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-   -   Options for R20 rear hub upgrade (or not bother?) (http://www.bikeforums.net/folding-bikes/533548-options-r20-rear-hub-upgrade-not-bother.html)

rossmcloch 04-21-09 07:16 PM

Options for R20 rear hub upgrade (or not bother?)
 
Hi,

What options do I have for a R20 rear hub upgrade or should I stick with the 3 speed? Re-spoking a wheel is not cheap and I want to do it with the right hub (or maybe not have to?).

What have other people here used? I want to keep cost low.

If I'm respoking what are some favorite rims to use?

Thanks for the help.

rhenning 04-21-09 07:33 PM

i have 3 of these Raleighs. A 1970 Twenty. A 1976 Folder. The last was a non folding frame I built up with no decals using a BMX aluminum wheel set. Stock BMX front and a laced SA in to the aluminum rim in the rear. All three bikes are still run with SA 3 speeds and all work well with little or no maintenance. They have different sized chain wheels so are geared differently but 3 gears seem to be enough in all of them. Roger

stevegor 04-21-09 09:12 PM

I have two R20s with the SA 8 spd hubs and one R20 with a Sachs 3x7 hub, these options might be too expensive for you, but there is a cheap way of increasing your 3 speed to a 6 speed.

I can't recall which member has done this modification, but this is how he did it:

1:The SA rear cog is dished, remove it, it might be a 16 or 18 tooth. Buy another SA cog, maybe 14t or less, then reinstall both cogs back to back onto the hub. They will fit, maybe without the washer, then install the locking ring.

2: Buy a rear hanger, like you get on el cheapo bikes, they're pretty cheap. You might have to grind off the small ridge so it sits flat against the R20's drop out, then drill a hole in the drop out, for the locking nut that holds it onto the frame.

3: If you can find a 2 speed RD or are happy to experiment with other RDs, then install that.

4: All you need now is a 2 spd shifter and a little trial and error, and you have a 6 spd SA hub on the cheap.

According to the member that has done this conversion, it's inexpensive and quite easy to do and the gear range covers all that you'll need.....Good luck.

badmother 04-22-09 12:59 AM

Sixty did it!

http://www.bikeforums.net/folding-bikes/398693-another-damn-twenty-thread-twist.html

rhm 04-22-09 06:25 AM

Quote:

Originally Posted by stevegor (Post 8776326)
...this is how he did it:

1:The SA rear cog ... might be a 16 or 18 tooth. Buy another SA cog, maybe 14t or less...

My R-20's came with 15T cogs and were a bit over-geared. I'd suggest an 18 for the second cog; that should give a nice range.

rossmcloch 04-22-09 07:32 AM

I hadnt even thought about that. Pretty neat!

bentox 04-23-09 01:06 AM

It's maybe a stupid question but,

if I change the cog (15t) of my twenty for a bigger one (18t), what do I do with the chain ?
It'll be too short. Should I buy a new chain ?

badmother 04-23-09 02:24 AM

Quote:

Originally Posted by bentox (Post 8783985)
It's maybe a stupid question but,

if I change the cog (15t) of my twenty for a bigger one (18t), what do I do with the chain ?
It'll be too short. Should I buy a new chain ?

It depends. Maybe the chain is still long enough, but also changing the chain when buying a new cog can be smart. I keep some old chains lying around as spares and also to use when I am trying out a new setup, before I have decided vhat cogs and chainwheels to use. At this stage I can also join a piece from one chain to the other to make it long enough. When I am satisfied and have made up my mind I buy a new chain and cut it to the right size.

bentox 04-23-09 03:10 AM

Thx Badmother,

I kow how to reduce a chain.
Which tool should I use to make it longer ?

wahoonc 04-23-09 03:18 AM

You can put about any hub you want on a 20, within reason. I just got my 20 a couple of weeks ago and haven't had time to work on it at all.:notamused: BUT I have been ordering parts:thumb: There are quite a few rims out there, for this go around I am going with the Sun CR18 because they are relatively inexpensive and readily available. The plan is to use an old Sturmey Archer AG hub (3speed with a built in generator) for this go around. Then perhaps in the future upgrade to an 8 speed, possibly the new Sturmey. You need to learn to build wheels. I quite often lace mine up and have the shop do the final truing, however they only charge $30 labor to build one up. I usually pay ~$65 on average for a wheel when I provide the hub.

I have done the 2 cog thing in the back before; I carefully measured the chain and had it so all I had to do was slide the wheel back a bit when using the smaller cog, slide it forward when on the larger. I did it on an old Raleigh Sports and the slots were long enough to let me get away with it.:p

Aaron:)

stocksy 04-23-09 02:29 PM

Quote:

Originally Posted by rossmcloch (Post 8775645)
What have other people here used? I want to keep cost low.

If I'm respoking what are some favorite rims to use?

I did it with some sun CR18s, I was pleased with the result. Going to 406mm rims gives a better choice of tyres, too.

I've posted this here before, but what the heck.

badmother 04-24-09 12:51 AM

Quote:

Originally Posted by bentox (Post 8784112)
Thx Badmother,

I kow how to reduce a chain.
Which tool should I use to make it longer ?

Same tool (or one extra "lock link"). hen you cut a chain by pushing out the pin make sure you do not push it all the way out. Then put the piece you want to add in place and push the pin back inn and the two are joined together. Iam sure you can find instructions and videos on the net if you need more.

griftereck 04-25-09 03:05 AM

to make it longer you will need a replicator from Star Trek to make more links :D

the drop outs on the R20 are designed for a 3 speed hub
if you replace that with a hub that has a round axle instead of round with flats, you may need to file the drop outs a little.
especially the old Shimano 3 speed hub. Its got a steped axle. So is larger diameter at the hub lock nut. Also 15 tooth is the smallest cog that fits them as the chain hits the hub.
My BSA 20 came with a AG dyno hub on 28 spoke rusty steel 451 rims.
http://i29.photobucket.com/albums/c2.../20Dynohub.jpg
Im going to cut some spokes so I can build it into an alloy 406 20 X 175 rim

there is supposed to be problems with spoke angles with using large flange hubs and small rims. But my RSW has 16" wheels with a front dyno hub.

and nowadays you can get electic motor hubs in small wheels. with spokes that are real short. with a heavy battery to lug about. havent heard of them being harsh to ride. or breaking spokes


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