Bicycles Are Bad At Towing, Even With Crawler Gears

Gearing can make a huge difference to a cyclist, enabling even the least fit rider to climb a steep hill, albeit slowly. [Berm Peak Express] took that to the next level, creating a super-low geared bicycle capable of actually towing seriously heavy loads.

The build consists of a custom 74-tooth sprocket for the rear wheel, paired with a 24-tooth chain ring for the pedals. The custom sprocket doesn’t have any holes drilled or other lightening measures taken, but given the slow speeds involved, the extra rotating mass probably isn’t much of an issue. With that gearing, 3.08 turns of the pedals will result in just one turn of the rear wheel, with the aim to provide tractor-like torque with the trade-off being incredibly low forward speed.

Installing the giant rear cog required using a 3D-printed guide to keep the chain tensioned, and the rear brakes are entirely absent, but it all came together. Bikes aren’t built for towing, and some issues are faced with dragging a Jeep as the bike struggles with balance and traction. However, with some effort, a grown adult can be towed in a child carriage up a hill, no problems.

The bike proves difficult to ride as the forward speed is so slow that balance is problematic. However, it was interesting to see the experiment run, and the wear marks on the hub from the huge loads put through the rear wheel. If you’re digging the weird bikes, though, check out this hubless design as well. Video after the break.

43 thoughts on “Bicycles Are Bad At Towing, Even With Crawler Gears

    1. And worn out knees & hips years earlier than otherwise. Why do I say that? At 55 I had to quit riding. I pushed higher gear ratios than other kids starting at about 12 years old. My knees are not yet at replacable, but the doctor says walk or swim for exercise – no bicycle.

      1. Good advice. From a brief flirtation with bicycle racing in high-school, I learned about the effectiveness of pedaling at a higher rate (70 to 90 rpm) vs grunting in a too-high gear… and since then I’ve always kept a higher cadence. I was never much of a racer, but I still enjoy bike rides as a senior, with no joint issues.

        And yeah, bikes suck at towing much more than a toddler (or the equivalent weight in camping gear).

  1. With a 30 tooth chain ring and 42 tooth sprocket and 700c wheels I find on a steep damp road surface my touring bike loaded with 4 panniers and a tent still reaches the dual limits of spinning the rear tyre if I lean forward and lifting the front wheel if I lean back. A sort of cycling coffin corner. And I’m a not very fit middle aged bloke. To actually make any use of such a low gear as this you would need to seriously ballast the bike!

  2. 1) Don’t use a rope or chain to tow – use a rigid connection. Otherwise your trailer will want to run you over when you stop.
    2) Notice how he kept tipping to the left? Connect your hitch to both sides of the rear axle to help maintain balance.
    3) Fat tires will help traction.
    3) Don’t coast downhill on that thing, towing a load or not. With only front brakes you’re just asking to be thrown over the handlebars.

    1. (3) don’t slam on the brake… or you _will_ be thrown. It’s also a lot harder for the bike to throw you if the rear is heavily loaded down, as would be the case here by the trailer load.

      I use the front brake most of the time with little consequences.

      1. Good thing, too, since your front wheel contributes somewhere between 60 and 100% of your stopping power on a bike. In the shortest possible emergency stop your rear wheel has no weight on it. (Nose wheelie.)

        1. After reading [this]( article I started using the front brakes exclusively … one of the points claimed there is that it is literally impossible to lock up the front wheel on dry asphalt … and I vigorously tested that.

          It is honestly quite remarkable how fast you can get to a stop if you really lean into the handle bars and hit the front brakes hard. I go down a small hill every day relatively fast (avg. 40 km/h; max. 51 km/h) and am able to stop that in what feels like five meter before the next crossing.

          The only time I was able to lock up the front was on dry packed sand, which is honestly not a great feeling, but wasn’t really critical as I instinctively let go of the brake.

          Once you utilize the front brake extensively the rear one is basically useless as it locks up nearly instantly as there is no load on the rear wheel anymore.

          Also, not using the rear brake might actually be safer, as the bike quickly starts to skid sideways when the rear wheel is braking less hard than the front wheel. I guess this exact thing would happen if you engage both breaks hard when panic braking.

  3. There used to be a New Mexico company called GIOS (different than the italian bike manufacturer) that built a part called the tamer quad. It was a five bolt spider that bolted on under the smallest (24 tooth) chainring of a 1980’s style mountain bike triple chainring, and provided a place for a fourth front chainring, using Suntour rear cogs, so you could run a 12 tooth front chainring, with a (at the time common) 14-38 rear and get a similar gear reduction.
    What we found is that even without towing a load, the torque this could produce was ruinous. It broke chains, crushed freewheel pawls, and on one occasion sheared the whole splined section of a Shimano hub right off the hub itself, so the freehub cogset section was no longer connected to the hub.
    A person on a mountain bike can produce about 100 foot pounds of torque briefly and bike parts are barely built to handle that: they anticipate a minimum of 1:2 reduction, not 3:1 reduction.
    This is particularly the case for newer, lightweight, high performance bikes. My ex-gf had an amazing mountain bike, very lightweight, with 17 gauge titanium spokes, and even with stock gearing (28 front 34 rear) I could snap spokes purely in tension by doing things like hopping the front wheel up a log and then trying to power the rear wheel over it.
    This kind of use needs a cargo bike with motorcycle-like rims, spokes, and drivetrain.

