2WD bikes - Do they actually work?
 

On our local Craigslist page I found this 2WD mountain bike with a flexible drive shaft to drive the front wheel. Not that I want to buy it but I have never seen one of these.
https://dallas.craigslist.org/dal/bi...239390279.html
But this driveshaft looks heavy and cumbersome. Plus I wonder how they handle the different speeds of front and rear wheel while turning. Every car has a differential but this bike probably doesn't.

Buy it and report back , take a risk.. the drive connection is a cable, like speedometers or curved shaft weed whackers.


any more you'd just get a front wheel with an electric motor hub, , get another or a mid drive for the back.

maybe a mid drive with a Kw motor will have enough power to turn both wheels..





....

I could see a system like this having potential on a fatbike that's used for sand and snow riding, but outside of such very loose terrain, I don't know how much the extra drive traction from the front wheel would help.

A classic case of a solution looking for a problem.

When I owned my shop a local lawyer acquired a warehouse full of those and kept trying to get me to sell them for him. He dropped one off without my permission and wouldn't respond to my calls to pick it up. Eventually I threw it, unopened box and all, into the dumpster. About 3 months later he called to ask about it. He didn't believe that I considered the space to be worth more than the bike.

The seems awfully wasteful, I'd have put the box outside the store with a "FREE" sign at least.

Were they available in red???

I'd have to assume that a 2WD bike would be a failure without a differential between the two wheels.

I have seen a few here in Japan, but not the cable-type as in the photo. The ones here use a secondary change which runs up the downtube to an idler gear, which then runs to a sprocket on the front wheel. These were sophisticated bikes, and rather expensive.

Personally, I haven't really seen the need for an 2WD bike. When climbing, most weight is on the rear wheel, and any additional traction provided by the front would probably not be worth the effort required to turn the extra machinery.

BTY, tire slip releases driveline tension if one wheel turns more quickly than another. Unless one tire is a much different size, a 2WD system will not need any differential gearing.

This subject has come up multiple times over the years, and I've already replied to it, but anyway--

1. Years ago I got to test ride one of those bikes at a LBS. The 2WD does work, but only if you are in a very-low-traction situation, such as deep mud or snow.

2. the cable drive did add some drag, and there was no way to "turn it off" so to speak. If you could disengage the cable from spinning when 2WD was not needed, it would have been a much more practical idea.

3. The rear plastic gear was fixed to the rear hub. The front hub was a rear hub, that had a freewheel that the front drive gear was mounted on. Since the front wheel rolls farther in a turn than the rear, that prevented the cable from twisting up. The front wheel could always coast faster than the rear, but the front wheel couldn't ever turn slower than the rear wheel.

4. The plastic gears actually did last a pretty long time and were cheap to replace... but there's nobody making them now, so that hardly matters. They were made extruded nylon, the same tough stuff that OLD milk crates used to be made of.

5. The bike overall was pretty low quality. I remember it cost $400 and was about equal to a $150 wal-mart bike at the time, except for the extra 2wd parts added/welded on.

6. There's been at least 2 or 3 people/small companies in the US that have tried building bikes with flexible-cord drive, since the 1980's or so. Two were selling MTBs, and one was selling a BMX bike frame.

Not to mention an awful lot of friction has to be introduced with that cable system. Not to mention a maintenance nightmare. I can't imagine the corrosion that might build up, especially for a mountain bike.

I wouldn't say an "awful lot." I've ridden quite a few bikes with old school speedometers and taking the spedo and cable on/off made no noticeable difference in pedaling efficiency or rolling speed. I'd say the cable on the 2wd bike adds less than 10w, probably closer to 5.

ENORMOUS difference between driving a speedometer and driving a wheel. Cable is going to be much, much thicker.

I remember seeing the design 20-30 years ago. Apparently the design never took off or it'd still be in stores. It was a low-quality bike then, and like Doug5150 says, don't count on spare parts being available.

If you wish for higher quality modern bike, there is one outfit that designed and manufactured them for an Antarctic expedition, and sell to the public: http://christinibicycles.com/

Appears to be of much higher quality, and has a clutch/disengagement mechanism

That is pretty cool!

The guy hooked a concrete vibrator on that thing and is BS'ing the world. :)

As mentioned in the thread, there is in fact a bmx that was made with a AWD set up. They also did a set up for Mountain bikes. The company was called Turner Drive Systems. I have a bmx and a mountain bike setup. Someone said earlier in the thread that it would be much more useful if you could disengage the AWD set up for MTB use. With the set up that I have, you are able to disengage the AWD.

Didn't check, but I thought a lady rode to one of the poles on a Christini. Also, he was fiddling with attaching an e-motor to the system. Not for me, a semi-weight weenie though.

That's funny, I was going to say the same thing. Any gains of traction you might get from 2WD means you're just going to have to pedal a bit harder to get it. And then you have to contend with the friction losses in the cable/gearing system when you just want to coast. And I suppose it also means wearing out both tires faster instead of just the rear tire.

That cable is A LOT bigger than a speedometer cable.

In Dallas that 2wd setup is completely useless. The soil type here is unrideable when wet. If you do go out when it is wet and the trails are closed you can be ticketed in some cases. The steep, loose climbs we do have are best tackled with momentum.