THE RALEIGH TWENTY

Your ever-expanding web resource for the Raleigh Twenty
and other classic small-wheel bicycles.

Technical Data:

The Raleigh Twenty uses a mixture of ISO (standard) and proprietary (non-standard) parts. Here is some technical information and suggestions which can help you maintain and/or upgrade your Raleigh Twenty.

Bottom Bracket
- 76mm wide shell. Raleigh proprietary threading (26tpi whereas ISO is 24tpi)
.

- There are 11 loose 1/4? Ball Bearings on each side.

Head Tube Bearings (original)
The upper Head Tube Bearing is a nylon sleeve bearing and should last a good long time with little maintenance.
- The lower Head Tube Bearing has 25 loose 5/32? Ball Bearings.

Forks
- Narrow Spacing (90mm) and Raleigh Threading (26tpi Raleigh Proprietary).

- The front hub has 10 loose 3/16? Ball Bearings on each side.

Frame
- The rear triangle is spaced at 114mm to accept Sturmey-Archer AW hubs.

Seat-Post
- 28.6mm diameter, chromed steel

Wheels
- ISO 451mm or ISO 406mm, typically 28-spoke steel rims.
   (See this article outlining these two wheel sizes)

Ball Bearings for the Original Configuration Raleigh Twenty
- The standard Sturmey-Archer front hub (not a Dyno-Hub) has twn (10) 3/16 inch Ball Bearings on each side for a total of twenty (20) balls.
- The Bottom Bracket has eleven (11) 1/4 inch Ball Bearings on each side for a total of twenty- two (22) balls.
- The bearing at the bottom of the Head Tube has twenty-five (25) 5/32 inch Ball Bearings in the bearing race.

Rear Hubs and Gearing
- Single speed with coaster brake
- 3-speed (Usually a Sturmey-Archer AW, but sometimes a Sturmey-Archer AG dynohub).
- New-Zealand built versions offered a 2-speed "duomatic" rear hub with coaster brake.
- Some versions have Shimano 3-speed hubs.
- 46-tooth Chain-wheel and 15-tooth sprocket, giving gears of approx. 46 - 61 - 83 gear inches.
-  This video provides instructions for adjustment of the AW/AG gears of a Raleigh Twenty.  https://www.youtube.com/watch?v=9Bma6jVvUb8
-  The majority of Raleigh Twentys came with a Sturmey-Archer AW hub and there has been much discussion about their maintenance and adjustment.  Here is a link to the official Adobe (.pdf) format Sturmey-Archer Heritage 1972 Manual, this includes the parts list, dismantling, assembling, maintaining and trouble-shooting with an exploded view of the hub.  http://www.sturmey-archerheritage.com/files/view-1046.pdf

Sturmey-Archer Trigger Shifters
- An excellent article on Sturmey-Archer Trigger Shifters for its 3 and 4 speed hubs, 1938 - 1960, was published by Martin Hanczyc in July 2006.
- The article is much too long and detailed for inclusion here but this link will take you to the article: http://genetics.mgh.harvard.edu/hanczyc/pdfs/satriggersjuly06.pdf 

- Lots and lots of good information with drawings and pictures, enjoy. 

Brakes
- Standard Raleigh Brakes on ISO 451mm wheeled versions.
- Weinmann Long Reach Callipers on ISO 406mm-wheeled versions.

Handlebars
- There appears to be three main types of handlebar used on production Raleigh Twentys.
1.) One-piece "All-Rounder" bars.
2.) Two-piece "All-Rounder" bars.
3.) Two-piece "North-Road" bars.

The "All-Rounder" style is similar to modern MTB Riser bars, but with considerably more rise. The "North Road" type have a more generous back-sweep on the grips, similar to what many dragster bicycles later used, but with less rise than dragster bars.

All production handlebars were held on by a clamp around the top of the forks, and the stems do not have binder bolts.

