BMX - Derailing a BMX

Here's the story.

1. A long time ago, i saw a 7 speed BMX. The guy owened a bicycle workshop btw.

2. I found a perfect bmx frame with wheels etc etc at the junkyard.
(you can assume my financial bandwidth from statement 2)

3. I work 7 miles away. Single speed would most prob kill me though i haven't tried it.

4. I've spent three days searching for related articles with barely any results. Furtheremore, while i'm mechanically inclined, i've never consulted the internet for bike, hence is unfarmiliar with the lingos associated to bikes.

Here's the question.

Is it even possible to fix derailers onto bmx without modding the components? Aside from that guy i met years ago who's also currently 12,000KM away from my location. I haven't found any article featuring a successfull multi geared bmx. What are the problems associated with sticking multispeed gears to a bmx?

any advice, info, knowledge yada yada would be apprecieated. Thanks

PS: i've also seached this forums but have failed to located any relevant articles.

One problem is that cassettes with more than one gear are pretty wide, and might not fit in a BMX frame. If you got one to fit, then I think it'd just be a matter of attaching the derraileur so it didn't rotate (easy enough), and adjusting it to actually work (no way I'd tackle that one.)

I think you'd be better off just making do with one gear. In my experience, to have gears on a bike work properly you need pretty high quality stuff and a lot of skill to keep it working right. Maybe you can find one of those single speed beach cruisers from walmart, etc, and ride that instead of the BMX bike for commuting. It'll go faster easier because it's got bigger wheels, and maybe you could put on a bigger chainring.

I don't think that a single speed is what's going to limit your range. BMX bikes are small and not designed to ride over distances. Good luck though.

7 miles ain't **** c'mon.

7 miles ain't **** c'mon.

Word, I rode a BMX to a town that is 30 mins in a car I forgot how long it took but it sucked.

BMX's are not designed for real riding, you cannot get a proper extension of your leg which will kill your knees sooner or later.

The frame needs a derailler hanger to attach the derailler to.

You'll need a new 3/32" chain and chainring.

How will you attach a freewheel? (I don't know much about BMX hubs).

All kinds of other crazy issues.

The easiest way to get gears on a BMX is with an internally geared hub, which you cannot afford.

find a kids mountain bike with a 20" wheel and 5+ speed freewheel rob the wheel, mech etc from that, a lot of cheaper older bikes seem to have a hanger that just screws into the dropout witha D shaped plate thing on the insidde of the dropout

even better a folding bike with 20" wheel and internal gearing as this`ll look a lot cleaner and theres less chance of bashing the mech to bits

stick the changer for the deraileur somewhere on the frame or bars, then bang your seat up nice and high so you can strech out your legs a bit

et voila

you have a butt-ugly stupid looking bike that not much use for anything BMX and kind of crappy for going any distance

but then if you need another bike for donor parts to make it into a road going super-tourer why not just get a bike desgined to travel distance on?

(by the way depsite my derisory commments i have been planning something similar myself,

allready have the BMX (a mid 80s diamond back running a crappy set of wonky mags that are so out of true i`ll never get a brake to worK) and a little girls mountain bike.

it will look like total cack but my girlfriend wants a ride with brakes and gears so i` m gonna give it a go)

buy 2 bikes.

One problem is that cassettes with more than one gear are pretty wide, and might not fit in a BMX frame. If you got one to fit, then I think it'd just be a matter of attaching the derraileur so it didn't rotate (easy enough), and adjusting it to actually work (no way I'd tackle that one.)

I think you'd be better off just making do with one gear. In my experience, to have gears on a bike work properly you need pretty high quality stuff and a lot of skill to keep it working right. Maybe you can find one of those single speed beach cruisers from walmart, etc, and ride that instead of the BMX bike for commuting. It'll go faster easier because it's got bigger wheels, and maybe you could put on a bigger chainring.

That's a very good points actually and it totally escaped me. The gears simply won't fit. And the leg space.........well i figured a small bike would be easy to haul up a train but that doesn't happen very often.

