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-   -   Birdy Owners .... hot upgrade available (http://www.bikeforums.net/folding-bikes/674862-birdy-owners-hot-upgrade-available.html)

brakemeister 08-25-10 01:17 PM

Birdy Owners .... hot upgrade available
 
http://www.thorusa.com/dahon/accessories/wheels.htm

hate to bring this up as it could be viewed as spam. But still want to spread the word.
Birdys are rolling on 18 inch wheels ... and I know a few folks who would like to switch to 20 inchers due to better tire selection and all ....

i found the solution .. V brake extenders ....

http://www.thorusa.com/images/dahon/...0inchbirdy.jpg


they also work on 20 inch Dahons to run 451 wheels

thor

p.s. I also have in stock a front derailleur hanger for the Birdy :-)
http://www.thorusa.com/dahon/accessories/special.htm

jmaher 08-25-10 01:58 PM

Can it be this easy? Buy this and maybe the Kinetix Pro wheels and off you go?

Jim

brakemeister 08-25-10 02:09 PM

should be that easy ... indeed...
my only problem is that I dont have any compe wheels and only rear Pro S wheels in stock at this moment ... but the wait should be over soon
Thor

jmaher 08-25-10 02:26 PM

I assume no difference on an older Birdy (a red from a few years before the changeover to the monocoque style) ?

yangmusa 08-25-10 02:31 PM

Very, very cool... Hmmm.... A while ago I emailed with the Australian Birdy dealer, and he wrote that a front derailleur and double crankset could not be retrofitted to a regular Birdy because on the small chainring the chain would not clear the rear swingarm. He wrote their 20" racing Birdy had a customized rear swingarm. Looking at my bike, it does look like chain clearance might be an issue.

Thor, have you tried this mod? Does the bottom bracket spacer included in the kit take care of the clearance problem?

JulianEdgar 08-25-10 02:32 PM

any close-up pic of the front derailleur mount on a Birdy?

brakemeister 08-25-10 03:13 PM

I dont have a Birdy here, I more or less rely on the manufacturer that it will fit ....
Its a tight fit most likely same as the Dahons are a tight fit. Yes the bottom bracket spacer comes with it ...
I think I saw a birdy on a taiwanese website with this conversion but having trouble finding it at the moment
Thanks Thor

jur 08-25-10 03:27 PM

Some time ago I put an inner chainring on mine and it didn't work. You will need a wider bottom bracket (or a spacer).

Thor, the brake adapters are clever... just one issue, the effective ratio pull changes from about 2:1 going towards 1:1, so you may need to post a caveat about this. Not sure it is a real issue though.

What a pity I just bought a new front rim... I'll see if I can exchange it again. OTOH I'm not that fussed about it any more. May be nice for touring because the smaller wheels didn't do too well.


* ponders possibilities *

brakemeister 08-25-10 06:58 PM

interesting observation Jur
I wonder however as the leverage points of the long brake legs are the same if the pressure applied is the same on the plane ...
its late and I still need to work and my brain might be fried ..lol

thor

jur 08-25-10 07:58 PM

I just had a quick look at the Birdy V-brake; the pads are mounted about 1/3 of the length of the caliper. The V-brake cantilever (or whatever it's called) is 100mm on the Birdy and the pads are mounted 30mm from the pivot. So this translates to a 3:1 force exerted by the pads on the rims.

With 406mm rims, the extra distance required looks to be about 25mm, so that places the pad at roughly 2/3 distance from the brake pivot. This translates to a 3:2 force, close to 50% of the original value.

To me this implies that road brake pull is needed which are about 2:1 ratio compared to V-brakes. I wonder if there is mention of this at the original web site?

vincentnyc 08-26-10 02:20 PM

i noticed that the chain is kinda low, i can see a problem when ones is doing a tight turn. any1 here ever have that problem?

ratdog 08-26-10 02:58 PM

Wouldn't going to a larger tire affect the fold?

brakemeister 08-26-10 04:10 PM

http://www.thorusa.com/images/dahon/...inchbirdy3.jpg

yes it does ....

thor

p.s. Jur.. about that leverage thing, the rim has a larger diameter therefor some of the "lost" leverage should be compensated for ..right ?

jur 08-26-10 07:26 PM

Quote:

Originally Posted by brakemeister (Post 11360554)
p.s. Jur.. about that leverage thing, the rim has a larger diameter therefor some of the "lost" leverage should be compensated for ..right ?

No, unfortunately that leverage you refer to is related to something else... braking force is not impacted by wheel size except for the distance between the braking surface (ie the rim) and the actual road. So braking is reduced if you have big fat tyres and even more with disc brakes (which have a huge leverage force built into the pad actuators to compensate for this loss of leverage).

But that pic ypu posted - pretty! the pads are about halfway along the cantilever so probably not an issue.


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