Hello, I am not sure if it is the right place to ask but if I want to make a diy/cheap version of mini velo. Is it possible to take a small bike frame and put 20 inch wheels on it to make it into a mini velo? There are several 20 inch hybrid frames, 16 inch mountain bike frames. I was wondering how can I know if 20 inch wheels (406mm to 451mm) can fit? or am I going the wrong way? I know I will have to extend the headset by having spacers or a handlebar Rise and have a longer bike post. All three bikes that I eyed on have cantilever brakes if that helps my case.

It might be possible but cost more than you realize. What prices do you see for a mini Velo in your area before you start such a project?

I'd suggest using a purpose built frame.
You're getting into geometry, compatibility, and fit problems right from the start and any money you save will be spent in time and effort to get a kludge to work.

If money is really a priority, wait until BD sell their mini velo again and customize it
(see massive thread: Bikesdirect Mini Velo upgrade thread )

A BMX bike with an igh (internally geared hub) is something I'm eventually going to do myself, so I say GO FOR IT! Just remember to post some pics, so I can get some inspiration. This is Dahon's folding version of a BMX style bike. I see nothing wrong with what you plan on doing.

Thanks for the inspiration and will do post!

What are the main costs if I can find/have cheap parts apart from the 20 inch wheels? There are no used mini velo in where I live, so it will require me buying a well established mini velo frame or complete set to Montreal, Canada.

One issue is with using smaller wheels on a frame designed for larger ones . Will the brakes reach the rim? Disk brakes could be a solution but then cost becomes the next issue. Building a Minivelo in Canada is $$$. My estimate is at least about $1000. A v Orange Nutrino will be about $2000. The frames have to be imported. There in one on sale in Montreal on Kijiji. It looks like my old Fuji. It has 451 wheels. Winter tires won’t fit but its a nice Minivelo at a good price. I do have my Lombardo 2000 Minivelo frame with all the parts that I’m thinking about maybe selling. Maybe tds101 who posted above has his for sale.

what is the link for the fuji or similiar one-like. Yes well if I cannot find a solution buying silverock frame is a cheap solution as well.

Well I thought if the bike has canti-lever brakes, there is more potential of reaching the rim but I could be wrong.

https://www.kijiji.ca/v-view-details...teLocale=en_CA

https://www.kijiji.ca/v-view-details...dId=1657439948

The Soma looks interesting. I don’t know the wheel size.

All I want you to do before you commit to this project is to look at both sides. It’s like before you engineer solve the problem, you reverse engineer the solution.

now I know you are in Canada, seems to be an expensive location. Personally, I would buy a ready made MV bike or frame then build as I want.

Mercier Nano is my go to.

As bought

Many mods

Recent mods

if the frame is not design for 20" wheel, you will get some issues with the brakes.

you could start from a children mtb like frog 52/55 or equivalent. then either you fit a steerer extension or a new uncut fork or a BMX handle bar. Your main issue will be the saddle/seat post. they are usually 27.2 when foldinding bikes tend to use 33.4.
My S-work seatpost is 350mm long and requires 100mm minimun insertion so, 250mm max protusion. If I was to fit that on the kid frog 52, it would be borderline safe and still too small for me.

Like jfouellette, I have a Frankenstein Smooth hound X9 (2008 frame, 2010 fork and many bits from the part bin) and built a hammerhead 8 D7 for my mother. In both cases, I started with a frameset and then fitted standard parts found either on 20" foldingbike or road/hybrid bike. Cost was low (£800 for mine, £400 for my mother's). As others said, if you ready want a minivelo, bit the bullet and commit to a frameset.

Here is another one

https://www.aliexpress.com/item/1005005218086469.html

Disc brakes would make the conversion easier, but 20" or 16" disc wheels are somewhat limited in choices.
I bought my SUNDEAL mini velo from Nashbar while they were on closeout for $275 and free shipping.
It's been 5 years since, I ride it occasionally when I need something light and easy to hop on and just ride away to the store.
8 spd, disc brakes, 20" BMX tires, not sure of the weight, but it's not heavier than a typical mt. bike.


Java Mini bike is a 16-spd, $650 on eBay purchase.
Has hydraulic disc brakes, very nice feel even with small 20" deep alloy aero wheels.

thank you for everyone and everyones advice, I guess I will wait until that mercier is on sale again, otherwise I will keep looking in my market for a used one!

https://toledo.craigslist.org/bop/d/...662660039.html

I don't see how the bottom bracket height would be adequate if you just put small wheels on a frame intended for much larger ones. You need adequate pedal clearance when cornering. Some mini velos in pictures appear to have a lack or BB height that would concern me. Pictures can be misleading, but that includes some in this thread.

I have always lusted after a mini velo, but will hold out for a dedicated frame if I do buy one.

For a Mini Velo or BMX conversion as mentioned above, what's the largest chainring anyone has been able to place on their bike. I'm thinking of a singlespeed version of something similar to OP but still want the gear ratio to be similar to a 700c bike. Aiming for 80 gear-inches or so.

Also, for something like a bmx conversion or similar, has anyone had trouble sourcing longer stems and seat posts? Anytips on where to get these?

Also, Also, Does having a different crankset style on BMX bikes create problems with compatability? i.e. Not a square taper like most road bikes. Is this the limiting factor for chainring size potentially?

Yeap. BB height is something that budding minivelo builders often overlook, and it is key for maneuverability as too short a BB drop will limit how fast and far you can lean.

A 56T chainring will get you in the low 80s GI range on 16", ISO305 wheels. Higher than that is, of course, possible, but imo an fool's errand as these things ain't meant for speed and the rotational losses of these small wheels becomes increasingly apparent.


56T

Looks very nice.
That large cog in the rear seems unnecessarily big with 16" wheel.
And the rear derailleur would need a pretty long cage to be able to shift between the small cog and large cog.

Thanks.

The cogset is an 11-40T which has been shown to work in real practice with the short-cage Shimano Zee RD-M640-SS RD. I can be pushed still to 42T no problem. Note also the higher profile 58-305 tires.






As for necessity, given my terrain and touring, it is often needed and necessary. As the crow flies, I am under 50km from 3,000masl.

I would add a couple of links to that chain in the video, that's just me.
3000 meter climb still doesn't need that low of a gear with 16" wheels,
likely you would fall backwards on your mini velo if a steep hill that require that low of a gear due to short wheelbase/chain stays.

I would counsel you to refrain from telling me what I need or don't need, that you know more about 305-wheel gearing or handling than I do, or that you know the wheelbase of that rig I showed. I sure need a 22 gear-inch low given the very steep inclines that Bali (or Taiwan where I've toured, for example) has to offer, particularly when carrying a touring load, which is exactly the low gear returned by a 11-40T cogset with a 56T chainring and 50-305 wheels/tires. Did you even calculate it before commenting? No, you don't fall backwards when climbing on a short gear on a short wheelbase rig. Happy to entertain other conversations, not this one though.
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Whatever floats your boat.
You'll find out for yourself soon enough once you get on a steep grade.

The thing is that I already have. Over the many years I've ridden ISO305 wheel bikes in steep terrains, touring, overseas and at home. Your concerns about the Zee RD and about low gearing on 305 wheels have no merit and have both been debunked in real practice. You are out to lunch.

Careful, that derailleur looks pretty close to the ground.

Good thing you didn't post it with the chain on.