So the bmx with gears that i saw a while basck must have needed a lot of work.

get an ss road bike

NEW IDEA. I might get a kids moutain bike for free. It looks more or less the size of a bmx. Do you guys think that rides like a bmx? Can i technically convert that into a bmx with gears?

Your opinions are highly apprecieated.

Shimano Nexus 8 on a cruiser. Rob a liquor store if you have to, it would be so worth it.

kensington (philadelphia) to cottman (10 miles north) and back.
then over the ben franklin to camden and back the same day.
30 miles total.
all on a 1987 diamondback hotstreak 20".

and like the guy who started this thread, i too have been fruitlessly researching retrofitting gears onto my bike.

gears on a 20" for distance-riding makes sense for me, as i'm 4'11" and already have become accustomed to sitting and pedaling 90% of the time with my seat post pretty high up for proper leg extension... i just want gears so i can stop spinning so damn much on flat terrain/smoother asphalt.

find a kids mountain bike with a 20" wheel and 5+ speed freewheel rob the wheel, mech etc from that, a lot of cheaper older bikes seem to have a hanger that just screws into the dropout witha d shaped plate thing on the insidde of the dropout

even better a folding bike with 20" wheel and internal gearing as this`ll look a lot cleaner and theres less chance of bashing the mech to bits

stick the changer for the deraileur somewhere on the frame or bars, then bang your seat up nice and high so you can strech out your legs a bit

et voila

you have a butt-ugly stupid looking bike that not much use for anything bmx and kind of crappy for going any distance

but then if you need another bike for donor parts to make it into a road going super-tourer why not just get a bike desgined to travel distance on?

(by the way depsite my derisory commments i have been planning something similar myself,

allready have the bmx (a mid 80s diamond back running a crappy set of wonky mags that are so out of true i`ll never get a brake to work) and a little girls mountain bike.

It will look like total cack but my girlfriend wants a ride with brakes and gears so i` m gonna give it a go)
+1

kensington (philadelphia) to cottman (10 miles north) and back.
then over the ben franklin to camden and back the same day.
30 miles total.
all on a 1987 diamondback hotstreak 20".

and like the guy who started this thread, i too have been fruitlessly researching retrofitting gears onto my bike.

gears on a 20" for distance-riding makes sense for me, as i'm 4'11" and already have become accustomed to sitting and pedaling 90% of the time with my seat post pretty high up for proper leg extension... i just want gears so i can stop spinning so damn much on flat terrain/smoother asphalt.

Well i finally yield and bought a £160 touring bike. Works wonders until the wind blows and grinds me to a halt. That bmx frame i found is still just sitting there. Not sure what to do with it. It's missing many parts to begin with and has to be built ground up and would cost at least £50-70 to do it. I find that ridiculous since you can buy a working 2nd bmx for that price.

i dunno i find that anyone serious about riding their bike and maintaining/customizing it gets fairly used to the cost of things being ridiculous... could have bought 2 or 3 brand new (but quite awful) huffy's for what i've put into the dback to get it riding right again after 20+ years in a friend's basement in maine.

let's see here, 3 speed internal hubs for freewheel...

Sturmey-Archer SRF3 __ gearing: 177% transition // -25%, direct, +33%
http://www.sturmey-archer.com/hubs_3spd_SRF3.php
Sturmey-Archer R-SRF3 __ gearing: 177% transition // -25%, direct, +33%
http://www.sturmey-archer.com/hubs_3spd_RSRF3.php
Sturmey-Archer AW __ gearing: 177% transition // -25%, direct, +33%
http://www.sturmey-archer.com/hubs_3spd_AW.php

sturmey-archer seems to be a bit of a broken record with their gearing... and searching froogle yields a mess of individual parts, no kits or matched parts. and actually, no exact matches for SRF3, R-SRF3 nor AW, just other 3-speed product sku's. i get the overall impression one could make a tidy living merely ordering, installing & configuring Sturmey-Archer parts... hmm.

heard lots of good things about sram, let's give them a shot...

