veloceleste

I just received a pair of NOS Sun CR-18 36 hole rims that were advertised/auctioned as 20" BMX rims. It turns out that they aren't 406 but 451 rims and quite a bit narrower than I thought they would be. I want to be certain the rims can be safely used on the Twenty before I start spending more to build new wheels. After searching here and reading on Sheldon's page about rims I'm a little confused in trying to determine their width. Is the width measurement taken on the inside of the rim? These measure 18mm across the inside top of the hook. Also, will the brakes need anything more than an adjustment and re-alignment? Thanks for any information.

LittlePixel

Firstly they should fit into the frame ok; British Twentys came with 451s not 406 and the only differences aren't in the frames, but in the length of the brake callipers on an export version. I doubt the stock 451s would have been as narrow as the ones you've got hold of as these bikes were always marketed as short-hop utility bikes, not the long legged tourers/commuters us fans always seem to be converting them to. Whether the width you have got is an issue really depends on what you plan to use the bike for and the kinds of tyres you want to use. Narrow 451s are most often used with smaller profile, sometimes slick road tyres for higher end folding bikes, like the Bike Friday and some recumbents but you can get wider more durable low pressure examples for more sedate or minor path riding - the bike friday site actually has a good selection to look at. How well a more rugged tyre would fit on such a skinny rim is a good question and one you did well asking. I think a tyre up to 1 1/4" in profile should be fine - larger than that and I think it may risk being easily unseated. I should qualify that by saying that I'm only pontificating and don't have exact experience of this - it's just my gut feeling based on the sizes you mention.

As for your brakes - the difference your brake shoes will need to move is half of 45mm - ie 451-406=46/2 =22.5mm - so if you can reposition them upwards in the caliper that far then you should be fine - if not - you might need to get hold of some shorter reach calipers which is a breeze as they are pretty much everywhere. Getting the long reach callipers you already have for people converting the other way [from 451 to 406 - like we do in the UK] - is usually a lot harder.

Not 100% sure about the 'correct' way to measure rim width so I'll leave that to someone that knows a bit more.
FWIW: I think Twentys look better on skinny 451s but don't let that sway you - I'm a notable form-before-function bike glamour sufferer!

Couple of nice pix of Chris Slydel's 'roadie' Twenty on skinny little 451s from this page:

caotropheus

I have a R20 frame and a very similar Kama frame (made in USSR, converted to road single speed bike), and obviously I decided for 451 rims because in first place it is easier to find tyres for this size whose width is arround 25-28 mm and pressures 100 - 120 psi. Second The R20 frame is adopted to use with 451 mm wheels and not the 406 mm wheels, giving you advantages on adopting modern brake technology to the frame - rim and also bigger wheels set your bottom braket higher obove the ground giving you more pedal clearance.

veloceleste

Thanks for the responses. I'm thinking of going with a Sturmey 8 speed. I don't want to have to re-space the frame or spread the fork so I'll talk to my LBS about an appropriate front axle. He is long time Raleigh dealer and may have something in the shop that will require only minimal work on the fork. I also like the idea of being able to return the bike to original stock condition.

LittlePixel

With an SA 8 hub you may well need to 'spread' the rear triangle by cold setting (basically controlled bending) as a Raleigh SA3 hub has a rear axle of around 120 OLN whereas the new one will likely be 135. This is only 7.5mm on each side though and I can testify having gone from a 120 original hub to a 135 Sachs hub and back to a 120mm track hub that if you do bend them out a little you can still get enough flex to refit a narrower or restore the original hub setup.

LWaB

SA8s are available in narrow configurations, cold-setting is not required.

EvilV

Some of these done up Twenties look fantastic. Very attractive looking bikes.

