Hello there fellow bike freaks. After owning a 20" minivelo for a couple of years now I have decided to go even smaller wheel wise. I drifted towards brompton sized wheels, which are 16" but not really (349 instead of 305c). I want to build a steel road bike frame with normal 56cm sizing.
I’d love to hear your suggestions on a couple of things:
moustache bar or drops
hardware options (has to be mechanical and preferably in chrome finish)
standard BB height and cranks or go lower with 165 cranks
brompton derailleur? (never actually held one, so don’t know about the compatibility)
My brain wants to scour the aliexpress for folding bike hardware, but my heart wants to build a mix of classic road components, maybe a 1x9 with a friction shifter on the TT or HT.
Bike Friday also builds 349mm bikes and uses standard 8/9/10sp derailleur drivetrains without issue. I think I even have a HG 135 wheel from a Bike Friday Tikit in my stash.
The only real problem with 349 is that all of the tires are too skinny. The best wide ones are Greenspeed Scorchers. The best fast tires are Schwalbe GOne, but I sure wish they were wider than 32mm.
You’ll have to get creative in figuring out how to get a long enough steerer or steerer/stem combo to get good stack.
Those work really well, but aren’t silver and classy. 9-10sp era Ultegra and 105 derailleurs look really nice, are short, and can be pushed into shifting up to a 32t cog. XTR M900 is really beautiful (though not silver) and handles a 36t cog in short cage.
I went for a set of wheels that can take a 10s casette. As for the tire choice, it is indeed limited to 32mm, I’ll have to live with that. I have 28mm continental contact speed on my 20" speedster and they prooved themselves as a reliable option. Schwalbe’s come in a nice tan wall version - very tempting. Regarding the steerer, yeah the headtube will have to be around 400mm, so I probably will have to extend a steerer from a donor fork. This will be a headscratcher for sure.
Yeah, I have the tan wall Schwalbe on the rear of my Brompton (I use a Greenspeed Scorcher up front, but it won’t fit on the rear). It’s a nice tire, I just prefer more meat on my tires – especially with small wheels.
I’ve had good luck making long steerers by using 1.125x0.058 tubing and then making a tapered shim out of 1.125 x 0.095 (about 2.4mm thick) that is turned down to 1.010 on the OD and tapered at the top end. This is inserted with force (freeze the insert, heat the steerer, use a big hammer) before the crown is brazed up. I don’t know for sure that this is a good solution, but an old tandem builder who I trust a lot recommended it. I made a few 500mm long steerers (for cycle trucks) using this solution.
The other solution is to just live with a 400mm steerer and a short headtube, then use a tall curved stem.
Thanks, looking into that. If only they had a more classic looking option. What happened to shimano’c CAPREO? I only had a chance to buy one set and it dissapeared from the market entirely.
I much prefer to extend the steerer and use a longer headtube. I think this will put less stress on the bearings than an overextended stem would. I’ve had some success with extending steerers using industrial precision seamless tubes and tig welding them in place. You can get 22,23mm ish tube and press it into a 1" threaded steerer or get a thicker one and turn it down to size as you said. Worked nice for a couple of cargobikes.
Here’s a very rough mockup, to give you an idea of what I have in mind. The parts are random at this point. There will be lots of real estate on the headtube and chainstays for front and rear racks, so I’m thinking of a radonneur like setup.
Avoid using a Brompton derailleur. They’re designed the way they are because the bike needs to fold and they’re goddawful things.
Brompton wouldn’t get away with such an agricultural solution if it was possible to fit a simple Shimano. It doesn’t look like your bike needs to fold so I wouldn’t use one.
The one piece of Brompton hardware that you absolutely should have is the front bag block. It’s such a smart solution for holding small to mid-sized luggage. If I remember correctly it is an 8x8mm square solid chunk that is about 70mm long brazed to the front of the headtube. A friend has good measurements if you don’t find them.
I’ve extended headtubes using an internal sleeve, but the approach that I mentioned above is lighter and probably stronger at the end of the day.
Keep in mind (maybe you already are) the challenge of reaming / facing a head tube that’s longer than the standard shop tools will accommodate.
You could make a longer central shaft piece (there is a funny name for this type of threaded rod and I’m blanking on it at the moment) for the reamer / facer but that’s an expense and complication it’s good to plan for.
edit: another thing, and forgive me if you have thought of this too, is chainline / shifting. With a super short chainstay, crossover issues with the chain become exaggerated.
Yes, I will probably have to come up with some tooling for the reaming/facing part. I have some long shafts I used for cargo bikes, I think I will cobble something together. I usually make all my tooling as there is no second hand market in my country and the prices of new bike specific tools make my skin crawl. I’d rather put in some extra work.
As for the chainstay lengt, yes, it has crossed my mind. My previous mini velo has super short chainstays and indeed there wouldn’t me much place for the chain to flex (I used a geared hub). This time I opted not to shorten the chainstays in comparison to a standard 28" wheel road frame. There’s also one more reason: the previous bike is a wheelie machine. I mean it’s fun at first but it wears on you when you can’t start quickly without hanging yourself over the front of the bike.
I’ve experienced the wheelie thing! Agree, it’s fun for a while. Also there is this feeling that’s hard to describe where when you turn, you are pivoting around a point that’s much closer to your own center of gravity, so initially as you go into the turn your weight is moving less. It’s an uncanny and fun feeling. This cargo bike had that feeling and, combined with the long front, was quite fun though a bit uncanny as well.
I am only commenting to say the Microshift rd actually works well, definitely works with 30t and maybe even 32t. An older road rd might look better, but I don’t mind motivating Microshift to keep making these… with immense buying power of like 7€. Pictured on a 305 wheel.
