My wife and I have already spent too much on new bikes this month, but folding bikes would definitely give us a resource that would be valuable. But OMG expensive. So I've been thinking about the possibility of buying a cheap (meaning 3- or 5-speed) folding bike and converting it to an 18, 21 or 24 speed. Questions:

• How possible is this? (I know all things are possible, but I mean, without welding or hard core metalwork on the frame. I'm handy and have a good deal of confidence in my ability to do the conversion--maybe more confidence than skill--but I'm not Superman, you know.)
• If a cheapo Folder has a multi-gear rear cassette, how possible is it to add a multi-gear front sprocket?
• I've heard people convert 5 or 7 speeds to 15 or 21 by "merely" adding an internally geared multi-speed hub. Does this actually work?
• In terms of cost effectiveness, would buying a sub $500 bike and converting it actually save me money over the $1000+ 18, 21, 24 speed folding bikes?

Thanks in advance for all of your thoughts.

its possible to do it.
one good route would be buying a lightly used folders on your craigslist.
buy more quality stuff like dahon speed d7.
from there, its esy to add a front derrailer.

I converted my helios from D7 (budget 7 speed) to x18 (premium 18 speed) for ~£250 . I was going to build a 2nd one as there was a donor for sale £40 on Facebook...
So, if you are handy and have time to wait for parts to come from asia, I think you can build a very good folder for $500 if you're happy with good 2nd hand parts. I found that folder can use mixture of MTB and Road gear and there are always people who want the latest piece on kit and sell 1, 2 yrs old bits in very good condition...

My helios (~$320 of upgrades and ~~$550 when bought 10 yrs ago) is not far of a tern x18T which is worth $1900
Helios... race bike type or TT?

If I am totally honnest, I wanted a dash x18 (fast etc.) but a dash would have cost £850 for a P18 and I would have had to add £150/200 for a fast road drop bar conversion... so I didn't spend £800 / ~$1000.

I got my Zizzo for under $400...

My purchased add ons were about $400... I had a bunch of stuff waiting for a project bike...

I didn't see ANYTHING out there that was exactly what I wanted, now I have it...

I am not sure that I understand where you are coming from. Yes, in general, you can add a double or triple up front to multiply the number of gear combinations, but this doesn't give you 18, 21, or 24 distinct gear ratios. It does add a lot of complexity, some weight, and usually some gear ratios that so low as to be useless. Is there a gear-inch range, or target, that you are trying to achieve with an large number of gear combinations?

OK, now that I know it's possible, I can explore the technical details like "gear inch range." I didn't know there was such a measurement! Next you're going to tell me there are newfangled things like air-filled tires and levers to move the chain rather than your fingers. Thanks for your input. There will undoubtedly be more questions down the road because I feel a distinctly troublesome urge. The one that starts: "How hard can it be?"

$20 10 speed cassette
$60 Hollowtech double crank (I chose a $200 Sugino OX601D for the 74/110 BCD, 165mm length, and narrow Q-factor)
$15 bottom bracket
$25 SRAM yaw FD with chain catcher (doesn't need trim, and has a little bit more inside clearance to the seat tube than Shimano FD)
$10 Shimano optislick cable and housing
$25 RD-4700-GS
$65 SL-4700 trigger set (the left trigger works with SRAM yaw if you setup the limit screws to ignore the trim)
(you can choose cheaper RD and shifter combinations if you want)
$12 KMC 10 speed chain
$15 newer cheaper litepro FD clamp adapter (I 3D printed my own adapter out of steel for $80)

Maybe $300 altogether including extra tools and broken stuff from trial and error.

Of course I added a lot of other components to my Dahon Vigor. Thudbuster seatpost, brooks saddle, Tern cargo rack, renders, MKS QR pedals, toe cage, 26mm wide rims that I built myself with new hubs and spokes, Schwalbe Big Ben Plus 2.1" tires, Ergon gp5 grips, Mirrycle side mirror, klickfix handlebar bag holder, klickfix phone bag holder, rollamajig at the FD and RD, TA chainrings 44/24t, custom built bashguard, Hexlock for the bolts, hex skewers.

