A Super Modified Raleigh Twenty

This is the latest version, faster and lighter. The only original parts are the frame, frame bolt, and the rear brake. .

This is the previous version, sort of a folding mountain-bike.
Part list is here

Many thanks to Sheldon Brown, Alex Wetmore, John Allen, Guy Bouchard, Tarik Saleh, and Mark Rehder (and others) for advice and inspiration.





This bike and this site were built by C. Heg
cheg01 at comcast dot net


Original Condition

Here is the original condition of the bike when I got it.
Good usable condition with a few little problems:
Missing seatpost clamp.
Missing front fender stay.
Missing rack.
Non-original seat.



Revision 1: 6 speed

This is the first mod, 6 speed with the original Sturmey-Archer Hub and rear wheel.


I had some chainslip on the small cog and frequent chaindrop problems in this setup. The chain was probably too long and needed more wrap on the small cog. The gears were also too low and the steps were large with 16/20 cogs, 53t chainring. I did determine that the dual cog, 6 speed SA hub conversion can be made to work.

Gear Chart
Cog SA Gear Gear Inches
16 3 88.1
20 3 70.5
16 2 66.3
20 2 53.0
16 1 49.7
20 1 39.8

Another problem was way the fork was installed. I bought a 240mm threadless steerer with the fork because it was the longest available. The head tube is so long that only about 3/4 inch of tube was above the top of the headset, so only 1/2 of the stem was clamped on to the tube. It looked nice and the height and reach were OK, but I was afraid of losing my teeth if the stem popped of while bombing down a hill somewhere. For the next revision, I took the front half of the frame to R&E Cycles in Seattle and had the steerer threaded and switched to a threaded headset and stem. Better safe...

Revision 2: Quasi-Bike Friday

The third incarnation of my Raleigh Twenty came from a lucky buy on ebay. I got the handlebars, shifters, brake levers, fenders, tires, and wheels from a Bike Friday Tandem Two'sday folding bike that the owner had upgraded. The wheels were 406mm diameter, like the Raleigh Twenty stock size. The rear wheel had Sachs 3x7 hybrid gearing and matching indexed grip shifters came with the handlebars. The front wheel had a Sachs VT-5000 drum brake, but I couldn't use it because the drum brake arm wouldn't fit between the RST fork blades.

This bike rides well. I put over 100 miles on it in the first week and it's not the fastest thing in the world but it's fun to ride. It's at least a contender for the most modified Raleigh 20 around. Part list is here.






I replaced the stock 12/16/18/21/24/28/32 Megarange cassette with a 12/13/14/15/17/19/21 to get a more useful spread of gears. The rear dropouts had to be spread from 114mm to 135 mm to get the rear wheel in and there is some interference between the chain and the right seatstay when shifting to the smallest cog. The temporary fix is to use only 6 of the 7 cogs on the cassette. It works because I have a 52t chainwheel so the current 18 gear range is:
Gear Chart
Cog Hub Gear Gear Inches
13 3 108.8
14 3 101.0
15 3 94.3
17 3 83.2
13 2 80.0
14 2 74.3
15 2 69.3
17 2 61.2
19 2 54.7
21 2 49.5
17 1 44.8
19 1 40.1
21 1 36.3

Initially, I had a problem with dropping the chain off the outside of the chainring every 5 miles or so. Based on good advice from rec.bicycles.tech, I bought and installed a used Shimano Alivio front derailleur to use as a chainguide. The Raleigh 20 has a non-standard seat tube diameter (a bit over 1-1/4 inch) and the downtube intersects the seattube right where a derailleur clamp would normally go. The bottom pull Alivio has the clamp below the top of the cage so it it clears the downtube. I got one with a 1-3/8 inch clamp and used a couple of layers of innertube rubber to shim it. I also got a chainring without the features machined in it to assist index shifting. Those two changes seem to have fixed the chaindrop problem.

The split Bike Friday handlebars are very useful for folding the bike up into a nice small package. I have seen on the Bike Friday Website that they sell many types of split bars and will even convert your favorite handlebars to split bars for a fee.



The frame has a brackets for mounting an old style pump, but I have not seen any new pumps that will fit them. I usually put the pump in a pannier or use Jandd Pump Ties to hold the pump on. There are no bosses for waterbottles, etc, but hoseclamps work just fine anyway. The bottle cage can go either on the seat tube or on the back of the head tube.

