Now that I’ve had a chance to do some off road riding on trikes, I can share a few observations. Those with more experience than I can chime in. I will posit some contrary views here. This may get a little technical in parts.
What makes for a good off road trike?
Rear wheel traction – Strangely I don’t see much focus on this, but the #1 problem I have triking on rough ground is loss of rear wheel traction. We’ve all known about this problem, it is why trikes usually don’t have a rear brake except for a parking brake. Anything you can do to move weight to the rear wheel helps off road. If you have a sliding seat and boom, like many TerraTrike or AZUB models do, move it all back as far as you can. ICE trikes have a fixed seat mount but ICE makes an accessory that will move the seat back for taller riders, which may be beneficial. Recline the seat as much as you can stand to. Rear hub electric motors and rear mounted batteries help, as does cargo loaded to the rear.
My feeling is the frames designed for 20” rear wheels have an advantage here since the rear hub will be tucked closer to the rider’s mass. Trikes like the Rambler and Rover we’re actually designed for 24” rear wheels but come standard with 20”, so they don’t get the full advantage. Big rear wheels are good for speed, but have less traction.
A caveat here is that having the seat adjusted far back on the frame works against stability because the rider’s mass is closer to the edges of the weight triangle. If that isn’t clear, imagine a triangle drawn between the ground contact points of the trike’s three wheels. Once you move weight outside that triangle, usually on a sideways sloped surface, you begin to unweight one of the wheels and move toward tipping. Still, this instability is manageable, and rear wheel traction problems are so common riding off road that you should address them, either through adjusting what you have or selecting the right trike.
Knobby tires are an obvious way to get more traction, as are wide tires, even if they aren’t knobby. Reducing your tire pressure is another big factor, and of course wide tires can roll at lower pressures better than narrow ones. I’ve never had a chance to directly compare knobby vs. street tires since I’ve only taken stock trikes out. Even our shop demo Full Fat has street tires on it since it is mainly test ridden in the paved parking lot. I know from riding the Full Fat that inflation pressure makes a big difference, and the biggest advantage of fat tires is your ability to ride them at 15 PSI. Whatever tires you have, lower the pressure as far as you can.
Ground clearance — This is what you usually see touted as defining an off road trike. Some trikes have higher ground clearance by design, such as the Rover, the Rambler, or the Adventure. They don’t need oversized wheels, they just have a straight frame tube, handlebars above the frame, and no chain idlers hanging down. Catrikes have idlers assemblies hanging below the frame, and AZUB trikes have handlebars under the frame, working against ground clearance. Trikes like the ICE Sprint and the AZUB Ti-Fly have curved frames that aid stability but reduce ground clearance. But these were designed to be faster trikes, and if you are going fast on-road and carving into turns you want that stability, and higher trikes suffer from tippiness.
Jacking up the wheel size, like when you turn a Rambler into an All-Terrain, or an Adventure into a Full Fat, does increase ground clearance, but this further increases tippiness. My problem is that Ramblers and Adventures already had a pretty high seat before increasing wheel size. I was impressed with the prototype 3×26” Ti-Fly, because the big wheels were paired with a dropped frame and (what started with) a low seat. Remember I said the Ti-Fly wasn’t an ideal off road trike, but when you put on big wheels then it does work well because the rider’s weight is lower relative to the hub axles. While the Full Fat is based off an Adventure frame, the original White Ice trike that Maria Liejerstam rode to the south pole was built on a Sprint frame. Remember what I said about the weight triangle and stability. Just getting some of the rider’s weight beneath the level of the hubs will bring benefits in stability. The instability of putting big wheels on trikes is a problem, but it is compounded by the manufacturers’ choice of what trikes (Ramblers and Adventures) they put the big wheels on.
An anecdote is the one time I took a group of inexperienced riders out on a forest trail, the one casualty we had was the fellow riding the Rambler All-Road. He was stopped on a sideways sloping trail and he looked back over his downhill shoulder at the rider behind him. That move alone tipped the trike downhill. Crazy-high ground clearance is not necessarily your friend.
