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Birdy thread

Old 08-16-21, 07:16 PM
  #1601  
Huggable
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Green Basikal didn't organise the pictures into an album, hence you can read up the comments in each photo to piece together the puzzle.

Posted on 9 July by Green Basikal on Facebook:

Birdy conversion from 1x to 2x Chainrings. Objective is to have lower gear ratios for ease in climbing.

Contrary to many commonly seen Birdy conversions where riders just want to ride fast, faster and fastest, with increasing bigger chainrings, we actually swap the original 52T to 50/34T chainrings.

The original 52T w/11-32T (9s) Birdy has a range of 27.9 to 81.1".

With the swap to 50/34T double chainrings, the new improved gear ratios became 18.2 to 78".

Now he can C L I M B.





Originally Posted by Jipe View Post
What model of Birdy do you have ?

What is the brand of the front derailleur mount used for the conversion ?

You could maybe post some pictures of it.
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Old 08-17-21, 02:56 AM
  #1602  
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81,1" is really short, 78" is even worse !

I have a Brompton with Rohloff (54x13), the 19” to 102” range is really excellent. 102" is about 25% longer than 81.1" !
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Old 08-29-21, 02:36 PM
  #1603  
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Originally Posted by Jipe View Post
81,1" is really short, 78" is even worse !

I have a Brompton with Rohloff (54x13), the 19 to 102 range is really excellent. 102" is about 25% longer than 81.1" !
The Birdy Rohloff is supplied with 52T / 13T which gives gearing of 19.9" to 104.4"and I'm planning to change the sprocket to 14T which drops the gearing to 18.4" - 97" which is very close to the gearing on my main bicycle. However, a double chainring with 11-32 casette will never give the gearing range of the Rohloff so theere has to be a compromise somewhere. My aborted project to put a double chainring (54 + 38) on a Birdy City (8 speed hub gear) would have given gearing of 22.3" to 97" with a 16T sprocket. 22.3" would be just OK for my worst local hill but it would have been easy to lower the gearing by fitting a bigger sprocket.
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Old 08-30-21, 02:24 AM
  #1604  
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The slightly longer gear range of the Birdy Rohloff vs. my Brompton Rohloff is due to the slightly bigger wheels and mainly the bigger/wider/higher Big Apple tires.
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Old 09-03-21, 07:34 PM
  #1605  
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Originally Posted by Huggable View Post
I see. Come think of it, there's hardly any hills here in Singapore, hence generally 7-speeds onwards is sufficient for most of our commuting needs.

I'll be swapping out my SRAM X5 10 speed to the Rohloff hub next month, looking forward to the modification!
Hi- Is there a dealer in SG that actually help to convert to Rohloff Hub? If so I am keen to look at that also on my GT.

One qn - has anyone used a larger chainring say 58T vs 13t sprocket on Rohloff? I know is not known as a speed demon but technically the largest gear inch at gear 14 here (118) would be much longer than most including R20

So at same candence rohloff would be faster? Or did i miss something?
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Old 09-06-21, 08:59 PM
  #1606  
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Yes, Green Basikal is the Rohdoff dealer in SG. and I think for MY as well.
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Old 09-09-21, 10:23 AM
  #1607  
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Originally Posted by desmondk07 View Post
One qn - has anyone used a larger chainring say 58T vs 13t sprocket on Rohloff? I know is not known as a speed demon but technically the largest gear inch at gear 14 here (118) would be much longer than most including R20

So at same candence rohloff would be faster? Or did i miss something?
I haven't tried using a larger chainring and wonder if this would affect the foldability. My calculation suggests that extra 6 teeth increases the chainring diameter by about 24mm and you could do a visual check on the implications of this. A longer chain would be needed which might affect how easily it can be folded.

You are correct that a larger chainring will give a higher speed at a specific cadence and this applies through the whole gearing range. 58T instead of 52T increases the gearing by about 11.5% which is close to 1 step in the Rohloff gears. If you live in a relatively flat area with no need for the bottom gear or two then I would suggest that you try using a bigger chainring if only to find out if it works.
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Old 09-09-21, 03:07 PM
  #1608  
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The current chain tensionner arm placed around the chainring limit the chainring size.
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Old 09-09-21, 07:00 PM
  #1609  
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I'm using a Ridea 56T oval chainring currently, and will be pairing it with at 13T sprocket on the Rodloff hub for a 20" to 108" range.

I have no problems folding with the 56T chainring, but not sure if 58T would be too big for folding.
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