To Boldly Go … The Christini All Wheel Drive BBSHD Electric Fatbike

To Boldly Go … The Christini All Wheel Drive BBSHD Electric Fatbike
Karl Gesslein

When I was a child I was completely obsessed with Lego. I spent most of my free waking hours in my youth sitting on the floor for hours at a time building anything I could imagine. I distinctly remember one of my creations was an AWD motorcycle with a complex drive system that engaged the front and rear wheels together so that they would spin at the same rate while the fork still swung back and forth. This motorcycle even had a little tiny one cylinder engine with a piston that went up and down. I remember distinctly the joy that building that creation brought me even though it was ugly as sin. When I first heard about Steve Christini’s AWD fatbike that was going to be used for Kate Leemings pedal-powered trip to the south pole I was immediately excited about his bike. I knew I wanted to try it, even if I had to truck down to his shop in PA to check it out. If Steve was going to build an AWD fatbike that could trek the 1850km across Antarctica via the South Pole then I suspected that it might even be tough enough to stand up to my level of abuse. This article is about the two weeks I got to thrash on Steve’s AWD BBSHD powered ebike every day and how I discovered that this bike was nothing like I thought it was going to be.

The Christini AWD system is not that obvious unless you look very closely

Before I start talking about my actual experiences with the Christini AWD efatbike I should mention what my expectations were before I first got to ride the bike

  • A complex system with lots of moving parts that were going to get clogged up with mud and ice
  • Expensive to buy, expensive to get parts for when things break
  • Everything was going to be fragile and break easily under power
  • Noticeable drag on the bike when AWD system was engaged
  • The AWD system would not really make a noticeable performance difference when riding in mud, snow and ice

I could not have been more wrong on every one of these preconceptions about this ebike. On my first ride out I really fell in love with this efatbike and knew that I would eventually probably have to get one for myself (as soon as I win the lottery or pay off my existing debt to the US criminalized banking system).

This closeup shows the clutch engagement mechanism for the rear hub, it works like a champ

I experimented with AWD efatbikes several years ago when I threw a 12T Mac motor on the front of my Boris X9 BBSHD efatbike. This setup was pretty marginal because the problem with having a front motor spinning at a different speed than the rear wheel is that most of the time the front wheel would just spin out. That would end up making the ebike even more out of control than it would be if there was no motor on the front wheel at all. When you use a Thudbuster LT with a soft shim it pushes the seat position back several inches which makes the fatbike weight distribution totally off and turning it into a wheelie machine. On top of that having an extra 10 lbs on the front wheel just make for an absolutely awful riding experience. At that point, I had basically written off AWD ebikes as being something that was not worth the time and effort. The incredibly lightweight 2.3lb Christini AWD system really changed my mind about what a real AWD system was capable of on an electric bike.

Behind a plastic plug, the front gearing can be found hidden inside the head tube

The way the Christini system works is pretty ingenious. The engagement clutch is near the rear hub which engages the pinion with a large gear that attached to the rear disc attachment point. The power is routed through drive shafts up the body and through several universal joints and into a beveled gear inside the headtube. This then goes down and then is spaced out into the fork and the drive shaft goes down the outside of the front fork and engages with a freewheel gear on the non-disc side of the front wheel. This means when the clutch is disengaged none of AWD the drive system moves at all. It also means when the AWD drive system is engaged and you crank on the rear brakes, the back wheel can skid out but the front wheel can still turn as the freewheel in the front fork allows it to spin at a higher rate of speed than the rear wheel. This freewheel also fixes a common problem with AWD systems where if you turn the front wheel sharply the entire vehicle will ‘jump’ because of different rates of turning on the front wheel (faster turning in a steep turn) vs the rear wheel (which turns slower in a steep turn). The beauty of the Christini AWD system is that you don’t have to know any of this stuff, the bike just works the way it should.

The front fork sports carbon tubing and you can see the drive shaft run up one fork

Normally when I ride on the snow with an efatbike like the Phat Phuk I run the tire pressures insanely low and just go out and ride in a very low gear with the motor cadence running much faster than I could ever pedal. The 60 amp Lunacycle Ludicrous controller makes the fatbike a wheelie machine and most of the time I feel barely in control at all. I point the front end where I want it to go, but the reality is that the bike does what it wants to. The back tire is constantly skidding out and the front tire drifts through turns and often will kick out and go in a direction that I really don’t want it to. It’s not uncommon for me to hit trees or end up with the bike completely out of control careening completely off the trail. Good times.

The 30T mighty mini is the perfect sized chainring for this build

95% of the days in the winter I can ride, the days are few and far between when conditions are just too bad to ride. The day I met up with Steve and he showed my this efatbike I had already gone out in the morning with my Rebel Scum II build and decided that the 3-4 inches of wet slush that was just impossible to ride in. I had no control at all and I couldn’t safely ride without the potential for serious injury. After I met with Steve I grabbed his AWD fatbike and headed right back into the woods with the same poor conditions. I was shocked at how well the Christini AWD fatbike worked. Even in the wet slushy snow, as soon as the rear wheel started to spin the front wheel would catch. The craziest part was that the front wheel wasn’t just going wherever the hell it wanted to all the time. Instead of heading back home with my tail between my legs, I was giggling like a school girl and actually started singing Disney theme songs to myself (that’s when I know the cray, cray is really setting in). “weema whoppaweema whoppa!”

