Over the past couple of months I’ve gotten my hands on the 3000W Astro 3210 based Tangent Ascent as well as the 6000W Astro 3220 version. These mid drive units are built using a cycloidal gear with massive 40:1 or 20:1 reductions. I can say in no uncertain terms that the Tangent Ascent is completely unlike any other ebike kit on the market right now. It is designed for the discriminating buyer who wants a no-compromises ultra light drive system with massive amounts of power on demand. Riding the Ascent does not feel like you’re on a bicycle, with the massive wheelie popping torque available to you at a twist of the throttle it is much more akin to riding an impossibly light dirt bike. There is no other motor I have ridden where I could scream up a 15 degree slope with bumps and obstacles at 25mph with power to spare.

This drive system is just unreal.

One of the first things you notice about the Ascent Tangent kit is the weight. With a 7lb motor this kit weighs a whole lot less than anything else I have found in that power range. Both the 3210 3000W kit and the 6000W 3220 kit should be able to be installed on any bike with a 68,73,85 or 100mm threaded bottom bracket, but make sure to tell Dave what size your BB is when you order the kit so it fits right. There are also 2 options for the brackets, a standard length or a long one. I highly suggest the longer bracket as it will keep your expensive Astro motor up out of the way and keep you from smashing it on logs or rocks, although there will be a small weight penalty. The 6000W kit ships with the Castle Creations 120Amp Talon controller and the 3000W Ascent kit ships with a much smaller Castle Creations 60Amp ESC. Both controllers are much smaller and lighter than a comparable ebike controller and perform remarkably well under load. The 6000W kit is priced $300 more and as of the writing of this article is not listed on the Tangent website, but I assure you that it does exist.

If you opt for the 3000W kit then you should be able to run it with a standard derailleur and steel freewheel and cassette. If you go for the 6000W kit that setup is probably not going to work. I tried a bunch of setups with the 6000W kit including a fixed cog without any gears, a N171, and a Nexus 3. Of the 3 options I highly recommend going the Nexus-3 route. The N171 was super heavy (+8lbs) and started to leak over 4000W and it was scary fast in the tallest gear (over 45mph), The fixed gear had too much trouble getting going and the top speed was too low. The Nexus 3 seemed totally bulletproof if you exercised some discretion and did not shift it under load. The top speed was still much faster than I felt safe going on a $400 fat bike and the lowest gear could still climb 30+ degree grades without making the motor sound too labored. The Astro does not like producing lots of power at lower RPMs. It does like producing insane amounts of power when spinning fast. If there is a production mid drive on the market that has a better weight to power ratio than than the Ascent, I haven’t heard about it.

The construction of the Ascent is top notch. Everything from the custom 3D printed chain tensioner to the aluminum mounting brackets looks top notch. If you want to run the Ascent in the snow I would use a little silicon where the phase wires enter into the RC controller and around some of the Cycle Analyst connectors near the motor to keep the water out. The only real downside of the Ascent that I can find is the cost. For the 3000W 3210 version it runs about $1950 and for the 6000W 3220 version its $2300. Everything is made in the US and Dave from Tangent gives a level of customer service that is second to none.

Many people using the Ascent are going to be running a 12S Lipo pack from Hobby King. When you’re looking at putting out insane power bursts and using the lightest battery possible, nothing beats Lipo. I tested it with a variety of 18650 packs and found that the BMS was often the limiting factor for being able to maximize my power. Running with a 52v 14S 18650 pack I could often get 3000W for short bursts fresh off the charger, but once the I went a few miles I could only get around 2600W. Eric from Lunacycle.com sent me a 48V 13S 18650 25R pack with an ‘unlimited’ BMS but even that small 7lb pack would not produce more than 4000W  for very long. If you want a high power pack the 25R is a good cell to use as it is rated for 20Amps per cell cont discharge. No other cell really comes close to that. I found that I prefered using the Ascent with a backpack battery to keep the weight off the ebike.

Riding through the woods on the Ascent in many ways did not feel like mountain biking. There was just way too much power available all the time. With the 40:1 reduction ratio the Astro produced far more power at normal pedaling cadences, but the 20:1 reduction ration Ascent produced the best power bands at cadences that were far to fast to keep up with. The noise that the cycloidal gears produces sounds a lot like a swarm of angry bees and when you are riding it you feel like it is as loud as a chainsaw. When you loan your ebike to other people you will quickly learn that the system is much quieter for bystanders and really can hardly be heard from even a few yards away. When the unit first arrives it is also much noisier, but after about 50 miles or so the cycloidal gear breaks in and gets much quieter. I have to admit when I first got it I found the noise very distracting as I had been spoiled by the nearly silent operation of the BBSxx units, but once I got used to it then it didn’t bother me anymore.

The cycloidal gears require lubrication and every 100 miles or so you need to remove a small cover and push about 1ml of lubricant into the hole with a syringe. The entire process takes about 2 minutes and I for someone who lubes his chain before every ride I did not find it to be a distraction from my enjoyment of the Ascent at all. The hardest part was remembering to do it, luckily the Cycle Analyst has a trip odometer so if you don’t reset the CA after every ride and only reset if for maintenance intervals you will be set.

