It depends on the wheel size and the gearing.

If it has a "normal" bike wheel size with the same gearing, it can reach the same speeds.

Bikes with smaller wheels need bigger chainrings and/or smaller sprockets to reach high speeds. Another option is using an IGH.

I have reached 70km/h with a 20" Dahon with SRAM DualDrive, a 52t chainring and 11t sprocket. It has a higher gearing than most road bikes.

Sorry my friend, but its not true.
To archieve that speed with that gearing you shoulb be pedaling at 160 rpm cadence, witch is hight doubtfull.
You can check calculations in BikeCalc.com - Speed at all Cadences for any Gear and Wheel.

best from Brazil,
Pedro

Xhim, folding bikes can go quite fast if you can gear them properly -- but that can be challenging because the smaller wheels present some more difficult gearing scenarios.

For under $800, I would suggest a Dahon Speed P8, sold by Thor. I would get the Tangerine model, which has nicer components; though I'd personally swap out the tires for Marathon Big Apples or maybe some other medium-fat tire. I would also consider asking Thor about the cost to mount a decent rear rack so you could attach panniers for biking to work.

It is possible that there is an equivalent Tern in this price range, but I don't know what it would be. Thor would know however and could tell you directly, call him at 1-800-222-8356.

This bike's top gear will be more than plenty for a typical commuter, but not for a racer.

I would not get a Citizen nor a Crane: I do not think they are of sufficiently high quality.

If you had more money to splurge, I would look at a Dahon Mu P24, which has better gearing.

As to chainguards -- like most street bikes, folders don't have plastic straight chainguards. Instead, you should just get a strap to keep your pants close to your leg. Any bike store sells them.

My friend Pedro.. he is running a SRAM Dual Drive hub .. 3 speed hub +cassette .. so very large gear spread.. remember to input the SRAM Dual Drive in your calculations..

You haven't taken the dualdrive into account. Use Sheldon Brown's Bicycle Gear Calculator and the result table at 120rpm says it can reach 69.1kmh. Close enough to 70... And 120rpm are clearly achievable, at least for a while.

Oh, thanks.
Sran dualdrive increases the gear ratio dramaticaly.
For my calculations, i see his setup with sran dualldrive 53t crankset and 11-? would take him up to 177 gear inches on his heavyest gear.
177 gear inches is archived on smallwhell folding bike with an regular setup with 72t chainring on front and 11t cassete on rear. Wich is very high.
To archieve 70km/h with that gearing the he should be at 120rpm cadence.
The frame would flex so mutch that i think is impossible to folding bike.
Even dahon 30 anny or other premiun terns or multons cannot hold this forces.
Pehaps with an recumbent? Or with a pod fo avoid air resistance?
My bet is that his archieve this speed at an botton of a huge downhill, not on flat.

Best,
pedro

Of course, this speed is on a downhill, I don't know anyone who can reach 70 on the flats.

On the flats with no wind I usually cruise at around 28/30kph, although I can sprint for a short time at 38kph. No need for a DualDrive to achieve this speeds though.

Folding bikes can be quick, but the term quick is relative. I don't ride a folder for it's speed, I ride one so I can take it with me on the bus or train (I don't have a car). I can get around quickly enough on a folder, but for very long rides at a consistently high speed, I will use my old road bike. I used to do almost all of my regular riding on my folder, until it was stolen last month. Now that I have to do my commuting on my road bike, I find that it takes nearly half as much time as it did on my Brompton. But, on the other hand, I can't take my road bike on the train or subway, so I am not going out to the countryside as much as I was.

If you are going to get a folder, speed should not be the main priority. You should choose a bike which is reliable, reasonably light, folds quickly and easily, and has a wide enough range of gearing for the type of riding you will be doing.

120 mph ......

well ....I passed a truck and got carried away

my bike in the trunk , obviously


thor

My folder is a Tern Verge X30h. I bought it specifically for the speed. It has the SRAM dual drive which makes up for the 20" wheels. My daily ride is a Kona Jake ( my commute is a mix of gravel and pavement) and the Tern is a faster ride on pavement. I bought a folder for exercise when on my frequent business trips and so I didn't want a commuter but something to get some speed.

The dual drive is definitely the key to this. Unfortunately this is significantly above the OPs budget.....

I may have to get a SRAM Dualdrive on my TernJoeP24. It sounds perfect,...

Somebody must have done a trans-Atlantic flight with their folder...

From the Moulton web site: 1985-1986 - In the Autumn of 1985, at the International Human Powered Speed Championships, a fully-faired Moulton ridden by Jim Glover broke the 200 metres flying start speed record, at 50.21mph (80.79kph). Then on August 29th 1986, at the same event, he broke his own record at a speed of 51.29mph (82.54kph) which still stands today for the conventional riding position. The Moulton ridden was an AM SPEED with the fairing designed by Doug Milliken of Buffalo, NY.

Thank you all who have shared this info. FYI, I ended up ordering a Crane 8. It seemed to come closest to what I was looking for (at least according to the descriptions!) -- and I do have 2 weeks to return it if I don't like it.

