I had been itching to do a full suspension electric fat bike back when I first started this blog several years ago. The bike I had my sights set on was the $1500 Bikes Direct Quigley which promised a full suspension frame, X9 derailer, X7 everything else and a Bluto front fork. I knew there was no way I could build a bike myself for less than that so I anxiously awaited the coming of the Quigley. About a week after it was released it was suddenly marked as ‘sold out’. Apparently what actually happened was that Bikes Direct suffered a rash of frame failures and was forced to stop selling the bike. For people who had already taken delivery of the Quigley, they were shipped replacement Boris frames and promised a new Sniper frame when it was released. Some people opted for a full refund, but many took the frame swap deal with a partial refund and all was right in the world again.
Several months later the Sniper was released with a reinforced heat-treated rear triangle it seems that the problem with frame failures was finally fixed. I can’t seem to find a single person whining on the world wide web about their Sniper frame breaking which is great news because that means I can be first at something. My Sniper arrived with a bunch of issues including 4 paint chips on the frame, a missing lower headset bearing, and a very leaky rear shock right out of the box. After buying 15 Bikesdirect/BikeIsland bikes without a single issue I was incredibly disappointed. To say it took me a long time to finally get this build right would be a massive understatement. I have never spent this much time on any build I’ve ever done.
I swap around drive units on my bikes like I change my underwear (meaning I do it religiously at least once a month) and Rebel Scum was no different. Originally I started off with a BBS02 drive unit, then I upgraded to a BBSHD unit. The problem I kept having is that the pivot was so high and the shock was so leaky and squishy that I kept smashing the drive unit on every single log I rode over. I also felt like I really needed more power on this build than either of these drive units could provide. I had tried using the Cyclone 3000W drive unit on trails with my Dark Side build but I found the mounting bracket was too sketchy and the drive unit was just too heavy to enjoy myself fully. I read about the Tangent Ascent drive from a devoted blog reader which promised a full 3000W in an ultra lightweight 7.5lb package and I knew that I had to give it a try. Ron did an article about the Ascent here a month ago on our evil-twin stepsister site electricbike.com which is a good read, but left me hungry for more.
I contacted Dave at Tangent and told him to sign me up and several weeks later a 100mm drive unit showed up complete with everything I needed to get riding. I was really impressed with the quality of construction and the engineering that was put into the Ascent drive system. The unit is available now for 68, 73, 85 and 100mm bikes right here for around $1900 – $2020 depending on your BB size. It was remarkably easy to install the 7.5lb drive unit and it took about as long as it takes to install a BBS02 or BBSHD once you get the existing BB out. In order to install the ISIS BB you will need a threaded BB or it just won’t work. You will need a special ISIS BB tool which I didn’t have, but my local bike shop did have one and they were happy to let me use it for free. If you need to get one then just buy the Park tool BBT-18 which runs about $14 or so on ebay. For DIY builders you can also just buy the barebones housing for $750 and add your own Astro motor and controller right here. The housing will support the more powerful Astro 3220 which runs about $695 before options from Astroflight here. Be aware that the 3220 is much longer than the 3210 so it may intrude on the crankarms for a narrower BB bike. There are also plenty more Castle Creations controllers to choose from which go all the way up to 160Amps in an incredibly small package here. If you use a different controller than the HV80 be aware that the mounting holes will not line up and you’ll probably have to drill new ones. I would not waste your time putting this drive on anything but a full suspension bike, you’re just going to have to trust me on this one. One of the greatest pleasures with this drive is to be able to ramp up the power and hit jumps which can be incredibly sketchy on a front suspension or no suspension ebike.
I got the Ascent with the extra long extended bracket so that I wouldn’t have to worry about hitting it on logs or going over log piles. Even with the very loose shock I never hit the drive unit on anything for the full week that I tested it. The drive unit I got was a 40:1 reduction which produced an insane amount of torque at very low pedaling cadences. I got in the habit of going off jumps while going up 25-degree grades at over 20mph which gives you some idea of the insane power of this kit. The biggest problem that most people have had custom developing custom Mid Drives around the Astro drive unit is things like jackshafts breaking. The 3210 Astro produces an insane amount of torque (200 ft/lbs) for a little tiny motor and it is designed to be installed on large RC airplanes, not to mid drive bicycles. The air never offers resistance the way a fully loaded ebike with your fat ass in too high of a gear does. I rode the Ascent in a variety of conditions for about 50 miles before the drive unit failed on me most likely due to a bad reduction gear bearing. The kit still ran but was clearly having serious power problems, and I noticed when I rolled the bike backwards without any power there was much more resistance than there should have been.
