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 Post subject: Re: Twentys for 20
PostPosted: Wed Oct 17, 2018 9:39 pm 
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Location: Saaa'fend, Essex
kingoffootball wrote:
Good to see another Raleigh Twenty project! I'm looking forward to see how you choose to build it up.

I got used a Mavic bottom bracket to get around the shell issues, which was a little work, but I'm happy I took that approach. I might even have a spare of those bottom brackets, though I need one for my Aende, so I'd have to work out which is needed for that before parting with any.

What are you doing about brakes?


Oooo.....Tell me more about the Mavic bottom bracket - what makes these an option? What is involved in fitting one? Something I'm considering is a modified sq taper spindle (lengthened) fitting in the original cups. Quite a bit of effort to machine one in half, add a spacer and braze it all together.......but I've read that it's been done before and it means that I don't have to modify the frame.

Not sure about brakes yet. There are new long drop calipers available from Tektro but I think these would be just long enough to use on 451mm rims.....and currently I'm going with the 406mm bmx size rims.

bluetomgold wrote:
sherlylock wrote:
bluetomgold wrote:
Looking forward to seeing what you do with this. The Kingpin's awaiting a new stem... getting there!


Any ideas what stem are you going for?


Nice work on the twenty... getting those BBs out can be a pig - I bought a special tool, but your technique looks great.

Re the stem, one of these just arrived in the mail. Feels solid, but heavy.

https://www.ebay.co.uk/itm/PROMAX-EXTRA ... 2420460364

If you are keeping the original forks and headset you might be better off in some respects to keep the original stem / bar setup. Nice to have a quick release on the stem on one of these.


I think I'll stick with the original arrangement for now and see what a set of drops looks/feels like in the standard stem. Looks like there's a few long stem options if I decide to go away from standard.

Spotted this frame for sale on fb tonight. A colour scheme along these lines would be great I reckon......if I had a mood board for this project it'd be right up there ;)

Image


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 Post subject: Re: Twentys for 20
PostPosted: Thu Oct 18, 2018 8:38 am 
retrobike rider / Gold Trader
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sherlylock wrote:
kingoffootball wrote:
Good to see another Raleigh Twenty project! I'm looking forward to see how you choose to build it up.

I got used a Mavic bottom bracket to get around the shell issues, which was a little work, but I'm happy I took that approach. I might even have a spare of those bottom brackets, though I need one for my Aende, so I'd have to work out which is needed for that before parting with any.

What are you doing about brakes?


Oooo.....Tell me more about the Mavic bottom bracket - what makes these an option? What is involved in fitting one? Something I'm considering is a modified sq taper spindle (lengthened) fitting in the original cups. Quite a bit of effort to machine one in half, add a spacer and braze it all together.......but I've read that it's been done before and it means that I don't have to modify the frame.

Not sure about brakes yet. There are new long drop calipers available from Tektro but I think these would be just long enough to use on 451mm rims.....and currently I'm going with the 406mm bmx size rims.



The Mavic bottom brackets don't use the threads, so the different threading doesn't matter.

Image

The bottom bracket shell should be chamfered (I borrowed the Mavic tool from danson67 ) and I also needed to remove a little material from the middle of the shell, between the threads, to fit it in.

The bottom brackets aren't light, but they are stiff and apparently last a very long time. I'm glad I chose that option.

I have Dia Compe BRS 202 brakes on mine, which just have long enough drop for 451 wheels, but are definitely no use for 406.


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 Post subject: Re: Twentys for 20
PostPosted: Thu Oct 18, 2018 6:31 pm 
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kingoffootball wrote:

The Mavic bottom brackets don't use the threads, so the different threading doesn't matter.

Image

The bottom bracket shell should be chamfered (I borrowed the Mavic tool from danson67 ) and I also needed to remove a little material from the middle of the shell, between the threads, to fit it in.

The bottom brackets aren't light, but they are stiff and apparently last a very long time. I'm glad I chose that option.

I have Dia Compe BRS 202 brakes on mine, which just have long enough drop for 451 wheels, but are definitely no use for 406.


Ahh ok - so threadless? Is it the right length then i.e. no need to shorten the bb shell to 68mm?

Regarding brakes I'm now considering designing an ally bracket - cnc'd to bolt into the original brake plate to act as a drop bracket (I know a friendly CNC machinist with a Haas 5-axis machine).....for the rear at least.

I spread the stays, filed out the dropouts and generally chucked some stuff at the frame to see how it looks.

