Raleigh Twenty and UN72
 

I recently purchased a Raleigh Twenty in fair condition and am planning on going all out on the upgrade route... First thing that I have decided to tackle is the bottom bracket. I managed to find, locally, a UN72 bottom bracket. Most of the websites I consulted mention a UN72 with a 113mm length as ideal, but the one that I found locally is 122mm. Will 122mm be OK for the Raleigh Twenty or is it too long?

I'm still debating on whether or not I should just have the bottom bracket re-threaded or not, it might be a wise investment.

Thanks,

TB

It sounds like it might be a little long - though you *might* be able to run your chainring on the inner side of the crank and still get a good chainline if you use longish bolts and possibly the odd washer to counter the length. I think on my Twenty it was a 115 or even a 117 - it's hard to measure now it's on the bike...

Thanks, I'll see if I can source the proper size from a LBS... Those UN72 are not easy to find, even on eBay.

That's because they're no longer made, Ebay is the place to find them

Still looking on eBay for one...

You can use a same sized UN54, the UN72 differs in material spec only.

hi guys- sorry to jump in here, i'm a newbie, excuse the ignorance...will that un73 that soil sampler links to fit on a r twenty without getting the frame rethreaded? and then i can use any modern crank? thanks in advance...

The UN72 BB was unique in that it had 2 loose cups. The UN73 is same as all the others, the RH side is a fixed cup.

The idea behind the UN72 BB is that you get a set of Phil Wood cups to go with the UN72 BB, discarding the original UN72 cups. The Phil Wood cups can be ordered in 26 threads per inch (26TPI).

So the UN73 won't work unless you get it re-threaded. Then I'm also unsure about what the imact on shell width is. I had mine rethreaded in the end as well as narrowing the shell to the standard 68mm to give me maximum flexibility.

According to this website: http://house-of-yes.com/phil-wood-y-bottom-bracket/ only the UN72 will work, not the UN73. The UN72 is to be used in conjunction with Phil Woods retaining rings, and with that setup, you do not need to get your frame re-threaded. Of course, if you get your frame re-threaded, you can use standard ISO bottom brackets.

I'm still debating whether or not re-threading is the better alternative. After purchasing a UN72 with Phil Woods retaining rings + special tools, it might be more cost effective to simply go the re-threading route.

With the ever dwindling amount of available UN72s around the rethreading route may work out better in the long run. Does anyone know of a way of filling the old threads by brazing prior to rethreading so as to make for a stronger new thread?

It's been mentioned many times but not in this thread so maybe the alternative 'F.A.G.' bb option Vince talks about is a valid plan b here? Details on his page

LittlePixel,

One question in my mind is when all the un 72's are gone and rethreading is one of the main options, how strong will the new 24 tpi be? Now I'm no huge thighed track sprinter, but I've cracked racing frames with continual hard riding, so I wonder if the rethreading is strong enough for anything but moderate riding. Maybe brazing is a good idea, tricky but.
Vince's F.A.G. idea seems good, but I still wonder how it would perform under long term hard riding.
There are as you know multiple choices to use at present, but in the back of my mind is the Phil Wood BB...most expensive, but so well made, and by the time you find a good LBS with the interest to rethread, you've probably spent the difference in time and money anyway??
It would be interesting to how see Jur and other's rethreaded R20's are holding up....Jur?

So far so good. I ride it perhaps 300km per week, with all sorts of riding including plenty of standing on the pedals on those sharp little climbs on my commute. Unfortunately I'm bad when it comes to keeping records, but I don't think it's more than 2 months' riding, so perhaps 1500km.

The LBS close to work did the rethreading work for me, $40. Then I filed the shell down as well as I could to 68mm, then another LBS did the shell re-facing, another $40 IIRC. As new Ultegra 6500 crankset & BB, $57.

i'm about to file the bb shell down. luckily, one of the local mechanics has taken an interest in the bike, and will do the rethreading and refacing for cheap.

did you take the same amount off both sides of the bb shell?

Yes. I assumed they were symmetrical, never checked. On one side a bit of the welding was removed too. The 2nd LBS who did the refacing expressed concern about that.

I have a spare un72 bb which I will use with Phil rings for my wife's R20 rebuild, but any other R20 after that I think the rethreading is the go, I've got a LBS who is quite willing to help.

I've mentioned in previous posts that a local frame builder here is willing to make me a frame from steel or aluminium to the R20 design, but with a 68mm bb shell with 24tpi. He could also make the rear end for a 9 spd hub using a triple crank upfront and even lenghtening the downtube a tad for more cockpit room. Braze-ons for bidons and for using V-brakes, cantilever or even discs. It's very tempting to do it, just wish he would give me a price first......Oh yeah, he works with carbon fibre too.

Steve - if you get that bike made it will rule from the centre of the ultraworld! :)

L.P.,

Probably very close to a Bike Friday Pocket Rocket Pro, except I would have, if possible, a cf front fork, saddle post, head stem and a 60/50/40 triple crank, on 451 rims, of course ;) If I lived in the US or GB I could see great potential for success for this guy in making frames for small wheelers, alas Aussies are only slowly catching on.

Hey stevegor, that sounds like it would make a great bike! Won't the framebuilder even give you a Ball Park estimate? Like are we talking $ 400 - 1000 or $1100 - $ 2000 or even crazier?

Big difference compared to a BF would be that the 20 clone would offer a much more usefull/quick fold for multi mode transport. In fact if i were commissioning such a bike i'd want the hinge to be exactly the same but perhaps would want the L shaped bolt replaced by something even more convenient and quicker, though i am not sure what at present..

As for the material, i think it should be steel!!! A Twenty in Alu kinda sounds like blasphemy! ;)

Reynolds 953, to be precise.

Yes, Reynolds 953 would be nice, however blasphemy or not, Specialized use a wonderfully light aluminium in the Allez range which would make the R20 clone strong, but light as a feather.

Let me go away into my own little R20 utopia for awhile, (don't we all do this?*), and I will meditate deeply on this matter, and having done so, I will return with a wise answer.....or a ball park price!!




* I sometimes lie awake at night, thinking about what else I can do to my R20's, sleep escapes me, I get restless and toss and turn.........Is this R20 fever?

It's love.

A Raleigh 20 clone in ally would be much like a no-suspension Downtube, methinks. If nothing else it would be a helluva lot lighter as you say. I think I weighed in mine's frame at a heart-rending 5kg.

Although, even if I lose 3kg off the frame, my little steam roller still puffs in at 13-14kg! It put on a lot of weight when I installed that SA 8sp with uber strong rim and a gazillion heavy spokes.

With the S/A 8 spd hub the Wasp still rock n rolled on it's recent 1st bunch ride, so imagine the sublime experience of a super light R20 clone, Ultegra or Durace equipped.....like floating on the ethereal zephyrs of cycling paradise......
As Homer would say "Hmmmm :love:

Well there us Alu and there is Alu, a really good grade would be ehm 'acceptable'... :)

The 20 has never been about Weight weening for me, but to be sure if the frame is truly 5 K then it is real heavy! Are you sure about that, seems pretty high/hard to imagine!

Yes quite sure. Unfortunately the particular thread where I posted the exact weight of all the frame parts is lost due to a server issue that happened that time, but it was close to 5kg all up.