For gearing, I have custom mixed cogs from 3 sets of cassettes: 12, 13, 14, 15, 17, 19, 21, 24, 28, 34. With a 44/24T chainrings, I get 14.0 - 72.6 gear inches. I can use the 14 gear inches to go up really steep inclines. I top out at 72.6 gear inches around 28-29 kmh, and it would be nice to have up to 76-80 gear inches, but it's only maybe 1 minute out of 2 hours that I exceed the 72.6 gear inches, so I'd only save less than a minute of time per ride.

I wanted a wider gear range, I added a Sram Dual Drive to my folding bike. Sram no longer makes them, but I have heard that Sturmey Archer makes something similar.

The Sram required 135mm rear dropout spacing, I have no clue what the Sturmey Archer would require.

For shifter control, I got lucky and found that the Sram would work with the Sturmey Archer bar end shifter, so that is how I shift mine. I also use a bar end shifter for my derailleur.



I am not sure cost of the hub and shifter, that was several years ago when I added it but I think it was between $200 and $250 to add. I used to work as a bike mechanic, I build my own wheels so there was no wheel build charge. That cost would be the hub, shifter, spokes. I am not counting the cost of rim since I could have used my old rim, but chose to retain my old wheel as a complete wheel.

I picked up a secondhand Dahon Speed TR which is fitted as standard with a SRAM dual drive but beforehand I was looking into fitting a dual drive to another secondhand 8-speed folder. The hub gives you three speeds like a triple chainset with a rear mech and cassette for another eight. Living in a hilly city it’s about as widely geared as my 26” wheeled touring bike.

These days Sturmey-Archer makes these - search for a CS-RF3 hub. They can fit 130mm dropout widths by omitting a spacer on the axle as well as their specified 135mm width. Any indexed triple shifter will move them. The one issue is that they seem to be only available for consumers in 32 and 36 spoke versions while the 28 spoke version can’t be found. This is annoying as most folding bikes use 28 spoke rear wheels, so it’ll usually mean building a whole new wheel instead of reusing the existing rim.

I would recommend picking up a secondhand folder from a decent brand and seeing how you find it. I ended up installing a smaller chainring on a Tern Link D8 which dropped all the gears enough for it to manage most of my local hills and changed the bars to make life more comfortable for example.

Both hubs require 135mm dropouts. Almost all dahon have 130mm. There is a list somewhere someone compiled showing the dropouts if the different models. Only special models have 135mm.
Dual drive is 186% while the Archer is 177% so there is a difference in gear range. If you're using for example 12-34, that's 527% vs 501%.

My 44/24 12-34 10 speed cassette gives me 519%. If I went to 11 speed and added 11t cog I'd get 566% which is just 9% above the 12t cog.

Good point. On my bike in the photo above with the Dual Drive, that bike came with a 52T chainring. I went with the Dual Drive because I could not fit a front derailleur, thus to get wider gear range needed the IGH. But I only wanted lower gears, the stock 52T chainring gave me all the high gears I needed.

The Dual Drive in 2nd gear is direct drive, in 3rd gear is an overdrive. I changed my chainring to 39T which with the overdrive in 3rd retained my higher gears but gave me much lower gears.

My folder has 24 inch wheels, if you have much smaller wheels you might not want to reduce chainring size as much as I did if your bike lacked the higher gears to start with.

I've added a front derailleur on a bike (26") that had no front derailleur brackets. Being mechanically inclined, I found it was fun. Will it make a $500 folder more like a $1000+ folder? Well, it will shift like one if you do it right, but you won't have the weight savings..

I have been commuting on a $125 Sundeal folding bike since AUG 2019, until COVID started back in MARCH.
I take it onto NJ PATH train & NYC subway system, ride it from Coney Isl. to WTC in the warm months.
I rarely get speed above 16 mph, just surviving among NYC traffic.

As a folding bike must accomplish more than a regular bike, there need to be compromises somewhere, such as fewer speeds, smaller wheels, getting subjectively less for the price, etc. For most people 5 or 6 speeds is plenty enough under most circumstances. The majority of people answering that yes they have done it, or it is of course possible, have experience, skills, bike parts, tools and auxiliary parts, such as bolts and nuts, and they enjoy engaging in the effort as a project. Unless one wanted this to turn into a project where one learns bike mechanic skills, for an average person without such skills it makes no sense, both economically and in terms of a project that gets completed in time. In fact, this can easily turn into a project that never ends.