Please note: The stem has a height-limiter in the form of a loop of stiff wire which runs around the front brake bolt. To remove the handlebar and stem from the frame, you must first remove the front brake.

Rims & Tires (Tyres): There are often questions about rim and tire (tyre) availability for upgrading the Raleigh Twenty so, here's a fairly comprehensive list.  Remember that things change and there may be other Rims and Tires (Tyres) available as time passes.

(This section provided by member, davepalk and he uses British English spelling, forgive him.)

    Rims:

Alienation Ankle Biter  20 x 1-1/8" . Lightweight high-performance junior-BMX race rim. Double-walled. Eyeleted. Theoretically available in 28, 32 and 36 hole drillings. I have the 32H version on two bikes. They're very good. Patchy availability.

Sun Ringle ICI-1  20 x 1-1/8". Similar to above. 28 and 36 hole drillings. Currently available.

Halo JX-2  20 x 1-1/8". Similar to above. 28 and 32 hole drillings. I'm about to build a set. They look very good. Currently available.

Crupi Rhythm 20 x 1-1/8". Similar to above but non-eyeleted. Range of anodized colours. 28 hole drilling. Currently available.

Bombshell and RCR carbon-fibre  20 x 1-1/8". Currently available but WAY TOO EXPENSIVE!!!  And, may not take high pressures.

Ukai and Araya "old school" BMX race rims  20 x 1-3/8". These regularly turn up as "New Old Stock" on eBay. They were made during the BMX boom of the early 1980s, and are normally 36H only. Being single-walled and non-eyeleted, these are basic rims that are no match for the lighter and stronger modern alloy rims listed above. Patchy availabilty.

Ukai "mid school" BMX race rimes 20 x 1-1/8". From the 1990s or early 2000s. Occasionally turn up NOS on eBay. These double-walled and eyeleted (sometimes double-eyeleted) Japanese rims are top quality. Rare.

Unbranded Chinese 451 carbon-fibre rims, direct from the factory online or via eBay. Caveat emptor! Currently available.

See notes below on rider weight limits and size compatibility.


    Tyres:

Tioga Power Block  20 x 1-3/8". High performance BMX race tyre with skinwall construction. Largest volume performance tyre (37 mm section) available in 451 size. My choice for daily commuting, and I've only just had to replace the rear after about 8,000 miles! Good puncture resistance. Currently available.

Tioga Power Block  20 x 1-1/8".  "Skinny" (28 mm) version of above. Currently available.

Schwalbe Shredda Liteskin folding 20 x 1 3/8". The ultimate BMX race tyre. This is the most expensive 451 tyre on the market. Currently available. 

Schwalbe Shredda Liteskin folding  20 x 1-1/8". "Skinny" version of the above. Currently available.

Schwalbe Shredda wire bead  20 x 1-3/8". Performance BMX race tyre. Economy alternative to "Liteskin" version. Currently available.

Schwalbe Shredda wire bead  20 x 1-1/8". "Skinny" version of the above. Currently available.

Schwalbe Durano  20 x 1-1/8". High performance road tyre designed for recumbents and high-end Mini Velos. Fast rolling and with very good puncture resistance. My absolute favourite. Currently available.

Kenda K196  20 x 1". Narrow, high pressure road tyre. Currently available.

Scwalbe One EVO  20 x 7/8". 451 version of Schwalbe's range topping road-race clincher. This should be the fastest 451 tyre available. Let's hope they eventually do a 28 mm version, which would have less rolling resistance and give more grip and comfort. 23 mm currently available.

Maxxis DTH  20 x 1-3/8". High-performance BMX race tyre. Developed specifically for the 2008 Olympic Games. I found that these ride beautifully but are prone to punctures. Currently available.

Maxxis DTH  20 x 1-1/8". Skinny version of the above. Currently available.

Kenda Small Block 8  20 x 1-3/8". Fine "knobbly" tread for off-road use. Like a cyclo-cross tyre in 451 size, for you "Trekking Twenty" project!