The std stem has quite a small clamp diameter for the bars (24.2?) - the only ones I have that fit in the parts box are a set with a slight sweep back. I want to run drops ideally.....or bullhorns.......so a new stem is required.

Seatpost is about 100mm too short in that setup for my lanky legs......so a 400mm post is required.....in matt black pref.

Sold the original saddle from the shopper last night so the frame is now essentially free. I like a project that starts to pay for itself. :)

Image

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 Post subject: Re: Twentys for 20
PostPosted: Fri Oct 19, 2018 7:51 am 
retrobike rider / Gold Trader
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sherlylock wrote:
Ahh ok - so threadless? Is it the right length then i.e. no need to shorten the bb shell to 68mm?

Regarding brakes I'm now considering designing an ally bracket - cnc'd to bolt into the original brake plate to act as a drop bracket (I know a friendly CNC machinist with a Haas 5-axis machine).....for the rear at least.

I spread the stays, filed out the dropouts and generally chucked some stuff at the frame to see how it looks.

The std stem has quite a small clamp diameter for the bars (24.2?) - the only ones I have that fit in the parts box are a set with a slight sweep back. I want to run drops ideally.....or bullhorns.......so a new stem is required.

Seatpost is about 100mm too short in that setup for my lanky legs......so a 400mm post is required.....in matt black pref.


Yes, it's threadless and long enough to fit in the 76mm shell, so I chamfered it but did not reduce the width.

I seem to remember there were plenty of 400mm seat posts the right size. Really, I could do with one a little bit longer, but I think all the longer ones I found were expensive. If you find the Handsome Dog Lite Stik that I used on mine in black it seems a nice seat post - the silver has a nice satin finish and feels light.

The cramped riding position was why I went for a long stem forward and bullhorns and I find the riding position really comfortable now - I can pretty much ride as far as on any of my bikes before discomfort sets in.

Looking good so far!


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 Post subject: Re: Twentys for 20
PostPosted: Tue Oct 23, 2018 9:30 am 
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Little bit of progress......but not much.

Mavic threadless bottom bracket found and won on eBay.

Satin black long seatpost ordered and on the slow boat from China (took a punt on that tbh)

Secondhand, but hardly used Schwalbe Kojaks bought - I love these tyres, have used them before on 26" wheel mtbs and didn't realise they did them in 20". Should roll nicely on these :)

Image

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 Post subject: Re: Twentys for 20
PostPosted: Tue Oct 23, 2018 12:50 pm 
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Joined: Sat Jul 09, 2016 4:07 pm
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Location: Rutherglen
YST also do a thread-less BB and maybe considerable cheaper if cost is an issue.

https://www.sjscycles.co.uk/bottom-brac ... d-threads/


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 Post subject: Re: Twentys for 20
PostPosted: Tue Oct 23, 2018 1:00 pm 
retrobike rider / Gold Trader
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The YST one is designed for a 68mm shell. I'm pretty sure I read you can't really use them in a 73mm, let alone the bigger Twenty shell.


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 Post subject: Re: Twentys for 20
PostPosted: Tue Oct 23, 2018 4:46 pm 
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Yep. I'd seen those YST bbs for sale - presumably if you get the bb shell machined down to 68mm and can buy a long enough bb you should be able to get yourself a reasonable chainline?

How do you even calculate any of this stuff? I guess it depends on which cranks you are using too and where the chainring sits relative to the square taper on the bb.

Had a chat with the machineshop at work today and he's OK with chamfering the bb shell for me for the Mavic bb (and machining down to 68mm too if that happens to work out as the best option).


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 Post subject: Re: Twentys for 20
PostPosted: Fri Oct 26, 2018 6:16 pm 
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Mavic BB has arrived

What actual sizes are these usable for? It looks to me like 73mm shell width is probably the max that you can get away with (I didn't check before I bought it tbf.....just took a punt on it - it was cheap enough).

68mm width looks like this:

Image

Image

73mm looks like this:

Image

Image

76mm looks like this:

Image

Image

Looks like the lock rings wind off the ends of the bb too much here?

Spindle length is 114mm.

Presumably shaving 1.5mm of each end of the bb shell and chamfering each side should see this fit nicely - providing that the chainline I end up with is in a reasonable position.


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 Post subject: Re: Twentys for 20
PostPosted: Fri Oct 26, 2018 11:29 pm 
retrobike rider / Gold Trader
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That's odd, it must be a different model from mine. I just went to take a photo, but the crank gets in the way. There is only one circle of thread visible either side on mine when it is fitted.


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