SRAM i-MOTION 3 __ gearing: 186% transition // ??
http://www.sram-imotion.com/us/html/navigation_us.html
--> products --> i-MOTION 3

i really like the shifters designed for this hub... looks like a good solid package. and hey it's german-made, how bad could it be? froogle seems to suggest it's just shy of $100 for the freewheel hub, and $10-15 for a shifter. important note: this hub is designed to change gears under load OR while stopped/standing _how handy!_

how about shimano?

Shimano Nexus Inter-3
http://bike.shimano.com/publish/content/global_cycle/en/us/index/tech_support/faq_s/nexus_faq_s.html

couldn't locate specifics on its stock gearing, though the FAQ says you can alter it "by changing the rear cog sprocket... from 16 tooth to 23 tooth size"... this hub Does also change gears when at a standstill. doesn't appear to be available in a freewheel-model, specifically. the FAQ mentions modifying the one model to do away with the drum brake arm and optionally applying a resin cover. that seems a bit of a mess... still, the price is right: here's a whole kit including the shimano revoshifter for $57.99:

http://www.outsideoutfitters.com/p-3824-shimano-nexus-3c41-inter-3-hub-kit.aspx

i get a good feeling about either the sram or the shimano 3-speeds.
i guess now i have to figure out if either is compatible with my mags/axles and chainring.

heh... i guess amazon.com knows best. :D
searching their Entire site yields one answer: SRAM

hub, from elite cycling: http://www.amazon.com/dp/B001JI771C
shifter, from niagara cycle works: http://www.amazon.com/dp/B000VSWD4C

so now i guess the only remaining question is if this hub will fit inside the axle-space of my 5-spoke mags, and if i'll be able to anchor it to the mag somehow (since spokes aren't available for anchoring)...

or i could just fugghetaboutit: http://www.amazon.com/dp/B001DY4BQQ

You cannot fit the hub to a mag.

well you could hire a machine shop to bore out the mag to fit the hub and then you could gerry rig the spoke holes onto the hub so it stays put... but yeah that's ridiculous.

i spoke to trophy bike garage here in philly and unlike other shops i've mentioned this 'little' project/idea to, they said they've seen it done and it's possible... with a few caveats - more likely than not they'd have to extend my dropouts and/or reshape my frame to account for the 117mm+ locknut spacing since most all bmx frames are 110mm locknut-to-locknut... then it's a matter of building a wheel to fit the new hub and the new dropouts... apart from that though, the guy made the conversion sound reasonable.

which do folks around here prefer? sram i-motion 3 or sturmey-archer aw (or srf3) ?

'ang on a tick, if i find a hub with an OLN (over locknut) size of 110mm and my the gap between my dropouts is 110mm, then i shouldn't need to have the rear of my frame reshaped (w frame spreader) or my dropouts extended, right? if that's the case, i could just order THIS (http://www.sjscycles.co.uk/product-Sturmey-Archer-36-hole-Sturmey-Archer-AW-3-speed-hub-110mm-OLN-for-Brompton--BRITISH-BUILT-12011.htm) sturmey-archer AW - it's got an oln of 110mm.

update: i dropped by trophy bike garage to make my project known to them and we measured my current locknut dimension at 110mm... i said i'd find the parts for the 3spd myself since i've already done the research and sourced them and the guy said cool, and we'll make the necessary adjustments and build your wheels, and we discussed pricing for that, all of which was quite reasonable... and he reassured me that even if frame adjustments have to be made, that my frame would handle it and that it wouldn't be too difficult.

and i ordered a Sturmey-Archer SRF3, shifter, and cable from JensonUSA a little while ago.

i'm very excited to be working on this project and hope to post photos of my franken-bike soon! :)

I was out in Moab a few years back and my father and i took a guided mtn bike ride in the desert. our guide had a 24" bmx cruiser frame converted into a mtn bike. it was pretty awesome.