BIGGER HILL @ 42mph: 42 MPH on a Brompton! @ The Path Less Pedaled !!

Looked like fun!!! Thanks,...

Loving your work Fietsbob :0)

On cadence 90rpm is a reasonable pace and the most efficient on the flat I was told by a v experienced coach. 160rpm is doable for some and it depends on any differences in the lengths of your legs. The more symmetrical you are, the less this induces a rocking motion which destroys rhythm. Personally I can do about 130rpm, which equates to 35mph on my Chameleon and no I don't need a hill for that, just a gel :0) it would go faster if I changed the top gear and did some training. If you want to improve your cadence start riding a 700c fixie on medium gears (eg 44x17).

Theoretically a small-wheel bike sees increasing effects from bearing friction as it gets faster, in comparison to more conventional bikes. In practice any decent hill will show you this effect is outweighed by aerodynamics.

BTW Terminal Velocity is zero, when you think about it ;0)

SRAM is a brand name. The 11-32 "cassette" means your smallest gear in the back is an 11 tooth, and your biggest is a 32 tooth. 52x11 means you're in the 52 tooth chainring (big one up front) and the 11 tooth gear in the back (small gear.) RPM is well, how fast you're pedaling, also known as your cadence.

There's nothing stopping you from going fast on a folder, that's just down to gearing. However there is something stopping you from going fast safely (or at least stably) on a folder. And that's mechanical trail.

Mechanical trail is the degree to which the front wheel acts like a swivel caster, that is, the degree to which it resists being turned and only wants to point forward. Various factors influence mechanical trail, but for small wheeled bikes really only one of them is dominant: the wheel size. All other things equal, the smaller the wheel, the lower the mechanical trail.

There are reasons you'd want to have a low mechanical trail: notably if you're planning on loading the front wheel with heavy stuff (like a porteur bike or a bike with heavy front panniers on it). But without this, low mechanical trail just makes the steering feel unstable. Small-wheeled folders are notoriously difficult to ride no-handed, for this reason. There are claims that low mechanical trail can make a bike more "nimble" for serious racers, whatever that means. But for most people, I think it's safe to say that they're far harder to control at high speeds in anything but basically a straight line.

So while it's *possible* to ride over 40 miles an hour on a Brompton, it's rather difficult to do so stably (and safely I think) compared to doing so on a racing road bike.

Mechanical trail is still not well understood? It's the distance between the steering axis and the tyre ground contact point. So a larger wheeled bike is a greater distance. But a lot of trail also makes for increased wheel flop. I think there is a bit more to it than this. Maybe this is a factor for very small wheeled bikes and in my experience there is a big difference between 2o inch and 16 inch wheels.
There are other aspects like rear wheel caster effect, (long wheel base).
On a brompton I feel the unstability is due to the lack of stem extention. Extend the bars on a bromptom. By lowering bars and extending them 9 inches(see my threads)and it's the best handling 16 inch bike I have ever ridden. Do the same on a short wheeled mezzo with an already extended stem and it's very wobbly indeed.
Simple answers rarely work.
I believe the truth is that often small wheeled bikes are not optimised for handling in their design. Brompton is a good case in point. It's so much better with more stem reach, but it's designed to fold with out any. The folding aspect dictates.
Moultons are very stable at silly speeds, they are optimised for handling.

You also have to take into account the gyroscopic effect of a spinning wheel. A larger wheel is more steady as the the increased circumference generates greater leverage. When I switch between my folder and my road bike I can always feel the difference in effort as I steer or lean over. The road bike, even at slow speeds, requires more effort do turn, not from trail (known as caster), but gyroscopic effect. This is also the main reason that small-wheeled bikes are much harder to ride hands-free.

I'd add in planetary orbital and rotational velocity, to the speed of a falling body ..

It's that sudden stop I'd REALLY be worried about,...

I believe all the gyroscopic stability theory of the wheel spinning to keep a bike stable was completely debunked in the 80s by demostractions that bikes with contra rotating and 90 decree off set were all perfectly rideable.
I believe modern thinking is that rear wheel castering and the general rpm of the wheels yields the stability to be able to cycle.

Meanwhile, a folding bike going faster than the speed of light would require an infinite amount of energy to slow it down. Einstein tachioned this to the general theory of not getting on with his relatives. I might have not been listening to this physics lesson properly. Anyone seen my cat, hope he's ok.

Gyroscopic effect is not fully responsible for keeping a bike stable, but it plays a large part. You can experiment yourself, take a road bike wheel and a smaller wheel, spin it, and hold it at one end of the axle. The larger wheel will be more stable. Hold both axles and try to lean the wheel to either side, the larger wheel will be harder to lean. It is not rocket science. Ride a bike with small wheels, and one with full size wheels, and you will notice the difference in the effort it takes to turn the bars. It is not a matter of trail, spin the wheels with the bikes on a stand, and try turning the bars, you will notice the difference in effort.

I have spent time racing bicycles and motorcycles, and have felt the difference in gyroscopic stability when tires and wheels of different weights are used, though the steering and suspension geometry remain the same.