Those are the best kind.

For folding bike, I rather just get the work done and use it as intended with minimal maintenance/attention.

Now over 20 months of using my cheap folding bike for my 3-4 times a week commute in NYC.

The bike is holding up great, some minor pain chips, lots of dirt, winter salt & grime all over the bike.

Disc brakes are working great from day one, never seen to hear any rubbing, brake pads are at about 50%.
I've gotten 3 flat tires in 20+ month, but still running the original tires, rear tire really needs a replacement.
Upgraded to a $45 carbon seatpost for weight saving of nearly 1 lb. & added comfort for longer distance.
Changed out the foam grips last year since they didn't last very long vs the rubber grips on the bike currently.
Stem/headset came loose once last SEPT, just tighten it up and it held since.
My commute is about 8 miles one-way, the longest ride I've had on it is about 24 miles.
This bike has the longest reach of any folding bike I've seen, it actually works well for me; steering is not as sensitive as some short-wheelbased folding bikes that I've owned in the past.
Since I wear rain pants & jacket, I don't put fenders on the bike, just use removable plastic fenders when it's wet out; also save some weight.
I jump up & down curbs all the time, therefore also check for cracks throughout the bike regularly, so far it's holding up with no issues after my abuse of 20+ months.
I've very happy with my $125 purchase & delivered cheap folding bike. I hope it lasts another 20 months & beyond.

cat0020 I recognize that bike. I have the F1 without disc brakes, just the the usual V-brake setup and in lime green. I did change the tires to Continental Ride Tours and put the Kenda's on my older Dahon. Glad to see your review after 20 months of commute use. Since I am now retired, I just use the bike for quick trips to the store or nearby restaurant, and not more than 2-3 miles. I paid about the same as you, and glad I bought it too. Enjoy your ride....

cani ask where you purchased that bike? i had a sundeal mini velo that i loved that was stolen? got it from bike warehouse.

It was on eBay for few days, sold out rather quickly at the price they were selling, also had linear brake version at similar price.
I have their Minivelo also, still ride it once in a while running errands.
Never seen Sundeal bikes for sale again since.
Sundeal Bikes

awesome. the mini i had was igh 7 speed, got it in 2019 for 210 bucks. hard to beat. someone really liked it, apparently.

"Get a cheap Folder and convert" is an approach that could get very expensive, very quickly, and the cheep bike you attempt to upgrade certainly won't be trouble-free. As others said, a better way to get a quality folding bike is to look for a good, lightly used entry-level model from the top brands' higher-tier offerings; i.e. instead of splashing out on a brand new top-of-the-line Eclipse X22 or Verge X11, find a nice used entry-level Eclipse D16 or Verge D9.

yes or a established dahon d8 or p8 (helios/speed/boardwalk/mu)

then swapping groupset, crankset,BB is fairly easy but requires a few specific tools

As I put in my helios rebuilt thread, you can fine easily 9 or 10 speed good second hand groupset as many sport fanatics upgrade their kits all the time.
if you start with D8/P8, later having better wheels, you can put together a good 2x9 whichis simple cheaper and forgiving (easy setup) and.

go to 11s is expensive, specific and required a large rear frame, most older folders are 130mm so not suitable for 11 speeds

⬆️ Reminds me of this:




I really wanted one and could order one from the local store, but I decided to pass and wait and see if the next model comes with disk brakes.

Disc brakes on 20" wheels is a bit overkill; I haven't experienced skidding issues during hard braking to avoid impact with cars, but I can see/feel that could be a problem if disc brake offer too much braking force to create skids & cause rider to lose control.

Nearly 3 years since I've been using the $125 Sundeal 20" folder for commute in NYC, rear tire is desperate for replacement, disc brakes squeal like mad when applied, but everything is still pretty much OEM and works as intended.
I can't say that spending more for a Brompton or Bike Friday would allow me to commute any more efficient,
If anything, I would be more worried about getting the bike damaged or stolen while commuting in NYC if I had a more expensive bike.
With the $125 Sundeal, bright orange folding bike; I park it anywhere with minimal worry, I rarely even lock it. If someone steals it, it won't be a huge loss.