Weight Weenies
* FAQ    * Search    * Trending Topics
* Login   * Register
HOME Listings Blog NEW Galleries NEW FAQ Contact About Impressum
It is currently Thu Nov 23, 2017 11:40 pm

All times are UTC+01:00





Post new topic  Reply to topic  [ 50 posts ]  Go to page Previous 1 2 3 4
Author Message
PostPosted: Thu Jun 15, 2017 12:15 pm 
Offline

Joined: Fri Feb 18, 2005 6:50 pm
Posts: 212
Location: Wilmington, DE
Calnago wrote:
So why Pinarello still uses the Italian threads is beyond me. It doesn't matter, as the precession process is not relevant with todays BB designs, so functionally it doesn't present the issues that it did in the past,


Old post, but I'm pretty certain (but lack real world evidence of any issues) that this is incorrect. Even in a cartridge bottom bracket, the bearing races are essentially fixed to the cartridge (by means of being press fit into the cartridge) and thus subject it to precession loads. Even in instances where both threaded cups are not 'fixed' to the cartridge itself those cups are still designed to be a tight fit to the cartridge and would likely try to turn with the cartridge due to precession.

Sort-of modern outboard bearing cups share even more in common with old-timey cup and cone bottom brackets as the outer bearing races are press-fit into those cups providing a direct load path from the outer race to the cup. You don't want the outer bearing race spinning in the cup so it is always pressed in there quite tightly. As an aside, BB30 and PF30 designs where the bearings slip in are clearly poorly designed/manufactured as this is asking for issues; no bearing manufacturer would suggest designing a system like that where neither the inner or outer bearing race is tightly press fit onto a shaft or into a bore, respectively.


Top
   
Posted: Thu Jun 15, 2017 12:15 pm 


Top
   
 
PostPosted: Thu Jun 15, 2017 10:56 pm 
Offline
User avatar

Joined: Sun Nov 07, 2010 9:14 pm
Posts: 4749
@joejack951: Yes, that's getting to be an old post now... I had to go back aways in this thread to get the whole context. While precession is still present, it does not have nearly the same effect in today's world as yesterdays, before the advent of cartridge bottom brackets even. Today, even if you still have a cartridge bottom bracket, the actual bearings are inside that cartridge and likely to be cartridge bearings themselves, not loose. Then the cartridge is encased in some more cups, which have threads which thread into the Bottom Bracket (assuming threaded here). So, instead of loose bearings rolling directly against a race which is itself threaded into the shell, you have the bearings rolling against their own outer race if they are cartridge bearings. The outer surface of the outer race is pressed against the inside of the BB cartridge, and the BB cartridge is itself enclosed in some right and left cups, which finally get threaded into the shell. This is quite different than when the whole bottom bracket was like a cup and cone system, and loose bearings rolled directly against the race which threaded directly into the shell. If those combined cups/races weren't in the shell very tightly, they would loosen up due to precession and unthread themselves on the drive side, but only in a right hand thread (which the Italian threads are). Hence, high torques of 50Nm on the cups were the order of the day, and since no one would even think of using a torque wrench back then, sometimes they were tight, and sometimes they weren't. The ones that weren't came loose... guaranteed. So, enter the English threaded bottom bracket... with it's left hand thread. Now, even if precession was at work, be it old or even in the newest designs, the effect would simply be to tighten down the cups as opposed to loosen them. No problem. Hence, I can't understand why Pinarello seems to persist on using the Italian threads in their bottom brackets, except to say that at least that part of their bikes has some "Italian" to them, aside from the paint. You just think they might have picked a better piece of Italy to use than "Italian" bottom bracket threads. Does anyone else still use them, I mean anyone? Save for maybe a few independents building frames in the backroom of a Italian Pizzaria? I don't know... but I can't think of any outside of Pinarello.

_________________
Colnago C60 - PR99
C59 Five Years Later
My Special Colnago EPQ
Trek Emonda SL Campagnolo SR


Top
   
PostPosted: Fri Jun 16, 2017 6:30 am 
Offline
User avatar

Joined: Wed Aug 18, 2004 6:06 pm
Posts: 252
Location: Lower Saxony - Germany
Delorre wrote:
Beaver wrote:
Tour tested the F10 to be exactely as aero as the Madone btw.:

https://www.wilier.com/sites/default/fi ... nrader.pdf (German)


Does someone have the values (or a pdf link or...) of the F8 Tour test done in 2016? Would be intrestng to see the differences.


https://translate.google.com/translate? ... t=&act=url

_________________
Infos on wide tires, rims and aerodynamics


Top
   
PostPosted: Fri Jun 16, 2017 9:36 am 
Offline

Joined: Sat May 24, 2014 12:09 pm
Posts: 787
Beaver wrote:
Delorre wrote:
Beaver wrote:
Tour tested the F10 to be exactely as aero as the Madone btw.:

https://www.wilier.com/sites/default/fi ... nrader.pdf (German)


Does someone have the values (or a pdf link or...) of the F8 Tour test done in 2016? Would be intrestng to see the differences.


https://translate.google.com/translate? ... t=&act=url


Thx!! Bummer there are no stiffess and confort values in the text or in the graphs like in the F10 test.

_________________
Canyon Ultimate CF SLX 2013
Scott Addict Orica Greenedge
Canyon Endurace CF SLX


Top
   
PostPosted: Fri Jun 16, 2017 7:02 pm 
Offline

Joined: Sat Dec 13, 2003 2:25 am
Posts: 4962
Location: Canada
The BB? Really? How about the Trek 'suspension'? Have you ridden that thing? It is unreal. It will change your perspective on hoe a really stiff aero bike can feel.


Top
   
Display posts from previous:  Sort by  
Post new topic  Reply to topic  [ 50 posts ]  Go to page Previous 1 2 3 4

   Similar Topics   Author   Replies   Views   Last post 
There are no new unread posts for this topic. Replace my Bianchi Oltre XR.2 with a Trek Madone 9.9 RSL

in Road

gzon

11

1499

Fri Jan 06, 2017 10:44 pm

wheelsONfire View the latest post

There are no new unread posts for this topic. Attachment(s) Bianchi Oltre XR3

[ Go to page: 1 2 3 ]

in Road

thebucket

37

8347

Wed Sep 27, 2017 4:59 pm

TonyM View the latest post

There are no new unread posts for this topic. Colnago C60 or Bianchi Oltre XR4?

[ Go to page: 1 2 3 4 ]

in Road

Noctiluxx

56

4854

Thu Sep 28, 2017 2:42 pm

nismosr View the latest post

There are no new unread posts for this topic. Attachment(s) De Rosa SK Pininfarina vs Bianchi Oltre XR4

[ Go to page: 1 2 3 4 ]

in Road

TwinSpokes21

57

6799

Thu Nov 23, 2017 3:40 am

r_mutt View the latest post

There are no new unread posts for this topic. Attachment(s) Help me choose color for my Bianchi Oltre XR4

[ Go to page: 1 2 ]

in Road

Noctiluxx

27

1105

Thu Nov 09, 2017 8:08 pm

WR74 View the latest post


All times are UTC+01:00


Who is online

Users browsing this forum: Baidu [Spider], dvq, possibleweenie, PSJoyce, raggi, Seedster and 47 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Limited