that's pretty much what i'm doing!

i got a great deal on a mongoose frame on ebay (including cranks and fork)
which i'll feel better about having reshaped slightly to fit the hub
(from 110mm to 120mm, or so) than my current diamondback frame
(the orange hotstreak i'm told is the most rare)

and i'm putting a mountain bike stem and handlebar (v-shaped riser bar) on there.

got my sturmey-archer last week from jensonusa - it's really beautiful!
http://www.jensonusa.com/store/product/HU407C01.aspx
BTW - you do NOT need to buy a shifter & cable for it, it's in the box provided by SA.
so for about $60, you got yourself three speeds! hooray!
(not including shipping, and professional install of course :)

I wish i remembered that guys name, or anything about his bike for that matter. he let me ride it and it was damn comphy. oh and my dad almost rode off a ravine in the middle of the desert. that was funny.

edit: i had some nice words to say about JensonUSA so i put them in my own thread as to not thread jack.

i had a really positive experience w their cust. service too... as stated above the SA 3spd comes with a matching shifter & cable in the box but i didn't know that and ordered the classic shifter and standard cable... called them up explaining the error i'd made and the guy said just box it up and send it back... no RMA needed, even! i was amazed; i can't remember the last time i returned something just by sending it back w the receipt.

sturmey-archer on my bmx rebuild (as a take-apart travel bike)
is go! it works pretty darn well, i'd like to add.

http://farm4.static.flickr.com/3260/3122745669_051fce642d.jpg

i had to take out the standard spacers (which go between the inner locknut and the hub) with stainless steel washers so that i could fit it onto the mongoose frame dropout but after that installation was a breeze!

1st gear is pretty excellent for hills, i definately noticed it takes a LOT less effort to go up and down the hills in my neighborhood i was cursing up until yesterday before i finished this rebuild... 2nd gear is pretty standard, really (as it should be)... i don't imagine many opportunities for 3rd gear but when i'm on a nicely paved bike path or major arterial road's bike lane, it will definately equal fewer turns of the crank to keep moving forward.

so yeah, it's good! i recommend.
(don't expect 'amazing' gains in riding performance; but it does make a difference!)

p.s. you definiately want to Not turn your pedals while changing gears... just let it coast a bit before continuing. otherwise you'll feel the gear change and get a little spooked (it's a pretty harsh 'click'); and i'm sure it's not to great on the hub.

I vaguely recall seeing an article in a BMX magazine about a BMX track bike that had a 3speed cassette in the back, and short cage derailleur and trigger shift... and it wasn't some home-build amateur using it either, but a pro doing some development work for a some manufacturer. It's do-able but you need more than just basic mech skills for a project like this.

You have to definitely change the rear hub, that can accept a cassette.

You have to find a narrow cassette with as few gears as possible (9 speed is just too wide to fit in between BMX drop-outs - but the old 6 speeds are hard to find these days).

The key is to get a "short" cage derailleur, other wise it'll hang too low and scrape.

I can't think of way to do this on the cheap tho... other than what you said - get a cheap kids bike with gears and use that as a donor bike for parts.

All the best! :)


.

as far as fitting a 3-speed cassette (or 5-speed) i.e. Not an internally-geared hub, you'll have to go the trickier route of 1. finding a frame that's got a wider dropout (wider than the 110mm 'standard' for bmx or small-format mountain bikes) and 2. hiring someone to bend the frame to 'make room' in the dropout to accomodate somewhere between 126mm and 135mm for the wider hub and cassette. i imagine it's possible tho...

replacing manufacturer-supplied spacers on an internally-geared hub with smaller spacers or tough-metal (stainless, titanium, cold-forged brass, etc.) washers to make the assembly narrow is WAY EASIER, though :)