Revision 2.1


One thing that was not satisfactory about the bike after the mods was that it could not be ridden no-hands because it would try to veer off as soon as I let go of the bars. After trying several variations of the steering geometry, I solved the problem by installing a heavier tire in the front, a 20"x1.95" Maxxis Hookworm. The increased gyroscopic effect makes the bike much steadier overall and much more pleasant to ride. I also went to a Primo Comet rear tire because it has about the lowest roling resistance of any 20" tire.






Packing


One of the reasons for building a folder is to take it along when I travel without paying high fees to the airlines. My goal is to pack the bike in a suitcase that is below the size limit for checked bags, Length + Width + Height <= 62". I bought a Samsonite 29" Oyster Cartwheel bag because it is the closest to airline max I could find at under $100. The following description is my procedure for packing the bike. I don't have cable splitters, so the handlebars and frame sections remain connected by cables at all times. Life would be easier if the cables were split at the frame joint.

Remove chain, crank arms, fenders, rack, seatpost, and wheels.
Loosen stem clamp bolts and remove handlebars from stem (These are Bike Friday split flat bars).
Loosen stem fixing bolts and push stem all the way down and drop stem angle to zero degrees (this is a Kalloy adjustable angle stem). Separate frame at folding joint by removing the L-bolt and the locknut.

1) Place fork and front half of frame in the case. (Note: fork and stem are facing backwards)

2) Place Rack and pannier in case. (I also bought a folding Plescher rack so I can fit it in the case for travel.)

3) Place lower frame in case. Note: twist cables so that rear derailleur is down.

3) Place handlebars on left.

4) Place seat/seatpost, crank arms, and chain in case. Seatpost goes in between the chainstays. The chain and crank can be put in a plastic bag for cleanliness.

5) Place miscellaneous items like pump, spare tube, and seatpack around frame, keeping center of case clear.

5) Install center post. Post is a 10" long 1/2 inch galvanized pipe nipple with threaded flanges on both ends to stiffen the suitcase against pressure on the sides. The sides of the case are not very stiff by themselves. Install the post with the upper flange removed.

6) Place rear wheel with center post between spokes and cogs down. May need to put a rag under the cogs to prevent scratching the frame.

7) Place front wheel on top with center post through the spokes. For my bike, the QR has to be removed from the front wheel to get it to fit under the lid when the case is closed.

8) Thread upper flange onto center post.

For air transport, it is a good idea to put detailed packing instructions with pictures inside the lid of the case for the TSA if the bag is inspected. I also put my cel phone number in there so they can call me if there is a problem. I took it on a business trip to Florida from Seattle and had no problems at all. The TSA looked inside but apparently did not touch anything.

Future Plans


Eventually I will try to get more clearance for the chain by modifying the brake bridge so that the seatstays can bend higher up, If that works, I'll switch to a 48T chainring and use the full 21 gears. Another remaining project is to try some different bars on it to see how it feels with a more aero riding position.
I have a 451 rear wheel with a 7 speed cassette. I will eventually get that working so I can leave the 3x7 wheel at home if I'm going to be riding in a flat place like Florida.
COMPONENT DESCRIPTION
Frame 1975 Raleigh Twenty
Fork RST Sprite TL Suspension Fork
Headset Full Speed Ahead Duron DL 1" Threaded
Handlebar Bike Friday Split Mountain Bars with Profile Barends
Stem Kalloy Adjustable 1" Threaded
Shifters Sachs 3x7 Grip Shifters
Brake Levers Shimano Deore XT
Front Brake Shimano STX RC Cantilever
Rear Brake Weinmann Long Reach Sidepull (Original)
Seatpost Rockshox Mountain Suspension Post
Saddle Velo VL-6037
Seatpost Clamp 32.5 mm QR clamp
Front Derailleur Shimano Alivio (Fixed Chainguide)
Rear Derailleur Shimano Deore XT SGS
Rear Hub Sachs Torpedo 3 Speed
Cassette Shimano Hyperglide 7 Speed: 12/13/14/15/17/19/21
Rear Wheel Sun CR18 Rim
Front Wheel 20(406) Aluminum BMX Rim
Bottom Bracket Shimano UN72
Bottom Bracket Rings Phil Wood 26 TPI
Crank Arms Shimano 105, 175mm
Chain Ring Vuelta 52t, 130 BCD
Chain KMC Super Shuttle 3/32
Pedals Shimano M-515 SPD
Front Tire Maxxis Hookworm 20(406)x1.95, 110 psi
Rear Tire Primo Comet 20(406)x1.35, 100 psi
Fenders Bike Friday Molded
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