Big Diameter Wheels – I treat these separate from ground clearance though they are used mainly to increase ground clearance. Big front wheels do confer benefits that should be noted. In particular, since they come closer to the rider, it is easier for the rider to “wheelchair” the trike, laying hands on the front tires and pushing them directly, giving all-wheel drive when facing a challenging rise on loose ground. You will see my repeated concern with drive traction here. Also, “wheelchairing” gives you the ability to back up. In dense foliage it is easy to get into a situation requiring a very tight turn which the trike can’t make. If you aren’t on a trail at all then you may find yourself unable to move forward and needing to backtrack. This ability to “wheelchair” is the one true benefit I can see to big front wheels. One can argue that big wheels roll over obstacles better, but given enough traction a smaller wheel will do it too. The practice of wheelchairing argues against front fenders on an off road trike. A rear fender will keep water off you, but I’ll point out that going through water off road increases erosion and siltation. You shouldn’t be blasting through streams anyway.
I don’t see any benefit to a bigger rear wheel. It reduces traction. A wide tire is handy for not bogging down in sand and mud, but a larger diameter doesn’t help as much considering its drawbacks. This begins to paint a picture of a Full Fat with a smaller rear wheel. I will grant that this wouldn’t look as impressive as a 3×26” Full Fat, but I’m the sort who is more interested in what works than what looks good.
Suspension – Suspension is worth it, but not essential. Pay more, get more. You will cover rough ground more quickly and with less jostling to your load, less vibration on the bolts holding the trike together.
Steering type – Direct steering, like on newer TerraTrikes, turns much tighter. Its simpler construction means you can modify it for better ground clearance more easily. For example, the single steering rod on a Rambler should be mounted using longer bolts and spacers to move it as high as possible to improve the trike’s ground clearance.
Internally Geared Hubs – This is a great way to make a trike even more expensive, but worth it in this application. I’m never too concerned about rear derailers hitting the ground on-road, but on soft sand you could bury your chain in grit. I’m especially impressed with the NuVinci CVP hubs, which never lose torque during a shift. They don’t “clunk,” and even other IG hubs with discreet gears will have a moment of slip and clunk when shifting under load. And if you are downshifting then you are probably under load.
Summing up — What would I consider an ideal off road trike? Nothing yet.
I like the ICE Adventure 20”, though the quick release linkages in the handlebar aren’t rock solid and the indirect steering isn’t as tight as direct steering. (Update: ICE has improved how the handlebars lock into place) I like how the rear wheel is close to the rider. The modularity of the ICE frame would let you use an internally geared hub with a sprung chain tensioner, giving more ground clearance for the chain.
I was impressed with the stock TerraTrike Rambler, though the frame design keeps the rear wheel pushed back too much. It has high enough clearance with its 20” wheels, and the direct steering will get you through very tight turns in a switchback trail. It could use an IG hub without a chain tensioner by tensioning at the boom
I was impressed with the 3×26” Ti-Fly, though I’d like to see it done with a 20” rear wheel. Again, the indirect steering is a limitation. I don’t like how the handlebars are set under the frame, and some of its chain management drops too low as well. But its adjustable seat and boom give great flexibility in set up, and also the ability to use an IG hub without a tensioner.
How knobby a tire do you need? If your trike will only be used off road then I see no reason to go completely knobby, but if you will be on some pavement these will limit your efficiency. One compromise is to only put a knobby on the rear wheel. While there are semi-knobby tires with a smooth center and knobby edges these are aimed at two-wheelers who need the extra traction cornering. Front wheels are highly loaded by the rider’s weight and don’t have much problem with traction.
I’ll take a moment to tip the hat to a nearly forgotten design from S&B, the scruffy custom recumbent house from the Los Angeles ghetto town of Compton. S&B built a trike called the L.A. Pipeliner which was designed to be folded and dropped down through an 18” manhole into a sewer pipe, where it allowed inspectors to pedal their way through the L.A. sewer system. Note the extremely tight wheelbase and track. It had a very simple chainline and the USS steering was above the frame. S&B trikes had their cheap aspects, to be sure, but I’d be interested in putting a NuVinci N380 on that puppy and taking it down the trail.
I do have a few extra TerraTrike All-Road wheelsets around, and the All-Road is going out of production, succeeded by the All-Terrain, whose semi-fixed seat is more solid than its predecessor but lacking in useful adjustability. And the new Gran Turismo models are coming in. Direct steering, dropped frame. The semi-fixed seat is the same as the All-Terrain, but once can adjust leg length through seat recline. Hmm. Change out the crankset on the 2×10 model for an MTB compact crank. Hmm.