Kenda Small Block 8  20 x 1-1/8". "Skinny" version of above.


    Rim and Tyre notes:

1.) Don't be put off by the fact that a tyre has been designed for BMX racing use when you want a tyre for road use. Modern BMX racing tracks use tarmac-surfaced start straights and turns, so BMX race tyres are designed to perform primarily on hard, firm, smooth surfaces. They are effectively road-race tyres. The exception is the Kenda Small Block 8, which is a knobbly tyre designed for hard-packed dirt.

2.) Narrower tyres are not faster. All other things being equal, a wider tyre will roll more efficiently than a narrow one. The 23 mm tyres listed above may therefore not be the fastest, and they certainly won't be the most comfortable.

3.) Width is not necessarily consistent. Different manufactuers measure tyre sction (width) in different ways. For example, a Tioga Power Block 37mm tyre is wider (and taller) than a Maxxis DTH which uses the same (1-3/8" or 37mm) section designation. A taller tyre will be beneficial when riding fixed-gear.

4.) Diameter. There are several different rim size standards all described as 20"! 20" tyres with their section (width) described as a fraction (example: 20 x 1-3/8") are normally 451 mm and when described with a decimal (example: 20 x 1.75") are normally 406 mm. Continental brand tyres do not follow sizing description convention. Continental 20" tyres use a fraction but are actually 406! Always go by the ETRTO size description (for example, 28-451) to be absolutely sure. This is the official, technical size designation, and all tyes are marked (somewhere) in this way. The first figure is the tyre's section (width) and the second figure is the rim's bead seat diameter (diameter of tyre's wire bead) in millimeters.

5.) Pressures. Some of the BMX tyres listed have relatively low maximum pressure ratings. It is my experience that these can be exceeded somewhat, without problems. However, it obviously isn't sensible to grossly over-inflate a tyre. An accident could result! Oh, and putting modern, high-pressure tyres on original chromed-steel rims probably isn't a very good idea. 

6.) Rider weight limits. It is common for junior BMX race rims to be labelled with a rider weight limit. Remember, the original intended use of these rims involves getting airborne over big jumps. So, weight limits can be ignored for road use. If the bike is over-stressed to the point of something failing, your R20 frame or fork will collapse way before your rims give out! 

7.) Machined braking surfaces. Some rim manufacturers don't machine the braking surface of their 28H rims. This is because BMX race bikes have just one caliper brake, on the rear, and junior bikes generally run a 28H rim up front and a 32H at the back. There is no reason why you shouldn't run a brake on a 28H un-machined rim. The anodizing will soon wear through anyhow.

8.) Chrome-plated alloy rims. Some BMX rim manufacturers make a chrome-plated option available. BMX racing is a dry weather sport, and chrome gives sharper braking performance - IN THE DRY! Chrome rims give TERRIBLE BRAKING WHEN WET, and if used on salted (British) roads the chrome will eventually lift and flake. Chromed alloy rims should therefore be avoided.

9.) Will a 1-3/8" tyre fit on a 1-1/8" rim - and vice versa? Yes, but I personally wouldn't put a 23 mm (1" or 7/8") tyre on an "old school" 1-3/8" rim. Rims listed as 1-1/8" should accept any 451 tyre perfectly well.

10.) Availability. The listed availability is for the UK market at time of writing. Use a Google search to find suppliers and prices. That's what I did to check current availability.

11.) Where are the Schwalbe HS110s and Raleigh Records? Those are not performance tyres!

12.) What about 406 size wheels? 406 is only 20" with a 2" section tyre. A performance skinny (say 28 mm 1-1/8") tyre in 406 size effectively gives you 18-1/2" wheels. The bike will be too low! Your pedals will strike the road when you corner!!! Then there are brake reach and gearing issues to consider. 451 is way better than 406 for performance conversions.


    Other options...?