If I had to describe the Christini AWD efatbike in one word it would be : ‘Epic’

The Ludicrous Experiment

The Christini ebike does not ship with the 2500 watt Lunacycle Ludicrous BBSHD controller and probably never will. Eric from Lunacycle doesn’t sell these controllers to hardly anyone and if you want to get your hands on one you have to buy a whole ebike from Luna (most Luna BBSHD ebike models have a +$250 Ludicrous option). I figured that the best way to really test the AWD Chistini system was to just run a lot more power through the drivetrain. I made it my diabolical mission for the 2 weeks I had Steve’s ebike to do everything I could to break it. To give you some idea of the power a stock 1500W peak BBSHD with a 30T chainring can easily plow through about 3 inches of heavy slush or 6 inches of snow as long as you’re not on a serious incline. The Ludicrous 2500W peak BBSHD can plow through about 5 inches of slush or almost a foot of regular snow (again as long as it’s not on a serious uphill incline). When it comes to deep snow the drive unit is much happier on level ground or going downhill. I generally cut my trails so I go uphill on plowed or snowmobile tracked trails and then back downhill through the deep powder where the motor doesn’t have to fight the snow and gravity at the same time.

You can see the rear AWD gear is integrated into a custom rear disc brake rotor

While the AWD system did not fail with the Ludicrous controller, it did become a lot less relevant. When I pegged the throttle in a really low gear the ebike was all wheelies, all the time. The extra traction from having AWD is lost when the front wheel is off the ground. I found myself having to stand up on the bike and lean pretty far forward just to keep the front wheel tracking properly with all that power. The fun factor on the Christini AWD ebike increases by a significant factor if you have a 2500W Ludicrous controller and a battery that will provide 50 Amps continuously. The frame pack that comes with the Christini is only rated at 30 amps continuous and seemed to have a hard time doing even that for more than a minute or so without noticeable voltage sag. I used a backpack battery with my homemade 14S7P 24Ah GA pack which worked swimmingly with the Ludicrous controller. If I was rich, I’d probably buy something awesome like a Crusher 2 with the Ludicrous 2500W controller and then also buy a 5″ tired Christini. Then I would swap the Ludicrous controller over to the Christini in the winter time (a 5-minute job) and back to the Crusher 2 in the summer. That being said, Steve Christini is also building a hardtail 29er ($3495) and full suspension 29er ($3995) to be released this summer (my wife is going to be so upset when she gets her credit card bill).

I was impressed at the durability of the all-steel SRAM 42-10T 11 speed GX gear set

Pros

  • Unreal traction in snow, ice and deep mud, there is nothing like it that I have tried yet
  • AWD system only adds 2.3lbs to the weight of the fat bike
  • AWD system didn’t clog with mud and snow even when riding it around in horrid conditions
  • AWD system is remarkably durable, drive system survived a 2500W Ludicrous controller
  • X11 drive system gives you great range and a real 42T steel granny gear and the cassette is still <400g
  • The 30T front chainring means if the battery dies you can pedal out of the woods without a motor
  • Choice of 3 different sized custom frames for either 4″ or 5″ fat bike tires (spoiler alert: get the 5″)
  • Engaging the 4WD system does not noticeably increase pedaling drag, the 4WD engage clutch is awesome and located conveniently on the handlebars
  • The bike actually has a decent warranty, Steve is such an awesome guy who seems really obsessed with building cool stuff and not really with making lots of money
  • For a custom AWD ebike made in the USA, the price is incredibly reasonable at $5595 for the tested configuration

Cons

  • Front and rear tires must be identical, if not identical then front wheel must be smaller in diameter or bad things will happen (massive drag on the AWD system)
  • You can only get parts for the AWD system from Christini
  • Costs more than a comparable non-AWD fatbike
  • Need to spray lube the 4WD hubs before every ride, don’t hit the brake rotor with the lube (free can of lube with every bike)
  • Not crazy about the 48v 30 Amp frame pack that ships with the ebike (I prefer 52v 14S packs)
  • Can’t fit the Snowshoe 2XL in this frame, although Steve is thinking about building a 2XL capable frame in the future as they already are out there on the fringe, might as well go ‘all the way’
  • The ‘Med’ size I tested felt a little small for me at 6’10”, Steve says I’m going to need a custom 22″ XL frame (not listed on the website)
  • The pedals that came with the bike iced up and sucked, I’ve found that cheap-ass steel/plastic bear claws are the only way to fly in winter
  • The hubs are not QR and require a hex wrench to remove the axle for either wheel
  • Bike is heavy – 60lbs as tested (larger 5P battery, cargo rack and some extra mud)

A rare earth magnet is JB Welded on the rim edge for the speedo which is pure genius

There was only one icy snow-covered hill that I could not make it up which was well over 40 degrees and covered with wet roots. Other than that slope (which I can’t make it up with any ebike I have) the Christini AWD fatbike handled everything I could throw at it. While you are limited by the 1500W that the stock BBSHD can up out, having it geared down to a 30T front – 42T rear combination means you can snail crawl up just about anything. As long as the snow isn’t heavy wet slush you should easily be able to handle about 6″ or less of snow with the stock Christini 1000W BBSHD. I would not even consider getting the 750W version, although it saves about 3 pounds, you will almost certainly be disappointed by the lack of power when riding in snow. You have been warned.