When I first setup the Ascent system I was pretty annoyed by the CA system. It looks clunky and unrefined and programming it with only 2 buttons feels pretty silly. Over time I got used to it and decided it was actually a decent system for what it was designed to do. The power rollback when the motor temps get too high is also a very nice feature that I have not seen on any other ebike. The Cycle Analyst v3 is built for over Watting ebike motors and the reality is that you’d be lucky if you could ever get the Astro motor to overheat. I beat on it pretty hard and it never got close to the 400 degrees that I understand it is capable of getting to without damage. That being said most of the time the motor is too hot to touch without getting burning. You’re much more likely to get overheat beep codes on your Talon or Castle Creek controller especially if you are putting large amount of amps though the motor at very low RPMs.

The Cycle Analyst comes preprogrammed from Tangent with all the settings you need to get going. Although there is a programming interface cable for the CA, you can also access all the settings through the display. Installation for the mid drive system was very similar to any mid drive setup. More detailed installation instructions with pictures can be found on the Tangent website here.

1. Pick a decent donor bike (preferably a full suspension trail bike) with a threaded 68/73/85/100mm bottom bracket
2. Remove the BB and crankset
3. Insert the Isis crankset with the ascent aluminum frame between the frame and the BB bearings and tighten with the BBT-18 Park tool
4. Install the right length single speed KMC reduction chain on the Astro and the chain tensioner
5. Build up the freewheel chainring with the right size BCD104 chainring (not included)
6. Install the Cycle Analyst, throttle and run the wiring. Plug in the connectors that fit together and test

The entire install for me took less than 2 hours and I had no issues at all. I would classify it as slightly more difficult to install than the BBSxx units from Bafang but much easier than the Cyclone 3000W kits. I was impressed with the quality of the ISIS BB and crank arms which are not likely to fail even at very high power levels. The freewheel was also very heavy but very robust and should not give you any problems. The only issue I had with the 6000W Ascent drive unit was that the Talon controller became detached after the first ride. I ended up just Velcro One tying it to the aluminum bracket and forgetting about it. You can also epoxy the controller to the metal which would be the smart way to deal with it.

20:1 or 40:1 Reduction?

The hardest decision you will have make before you order your Ascent is whether to opt for the 20:1 or 40:1 reduction in the primary reduction cycloidal gear. Having tried both I have to say if you want an ebike that you will be able to pedal along with on the trails then chances are you will opt for the 40:1 reduction. This 40:1 reduction becomes a 70:1 reduction when you take into account the secondary chain reduction. With this much reduction the Astro never seems to whine or complain when loaded up at low RPMs because even if the ebike is barely crawling along the motor is still spinning very fast. The torque you get from a 40:1 cycloidal reduction is pretty insane but the motor seems to wind all the way out at a pedaling cadence you can actually sort of keep up with. That being said if you want really high speeds you’re going to be limited with the size of your rear cog which will likely be an 11T and the size of your front chainwheel which will be limited by the BCD 104 mounting bracket. After testing the 40:1 for about 2 weeks I have to say that having this much reduction puts a tremendous load on the drive train, much more so than the fast spinning 20:1 reduction.

The 20:1 reduction feels more refined with a wider power band. It doesn’t feel like all wheelies all the time, but the power is totally there when you need it. The 20:1 suffers when the ebike has grinded to a halt and is trying to get going again up a steep incline. You can tell that some of the power you dump into it is getting shed as waste heat as the Astro squeaks and complains getting up to speed. Once the ebike is moving all your power is suddenly available again and all is right in the world. The Astro motors are designed with top quality components to drive the prop on extremely large RC planes. When driving large RC planes there will never be so much resistance against the motor, and you get an abundance of cooling as the prop washes air over the motor housing. When you take a motor designed so specifically for one application and utilize it in another application there is bound to be a few issues. The Astro works very well as an ebike motor and produces more torque than any ebike I have ever ridden by a far margin. It feels much more like riding an impossibly light and nearly silent motocross bike and not so much like mountain biking. With every other ebike I have ever ridden you end up crawling up steep inclines. With the Ascent you scream uphill and can actually hit jumps on the way up.

This is not your daddy’s ebike.

In the end I trashed the bearing on the 40:1 reduction and I was all to happy to settle on the 20:1 reduction which is what David from Tangent uses on his personal ebike. There was so much power available I never felt like it was worthwhile to pedal and I was better able to keep my balance with the pedals being still. Even with the unlimited BMS 48v 25R pack from Lunacycles I was never able to get more than 4000W to my 6000W drive system. I like that I ended up with a drive unit and controller that can take more power as I get more powerful batteries in the future, but for right now I feel like 4000W was more than I ever needed in the woods. My Astro 3220 build was so fast on the road it was scary and it takes real cohones (or stupidity) to take a $400 fatbike without a suspension over 45mph on the highway. The 6000W Ascent drive system can do this easily and probably even more. The top speed on the flats was not what impressed me, it was the speed at which the ebike screamed uphill. Be warned that going up steep hills at 30mph takes a tremendous amount of power. You will quickly burn through your ebike battery capacity if you don’t exercise some throttle restraint on the hills.

Looking for more info on the Ascent Tangent? There is a brief article written by Spinning Magnets on electricbike.com right here or you can check the official Tangent website here (although the 6000W unit option is not currently listed only the 3000W unit). There are also two build threads I did, one with a full susp fatty and the 40:1 3000W Ascent kit here and the other with a no suspension fatty and the 20:1 6000W kit right here. I would rate the Ascent a 9 out of 10 and only misses the highest rating because of the noise that the drive train produces and my general disdain for full twist throttles. I can say with some certainty that high power builders will NOT be disappointed after purchasing and installing this drive unit.

Ride On.