Weight Weenies
* FAQ    * Search    * Trending Topics
* Login   * Register
HOME Listings Blog NEW Galleries NEW FAQ Contact About
It is currently Sat Jul 02, 2016 5:04 am
Recently the board software has been updated and there are some known bugs/failures:
- Avatars are currently not being displayed ✔ FIXED
- Tapatalk connection is currently broken ✔ FIXED
- Avatars cannot be uploaded ✔ FIXED

Please note that we will soon do some changes in WW board template design in case to get a fully mobile/desktop responsiveness board!
If you find more errors please post it here: http://weightweenies.starbike.com/forum/viewtopic.php?f=7&t=139062


All times are UTC+01:00




Post new topic  Reply to topic  [ 9 posts ] 
Author Message
PostPosted: Mon Nov 18, 2013 6:16 am 
Offline

Joined: Wed Jan 12, 2005 6:04 am
Posts: 558
Location: USA
Lately on our large group training rides there has been a trend towards these balls out drag race accelerations after each stop sign, and there are quite a few. Add to that rolling terrain, complete with sharp bergs within technical narrow country roads and you are going to expend a lot of energy. Even though the long flat sections make up a fair percentage of these rides some people have found they have adapted better by switching to smaller profile, hence lighter rims.

What I find interesting is that this wasn't the case before this change in tactics. People benefited from the deeper wheels here. We've were discussing how this isn't the case in racing conditions, even in crits, cause at least you can carry a lot of speed through the corners.

Just something to consider if you're thinking of taking that next step towards racing and are training in similar conditions.


Top
   
PostPosted: Mon Nov 18, 2013 7:21 am 
Offline

Joined: Sat Feb 23, 2013 10:51 pm
Posts: 152
Looking for some sort of evidence, outside of anaecdotal, in the post to support the claim...


Top
   
PostPosted: Mon Nov 18, 2013 7:36 pm 
Offline
Shop Owner
User avatar

Joined: Tue Mar 10, 2009 5:27 am
Posts: 1244
Location: McCall, ID
Lighter rims will definitely make accelerations feel more responsive and lively, but does that correlate to real world speed increase? Thats debatable. Maybe a very, very small amount. But if someone ever uses the excuse, "Ahh I lost that sprint because I'm on my Deep Vs instead of my Alpha 340s", then they should receive a swift Chuck Norris roundhouse kick to the dome piece.

_________________
http://www.zencyclery.com


Top
   
PostPosted: Mon Nov 18, 2013 8:16 pm 
Offline

Joined: Fri Dec 15, 2006 7:45 pm
Posts: 3969
Location: Natovi Landing
physics suggests zen is right. shallower and lighter rims do feel very different though which counts for a lot IMO

_________________
----------------------------------------
Stiff, Light, Aero - Pick Three!! :thumbup:


Top
   
PostPosted: Mon Nov 25, 2013 2:38 am 
Offline

Joined: Tue Nov 11, 2003 9:47 pm
Posts: 2182
Location: Santa Cruz, California, USA
Here is a good discussion: https://en.wikipedia.org/wiki/Bicycle_p ... ght_wheels

The benefit of lighter wheels on accelleration is small, and could be equaled or outweighed by heavier but more aero wheels depending on how heavier and how much more aero.


Top
   
PostPosted: Tue Nov 26, 2013 5:52 am 
Offline

Joined: Wed Jan 12, 2005 6:04 am
Posts: 558
Location: USA
Thanks for the math compilation reference Eric. It will be interesting to go through some numbers, thought it suggests wheel weight makes little difference.

The point I was trying to emphasize was the numerous changes in dynamics. Some days it smooth and fast while other days it's very choppy and fast.

The consensus here is that when you sum the effects of 10 to 12 very hard accelerations from stops signs along with the chaos from other sources (cops, vehicles and other cycling groups, etc.) yielding very dramatic changes in velocity, you may be better off with lighter wheels. Conversely, when it's smooth, with gradual accelerations to very high speeds then aero should be more beneficial. This is going with the assumption the power account is finite.

I am merely passing along observations from riders after the rides, though I would tend to agree. Under these extreme conditions heavier wheels can take their toll, or so it would seem.


Top
   
PostPosted: Wed Nov 27, 2013 12:31 pm 
Offline

Joined: Sat May 12, 2007 3:40 am
Posts: 477
Location: Triange, NC
I would think that wheel stiffness could make it less clear on any perceived advantage. A stiff deep profile wheel when might accelerate faster than a softer, yet slightly lighter box rim wheel.


Top
   
PostPosted: Wed Nov 27, 2013 8:36 pm 
Offline

Joined: Wed Oct 30, 2013 12:52 am
Posts: 301
If you have the opportunity - ride different wheels and tires and pressure. Its a lot easier and IMO more accurate than calculations.

Most calculations treat the bike and cyclist as if they go in a straight line and the bike is perpendicular to the ground at all times. I agree on the average the bike goes in a straight line and on average it is perpendicular to the ground, however there is lots of side to side movement in real riding and the rotational inertia of the wheel has bearing on that and it is changing constantly as the rider does mini turns right and left riding at 25mph just balancing the bike. Then there is the stiffness part. Energy gets scrubbed off in tire casing deformations, bumps, flex in wheels - without the rider even standing and sprinting.


Top
   
PostPosted: Fri Nov 29, 2013 8:48 pm 
Offline

Joined: Tue Nov 11, 2003 9:47 pm
Posts: 2182
Location: Santa Cruz, California, USA
Unfortunately the "ride it" method also introduces rider perception into the equation... and that may mask the relatively small effects from lighter weight on accelleration or aerodynamics on speed.

I'd love to see some energy loss calculations from wheel deformation. My gut feeling is that most of it is in the spokes (especially on deep section carbon rims which are stiff due to their cross section) and the majority of spoke flex is returned- i.e. they act as springs.


Top
   
Display posts from previous:  Sort by  
Post new topic  Reply to topic  [ 9 posts ] 

   Similar Topics   Author   Replies   Views   Last post 
There are no new unread posts for this topic. Weenies, thought you might enjoy this

in Road

xena

3

864

Tue Dec 15, 2015 5:18 pm

jimborello View the latest post

There are no new unread posts for this topic. Need some help choosing...

in Everything wheels

Glu

5

486

Sun Dec 27, 2015 2:59 pm

dvdslw View the latest post

There are no new unread posts for this topic. Help Choosing Rim Depth

in Everything wheels

Zoose

3

334

Fri Feb 12, 2016 3:17 pm

Zoose View the latest post

There are no new unread posts for this topic. Choosing between Stumpjumper M4 and Santa Cruz Superlight

in MTB

nigelnigel

1

337

Tue Dec 01, 2015 12:24 pm

TheRookie View the latest post

There are no new unread posts for this topic. parlee z5, SMALL vs MEDIUM, trouble with choosing size

[ Go to page: 1 2 ]

in Road

seokyseoky

15

547

Mon Jun 27, 2016 2:57 pm

kode54 View the latest post


All times are UTC+01:00


Who is online

Users browsing this forum: Google [Bot] and 2 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:  
cron
Powered by phpBB® Forum Software © phpBB Limited