Anyone ever mount a derailleur to a BMX bike?

[Rondo]

Will this work if I mount up a 20" wheel with a 6-speed cassette?

[yeti575nut]

never seen it done, you may be the first...

[Broseph]

i think brian lopes did it back in the day. might have been a custom frame though.

[wschruba]

As long as there is a hanger, it's theoretically possible.

[Rondo]

Why does the frame need a hanger? Shimano has a couple styles that bolt directly to the frame I think. Correct?

[ryguy135]

Shimano has the Direct Mount version, which eliminates the B-link on Shimano derailleurs, but it still needs a special mount to attach.

[shiggy]

Will this work if I mount up a 20" wheel with a 6-speed cassette?

Hub width for BMX frames is much narrower than MTB frames. Will not get a geared hub to fit.

[trailville]

I would think you could squeeze an old 5 or 6 speed hub on there and use an old style axle-mount derailleur.
The other kids are going to laugh at you though.

[driftincowboy]

I seem to recall in the mid '90s they sold 3 or 5 speed BMX bikes, people thought they were going to take over BMX but they were quite the failure.

However for an around the neighborhood bike I think it would be kinda cool.

[Rondo]

The idea I'm toying with is because I live in the mountains with steep ups & downs. I want to get something better for my 6year old son than what you normally buy in a bikeshop as a 20" wheeled mountain bikes go.

I can build a titanium BMX bike with some gears at around 16-18 Lbs. Store bought bikes like the Trek Hotrock, Diamondback Octane, Scott Spark etc., are about double that. Hopefully a lighter bike (half the weight) would allow him to ride better and longer.

Him weighing 50lbs. and the bike weighing 30lbs. is not a good weight ratio in my mind. I weigh 220lbs., I could not imagine peddling a 150lb bike uphill.

[shiggy]

The idea I'm toying with is because I live in the mountains with steep ups & downs. I want to get something better for my 6year old son than what you normally buy in a bikeshop as a 20" wheeled mountain bikes go.

I can build a titanium BMX bike with some gears at around 16-18 Lbs. Store bought bikes like the Trek Hotrock, Diamondback Octane, Scott Spark etc., are about double that. Hopefully a lighter bike (half the weight) would allow him to ride better and longer.

Him weighing 50lbs. and the bike weighing 30lbs. is not a good weight ratio in my mind. I weigh 220lbs., I could not imagine peddling a 150lb bike uphill.

BMX rear hubs are 110mm. Getting even an old 125mm 5-speed freewheel hub in the frame would be tough to impossible.

Unless you have a custom frame built, which you could do for the price of a production Ti BMX frame

[trailville]

You could also look into internal geared hubs. A cheap 3-speed would probably be fine for a kid. Or look at some used kid's mtbs and see what they are using for rear hubs. I would guess there are some non-standard narrower hubs on some of those. Also browse some BMX forums, I'm sure there are others that have done this. I'm assuming you've already been on the "riding with kids" forum here?

[Rondo]

Yup! I just went and measured my kids 20” mountain bike hub and it is 130mm spacing.

I see where my dilemma will be.…

Thanks!

[GrapeNutsRobot]

I seem to recall in the mid '90s they sold 3 or 5 speed BMX bikes, people thought they were going to take over BMX but they were quite the failure.

However for an around the neighborhood bike I think it would be kinda cool.

I remember them being 2 speeds, one for the start of the race and the other for once you got up to speed. Its been a long time and i could be wrong though.

[GhostRing]

What about a tensioner and a 2 speed front? At least a granny gear for longer clibs?

[DennisF]

Barry Nobles implements two-speed hub, derailleur on BMX bike - ESPN

[DukeNeverwinter]

There's a guy here in S.D. that has a multi gear rear hub. And xt trail disc brakes. I don't know his name, but his kid races for GT.

Sent from my MB855 using Tapatalk 2

[Bill in Houston]

i have 5 or 6 or 7 speed haro bmx bike in my garage that we got from a neighbor. i'll take a look at it tomorrow and see if i can provide more details.

[Shark]

Kids are tough, they need heavy bikes

[gmats]

Will this work if I mount up a 20" wheel with a 6-speed cassette?

We did this kind of stuff back in the late 70's and early 80's. Simple old simplex or similar cheap derailleur mounted on the frame like the old department store bikes (Sears, Schwinn Varsity/Continental). We cannibalized old freewheel parts to make a 2 speed spin on freewheel. We mounted a spring loaded shifter that would default to high gear.

Hold the shifter in low position while in the gate and right after leaving the gate, we'd let the shifter go and the bike would shift and stay in high gear for the rest of the race.