I wonder how they'd have sold if Raleigh had sold some in that kind of form. I bet they would have sold well. They might have doubled their profit on the already VERY succesful line. They might have revolutionised cycling forever more.

jur

There is only 1 SA8 hub, all you do is remove some of the nuts.

stevegor

The Wasp runs Velocity Aero 451 rims with a SA xrf8 8spd hub and a 48t chainring, using Schwalbe Stevlio 120 psi tyres......nice 'n quick and good handling, and of course no crank clearance problems.
I also have some narrow steel 451 rims which are way skinnier than the stock R20 451 rims, also they have a 5spd cluster which I think is threaded, so a more modern 6 or 7 spd might go on, AND if I can work out how to mount a front derailliuer .....a future project R20??

For my wife's R20 I will be using 406 rims, but I've got 145mm cranks to suit and I will be brazing on mounts for V-brakes front and rear.

norfolk bolt

These modded r20's have revolutionised cycling for me, totally personalised the experience and moved me to a realm beyond mass cycle/culture/taiwanese consumption: which is why I rode/ride in the first place...the fact is we are unique in our quest, on the one hand paying homage to a fantastic legacy of cycle technoloy, and on the other furthering it by keeping the quality of our history 'competitive' with the masses...It's a buzz going to high end cycle shop and have the staff 'not understand the concept'!!!..because those serious cyclists are missing the point...cycling is an art, not technology and not a science. (Although technology and science are an enabling factor in the manipulation of our Raleigh 20 craft)

Stevgor has the right idea...he just needs to up his valium to 20mg, or else get a softer seat :-)

Ride on My Raleigh Brothers!!!

stevegor

Norfolk Bolt,

Hmmmm..........Valium....DOH!!

What I enjoy about cycling now that I'm not racing, is that I can ride whatever type of bike I feel like on any given day, some days it's the MTB, others it might be a roadie, a tandem or a R20. With the R20 I love the fact that I might get smart comments or strange looks, but once out on the road and rolling it's great to teach a few uneducatedboof headed roadies what these addictive little wonders can do.

awetmore

The similar (same geometry) UK-market Dawes Kingpin came with a third size wheel too, 500A. This is ISO 440mm. My mom still has a Dawes Kingpin using this size of wheel.

My advice would be to return the 451mm rims to the seller (and have them pay shipping if they mislead you on the size) then buy 406mm rims. There is a much wider variety of tires in 406mm. You can get tires that are both faster and more comfortable such as the Avocet Fasgrip Freestyle.

I do think that the seller needs to compensate you (either by taking them back or changing the price) for misleading you on the size. It isn't okay for eBay sellers to advertise one thing and sell a different thing.

alex

kraftwerk 

I also bought BMX wheels off ebay, which turned out to be 451's. Must be a good way for people to dump their 451's! But I kept them and learned to love them. With the Raleigh 20 it was a plus for running short reach brakes. (I adapted the frame and fork with a drop link to lower the brake bolt -- so I was less of a gap to "drop" the brake) It is also nicer to have slightly bigger wheels if you are used to riding 700 cc. It is just more stable, if undetectably so... they "fill" the frame well as the above photo's well illustrate. It is a visual thing more than performance. it is interesting to read that they were in fact the R 20 standard.
The only NEGATIVE and this is a biggie: the tires are harder to come by and there is less choice. It is the only PITA. I run Stelvio's which are nice and fast, high psi but also a bit "delicate". If you keep the wheels you might end up liking them. But if you will travel where there are no 451 tires you must think about taking a spare tire or two...not so bad really.

stevegor

[QUOTE=kraftwerk;5515152]
The only NEGATIVE and this is a biggie: the tires are harder to come by and there is less choice. It is the only PITA. I run Stelvio's which are nice and fast, high psi but also a bit "delicate". If you keep the wheels you might end up liking them. But if you will travel where there are no 451 tires you must think about taking a spare tire or two...not so bad really.[/QUOTE]

I agree, however, Stelvios also come in a fold up version, so if touring, they don't take up too much room.

One problem with 406 rims is crank/pedal ground clearance, a shorter crank is wiser to use.

Sammyboy

[QUOTE=stevegor;5517625]This is something I hadn't considered. I'm going from 451 to 406, and the only cranks I have right now are 170's - no problem with the current wheels, but might be with the new ones. Hmmm.