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PostPosted: Wed Oct 10, 2018 3:19 pm 
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Joined: Tue May 11, 2010 6:39 pm
Posts: 645
Location: North London
sherlylock wrote:
With regards to brakes - the Puch has a set of Weinmann 1020 long drop calipers which seem to fit OK - and it's got 20" BMX wheels on it. Not sure what size the originals would've been but the calipers seem to reach and work OK.

I'll measure the drop on them later to see if that offers you a potential solution. Loving the idea of a coaster brake though :)


Haha nice.

The Puch would always have had BMX size/metric wheels. Continental European innit? It's just English stuff like Twenty and Kingpin that have the bigger wheels.

I won't be using a coaster brake as I've already re-spaced the back end for a derailleur hub. But it's a good option, especially if you fancy the 3 speed shimano hub. My mate loves his. Maybe I'll try and dig out some pics.

I wouldn't worry about preserving a Twenty for posterity. They are common as muck. ;)


Last edited by bluetomgold on Thu Oct 11, 2018 8:07 pm, edited 1 time in total.

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PostPosted: Thu Oct 11, 2018 6:58 pm 
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Joined: Wed Aug 17, 2011 1:03 pm
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Location: Saaa'fend, Essex
Ahh ok - so as I understand it there are two rim sizes of 20" wheel......(I'm new to these small wheeled bikes - lots to learn!)

Metric 406mm dia ("BMX" wheels)
Imperial 451mm

Tyres really common for the 406mm size but not so for the 451mm size?

Apparently the Twenty was fitted with both during it's production run - the longer reach for the smaller metric wheels being achieved with long drop Weinmann brakes......which is what I have on the Puch. They look like they flex around a lot though...........measured them this morning and they are around a 90mm reach!


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PostPosted: Thu Oct 11, 2018 7:16 pm 
King of the Skip Monkeys
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Joined: Wed Nov 07, 2007 4:34 pm
Posts: 29660
Location: in the shed
needs disc wheels!

https://www.ebay.co.uk/itm/QR-20-inch-F ... :rk:7:pf:0


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PostPosted: Thu Oct 11, 2018 7:47 pm 
Retro Guru

Joined: Tue May 11, 2010 6:39 pm
Posts: 645
Location: North London
sherlylock wrote:
Ahh ok - so as I understand it there are two rim sizes of 20" wheel......(I'm new to these small wheeled bikes - lots to learn!)

Metric 406mm dia ("BMX" wheels)
Imperial 451mm

Tyres really common for the 406mm size but not so for the 451mm size?

Apparently the Twenty was fitted with both during it's production run - the longer reach for the smaller metric wheels being achieved with long drop Weinmann brakes......which is what I have on the Puch. They look like they flex around a lot though...........measured them this morning and they are around a 90mm reach!


That's pretty much it... but (as Xerxes pointed out) to add to the complication the Kingpin's original wheels are a third, different size, "500A" (440mm), which is probably the most obscure.

The easy way to tell the other two sizes apart is that English (451mm) wheels are designated as 20 x 1 3/8" tyre size whereas BMX/European ones are 20 x 1.75", or 1.5, or whatever depending on the tyre width. If it's expressed as a decimal figure rather than fractional, it's the smaller wheel.

You may be right that some later Twentys had the BMX size wheels, but I've never come across one. I think it's generally safe to assume that they will have 20x1 3/8" (451s). Not sure Weinmann made anything long enough for the drop required on my Kingpin although I might be wrong.

I have the original 3 speed wheels and tyres for the Kingpin if anyone wants them...


Last edited by bluetomgold on Thu Oct 11, 2018 8:05 pm, edited 3 times in total.

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PostPosted: Thu Oct 11, 2018 7:47 pm 
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Joined: Tue May 11, 2010 6:39 pm
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Location: North London
legrandefromage wrote:


That would be a bit posh. ;)


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 Post subject: Re:
PostPosted: Fri Oct 12, 2018 11:19 am 
Old School Grand Master
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Quote:
the Kingpin's original wheels are a third, different size, "500A" (440mm), which is probably the most obscure.


The 500A thing is a French sizing system along with 650B and 700C. The letters A, B, C and D denote the tyre width, with A being the narrowest and D the widest. The number is supposed to be the overall diameter of the wheel in milimetres when the tyre fitted.

Of couse the overall diameter of a wheel will vary wildy depending on the width of the tyre and how wide is "A"; it was a bonkers system, which is why we now have the ETRTO system.

If you look at a bicycle wheel/tyre size chart, there are often half a dozen different actual sizes whithin each nominal wheel size, there are 7 different 20" wheel sizes and 5 different 26" wheel sizes - madness: https://www.internet-bikes.com/en/size- ... yre-sizes/ :shock:

To add to the confusion, we now refer to 650B rims/tyres as 27.5 inch and 700C as 29ers, depending on whether we're talking about road or mountain bikes.


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 Post subject: Re:
PostPosted: Fri Oct 12, 2018 7:53 pm 
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Location: North London
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Swapped the saddle with a WTB one that came on my Saracen Trekker. It's too modern for the Saracen but looks good on this I think. It's pretty light, and hopefully reasonably comfy.

I'm not going to use the LX mech pictured after all because the combination of long cage and small wheels has the potential for ground clearance issues. I picked up a short cage XT one off here... want to clean it up and see if I can find a replacement for the worn jockey wheel before I fit it.

Found a brake caliper for the back. This has actually got way more reach than I needed... It's branded "ZALUN, Taiwan" but it came as part of an Oxford MX brakeset. They're still readily available e.g. http://www.alansbmx.com/1353581/product ... e_set.aspx - the little levers can be handy too.

The best thing about it is that I was able to swap the pinch bolt and barrel adjuster around so I can route the cable from below. This can be a bit of an issue when upgrading step-through / ladies bikes...

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PostPosted: Tue Oct 16, 2018 1:48 pm 
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Posts: 1329
Location: Saaa'fend, Essex
Cool, really starting to come together!

What wheel/hub combination have you got there? I've started trawling the free-ads trying to find a cheap kids bike (with 20" wheels) that I can rob the wheels off....but it all seems to be low end tat (which is the nature of kids bikes I guess).

Best ones I can find so far are on a Specialized HotRock......the search continues.


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PostPosted: Tue Oct 16, 2018 2:08 pm 
Retro Guru

Joined: Tue May 11, 2010 6:39 pm
Posts: 645
Location: North London
sherlylock wrote:
Cool, really starting to come together!

What wheel/hub combination have you got there? I've started trawling the free-ads trying to find a cheap kids bike (with 20" wheels) that I can rob the wheels off....but it all seems to be low end tat (which is the nature of kids bikes I guess).

Best ones I can find so far are on a Specialized HotRock......the search continues.


Thanks man!

Wheels are off a kids bike I think and were picked up very cheaply off eBay. Alex rims and low end steel hubs - which seems to be par for the course with kids bikes. They spin smoothly enough though, (new grease in the rear hub, and just adjusted the front) have hardly been used, and will do for the time being. At least the alloy rims will give decent braking compared to the chromed steel originals.

If I love the way the thing rides I might build some better wheels up at a later date on some old DX hubs I have.


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PostPosted: Tue Oct 16, 2018 9:12 pm 
retrobike rider / Gold Trader
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Location: a mote of dust suspended in a sunbeam
At last!, a Kingpin thread on RB that I can finally hit Nerdcon 5 over with my own golden Kingpin..

Watching and gaining inspiration with imterest.

And TGF, those disc wheels look ace!


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