Something that is fairly easy to find or possibly upgrade components to? New or used doesn't matter. $1,000 or less target price range.

That would be the Bike Friday Tikit, which you can find for around $1000 if you peruse eBay and Craigslist. MUCH more expensive new.

Or don't fret so much about ultimate speed and just get a 6-speed Brompton with the 12% + ratio option. They're great bikes.

If you are (for whatever reasons) after the highest gears you could i.e. combine the (aftermarket) S/A XRF8w with a factory 54t chainwheel on a Brompton and you'd end up with 11m of development / 139 gear inches (with the lowest gear being 3,4m / 43 gear inches). If this still is not enough you could go for a 60t chainwheel (roughly the max. that fits on the Brompton w/o modifications) or combine it with a Schlumpf HighSpeedDrive which would put you even further up. What kind of use do you have in mind? Speed-record on the Bonneville flats?

The Tikit uses 349 wheels as well and should therefor be pretty similar but can maybe handle even bigger chainwheels more easily (I don't know).

My factory tikit has a 74" top gear.

Under budget, a new Dahon Curve aftermarket fitted with that Sturmey-Archer XRF8W and geared 54x20 would yield

Screen Shot 2017-01-21 at 8.00.24 AM.png

Any setup over 100 gear inches would be a stretch to spin very fast unless you could adopt a bent over position to reduce aero drag and you went with low rolling resistance lightweight tires and rims. I believe the xootr swift site states that at 90 gear inches and 120 rpm you will go 27 mph. Anything over 19 mph the aero drag increases a lot with each additional mph.

Speed? Did this one already , look it up.

Florian Schlumpf's High Speed Drive gearbox crank has an overdrive gear in it, so the chainring turns 2.5X for every rotation of the pedals (Small gear acts huuge)

But remember, on Earth, you have an atmosphere , and air resistance goes up by a factor of 4 X as you double the speed ..

Yes Bike Friday hyper fold Tikit is the bike that folds the fastest,, once you get the knack, it's just a few seconds and gravity does most of the work.

I do not think you can put a 20 t sprocket on a Curve. Long time since I played with the gears on mine so I should be careful to trust my memory but I remember wery clearly that therer was a limited space at the back.

Not a fan of the Bike Friday look.

As far as the Brompton, yes I was looking at the S6E with 8% and it says that should give me 108", just not sure I want to spend that much right now.

What would the rough estimate be of those aftermarket parts for the fastest option? What would the lowest gear start out at?

And how reliable would this be compared to a stock bike?

I am new to biking etc.

So anything over 100" starts to get more serious as far as riding style, gear etc etc etc?

I am just thinking more speed is better, I am not trying to win any races but would be nice for the speed to be there when I wanted it is what I am thinking?

What bike are you suggesting this high speed gearbox in?

A bike you Buy then send it to a shop and have it Modified** ..

the BB edge has to Be re Machined , Chamfered,
as there is a Conic grip from both sides of the BB shell, and a conic friction washer that Gets Bite into the BB shell to transfer the torque
of the planetary gear box as it translates the crank arm rotation into the chain ring rotation..

Cycle Monkey . com In Richmond Cal sells and installs those cranks ..

I bought their schlumpf's other product.. the Mountain Drive is a Reduction gear , same 2.5:1 but when engaged

the crank arms turn faster than the Chainring .. it also has a conic interface with the BB , but because in low you are fighting Gravity

the Torque transfer is a solidly mounted Stop, on Brompton its a knob sitting between the BB shell and the rear fold axis pivot..

I have a 54t chainring

in between is the speed drive ..1.6:1 overdrive , With a 34t chainring (they come with a 110 spider) the overdrive is like a 54t chain ring..

Or, get it with a 130 spider or bigger chainring on the 110, and then using a 38 t chainring, in overdrive it acts like a 60.8t size.



so not a what bike do I buy already like that kind of solution,

But Some other Dealers May be able to get ** and install the parts before you take the Bike Home.



'/,

A 2.5:1 overdrive Schlumpf drive will introduce drag that wouldn't be there with a large chainring and small tooth cassette and will actually slow you down due to the inefficiency attempting high speeds.. 1:1 will be the low range and 2.5:1 the high range ..

There are few ways to get to 100gi on 16inch wheels.. without going to massive chainrings.. one that I've used is a Capreo rear hub with a 9t small cog.. the hubs are relatively inexpensive and the smaller cogs replaceable ..

