Cycling and bicycle discussion forums. 
   Click here to join our community Log in to access your Control Panel  


Go Back   > >

Folding Bikes Discuss the unique features and issues of folding bikes. Also a great place to learn what folding bike will work best for your needs.

User Tag List

Reply
 
Thread Tools Search this Thread
Old 07-05-07, 07:38 PM   #1
delwong
Member
Thread Starter
 
Join Date: Sep 2006
Bikes:
Posts: 31
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Brompton Bottom Bracket/ Crank Upgrade

Hi....anyone upgrade their Brommie bottom bracket and crank with lighter and more refined components?
delwong is offline   Reply With Quote
Old 07-06-07, 02:00 AM   #2
14R
Bromptonaut
 
14R's Avatar
 
Join Date: Feb 2005
Location: Jersey City, NJ
Bikes: 2012 Brompton S6R;1993 Diamond Back Racing Prevail ti; 2003 Litespeed Firenze; 1994 Diamond BAck Axis TT
Posts: 1,682
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 6 Post(s)
My BB was fine, but I did get an FSA crankset with 53 chainring for my Brompton.
14R is offline   Reply With Quote
Old 07-06-07, 05:45 AM   #3
LWaB
Senior Member
 
Join Date: Dec 2005
Location: Auld Blighty
Bikes: Early Cannondale tandem, '99 S&S Frezoni Audax, '65 Moulton Stowaway, '52 Claud Butler, TSR30, Brompton
Posts: 2,240
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
More refined is easy, lighter is more difficult than you might think.
LWaB is offline   Reply With Quote
Old 07-10-07, 04:01 AM   #4
maranen
Senior Member
 
Join Date: May 2007
Location: Finland
Bikes:
Posts: 139
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Hi
I donít know if Mercís and Bromptonís respective parts weigh the same, but with Merc itís quite easy to save about 100g even without going for titanium or carbon parts. Mercís bottom bracket + left crank + right crank with 53 chain ring + chain guard = 1010g. Pedals were removed. I made a comparison with FSA bb + crank-set with 2 chain rings (50 and 34) and the weight saving was about 130g.
maranen is offline   Reply With Quote
Old 07-10-07, 04:07 AM   #5
EvilV
Bicycling Gnome
 
Join Date: Apr 2006
Location: 55.0N 1.59W
Bikes:
Posts: 1,877
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by maranen
Hi
I donít know if Mercís and Bromptonís respective parts weigh the same, but with Merc itís quite easy to save about 100g even without going for titanium or carbon parts. Mercís bottom bracket + left crank + right crank with 53 chain ring + chain guard = 1010g. Pedals were removed. I made a comparison with FSA bb + crank-set with 2 chain rings (50 and 34) and the weight saving was about 130g.
To be honest, I probably carry 130 grammes of lose change in my pocket. I'd rather just leave that at home and not spend money buying new parts.

EvilV is offline   Reply With Quote
Old 07-10-07, 10:54 AM   #6
invisiblehand
Part-time epistemologist
 
invisiblehand's Avatar
 
Join Date: Jun 2005
Location: Washington, DC
Bikes: Jamis Nova, Bike Friday NWT, STRIDA, Austro Daimler Vent Noir, Haluzak Horizon, Salsa La Raza, Hollands Tourer, Bike Friday tikit
Posts: 5,589
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 28 Post(s)
Quote:
Originally Posted by maranen
Hi
I donít know if Mercís and Bromptonís respective parts weigh the same, but with Merc itís quite easy to save about 100g even without going for titanium or carbon parts. Mercís bottom bracket + left crank + right crank with 53 chain ring + chain guard = 1010g. Pedals were removed. I made a comparison with FSA bb + crank-set with 2 chain rings (50 and 34) and the weight saving was about 130g.
Would you use both chainrings or dump the 34?
invisiblehand is offline   Reply With Quote
Old 07-11-07, 12:56 AM   #7
maranen
Senior Member
 
Join Date: May 2007
Location: Finland
Bikes:
Posts: 139
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by invisiblehand
Would you use both chainrings or dump the 34?
I intended to use them both, but I will probably have to go for some other components because the axle length is not enough Ė bike will not fold Ė matter of 2mm. Otherwise itís very nice set FSA Gossamer Megaexo Compact with 50 chain ring same as K-Force Ė grooves and pins for better gear change. I had a chance to buy it quite cheaply and made a foolish thing not to check the folding first. The axle is integrated with the right crank. Actually weight saving would be 140g.
maranen is offline   Reply With Quote
Old 07-11-07, 02:56 PM   #8
LWaB
Senior Member
 
Join Date: Dec 2005
Location: Auld Blighty
Bikes: Early Cannondale tandem, '99 S&S Frezoni Audax, '65 Moulton Stowaway, '52 Claud Butler, TSR30, Brompton
Posts: 2,240
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Brompton's cranks are lighter than the Merc's. The chainline and folding problems eliminate most of the lightweight options. Sticking to a square drive BB gives more freedom in that regard. As well as the chainring/spider clearing the frame when folded, another trap for the unwary player is ensuring the end of the cranks clear the folded swingarm. If you have this problem, you have to have the crank in a certain position before folding, which can be a real pain in the neck (refer Birdy and others).
LWaB is offline   Reply With Quote
Old 07-11-07, 06:04 PM   #9
spambait11
SeŮor Mambo
 
Join Date: Jan 2004
Location: Fremont, CA
Bikes: Ti Sports roadie, Cannondale CAAD 3, Tern Cargo Node, Helix (soon)
Posts: 1,344
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by LWaB
...another trap for the unwary player is ensuring the end of the cranks clear the folded swingarm.
I can confirm 165mm cranks work without having to position the cranks before folding. It also helps if your pedals fold, or can be removed outright.

Also, 60T chainrings seem to be about the max size before the teeth and chain start rubbing against the chainstays.
spambait11 is offline   Reply With Quote
Old 07-11-07, 07:06 PM   #10
delwong
Member
Thread Starter
 
Join Date: Sep 2006
Bikes:
Posts: 31
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
What happens with a 170mm long crank?
delwong is offline   Reply With Quote
Old 07-11-07, 08:36 PM   #11
LWaB
Senior Member
 
Join Date: Dec 2005
Location: Auld Blighty
Bikes: Early Cannondale tandem, '99 S&S Frezoni Audax, '65 Moulton Stowaway, '52 Claud Butler, TSR30, Brompton
Posts: 2,240
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Quote:
Originally Posted by delwong
What happens with a 170mm long crank?
Stock Brompton cranks are 170 mm. The problem is getting the same lateral offset from the chainring to the back of the crank at the pedal. Greater offset results in a wider fold, lesser can hit the folded swingarm.
LWaB is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -6. The time now is 02:01 PM.