I contacted David about the drive unit failure and he was incredibly helpful and cooperative. One of the awesome parts of this design is that the bearings can be swapped out in less than 5 minutes and the entire drive unit can be taken apart with screwdriver very easily. I shipped the drive unit back and he suggested that I try the 20:1 reduction ratio instead so I’m going to get the drive back in a week or so with a different drive ratio. The 20:1 spins much faster but allows you to get much more access to the power of the Astro motor which really likes to spin fast. The only problem with the 20:1 ratio is that most of the time you are running the drive unit faster than you would want to pedal to keep up with. Since the unit was so powerful and was throttle only I felt like I wasn’t really pedaling at all anyway on most of my rides. Your pedal input feels positively pointless when you have 4hp at the twist of your wrist. The only exercise I got while driving this unit was trying to keep myself upright and not wrapped around a tree while going much faster than I really should have on the trails. Did I mention that it’s insanely fast?
The only two serious downsides I found with the Ascent drive system were the noise that the drive unit made and the fact that you have to add 1ml of grease to it every 100 miles. The drive unit does not make that much noise at lower RPM ranges, but when it is wound out, it sounds like a swarm of angry bees. Ironically when you’re riding the ebike it sounds a lot louder than it does to everyone else around you. When I would loan it to my friends I felt like I could barely hear the motor whine and it wasn’t that annoying. When I was riding the bike I yearned to have death metal blaring in my ears to drown out the sound of the motor. Greasing the motor was a simple task that took less than 2 minutes. For a bike enthusiast like me, it is no big deal as I am used to lubing my chain after every use anyway. For your average Joe it might be a bit of a stretch to remember to do the maintenance. Luckily the Cycle Analyst has a trip meter you can use to keep track of your maintenance schedule as long as you remember to look at your CA every hundred miles or so. I did the best job I could ignoring the fugly CA entirely.
The first rear tire I tested with this build was the Kenda Juggernaut Pro 4.0 tire which turned out to be a real loser as it only lasted about a mile before the sidewall ripped apart. I ended up settling on the Kenda Juggernaut 4.5 which is a much heavier and more robust tire which I am happy to say worked quite well with this setup with plenty of clearance on the rear chainstays. Although it was tested with ultralight Qtubes on it, I will set it up Ghetto tubeless in the not to distant future. I ran the front with a Bulldozer 4.7 tire that I stole off my Dark Matter build as I am running short on decent fat bike tires, but have a HUGE pile of crappy ones.
I used a backpack battery exclusively with this build, but construction is almost finished on a 52v 25Ah GA custom pack designed to fit in the top part of the triangle of the Sniper and put out 50Amps Cont. I highly recommend that with the Ascent drive system that you only use it with a battery that can put out 50 Amps continuous and runs at 52v. The power capability is there, so why not use it? The Castle Creations controller cannot take any battery over 52v, so don’t waste your time. I’ve had issues lately with batteries getting thrashed when I mounted them on the frame, so if you do it make sure you have a lot of padding around the battery, or better yet just keep it safe in your backpack.
I’ll be writing a longer separate article on the Ascent mid drive in about 2 weeks when I get the drive unit back with the 20:1 reduction ratio. I’m going to save more of my critiquing of the drive unit for that article. Suffice to say I have not ridden any drive unit that outperformed the Ascent from a weight\performance standpoint. Although the Ascent is expensive at around $2020 for the tested 100mm version, everything about this drive unit screams quality and the support from Tangent on it has been very excellent. I fully expect the Ascent will give me years of trail & snow shredding performance. After a week on the Ascent, it sure is hard to go back to the old 25 & 30 amp mid-drives. They all feel grossly and unforgivably underpowered.