From C&V not a bmxer but I definitely know this can be done, at least cheaper than buying a new internal gear hub (120 for a basic sturmey 3 speed annd then you need to build the thign into a wheel. They also can't handle the torque of wheelies or get jumped on). you can spread the rear dropouts of a steel bmx from 110 to 120 easily. Its called cold setting. Its a technique used all the time to cram 10 speed drivetrains (rear mech) onto 5 speed spaced bikes. As far as attaching a derailler get a cheap old one meant for a bike without a der hanger, it has a plate that bolts onto the dropout and will fit in a track/bmx end. using cable clamps you can mount a shifter almost anywhere. The most difficult part would be rebuilding the rear wheel for the road or mtb hub onto a 20 iinch wheel. Which will cost you at least $30 at a shop and a lot of "Huh wha?" from the employees. The thing is with the tiny 20 inch wheel you'll need to run a huge chainring to even make use of a few of the gears. Your best bet would be to just get a vintage biike boom roadie for commuting. Any old ralleigh, univega, peugeout etc in good condition and freshly overhauled will put 7 miles behind you in well under a half hour wheras a mutant bmx will just be a lot of money for a slightly more usable ride. If doing tricks when you get to town is of paramount concern just buy an older cromoly mtb. Run high pressure slicks, platform pedals, and really cheap rear mech (less than $20 for a shimano tourney and they work FINE for commuting) or a single speed mtb of the same general configuration will still be good for doing little jumps and stairs. Outside of major cities both of these stypes of bikes can be easily had at thrift stores, dumps, or yardsales. You might even find you like roadies or mtbs as much as bmx, albiet for different reasons.

120 for a basic sturmey 3 speed
...
The most difficult part would be rebuilding the rear wheel for the road or mtb hub onto a 20 inch wheel. Which will cost you at least $30 at a shop and a lot of "Huh wha?" from the employees.

$120 is a ton of mark-up.
jenson usa's got the SRC3 (coaster brake) / SRF3 (freewheel) for $63/$62.
box from sturmey is all-inclusive, with a really nice shifter and all hookup hardware (cables, etc.)
http://jensonusa.com/store/product/HU407C01.aspx

i encountered a whole lot of 'why would you want to do that??' when i asked around about fitting a geared hub onto a bmx wheel... the shop that actually heard me out is the one that got the job for wheel-build.

i encountered a whole lot of 'why would you want to do that??' when i asked around about fitting a geared hub onto a bmx wheel... the shop that actually heard me out is the one that got the job for wheel-build.

Cardinal rule in retail... "the customer is always right." :thumb:

.

How do you even adjust the frame? isn't it like welded solid?

not surprisingly sheldon brown has an excellent do-it-yourself guide to adjust frame spacing.

http://www.sheldonbrown.com/frame-spacing.html

this is called 'cold setting' because all you're doing is flexing the steel a bit wider.
but you can ONLY do this with a steel frame; you'll kill a carbon or other composite frame.

Here's the story.
3. I work 7 miles away. Single speed would most prob kill me though i haven't tried it.
[/COLOR]

You need to BMX more then;) back in high school I lived 12 miles away and it WAS uphill BOTH ways (first down then up) and I did it on my old Mosh *Similar to the one I got now*

But any whooo I saw a two speed kit a while ago for sale for racing bikes...May be able to find one used?!?

after a whole lot of troubleshooting i'm now glad to report the rush of speed offered by the sturmey-archer SRF3 in 3rd gear, even for a 20" frame, is totally awesome... i feel as if i myself am not strong enough to pedal hard/fast enough to reach top speed in 3rd; and whenever i get close i've zoomed past a few city blocks and it's time to stop at a light.

tips/trial & error here:
http://www.bikeforums.net/showthread.php?p=8248866#post8248866

I don't know too much about how to derail BMX bikes, but here's a pretty good example of how not to by my friend Steven: http://www.youtube.com/watch?v=fiOZNeGOUX8

Hahahaha. That vid is great.

single speeds or fixed gear bikes are great for commuting, your problem is the choice of frame...

go to the SS/FG section!!!

your problem is the choice of frame...

since when is personal preference a 'problem' ?
(mostly rhetorical question.)