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20" wheels on an MTB ?
http://www.retrobike.co.uk/forum/viewtopic.php?f=41&t=224238
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Author:  Raging_Bulls [ Sun Oct 07, 2012 8:00 pm ]
Post subject:  20" wheels on an MTB ?

We've all seen the usual 650B and 700c conversions, and some members here even have MTBs with one or more 24" wheels, but this one is new to me, so I though I'd share it.
I can imagine that something like this is a hoot to ride in city traffic.

Image

Ever since I came across this, I can't stop thinking about doing such a conversion myself.
I'd pick a better starting point than a Benz though, and I'd make sure I have enough ground clearance too.

Here's what the above bike is supposed to look like, BTW. I really understand why the owner changed the wheels.

Image

Author:  cyfa2809 [ Sun Oct 07, 2012 8:02 pm ]
Post subject: 

Oh wow i love that!
Please do one so i can copy you.
Surprised thet it actually looks like it has decent clearance.

Author:  Raging_Bulls [ Sun Oct 07, 2012 8:07 pm ]
Post subject: 

cyfa2809 wrote:
Oh wow i love that!
Please do one so i can copy you.
Surprised thet it actually looks like it has decent clearance.


Heh, I just might.

I've been doing some maths, and if I can find an XC full susser that has a 14.25" BB height (center of BB axle, that is), I can drop it and still have as much clearance as my Sbikes.
14" if I switch to a 170mm crankset.

As for loving it, I know the feeling.
Those fenders look just right on that bike, and it would look horrid without those. This thing really has that Supermoto look about it.

Author:  michael franks [ Sun Oct 07, 2012 8:26 pm ]
Post subject: 

What a brilliant idea and nicely carried out too. There does seem to be reasonable clearance, I wonder what sort of gearing you need to use or whether 'standard' gearing is OK.

Author:  Raging_Bulls [ Sun Oct 07, 2012 9:31 pm ]
Post subject: 

Hypothetically speaking, a 20" wheel has 0.7692307692 times the circumference of a 26" wheel (62.8" vs 81.64"). So basically the gearing will be around 25% shorter.
Sounds like a lot, but it isn't really. 42/11 on a 20" would feel like the 42/15 or 32/11 on a 26" bike.

I suspect one will be forced to run a single up front, or a double with a road cassette. Not because of the different gearing itself, but because you don't have enough ground clearance to safely run a long-cage rear mech.

Author:  michael franks [ Sun Oct 07, 2012 9:57 pm ]
Post subject: 

Yeah - it's surprising how small the difference is. Perhaps run 1 or 2 x 10 and then get really radical and fit a Moonlander tyoe wheel on the front......







.....looking for my coat :oops:

Author:  velomaniac [ Mon Oct 08, 2012 12:33 pm ]
Post subject: 

Check out an Airnimal Rhino
http://www.airnimal.eu/rhino.php
or a Bike Friday
http://www.bikefriday.com/bicycles/mountain
or even Sheldon Brown and his Raleigh Twenty's

Author:  Synthesis [ Mon Oct 08, 2012 1:26 pm ]
Post subject: 

I´m at the start of a build right now, and will be building a set of 20" wheels and a set of 26" also for the bike. Just for fun...

Author:  hamster [ Mon Oct 08, 2012 2:26 pm ]
Post subject: 

Sorry, I still don't get this - why do you want a 20" wheel on it again??? :?

Author:  velomaniac [ Mon Oct 08, 2012 5:27 pm ]
Post subject: 

Synthesis at the end of his last post answers your question.......Just for fun :wink:

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