Here you can see the drive shaft that runs between the top tube and the seat stay, most of the transmission is hidden inside the frame of the bike

Riding the bike without using the motor

A couple of times I got stuck pretty far into the trails and the battery died on me, that means a long pedal back without power. Honestly, it didn’t suck as bad as I thought it would, I left the AWD system engaged and just got my ass off the seat and pumped those little chicken legs of mine for all I was worth. If anyone out there is thinking about getting the Christini Fatbike version without the motor I would say that you should go for it. Nothing is more frustrating when riding in snow then pushing pedals and having the rear wheel just slide out and dig down into the snow. With good forward pedaling posture and strong strokes, the AWD system works even if all you are using is your legs. When you finally get to the downhills sections, they end up being so much more fun because you don’t have to worry about the front wheel sliding out so you can ride a whole lot faster.

There is a nice cover plate for the head tube that swivels with the steering system to provide access to hidden gears

Would I recommend the Christini AWD eFatbike to serious riders? Honestly, in most conditions for 9 months of the year, I’m not sure you really need an AWD bike, but when it comes to snow, ice, soft sand, slippery logs and sloppy mud it makes all the difference in the world. With this ebike, I was able to traverse conditions without putting my foot down for balance that I absolutely would NEVER have been able to ride with any other ebike I own without constantly putting my foot down to ‘catch’ the bike from sliding out from under me. At one point I was riding on a fresh logging road (the loggers have absolutely decimated my precious forest) and the bike sunk down to the brake rotors in mud. I hit full throttle and somehow the AWD system pulled me out of the mud pit. Insane.

As for the durability of this bike, in 2 weeks I rode so hard the crankarm almost fell off, the derailleur hanger got bent and I kept making the seat wiggle loose. Nothing really substantial on this ebike failed in the 30+ hours I beat on it. Considering that with my home-built ebikes I tend to have a ‘significant’ failure every 4-6 hours of riding I have to admit I was really impressed. I suspect since Christini built their business on AWD systems for dirt bikes that made it so when they scaled the system down to ebikes they already knew how to build an AWD system that could take some lickings and keep on ticking.

I’m falling in love with the 11-speed GX SRAM system with the all steel XG-1150 cassette

Part of the fun of riding in the snow is the constant and complete loss of control. Riding with the Christini AWD efatbike felt like a completely different sport. Instead of constant damage control, it felt like I could fly at high-speed across almost any terrain. The confidence and speed that the Christini AWD eFatbike afforded me in snowy conditions pushed my riding up to the next level. Am I ready to ride that hard and that fast in what really amounts to seriously dangerous conditions? Time will tell. I’m finishing up with my Last Will and Testament this week which will ensure that my estate is handled properly when I finally kiss a tree at high-speed.

Until then I’ll keep riding as hard and fast as I can.

Don’t worry, I’m leaving all my ebikes to you, my only faithful fan.

Ride On.

Below are the specs of the ebike I tested which runs about $5595 and is available here. The only differences my ebike had was a 5P (16.75 Ah) pack instead of a 4P (13.5Ah) pack and Vee Rubber Bulldozer tires instead of the Snowshoe XL tires.

FRAMESET

Frame 6061 T6 Aluminum with integrated direct AWD system
FORK
Fork CHRISTINI Carbon FAT 135mm

HEADSET

Headset CHRISTINI integrated headset with sealed bearings.
WHEELS
Front Hub CHRISTINI AWD one way clutching
Rear Hub Carver 197mm thru-axle XD Drive
Rims Sun Ringle Mulefut 80m Rim – Tubeless setup
Spokes Wheelsmith DB black
Tires Tires- Fat Vee Rubber Snowshoe XL 26×4.8 Pure Silca

DRIVETRAIN

Mid Drive System BAFANG 1000W system
Battery Panasonic Shark 48V 13.5ah
Cassette XG-1150 Cassette
Rear Deraileur GX Rear Derailleur
Chain PCX1 Chain
Pedals Wellgo Mtn WPD-95B Clipless with platform

BRAKES

Levers SRAM Level Hydraulic (or AVID FR-7 Cable)
Calipers SRAM Level Hydraulic (or AVID BB7 Cable)
Rotors SRAM Centerline 180mm

COCKPIT

Bars RaceFace Aeffect 35mm Riser
Stem RaceFace Aeffect 35mm 60mm
Seatpost RaceFace Turbine 31.6
Saddle WTB Pro Gel
Grips Ergon GP1

WEIGHT

18″ @ 55 LBS

I rode this build in a variety of conditions, including frozen mud … cold and wet, the best of both worlds

More Power… Less Boring