  4. Not that this needs to be done, I just would like to see this done: adult tricycle… stretch out the frame so that it’s 10 foot long and you sit up near the front. Drag racing motorcycle style frame with a long swingarm. Give it another try!

    1. There’s a weird subgenre of stunt bikes popular in the mideast that are kinda like this: normal front end, very extended rear end, like 2-3 meters, with no tire on the rear just the steel rim. They’re intended for drifting. People can oversteer and spray sparks all over. is a poor example. I’m not finding better ones with a quick search though.

  5. I have a bike with a more…sane crawler gear, possible in a conventional chain drive system made with off-the-shelf parts, and even with that, balance is a bigger problem than torque/traction when trying to ride up very steep inclines. You reach a point where even when leaning as far forward as possible, the bike is almost unicycling on the rear wheel and it’s very unstable, especially if the bicycle isn’t pointed directly uphill. This causes me to spill off one side of the bike or the other rather than tumbling off backward as you might’ve expected.

    If you’re towing something you may have the same problem with the direction of the load differing from the direction of the bike, especially when turning – the weight of the load could be pulling the bike over to the side. I imagine having the load connected to a pair of tow points below the rear axle close to the ground might reduce this as well as reducing front wheel lift.

    1. On a steep climb a standard bike’s geometry gets all wonky because the effective head tube angle is so low. Road climb specialists used to have bikes with very steep geometry so they’d ride correctly on steep protracted climbs. (This is for a pure climb race: they were just as awful on flat ground as a standard geometry is on a steep climb.)
      Of course, mountain bikes climb even steeper yet, and yeah on something with lots of traction like sandstone slickrock, it’s common to end up with your limiting factor being the handlebar placement because you’re so far forward the handlebar is pushed into your stomach and your legs can’t get full range of motion because of the handlebar placement. Front wheel has no traction so you can’t steer right, and as a result a minor deviation from pedal-induced steering means you end up off the side as you can’t regain balance through steering correction.
      I don’t think a tow bike would see geometry issues but it would see recovery issues through the unloaded front wheel.

  6. This is just giggly clickbait and a proof of the Wadsworth Constant. Any serious attempt to turn pedal powered vehicles into traction engines will eventually lead to an understanding of why tractors weigh a lot in the right places, and are built to be as stable as possible.

  7. i agree, self powered is a good idea.. I’m going to add that to my build list..

    I have a small trailer for my bike at my holiday house – and regularly do about 100Kg in it. I agree that is much lighter than the above, but it isn’t a problem to pull it around with a standard bike at quite a respectable speed.. So bikes can tow fine – but the same rule as your car applies ie don’t try and tow something heaver than your car/bike(plus passenger) as you can end up having ‘fun’.

  8. practically, i don’t tow anything heavier than 250lb with my bike.

    and just towing the two kids in a trailer, total weight around 150lbs, i broke the chain. i downshifted to the little chain ring, overall ratio around 1:1 or slightly less. the chain was worn, and it was a ridiculous hill to attempt. but it was a little disappointing.

    i am curious, i haven’t gotten a good handle on it…for the same final gear ratio, is there a difference in the chain loading between using the big chainring with the big cog or using the little chainring with the little cog? it seems like the distance the chain travels is different but somehow i don’t have an intuition for whether the force on the chain (tension) is different.

    1. The gear radius is essentially your lever arm, so for the same gear ratio, the greater the radius of the gears, the lower the tension on the chain, for the same delivered torque. And yes, with big gears, the chain moves faster.

  9. If you put it on a recumbent or anything where you don’t need to keep your balance, it would be a lot easier to pull loads. I once had a Schlumpf planetary hub transmission with a 6 speed cassette and in low gears across the board, it was much like this. I’d just kick back and climb hills with ease.

  10. When I saw that gearing, my first thought was, “Well, that’s going to be a wheelie machine.” Perhaps it needs a frame with a wheelbase stretched by 50 to 100 cm to be a bit more controllable.

  11. “Bicycles Are Bad At Towing, Even With Crawler Gears” Bad title. Anything is bad at towing if you exceed the vehicle’s capacity. I’ve seen people try to tow with short wheelbase vehicles like jeeps or small front wheel drive cars and have the tail wagging the dog issue. Or not balancing the load so there is too much tongue weight. Towing with a bicycle is just like towing with anything else, know your limitations.

    Lets see if this works

  12. Bad at towing?!?!

    Well, I never towed anything as large as the stuff I see here but as a kid I put very knobby tires on my Huffy, tied a sled to the back and towed people around town no problem, even across fields.

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