Another bike option is a used Birdy.. wheels are 355mm diameter, and compared to a 349mm Brompton wheel, are only 6mm larger diameter, putting it on the larger end of what is considered 16" wheels.. with the well thought out Birdy suspension, you would be able to maintain higher speeds more easily as road shock wouldn't be wearing you out as quickly.. Birdys also use pretty much industry standard drivetrain parts, so an upgear path is pretty doable..

If I was looking for a sub 406mm bike to go fast on, it would be a Birdy

Wind resistance will be more of a factor than the well lubricated swiss made gear box.

+ there is the hub , 3 speed ... overdrive is 4/3 of the 2nd gear...

a Moulton or another with a ZZipper fairing in front.. will get you a bit more speed , not laying back, low, on a Recumbent speeds ,

but the fairing smooths the air flow better than just your body..

To go really fast the bikes have a counter shaft ... and a second BB, a small cog on one end big chainring on the other , and a second chain driving the wheel hub

raising the gear to huge sizes, but they use a Motor Pacer blocking the wind and get towed to 60 Mph, before pedaling to the speeds of around 150 mph..

Bonneville salt flats speeds..

Check out the specs for a Downtube Mini with an Alfine 11sp on it. About $1000
https://downtube.com/downtube-minib-...-folding-bike/

I bought a used Dahon Curve D3 and upgraded to a Sturmey Archer X-RF8. I was able to do this for under $1000
Here is my thoughts and experiences.

https://www.bikeforums.net/folding-bi...8-120-old.html
https://www.bikeforums.net/folding-bi...tes-later.html

This 4 speed Rear hub takes a 13t rear sprocket and 4th is 210% of first ..Sturmey-Archer | X-RF4

like the 8 speed tcs mentioned Sturmey-Archer | X-RF8 the 1st gear in the hub is direct 1:1

but the smallest cog size , on it is 20t, top gear is 325% of first ..

get your Math On..




...

Ah, you're new to this. Have you ever ridden a bike with 16” wheels? I have a Dahon Curve D3 converted to a SRAM 2-speed Automatix hub, and a Brompton 3-speed with electric assist. I live on a very steep hill, so it's quite easy to get these bikes going faster than I'm comfortable with. The most I'm comfortable with on those little wheels is about 20mph before things start to feel squirrelly.

In my opinion you should find a folder you think will work for you, and not worry too much about top speed right now. My guess is you'll discover that the stock gearing will match the abilities of the bike.

any how
Bike fridays Tikit uses a lot of conventional Drive train parts ,,
so you can go into your Dura Ace and super record components if that is your goal

The company has Pre Loved resale section..
Also look at their 451 - 20" wheel Pocket Rockets.

Why Do so many newbies to this forum want to go as fast as possible on folding bikes ?

Wanting to stick with their buddies on club rides is a common motivator. Which may be possible on an expensive, lightweight Bike Friday or Tern with 20" wheels, but you're still trying to make a folder match speed with folks on 16-pound race bikes.

I think folders should be ridden at a reasonable pace in the conditions they were built for. Club rides with race bikes should be ridden on a race bike.

I am instead still scheming how to get lower lows...

Of course, that's not what I implied.. even Florian Schlumpf will admit that the High Speed drive,in overdrive, is not as efficient as a derailleur set up .. that has always been the knock on that particular hub with the 'bent crowd.. it's a nice piece, but if you are concerned with going fast, it'll take more effort to go the same speed when in 2.5:1 overdrive, than a conventional derailleur drivetrain.. I've installed and run all three .. High Speed, Speed Drive, and Mountain Drive ..

OP probably just started another fastest thing thread hamster wheel spinning and

wont do anything with it. like so many others before..


I own the mountain drive, high is 1:1. and i don't care about theoretical speed, having a 77" high,
and it being adequate..

the recent Brompton Mk4 BB shells come to an edge, so are sort of chamfered, just not perfectly,

like if I used one of those BB cutters like Mavic required for their BB's ,
when they were competing for market share in the pro component market.

so since we are just going back and forth with dueling opinions , this thread has, likely, run its course.

lets find out from the OP


why 16 inch wheels ?
why do you want to go fast ?
what is considered fast ?


:-)
Thor

1st gear is the 1:1 on the Shimano hubs, so it will be hard to get over 100 gear inches. Our chain drive mini uses a Sturmey Archer 8sp hub, in which 4th gear is the 1:1. That would be a much better candidate for the OP's needs.

Thanks,
Yan