seated in the cutout was about 6 or 8 mm and then the brake calipers were bouncing on the top of the rotor. That fix was simple. Just add 4 more washers as spacers to the brake extender bracket and one washer under the brake caliper.
WashersOnBrake.jpg


The new washers are the shiny ones. But the washers were just ever so slightly larger in diameter than the brake extender bracket and had started to rub a groove into the brake rotor, which I decided was probably not a good thing. If you tighten up the long bolt on the brake extender bracket and stick a thin flat blade screwdriver in between the washers and the rotor, you can move the washers out a little bit and create enough clearance on the rotor.
Clearance.jpg


Once all this was finished, the rear wheel seemed to spin better. I hooked up the base controller to the phaserunner software and was able to reduce the electronic freewheeling amperage from 1.88 to 1.44 amps and achieve a final spin rate of around 75 rpm for the freewheeling setup. You can also see how much I ground down the torque arm in this photo to get clearance on the frame.